Monday, December 12, 2011

JKstat at Play!

The Play framework seems to be quite popular around Cambridge.

For those not familiar with it, it's a java application framework built for REST. And, like Ruby on Rails, it emphasizes convention over configuration.

Rather than creating yet another boring blogging example I decided to use JKstat as an example, and see how involved building a RESTful JKstat server was using the Play framework.

Creating a project is easy:

play new jkstat

The one thing I'm not keen on is the way it manages dependencies for you to get you jar files. You can either mess about with yaml files, or drop the jar file into the lib directory of the project. Full details of the complex way are in the play directory of the JKstat source.

The next step is to decide how to route requests. The JKstat client only has a few requests, in a fairly fixed form. So I can write the routes file explicitly by hand:

# JKstat queries get sent to JKplay
GET /jkstat/getkcid    JKplay.getkcid
GET /jkstat/list    JKplay.list
GET /jkstat/get/{module}/{instance}/{name} JKplay.get

All this means is that if a client requests /jkstat/list, then the list() method in the JKplay class gets called.

Slightly more complex, something of the form /jkstat/get/module/instance/name will invoke a call to get(module, instance, name).

Putting this in a routes file in the application's conf directory is all that's needed to set up the routing. The other thing you need to do is write the JKplay class and put the java source in the application's app/controllers directory. The class just contains public static void methods with the correct signatures. For example:

    public static void list() {
 KstatSet kss = new KstatSet(jkstat);

JKstat knows how to generate JSON output, and the renderJSON()call tells Play that this is JSON data (which just means it won't do anything with it, like format a template, which is the normal mode of operation).

And that's basically it. All I then had to do was run the project (with LD_LIBRARY_PATH set to find my jni library) and it was all set. The JKstat client was able to communicate with it just fine.

Sunday, December 11, 2011

Editing cells in a JTable

For the recently released update to Jangle I wanted to do a couple of things for the cousin and sibling tabs.

First, I wanted to have the list of OIDs and associated data to be slightly better formatted and to update along with the charts. This wasn't too difficult - the chart knows what the data is, so I got it to extend AbstractTableModel and could then simply use JTable to display it, just calling fireTableDataChanged at the end of the loop that updates the data.

(As an aside, I'm irritated that the API doesn't include fireTableColumnsChanged. You can do the whole table, or a cell, or by row, but not by column.)

The second thing I wanted to do was to allow the user to select the list of items to be shown in the chart. The picture above shows the table with the data, and how I wanted it to look. (And is exactly how I managed to implement it.)

Now, the table is already showing the list of available data, so I just added a third column to handle whether it's displayed in the chart or not. I simply implemented getColumnClass and returned Boolean.class for the third column, and the JTable automatically shows it as a checkbox. (With the value of the checkbox simply toggled from the underlying model.)

The next step was to be able to edit that field - tick or untick the checkbox - and get it to update the chart. The first step is easy enough - just get isCellEditable to return true for the third column.

I then actually got stuck, because the documentation simply isn't clear as to how to connect that all back up. I was looking for all sorts of listeners or event handlers, and couldn't find anything. Searching found a number of threads where someone else clearly didn't understand this either, with responses that were rude, patronising, or unhelpful - from people who regarded the answer as obvious.

Anyway, the important thing is that it really is easy and obvious once you've worked it out. Making the cell editable automatically creates a cell editor, and all the plumbing is created for you. All you have to do is implement setValueAt which gets called when you do your edit. So my implementation simply adds or removes the relevant field from the chart. (And because that's what's supplying the model, the value displayed in the checkbox automatically tracks it.)

That's the sort of basic thing that ought to be covered in documentation but isn't; this blog entry is there for the next time I forget how to do it.

Saturday, December 03, 2011

Building current gcc on Solaris 10

While Solaris 10 comes with gcc, it's quite an old version. For some modern code, you need to use a newer version - this is the case in my Node.js for Solaris builds, for example.

Actually building a current gcc on Solaris 10 turns out to be reasonably straightforward but, as in most things, there's a twist. So the follwoing is the procedure I've used successfully to get 4.6.X built.

You first need to download the release tarball from, and unpack it:

bzcat /path/to/gcc-4.6.2.tar.bz2 | gtar xf -

There are 3 prerequisites: gmp (4.3.2), mpfr (2.4.2), and mpc (0.8.1). However, you should use the specific version mentioned, which may not be the current versions. Conveniently, there's a copy of the right versions on Go into the gcc source, unpack them, and rename them to remove the version numbers.

cd gcc-4.6.2
bzcat /path/to/gmp-4.3.2.tar.bz2 | gtar xf -
mv gmp-4.3.2 gmp
zcat /path/to/mpfr-2.4.2.tar.bz2 | gtar xf -
mv mpfr-2.4.2 mpfr
gzcat /path/to/mpc-0.8.1.tar.gz | gtar xf -
mv mpc-0.8.1 mpc
cd ..

You have to build from outside the tree. If you followed the above, you'll be in the parent to gcc-4.6.2. Create a build directory and change into it:

mkdir build
cd build

Then you're ready to configure and build:

env PATH=/usr/bin:$PATH ../gcc-4.6.2/configure \
--prefix=/usr/local/versions/gcc-4.6.2 \
env PATH=/usr/bin:$PATH gmake -j 4
env PATH=/usr/bin:$PATH gmake install

There are three things to note here.

First is that I'm installing it into a location that is specific to this particular version of gcc. You don't have to, but I maintain large numbers of different versions of all sorts of applications, so they always live in their own space. You can put symlinks into a common location if necessary.

The second is one of the key tricks: I just build c, c++, and fortran. They're the only languages I actually need, and the build dies spectacularly with other languages enabled.

The third is that I force /usr/bin to the front of the PATH. Not ucb, and not xpg4 either.

You'll have to wait a while (and then some), but hopefully when that's all finished you'll have a modern compiler installed that will make building modern software such as Node.js much easier.

Monday, November 07, 2011

Zooming into images

I spend rather a lot of my time working with images. Scanning and digitizing is one thing we do on a fairly large scale.

To allow customers to see image detail at high resolution, we use Zoomify extensively. We generate the images in advance, using ZoomifyImage. OK, so we end up with huge numbers of files to store, but this is the 21st century and we can cope with it.

There are other options available that do similar things, of course. Just to mention a few: Deep Zoom, OpenZoom, and OpenLayers. One snag with some of these zooming capabilities is that they require browser plugins (Flash or Silverlight). Not only does this hurt users who don't have the plugin installed, but some platforms (OK, let's call out the iPad here) don't have any prospect of Flash or Silverlight.

However, modern systems do have HTML5 capable browsers, and HTML5 is really powerful.

A quick search finds CanvasZoom, which is a pretty good start. Given a set of Deep Zoom tiles it just works. I tried it on an iPad and it sort of works, not really doing touch properly. So I forked it on github (with ImageLoader for compatibility) and played with adding touch support.

It turns out the adding touch handling is pretty trivial. There's just the touchstart, touchend and touchmove events to handle. You want to call event.preventDefault() so as to stop the normal platform handling of moves in particular. The only tricky bit was working out that while you can get the coordinates for touchstart and touchmove from event.targetTouches[0], for touchend you have to look back at event.changedTouches[0]. So, poke the image and it zooms, poke and move and you can pan the image.

One thing I mean to do is to look at whether I can point it at a set of Zoomify tiles. I've already got lots of those, and just having one set of image tiles saves both processing time and storage. If not, I'll have to generate a whole load more images - I'm using deepjzoom which seems to do a pretty good job.

Friday, October 14, 2011

Optimizing mysql with DTrace

I've got a mysql server that's a bit busy, and I idly wondered why. Now, this is mysql 4, so it's a bit old and doesn't have a lot of built-in diagnostics.

(In case you're wondering, we have an awful lot of legacy client code that issues queries using a join syntax that isn't supported by later versions of mysql, so simply upgrading mysql isn't an option.)

This is running on Solaris, and a quick look with iostat indicates that the server isn't doing any physical I/O. That's good. A quick look with fsstat indicates that we're seeing quite a lot of read activity - all out of memory, as nothing goes to disk. (We're using zfs, which makes it trivially easy to split the storage up to give mysql its own file system, so we can monitor just the mysql traffic using fsstat.)

As an aside, when reading MyISAM tables the server relies on the OS to buffer table data in RAM, so you actually see the reads of tables as reads of the underlying files, which gets caught in fsstat and makes the following trivial.

But, which tables are actually being read? You might guess, by looking at the queries ("show full processlist" is your friend), but that simply tells you which tables are being accessed, not how much data is being read from each one.

Given that we're on Solaris, it's trivial to use DTrace to simply count both the read operations and the bytes read, per file. The following one-liners from the DTrace Book are all we need. First, to count reads per file:

dtrace -n 'syscall::read:entry /execname == "mysqld"/ { @[fds[arg0].fi_pathname] = count(); }'

and bytes per file:

dtrace -n 'fsinfo:::read /execname == "mysqld"/ { @[args[0]->fi_pathname] = sum(arg1); }'

With DTrace, aggregation is built in so there's no need to post-process the data.

The latter is what's interesting here. So running that quickly and looking at the last 3 lines which are the most heavily read files:

  /mysql/data/foobar/subscriptions_table.MYD         42585701
  /mysql/data/foobar/concurrent_accesses.MYD         83717726
  /mysql/data/foobar/databases_table.MYD          177066629

That last table accounts for well over a third of the total bytes read. A quick look indicates that it's a very small table (39kbytes whereas other tables are quite a bit larger).

A quick look in mysql using DESCRIBE TABLE showed that this table had no indexed columns, so the problem is that every query is doing a full table scan. I added a quick index on the most likely looking column and the bytes read drops down to almost nothing, with a little speedup and corresponding reduction of load on the server.

I've used this exact technique quite a few times now - fsstat showing huge reads, a DTrace one-liner to identify the errant table. Many times, users and developers set up a simple mysql instance, and it's reasonably quick to start with so they don't bother with thinking about an index. Later (possibly years later) data and usage grows and performance drops as a result. And often they're just doing a very simple SELECT.

It's not always that simple. The other two most heavily read tables are also interesting. One of them is quite large, gets a lot of accesses, and ends up being quite sparse. Running OPTIMIZE TABLE to compact out the gaps due to deleted rows helped a lot there. The other one is actually the one used by the funky join query that's blocking the mysql version upgrade. No index I create makes any difference, and I suspect that biting the bullet and rewriting the query (or restructuring the tables somewhat more sanely) is what's going to be necessary to make any improvements.

Saturday, October 08, 2011

JKstat 0.60, handling kstat chain updates correctly

I've just updated JKstat, now up to version 0.60.

The key change this time, and the reason for a jump in version number (the previous was 0.53) is that I've changed the way that updates to the kstat chain are handled.

Now, libkstat has a kstat_chain_update() function, which you call to synchronize your idea of what kstats exist with the current view held by the kernel. And you can look at the return value to see if anything has changed.

This only works if you're running in a single thread, of course. If you have multiple threads, then it's possible that only one will detect a change. Even worse if you have a server with multiple clients. So, the only reliable way for any consumer to detect whether the chain has been updated is to retrieve the current kstat chain ID and compare it with the one it holds.

This has largely been hidden because I've usually used the KstatSet class to track updates, and it does the right thing. It checks the kstat ID and doesn't blindly trust the return code from kstat_chain_update(). (And it handles subsets of kstats and will only notify its consumers of any relevant changes.)

So what I've finally done is eliminate the notion of calling kstat_chain_update(), which should have been done long ago. The native code still calls this internally, to make sure it's correctly synchronized with the kernel, but all consumers need to track the kstat chain ID themselves.

This change actually helps client-server operation, as it means we only need one call to see if anything has changed rather than the two that were needed before.

Friday, September 30, 2011

Limiting CPU usage in a zone

By default, a Solaris zone has access to all the resources of the host it's running on. Normally, I've found this works fine - most applications I put in zones aren't all that resource hungry.

But if you do want to place some limits on a zone, then the zone configuration offers a couple of options.

First, you can simply allocate some CPUs to the zone:

add dedicated-cpu
set ncpus=4

Or, you can cap the cpu utilization of the zone:

add capped-cpu
set ncpus=4

I normally put all the configuration commands for a zone into a file, and use zonecfg -f to build the zone; if modifying a zone then I create a fragment like the above and load that the same way.

In terms of stopping a zone monopolizing a machine, the two are fairly similar. Depending on the need, I've used both.

When using dedicated-cpu, it's not just a limit but a guarantee. Those cpus aren't available to other zones. Sometimes that's exactly what you want, but it does mean that those cpus will be idle if the zone they're allocated to doesn't use them.

Also, with dedicated-cpu, the zone thinks it's only got the specified number of cpus (just run psrinfo to see). Sometimes this is necessary for licensing, but there was one case where I needed this for something else: consolidating some really old systems running a version of the old Netscape Enterprise Server, and it would crash at startup. I worked out that this was because it collected performance statistics on all the cpus, and someone had decided that hard coding the array size at 100 (or something) would cover all future possibilities. That was, until I ran it one a T5140 with 128 cpus and it segfaulted. Just giving the zone 4 cpus allowed it to run just fine.

I use capped-cpu when I just want to stop a zone wiping out the machine. For example, I have a machine that runs application servers and a data build process. The data build process runs only rarely, but launches many parallel processes. When it had its own hardware that was fine: the machine would have occasional overload spikes but was otherwise OK. When shared with other workloads, we didn't want to change the process, but have the build zone capped at 30 or 40 cpus (on a 64-way system) so there's plety of cpu left over for other workloads.

One advantage of stopping runaways with capped-cpu is that you can limit each zone to, say, 80% of the system, and you can do that for all zones. It looks like you're overcommitting, but that's not really the case - uncapped is the same as a cap of all the cpus, so you're lower than that. This means that any one zone can't take the system out, but each zone still has most of the machine if it needs it (and the system has the available capacity).

The capability to limit memory also exists. I haven't yet had a case where that's been necessary, so have no practical experience to share.

Monday, August 08, 2011

Thoughts on ZFS dedup

Following on from some thoughts on ZFS compression, and nudged by one of the comments, what about ZFS dedup?

There's also a somewhat less opinionated article that you should definitely read.

So, my summary: unlike compression, dedup should be avoided unless you have a specific niche use.

Even for a modest storage system, say something in the 25TB range, then you should be aiming for half a terabyte of RAM (or L2ARC). Read the article above. And the point isn't just the cost of an SSD or a memory DIMM, it's the cost of a system that can take enough SSD devices or has enough memory capacity. And then think about a decent size storage system that may scale to 10 times that size. Eventually, the time may come, but my point is that while the typical system you might use today already has cpu power going spare to do compression for you, you're looking at serious engineering to get the capability to do dedup.

We can also see when turning on dedup might make sense. A typical (server) system may have 48G of memory so, scaled from the above, something in the range of 2.5TB of unique data might be a reasonable target. Frankly, that's pretty small, and you actually need to get a pretty high dedup ratio to make the savings worthwhile.

I've actually tested dedup on some data where I expected to get a reasonable benefit: backup images. The idea here is that you're saving similar data multiple times (either multiple backups of the same host, or backups of like data from lots of different hosts). I got a disappointing saving - of order 7% or so. Given the amount of memory we would have needed to put into a box to have 100TB of storage, this simply wasn't going to fly. By comparison, I see 25-50% compression on the same data, and you get that essentially for free. And that's part of the argument behind having compression on all the time, and avoiding dedup entirely.

I have another opinion here as well, which is that using dedup to identify identical data after the fact is the wrong place to do it, and indicates a failure in data management. If you know you have duplicate data (and you pretty much have to know you've got duplicate data to make the decision to enable dedup in the first place) then you ought to have management in place to avoid creating multiple copies of it: snapshots, clones, single-instance storage, or the like. Not generating duplicate data in the first place is a lot cheaper than creating all the multiple copies and then deduplicating them afterwards.

Don't get me wrong: deduplication has its place. But it's very much a niche product and certainly not something that you can just enable by default.

Sunday, August 07, 2011

Thoughts on ZFS compression

Apart from the sort of features that I now take for granted in a filesystem (data integrity, easy management, extreme scalability, unlimited snapshots), ZFS also has built in compression.

I've already noted how this can be used to compress backup catalogs. One important thing here is that it's completely transparent, which isn't true of any scheme that goes around compressing the files themselves.

Recently, I've (finally) started to enable compression more widely, as a matter of course. Certainly on new systems there's no excuse, at the default level of compression at any rate.

There was a caveat there: at the default compression level. The point here being that the default level of compression can get you decent gains and is essentially free: you gain space and reduce I/O for a negligible CPU cost. The more aggressive compression schemes can compress your data more, but having tried them it's clear that there's a significant performance hit: in some cases when I tried it the machine can freeze completely for a few seconds, which is clearly noticeable to users. Newer more powerful machines shouldn't have that problem, and there have been improvements in Solaris as well that keep the rest of the system more responsive. I still feel, though, that enabling more aggressive compression than the default is something that should only be done selectively when you've actually compared the costs and benefits.

So, I'm enabling compression on every filesystem containing regular data from now on.

The exception, still, is large image filesystems. Images in TIFF and JPEG format are already compressed so the benefit is pretty negligible. And the old thumpers we still use extensively have relatively little CPU power (both compared to more modern systems, and for the amount of data and I/O these systems do). Compression here is enabled more selectively.

Given the continuing growth in cpu power - even our entry-level systems are 24-way now - I'm expecting it won't be long before we get to the point where enabling more aggressive compression all the time is going to be a no-brainer.

Thursday, July 28, 2011

A bigger hammer than svcadm

One advantage of the service management facility (SMF) in Solaris is that you can treat services as single units: you can use svcadm to control all the processes associated with a service in one command. This makes dealing with problems a lot easier than trying to grope through ps output trying to kill the right processes.

Sometimes, though, that's not enough. If your system is under real stress (think swapping itself to death with thousands of rogue processes) then you can find that svcadm disable or svcadm restart simply don't take.

So, what to to? It's actually quite easy, once you know what you're looking for.

The first step is to get details of the service using svcs with the -v switch. For example:

# svcs -v server:rogue
online - 10:06:05 7226124svc:/network/server:rogue
(you'll notice a presentation bug here). The important thing is the number in the CTID column. This is the contract ID. You can then use pkill with the -c switch to send a signal to every process in that process contract, which defines the boundaries of the service. So:

pkill -9 -c 7226124
and they will all go. And then, of course SMF will neatly restart your service automatically for you.

(Why use -9 rather than a friendlier signal? In this case, it was because I just wanted the processes to die. Asking then nicely involves swapping them back in, which would take forever.)

Tuesday, July 26, 2011

The Oracle Hardware Management Pack

I've recently acquired some new servers - some SPARC T3-1s and some x86 based X4170M2s.

One of the interesting things about these is that the internal drives are multipathed by default - so you get device names like c0t6006016021B02C00F22A3EED6CADE011d0s2 rather than the more traditional c0t0d0s2.

This makes building a jumpstart profile a bit more tedious than normal, because you need to have a separate disk configuration section for every box - because the device names are different on each box.

However, there's another minor problem. How do you easily map from the WWN-based device names to physical positions in the chassis? You really need this so you're sure you're swapping the right drive. And while a SPARC system really doesn't mind which disk it's booting from, for an x86 system it helps if you install the OS on the first disk in the BIOS boot order.

The answer is to install the Oracle Hardware Management Pack. (Why this isn't even on the preinstalled image I can't explain.) This seems to work on most current and recent Sun server models.

Now, actually getting the Hardware Management Pack isn't entirely trivial. So prepare to do battle with the monstrosity called My Oracle Support.

So, you're logged in to My Oracle Support. Click the Patches & Updates tab. In the Patch Search area, click the link marked 'Product or Family (Advanced)'. Then scroll down the dropdown list and select the item that says 'Oracle Hardware Management Pack'. Then choose some of the most recent releases (highest version numbers - note that different hardware platforms match different version numbers of the software) and select your desired platform (essentially, SPARC or X86 or both) from the dropdown to the right of where it says 'Platform is'. Then hit the Search button.

Assuming the flash gizmo hasn't crashed out on you (again) you should get a list of patches. No, I have no idea why they're called patches when they're not. You can then click on the one you want and download it.

What you get is a zip file, so you can unzip that, cd into it and then into the SOFTWARE directory inside it, and then run the install.bin file you find there. (You may have to chmod the install.bin file to make it executable.) I just accept all the defaults and let it get on with it.

On a preinstalled system it may claim it's already installed. It probably isn't - just 'pkgrm ipmitool' first. And if you're using your own jumpstart profile, make sure the SUNWCsma cluster is installed. It may be necessary to wait a while and then 'svcadm restart sma' to get things to take the first time.

So, once it's installed, what can you do?

The first thing is that there's a Storage tab in the ILOM web interface. Go there once you've got the hardware management pack installed and you should be able to see the controllers and disks enumerated.

On the system itself, the raidconfig command is very useful. Something like

raidconfig list all
will give you a device summary, and

raidconfig list disk -c c0 -v

will give a verbose listing of the disks on controller c0. (And. just to remind you, the c0 in c0t6006016021B02C00F22A3EED6CADE011d0s2 doesn't refer to physical controller 0.)

The hardware management pack is really useful - if you're running current generation Sun T-series or X-series hardware, you ought to get it and use it.

Friday, July 08, 2011

CPU visualization

Over the years, simple tools like cpustate have allowed you to get a quick visualization of cpu utilization on Solaris. It's sufficiently simple and useful that emulating it was one of the first demos I put together using JKstat.

Its presentation starts to suffer as core and thread counts continue to rise. So recently I added vertical bars as an option. This allows a more compact representation, and also works better given that most screens are wider that they are tall.

Still, even that doesn't work very well on a 128-way machine. And, by treating all cpus equally, you can't see how the load is distributed in terms of the processor topology.

However, as of the new release of SolView there's now a 'vertical' option for the enhanced cpustate demo included there.

So, what's here? This is a 2-chip system (actually an X4170M2), each chip has 6 cores, each of which has 2 threads. The chips are stacked above each other, and within each chip is a smaller display for each core, and within each core are its threads. All grouped together to show how the threads and cores are related, and each core and chip having an aggregate display.

Above is a T5140 - 2 chips, each with 8 cores each with 8 threads.

I find it interesting to watch these for a while, and you can see how work is scheduled. What you normally see is an even spread across the cores. Normally, if there's an idle core you see a process sent there rather than running on a thread on a busy core and competing for shared resources. (Not always: you can see on the first graph that there's one idle core and another core with both threads busy, which is unusual.) The scheduler is clearly aware of the processor topology and generally distributes the work pretty well to make best use of the available cores.

Thursday, June 30, 2011

Updated Node

As a result of a new version of Node being released, I've updated my Solaris 10 (x86) package, available here.

This updates Node to 0.4.9 and the bundled cURL to 7.21.7.

Building this was exactly the same as in my earlier posts. I've updated the patch, although the observant will notice that it's the same patch with the path updated; there's no functional change in the patch.

Tuesday, June 28, 2011

Node serving zipfiles

One problem I've been looking at recently is how to serve - efficiently - directories containing large numbers of tiny files to http clients. At the moment, we just create the files, put them on a filesystem, and let apache go figure it out.

The data is grouped, though, so that each directory is an easily identifiable and self-contained chunk of data. And, if a client accesses one file, chances are that they're going to access many of the other neighbouring files as well.

We're a tiny tiny fraction of the way into the project, and we're already up to 250 million files. Anyone who's suffered with traditional backup knows that you can't realistically back this data up, and we don't even try.

What I do, though, is generate a zip file of each directory. One file instead of 1000, many orders of magnitude less in your backup catalog (thinking about this sort of data, generating a backup index or catalog can be a killer), and you can stream large files instead of doing random I/O to tiny little files. We save the zip archives, not the original files.

So then, I've been thinking, why not serve content out of the zip files directly? We cut the number of files on the filesystem dramatically, improve performance, and make it much more manageable. And the access pattern is in our favour as well - once a client hits a file, they'll probably access many more files in the same zip archive, so we could prefetch the whole archive for even more efficiency.

A quick search turned up this article. It's not exactly what I wanted to do, but it's pretty close. So I was able to put together a very simple node script using the express framework that serves content out of a zip file.

// requires express and zipfile
// npm install express
// npm install zipfile

function isDir(pathname) {
if (!pathname) {
return false;
} else {
return pathname.slice(-1) == '/';

var zipfile = require('zipfile').ZipFile;
var myzip = new zipfile('/home/peter/');

// hash of filenames and content
var ziptree = {};
for (var i = 0; i < myzip.names.length ; i++) {
if (!isDir(myzip.names[i])) {
ziptree[myzip.names[i]] = myzip.readFileSync(myzip.names[i])

var app = require('express').createServer();

app.get('/zip/*', function(req, res){
if(ziptree[req.params[0]]) {
res.send(ziptree[req.params[0]], {'Content-Type': 'text/plain'});
} else {

console.log("zip server listening on port %d", app.address().port);

So, a quick explanation:

  • I open up a zipfile and, for each entry in it that isn't a directory, shove it into a hash with the name as the key and the data as the value.

  • I use express to route any request under /zip/, the filename is everything after the /zip/, and I just grab that path from the hash and return the data.

See how easy it is to generate something pretty sophisticated using Node? And even I can look at the above and understand what it's doing.

Now, the above isn't terribly complete.

For one thing, I ought to work out the correct content type for each request. This isn't hard but adds quite a lot of lines of code.

The other thing that I want to do is to have the application handle multiple zip files. So you get express to split up the request into a zipfile name and the name of a file within the zip archive. And then keep a cache of recently used zipfiles.

Which leaves a little work for version 2.

Saturday, June 18, 2011

Node and kstat goodness

Now I've got got node.js built on Solaris (see blog entry 1 and blog entry 2) I've been playing with using it as a server.

So the next thing I did was to augment node-kstat from Bryan Cantrill's original. There's the odd minor fix, I've essentially completed the list of kstats supported (including most of the raw kstats), and added methods that give the support needed by JKstat, and there's an example jkstat.js script that can run as a server under node that the JKstat client can connect to.

A collection of my Node stuff is available here, including a Solaris 10 package for those of you unable to build it yourselves.

Of course, in order to use the node-kstat server I've had to add RESTful http client support to JKstat, which has now been updated with the 0.51 release.

JKstat also loses the JavaFX demos. It doesn't appear to me that JavaFX is going to be terribly interesting for a while. The 2.0 beta isn't available for Solaris at all (1.x wasn't available for SPARC anyway), and appears to be essentially incompatible anyway.

Friday, June 17, 2011

Cache batteries on Sun 25xx arrays

I have a number of the old Sun 2530 disk arrays, and a batch that we bought 3 years ago have started to come up with the fault LED lit.

These arrays have cache batteries, and the batteries need replacing sometimes to ensure they're operating correctly. Originally, this was a simple 3 year timer. After 3 years, a timer expires and it generates a fault to let you know it's time to put in new batteries.

Current Oracle policy is different: rather than relying on a dumb timer and replacing batteries as a precaution, the systems are actually capable of monitoring the health of the batteries (they have built in SMART technology). As a result, they will only send out new batteries if there's actual evidence of a fault.

This is actually good, as it means we don't have to take unnecessary downtime to replace the batteries. (And it eliminates the risk of the battery replacement procedure accidentally causing more problems.)

Now, the management software version we have (6.xx) doesn't report the SMART status (but will report if a real failure occurs). So you can't see predictive failure, but if CAM just says "near expiration" then it's just the precautionary timer.

So, the solution is to check and reset the timer.

Go to CAM. (The exact location of the relevant menu item may vary depending on which version of CAM you've got, so you may have to go looking.)

Expand the Storage Systems tree

Select the array you want to fix

Click on service advisor

In the new window that pops up, verify that it's actually picked up the correct array. The name should be at the top of the expanded tree in the left-hand panel.

Under Array Troubleshooting and recovery, expand the Resetting the Controller Battery Age item.

Click on each battery in turn and follow the instructions.

This also applies to the 6x80 arrays as well, as I understand it, but I don't have any of those.

If you search for "2500 battery" on My Oracle Support, you'll find all this documented.

Wednesday, June 08, 2011

Node.js on Solaris, part 2

Here's a followup and slight correction to my notes on building node.js on Solaris 10.

If you read carefully, you'll notice that I specified --without-ssl to the configure command. This makes it build, as it looks like there's a dependency on a newer openssl than is shipped with Solaris 10. While this is good enough for some purposes, it turns out the the expresss module wants ssl (it's required, even if you don't use https, although all you have to do is delete the references).

So, a better way is to build a current openssl first and then get node to link against that. So for the openssl build:

gzcat openssl-1.0.0d.tar.gz | gtar xf -
cd openssl-1.0.0d
env CC=cc CXX=CC ./Configure --prefix=/opt/Node solaris-x86-cc shared
gmake -j 8
gmake install
I'm using the Studio compilers here, as I normally do with things like openssl that provide libraries that might be used by other tools, although gcc should work fine. The important parts here are that it matches the architecture of your other components (so 32-bit, ie x86) and you build shared libraries.

Then you can unpack and patch node as before, then configure with

env LDFLAGS=-R/opt/Node/lib CFLAGS=-std=gnu99 ./configure --prefix=/opt/Node --openssl-includes=/opt/Node/include --openssl-lib=/opt/Node/lib

Sunday, June 05, 2011

Building node.js on Solaris 10

Constantly on the search for new tools and technologies to play with, I wanted to actually try out Node.js on my own machine.

I'm running Solaris 10 (x86), and it didn't quite work out first time. But it was pretty trivial to fix. A couple of tweaks to the configure invocation and a simple patch to make things like isnan and signbit work with a vanilla Solaris 10 install.

So, to build Node on Solaris 10 x86:

First download node-0.4.8 and my node patch. (Yes, the patch to V8 is ugly, and it's likely to be specific to the V8 version and the Solaris rev and gcc version. And don't expect Node or V8 to work on sparc at all.)

Unpack node and apply the patch:

gzcat node-v0.4.8.tar.gz | gtar xf -
gpatch -p0 -i node-v0.4.8.soldiff

Then configure and build:

env CFLAGS=-std=gnu99 ./configure --prefix=/opt/Node --without-ssl
gmake -j 8
gmake install

Replacing /opt/Node with wherever you want to install it. (Somewhere you have permission to write to, obviously.)

You then want to install npm. You will need to have curl for this, although I recommend downloading the and running it by hand, like so:

env PATH=/opt/Node/bin:$PATH TAR=gtar bash

This way, it uses the correct version of tar and uses a compatible shell. (It actually invokes curl in the script, so you still need curl installed. That's not hard, or you can find one on the Companion CD.)

To actually use npm you need to continue with the tweaks. For example:

env PATH=/opt/Node/bin:$PATH TAR=gtar npm install express
or, if you want it to install express into the Node tree rather than "." you'll need something like:

env PATH=/opt/Node/bin:$PATH TAR=gtar npm install -g express

Tuesday, May 31, 2011

The trouble with tabs (in Firefox 4)

I use my web browser a lot. And I mean, a lot. (It's not that I necessarily want to, but the browser seems to have killed off a lot of proper applications, and the world is a poorer place for that.)

I've actually switched to Firefox 4. (OK, on Solaris you don't actually have all that much choice.) But normally it takes me very much longer to update to a newly released version of Firefox. Why the move this time? Primarily performance - I've found that some sites (and I suspect Twitter here) can make the whole browser feel sluggish. Certainly since I switched to version 4 the annoying lags I used to have are gone.

There are a few changes in Firefox 4 that really can't be described as anything but negative. That's my opinion, of course, but I'm a heavy user and it has really irked me that for the last couple of decades we've matched advances in computing with compensating steps backward.

The first thing that didn't actually bother me initially but soon got spectacularly irritating was the new "Tabs on Top" feature. (Ahem, misfeature.) What this really means is that the tabs for a page are separated from the page they apply to by a couple of tool bars (in my case, the Bookmarks toolbar and the Navigation toolbar). This makes the user suffer thrice: the interface appears to put the toolbars into the tabs, causing confusion; separation on screen causes a mental disconnect between the page and its tab; and you have to move the mouse further to get to the tabs, making them harder to use. Fortunately you can turn this off pretty easily by right-clicking (on the home button for example) and unchecking the option.

Far worse (because it can't just be turned off) is the switch to tab feature. So you want to open a site, you start typing its address and it appears in the dropdown list. Only if you've already got it open, you don't get to open it, you get to switch to tab - so the browser just goes to the already existing tab. Now, listen people: if I wanted to go to the tab I had already had open, guess what? I would have clicked on the tab! The fact that I'm entering it again means that I absolutely want a new copy. This behaviour is especially annoying when the tab is in another window on another virtual desktop, because it then brings that up (moving the Firefox window to a different virtual desktop in the process). Fortunately there's an add-on to disable this particular misfeature.

Browsing in tabs was a spectacularly useful advance, adding extra scalability to the browsing experience. Firefox 4 attempts to make them less usable; fortunately I've been able to sidestep that (for now).

Saturday, May 28, 2011

JKstat and KAR - JSON migration

There are a couple of new updates for JKstat and KAR.

For JKstat, version 0.45 brings in JSON support, and 0.50 solidifies it.

For KAR, version 0.6.5 likewise introduces JSON support, and 0.7 makes JSON the only supported data format, superseding KAR's private data format.

The only point of 0.6.5 is that it can both read and write in both the old KAR format and the new JSON format. So I needed that in order to be able to convert old KAR archives.

I've covered some of the advantages of JSON previously. While those were just early thoughts, subsequent tests confirm the advantages of using JSON for both the client-server communication and the KAR archive format. So these releases represent both a transition and a clean break (which is why there are two new versions of each).

Now I've got JSON format data available, I'm learning javascript so as to write a browser-based client. Stay tuned.

Sunday, May 15, 2011

About time to modernize Java

It's about time to modernize Java.

I'm not talking fancy things like closures or functional programming. I'm talking some of the basic interfaces in commonly used classes.

Exhibit A are the constructors for JTree and JList. These take a Hashtable and a Vector. How long have we had Collections built into Java? So why don't JTree and JList use Map and List?

Exhibit B are classes that still return Enumeration. For example, to get the contents of a ZipFile you get an Enumeration and have to work your way through it by hand. Now Java has the enhanced for-loop, there ought to be methods for returning a Collection directly.

I could go on, but I think you get the point - many of Java's own classes simply haven't been modernized to bring them in line with improvements elsewhere. And I get really irritated having to continue to write crufty old-fashioned code to deal with those deficiencies.

Saturday, May 14, 2011

JSON meets JKstat and KAR

I've been looking at JSON for a long time, wondering whether and how to best make use of it. After considerable experimentation, I'm convinced, and it's going to be an integral part of both JKstat and KAR.

So, the first thing I was looking at was the client-server code in JKstat. One of the things that's always irritated me about XML-RPC is it's obvious lack of a long data type. It doesn't seem to be bothered that the world is more than 32-bits. Sure, there are various vendor extensions (and I have to turn them on in the Apache XML-RPC implementation that I use) but the result is something that's horribly non-portable.

The other thing I've been looking at is the archive format used in KAR. I started out with simple kstat -p but that proved inadequate in that important data (metadata) was missing, so I developed a private format. This was better, but was a horrid hack.

So, enter JSON. It turns out that it makes an excellent serialization format for kstats.
  • Reusing a standard means there's less work for me to do.
  • I can use the same code for KAR and the JKstat client-server mode.
  • There are JSON bindings in almost all languages, so interoperability is easy to achieve.
  • The format is a string, so no messing about with extensions to pass longs.
  • For KAR, it's almost twice as quick to parse as my own hacked format.

As a result, the next versions of JKstat and KAR will support JSON as their archive and interchange format.

As an aside, this opens the door to wicked cool stuff.

Tuesday, May 03, 2011

SolView 0.56

Hot on the heels of an updated JKstat comes a new release of SolView.

Like with JKstat, there's a lot of tidying up and quite a bit of extra polish. Little things, like changing some of the label text to make it more meaningful, or telling you if a disk or partition is part of a ZFS pool.

There's one fairly visible change, to the start of the explorer view, which now looks very different:

This is getting closer to what I envisioned early on for this view, a much more graphically rich presentation. It's not finished, and what's shown (and how) will certainly change, but it shows the direction I would like to head in.

Monday, May 02, 2011

JKstat 0.44

It's been one day off work after another here in the UK recently. In between going to a beer festival and Newmarket races, I've found a little time to work on JKstat.

The result is a new version of JKstat available for download.

There's nothing earth shattering here, but a process of steady improvement. I've gone through the demos, removing some of the cruftier ones, enhancing some of the others, and moving some of those from SolView back to JKstat. So, the original iostat demo has gone, leaving just the table-based version; the load subcommand has been replaced by an uptime subcommand. The cpustate demo has been merged with the cpuchart demo, and has also had a vertical mode added.

OK, so it's not that impressive on my little desktop machine, but it works much better than the old layout as a display arrangement on something like a T5140 that has 128 cpus in it.

There's additional polish elsewhere. Apart from fewer typos, I've filtered out kstats from the chartbuilder that you'll never want to chart, so there are fewer kstats to munge through. The charts work a little better too: they now display the statistics in the requested order, and you can set the colors.

Another thing I've been playing with is an 'interesting' subcommand that tries to identify kstats with interesting behaviour - as in doing something out of the ordinary. This worked out a whole lot worse than I hoped. The problem, of course, is defining what constitutes normal (let alone anomalous) behaviour. The behaviour of any kstat certainly isn't normally distributed, and in fact many are very spiky as a matter of course. I may revisit this with KAR, which has historical data from which I can construct a baseline of the expected range of behaviour.

Something else I've been looking at is sparklines. I added a simple line graph to JStripChart to support this. At the moment they're not really sparklines, just little graphs, but it's a start, and expect to see more of that in SolView.

There's also a stunningly boneheaded bug fixed in KstatFilter. Filtering out things you don't want was matching far too much (it would match any of a module:instance:name specifier rather than the correct behaviour of matching all of them, so unix:0:kstat_types would throw away all unix kstats and all of instance 0, which wasn't what you wanted).

Friday, April 29, 2011

Nudging the Narwhal

As is customary with any Ubuntu release, I downloaded the recently released 11.04 and took it for a spin.

The installation started off well. I liked the fact that it got started on the install and then asked you the configuration questions, minimizing the overall install time. And it looked like the install was galloping along. Then it bogged down, and got slower and slower. Made a coffee. Drank the coffee. Install going nowhere fast. Checked the Royal wedding pictures, played a few ZX spectrum games. Install going nowhere fast. Updated a slew of other applications on my Solaris box. Install going nowhere fast. Finally, after over an hour, it finishes the install. That was gruesome.

After installing the guest additions for VirtualBox I got the new Unity interface. And it's not all that bad. It's not that good either, but I didn't get the horribly negative reaction to it that many have reported. In a lot of usage scenarios, I can see it working just fine.

So, what does Unity get you? Well, it works pretty well for simple task-based computing. If you just have a handful of applications that you use, and you only use one at a time, then it works great. It allows you to focus on the task at hand. It starts to struggle if you're multitasking or if you need to do a lot of different things because once you're outside the simple task metaphor it really struggles.

Is Unity radical? Not really. I've used dozens of desktop interfaces. So this one has panels on the left and top rather than placed elsewhere, but that's no big deal. The window controls have moved, but that's trivial. Seriously, there's nothing much new here.

The problems I have with Unity are really that it doesn't fit my normal working style (which tends to involve having huge numbers of applications open, often many windows of the same application). The launcher on the left only really scales up to a dozen applications or so; beyond that it becomes cumbersome. It folds up whatever's at the bottom of the list in the normal view, but expands things out (forcing the launcher to scroll) if you use the folded-up applications. And you can't clean things up by moving your applications across multiple virtual desktops - you get to see all the launcher items all the time, rather than just the ones relevant to the desktop you're on.

Dealing with multiple instances of the same application works really badly. There's no good way to organise 100 xterms, for instance. Double-click on the xterm launcher icon and they're sitting there in a 10x10 grid. But which one's which? Again, sorting them by virtual desktop doesn't really help. And right-click on the launcher icon gets you a menu, including quit - which quits all of them.

Another major change is the move of the application toolbar to the top of the screen. I hate this for two reasons: for one, it means you have to mouse all the way across the screen, and for two, it interacts really badly with a mouse focus policy of focus-follows-mouse. Fortunately, I tend not to use application menus very much.

None of the criticisms are necessarily aimed directly at Unity, of course. It's more that it has changed to a new usage paradigm, but all the rest of the desktop and all the applications haven't, and the mismatch shows pretty clearly. What would be really interesting to see would be what Unity would be like with applications designed around it, rather than with all the (legacy, for it) applications we have today.

Thursday, February 24, 2011

JProc 0.6

A little more tinkering, and an updated version of JProc is now available.

The primary addition in this release is that I've implemented access to the prusage struct, both for processes and threads. There's a new usage subcommand that shows prusage data in a table for processes. And, if you right-click in the info or usage display, you can display a breakdown of usage by thread.

Sunday, February 06, 2011

Pushing kar along

I updated KAR recently.

This follows my recent philosophy that code and bugs are the same thing, although I hope that each version squishes some bugs as well as introducing them.

Most of the bugs fixed this time were as a direct result of trying to use kar for real, generating graphs of system activity to answer question for users, developers, and management. In some cases, kar just gave up or gave the wrong data.

(A particularly insidious bug lies in the use of printf in C. You have to specify exactly the type and size of a variable. If the type you print and the actual storage type don't match, bad things can happen. Worse, different processor architectures behave in different ways. Printing a 64-bit value as 32-bit appears to work on an Opteron box, but fails miserably on a SPARC.)

One thing I'm actually doing is using kar's print subcommand to output the data, and then munging the data before feeding it into something like ploticus to do the actual plotting. The inbuilt chart support works well for predefined charts, but I often want something slightly different.

Monday, January 24, 2011

Code = bugs

I've come to the conclusion that all code is buggy, often hideously so.

This isn't necessarily an observation on other people's code. My code is perfect. Ha! Only it's not, of course.

Something like JKstat is reasonably mature and (I thought) reasonably well tested. But the latest release fixes a number of pretty basic numbskull bugs that had been sitting there for ages.

I place a lot of emphasis on code quality. I use jstyle (part of the Solaris ON build environment) to enforce a programming style. Enforcing consistency makes the code more readable, and this style is one that my eyes (and my typing fingers) are comfortable with. I use PMD to automatically check for basic errors and obvious code deficiencies. When I first started using PMD, it found lots of basic errors. What it doesn't catch are the doofus logic errors that my brain introduces.

For Java programming, I found Generics to be a great benefit. Java is a strongly typed language, but a major structural part of the language - the Collections framework - didn't impose any type safety at all. Everything was just an untyped Object. Whilst Generics adds type-safety, and the enhanced for-loop often precisely expresses your intentions (as opposed to looping over an array index), I found that adding Generics made be think about the types of object I was putting in my collections, which was one step in thinking more about the structure of the code itself.

Occasionally, I get to look at code written by others. Now, often, open source code isn't actually too bad - there's often a fixed style adopted by a community, and multiple authors can eliminate some of the more bizarre excursions into code obfuscation. But some of the code I get to see in the office truly horrifies me. Invariably without useful comments, with all the old code still in the source file but inactive, and as many different styles as we've had people work on the code (often in a language they're not entirely fluent in), just hacked in to the point where it would work with no attempt (because there's no money in this) to go back and improve maintainability of the code for the next person.

One of the problems is the languages themselves. Java is strongly typed (I like this, because it makes simple typing errors into compile failures which are obvious), but requires massive levels of boilerplate. I dislike the use of an IDE, because I want to feel comfortable with every line of code I write. So you're wedged in to a place where just feeding the IDE, or writing boilerplate code, takes far too many brain cycles away from actually implementing real functionality.

So change languages, you say! Well, I actually try and learn one new language (or a major area of a language) each year. So I wrote a monitoring application in tcl/tk once, then rewrote it as a webapp using JSP, then rewrote it to do graphics using Java2D, and then rewrote it in PHP, just so I could learn those languages. After several attempts, though, I have completely failed to acquire any significant competence in Python.

Something I have been looking at recently (after an excellent talk at the local Cambridge Java Meetup group) is Clojure. You may find this a bit of an odd choice, but hacking on lisp for emacs many years ago makes it moderately familiar, and being built on the JVM means that I may be able to leverage other skills.

Which leads to a question: what programming language (or skill) have you learnt this year?

New year, new JKstat

I've been quietly working on JKstat, and have just released another update, version 0.43.

I wasn't actually aiming to cut a release at this point, there are still a couple of things I'm working on. But I needed to get some fixes into KAR, and didn't want to push out a KAR release with an unreleased version of JKstat in it, hence a synchronization release.

Realistically, JKstat has largely stabilized. So it's more a case of fixing odd bugs (the network load demo wouldn't display anything if you resized it, and guessed the network speed wrong), adding features like stepping backwards in the browser when reading KAR data, and cleaning up the javadoc. Little features like keeping all the statistics underneath a chart, so that when you add another statistic to be graphed it shows the historical data rather than starting from the current time. Nothing earth-shattering, but (hopefully) making JKstat better.