Subunit is seven and a half years old now Conrad Parker and I first sketched it up at a CodeCon camping and coding, a brilliant combination in mid 2005.
revno: 1
committer: Robert Collins <robertc@robertcollins.net>
timestamp: Sat 2005-08-27 15:01:20 +1000
message: design up a protocol with kfish
It has proved remarkably resilient as a protocol the basic nature hasn t changed at all, even though we ve added tags, timestamps, support for attachments of arbitrary size.
However a growing number of irritations have been building up with it. I think it is time to design another iteration of the protocol, one that will retain the positive qualities of the current protocol, while helping it become suitable for the next 7 years. Ideally we can keep compatibility and make it possible for a single stream to be represented in any format.
Existing design
The existing design is a mostly human readable line orientated protocol that can be sniffed out from the regular output of make or other build systems. Binary attachments are done using HTTP chunking, and the parser has to maintain state about the current test, tags, timing data and test progression [a simple stack of progress counters]. How to arrange subunit output is undefined, how to select tests to run is undefined.
This makes writing a parser quite easy, and the tagging and timestamp facility allow multiplexing streams from two or more concurrent test runs into one with good fidelity but also requires that state be buffered until the end of a test, as two tests cannot be executing at once.
Dealing with debuggers
The initial protocol was intended to support dropping into a debugger just pass each line read through to stdout, and connect stdin to the test process, and voila, you have a working debugger connection. This works, but the current line based parsers make using it tedious the line buffered nature of it makes feedback on what has been typed fiddly, and stdout tends to be buffered, leading to an inability to see print statements and the like. All in-principle fixable, right ?
When running two or more test processes, which test process should stdin be connected to? What if two or more drop into a debugger at once? What is being typed to which process is more luck than anything else.
We ve added some idioms in
testrepository that control test execution by a similar but different format one test per line to list tests, and have runners permit listing and selecting by a list. This works well, but the inconsistency with subunit itself is a little annoying you need two parsers, and two output formats.
Good points
The current protocol is extremely easy to implement for emitters, and the arbitrary attachments and tagging features have worked extremely well. There is a comprehensive Python parser which maps everything into Python unittest API calls (an extended version of the standard, with good backwards compatibility).
Pain points
The debugging support was a total failure, and the way the parser depraminates it s toys when a test process corrupts an outcome line is extremely frustrating. (other tests execute but the parser sees them as non-subunit chatter and passes the lines on through stdout).
Dealing with concurrency
The original design didn t cater for concurrency. There are three concurrency issues the corruption issue (see below for more detail) and multiplexing. Consider two levels of nested concurrency: A supervisor process such as testrepository starts 2 (or more but 2 is sufficient to reason about the issue) subsidiary worker processes (I1 and I2), each of which starts 2 subsidiary processes of their own (W1, W2, W3, W4). Each of the 4 leaf processes is outputting subunit which gets multiplexed in the 2 intermediary processes, and then again in the supervisor. Why would there be two layers? A concrete example is using testrepository to coordinate test runs on multiple machines at once, with each machine running a local testrepository to broker tests amongst the local CPUs. This could be done with 4 separate ssh sessions and no intermediaries, but that only removes a fraction of the issues. What issues?
Well, consider some stdout chatter that W1 outputs. That will get passed to I1 and from there to the supervisor and captured. But there is nothing marking the chatter as belonging to W1: there is no way to tell where it came from. If W1 happened to fail, and there was a diagnostic message printed, we ve lost information. Or at best muddled it all up.
Secondly, buffering imagine that a test on W1 hangs. I1 will know that W1 is running a test, but has no way to tell the supervisor (and thus the user) that this is the case, without writing to stdout [and causing a *lot* of noise if that happens a lot]. We could have I1 write to stdout only if W1 s test is taking more than 5 seconds or something but this is a workaround for a limitation of the protocol. Adding to the confusion, the clock on W1 and W3 may be very skewed, so timestamps for everything have to be carefully synchronised by the multiplexer.
Thirdly, scheduling if W1/W2 are on a faster machine than W3/W4 then a partition of equal-timed tests onto each machine will lead one idle before the other finishes. It would be nice to be able to pass tests to run to the faster machine when it goes idle, rather than having to start a new runner each time.
Lastly, what to do when W1 and W2 both wait for user input on stdin (e.g. passphrases, debugger input, $other). Naively connecting stdin to all processes doesn t work well. A GUI supervisor could connect a separate fd to each of I1 and I2, but that doesn t help when it is W1 and W2 reading from stdin.
So additional requirement over baseline subunit:
- make it possible for stdout and stderr output to be captured from W1 and routed through I1 to the supervisor without losing its origin. It might be chatter from a noisy test, or it might be build output. Either way, the user probably will benefit if we can capture it and show it to them later when they review the test run. The supervisor should probably show it immediately as well the protocol doesn t need to care about that, just make it possible.
- make it possible to pass information about tests that have not completed through one subunit stream while they are still incomplete.
- make it possible (but optional) to pass tests to run to a running process that accepts subunit.
- make it possible to route stdin to a specific currently process like W1. This and point 3 suggest that we need a bidirectional protocol rather than the solely unidirectional protocol we have today. I don t know of a reliable portable way to tell when some process is seeking such input, so that will be up to the user I think. (e.g. printing (pdb) to stdout might be a sufficiently good indicator.)
Dealing with corruption
Consider the following subunit fragment:
test: foo
starting serversuccess:foo
This is a classic example of corruption: the test foo started a server and helpfully wrote to stdout explaining that it did that, but missed the newline. As a result the success message for the test wasn t printed on a line of its own, and the subunit parser will believe that foo never completed. Every subsequent test is then ignored. This is usually easy to identify and fix, but its a head-scratcher when it happens. Another way it can happen is when a build tool like make runs tests in parallel, and they output subunit onto the same stdout file handle. A third way is when a build tool like make runs two separate test scripts serially, and the first one starts a test but errors hard and doesn t finish it. That looks like:
test: foo
test: bar
success: bar
One way that this sort of corruption can be mitigated is to put subunit on it s own file descriptor, but this has several caveats: it is harder to tunnel through things like ssh and it doesn t solve the failing test script case.
I think it is unreasonable to require a protocol where arbitrary interleaving of bytes between different test runner streams will work so the make -j2 case can be ignored at the wire level though we should create a simple way to safely mux the output from such tests when the execute.
The root of the issue is that a dropped update leaves bad state in the parser and it never recovers. So some way to recover, or less state to carry in the parser, would neatly solve things. I favour reducing parser state as that should shift stateful complexity onto end nodes / complex processors, rather than being carried by every node in the transmission path.
Dependencies
Various suggestions have been made JSON, Protobufs, etc
A key design goal of the first subunit was a low barrier to entry. We keep that by being backward compatible, but being easy to work with for the new revision is also a worthy goal.
High level proposal
A packetised length prefixed binary protocol, with each packet containing a small signature, length, routing code, a binary timestamp in UTC, a set of UTF8 tags (active only, no negative tags), a content tag one of (estimate + number, stdin, stdout, stderr, test- + test id), test status (one of exists/inprogress/xfail/xsuccess/success/fail/skip), an attachment name, mime type, a last-block marker and a block of bytes.
The content tags:
- estimate the stream is reporting how many tests are expected to run. It affects everything with the same routing code only, and replaces (doesn t adjust) any current estimate for that routing code. A estimate packet of 0 can be used to say that a routing target has shutdown and cannot run more tests. Routing codes can be used by a subunit aware runner to separate out separate threads in a single process, or even just separate TestSuite objects within a single test run (though doing so means that they will need to process subunit and strip packets on stdin. This supercedes the stack of progress indicators that current subunit has. estimates cannot have test status or attachments.
- stdin/stdout/stderr: a packet of data for one of these streams. The routing code identifies the test process that the data came from/should go to in the tree of test workers. These packets cannot have test status but should have a non-empty attachment block.
- test- + testid: a packet of data for a single test. test status may be included, as may attachment name, mime type, last-block and binary data.
Test status values are pretty ordinary. Exists is used to indicate a test that can be run when listing tests, and inprogress is used to report a test that has started but not necessarily completed.
Attachment names must be unique per routing code + testid.
So how does this line up?
Interleaving and recovery
We could dispense with interleaving and say the streams are wholly binary, or we can say that packets can start either after a \n or directly after another packet. If we say that binary-only is the approach to take, it would be possible to write a filter that would apply the newline heuristic (or even look for packet headers at every byte offset. I think mandating adjacent to a packet or after \n is a small concession to make and will avoid tools like testrepository forcing users to always configure a heuristic filter. Non-subunit content can be wrapped in subunit for forwarding (the I1 in W1->I1->Supervisor chain would do the wrapping). This won t eliminate corruption but it will localise it and permit the stream to recover: the test that was corrupted will show up as incomplete, or with incomplete attachment data.
listing
Test listing would emit many small non-timestamped packets. It may be useful to have a wrapper packet for bulk amounts of fine grained data like listing is, or for multiplexers with many input streams that will often have multiple data packets available to write at once.
Selecting tests to run
Same as for listing while passing regexes down to the test runner to select groups of tests is a valid use case, thats not something subunit needs to worry about : if the selection is not the result of the supervisor selecting by test id, then it is known at the start of the test run and can just be a command line parameter to the backend : subunit is relevant for passing instructions to a runner mid-execution. Because the supervisor cannot just hand out some tests and wait for the thing it ran to report that it can accept incremental tests on stdin, supervisor processes will need to be informed about that out of band.
Debugging
Debugging is straight forward . The parser can read the first 4 or so bytes of a packet one at a time to determine if it is a packet or a line of stdout/stderr, and then either read to end of line, or the binary length of the packet. So, we combine a few things; non-subunit output should be wrapped and presented to the user. Subunit that is being multiplexed and forwarded should prepend a routing code to the packet (e.g. I1 would append 1 or 2 to select which of W1/W2 the content came from, and then forward the packet. S would append 1 or 2 to indicate I1/I2 the routing code is a path through the tree of forwarding processes). The UI the user is using needs to supply some means to switch where stdin is attached. And stdin input should be routed via stdin packets. When there is no routing code left, the packet should be entirely unwrapped and presented as raw bytes to the process in question.
Multiplexing
Very straight forward unwrap the outer layer of the packet, add or adjust the routing code, serialise a header + adjusted length + rest of packet as-is. No buffering is needed, so the supervisor can show in-progress tests (and how long they have been running for).
Parsing / representation in Python or other languages
The parser should be very simple to write. Once parsed, this will be fundamentally different to the existing Python TestCase->TestResult API that is in used today. However it should be easy to write two adapters: old-style <-> this new-style. old-style -> new-style is useful for running existing tests suites and generating subunit, because thats way the subunit generation is transparent. new-style->old-style is useful for using existing test reporting facilities (such as junitxml or html TestResult objects) with subunit streams.
Importantly though, a new TestResult style that supports the features of this protocol would enable some useful features for regular Python test suites:
- Concurrent tests (e.g. in multiprocessing) wouldn t need multiplexers and special adapters a regular single testresult with a simple mutex around it would be able to handle concurrent execution of tests, and show hung tests etc.
- The routing of input to a particular debugger instance also applies to a simple python process running tests via multiprocessing, so the routing feature would help there.
- The listing facility and incrementally running tests would be useful too I think we could go to running tests concurrently with test collection happening, but this would apply to other parts of unittest than just the TestResult
The API might be something like:
class StreamingResult(object):
def startTestRun(self):
pass
def stopTestRun(self):
pass
def estimate(self, count, route_code=None):
pass
def stdin(self, bytes, route_code=None):
pass
def stdout(self, bytes, route_code=None):
pass
def test(self, test_id, status, attachment_name=None, attachment_mime=None, attachment_eof=None, attachment_bytes=None):
pass
This would support just-in-time debugging by wiring up pdb to the stdin/stdout handlers of the result object, rather than actual stdin/stdout of the process a simple matter once written. Alternatively, the test runner could replace sys.stdin/stdout etc with thunk file-like objects, which might be a good idea anyway to capture spurious output happening during a test run. That would permit pdb to Just Work (even if the test process is internally running concurrent tests.. until it has two pdb objects running concurrently
Generation new streams
Should be very easy in anything except shell. For shell, we can have a command line tool that when invoked outputs a subunit stream for one instruction. E.g. test foo completed + some attachments or test foo starting .
So, the price of heating my apartment has gone up significantly since last year and a lot of people have noticed the same trend. As a geek, I want not just any solutions, but geekiest solutions possible to that enter a Smart Home system. The heating in my apartment is separated from all other apartments with a separate heat meter that measures both heating water flow and the temperature difference on the incoming and outgoing pipes, so if I reduce the heating consumption I will immediately see that in lower heating bills. This particular smart home system is very simple and made in Latvia and also relatively cheap, so I decided to give this a try.
The start was very simple I filled out a form on their home page and got a call the next day to verify the specifics. They already knew my building and had experience installing there, so they offered me two options: I could have two thermal sensors and a radiator controller on each of the 3 radiators in my apartment or (seeing how my apartment is relatively small and well ventilated thus reducing the efficiency of per-room control) one thermal sensor and one radiator controller installed on a new valve that they would build into the heating pipe just outside my apartment. I chose the second option as that was cheaper, simpler and involved less installation for me. Also they offered a nice discount.
A plumber of my building installed the valve at some point during the day, I did not even have to be there or arrange anything special, it was all included in the main bill. Then the next day a friendly guy came by to my office and gave me three very cute boxes. The packaging was very, very Apple-like. The three devices were named mother , spy and puller basically that is a base station, a temperature sensor and a radiator regulator a wireless stepper motor.
The installation was straight forward I connected the base station (something very similar to this thin in size and looks) to Ethernet and power, went to the web address specified on the sticker on the base station, completed a registration process there, entered a code from the base of the base station into the website and it just found it. After that I pressed a button on the temperature sensor (a Zippo lighter sized box with a built-in Li-Ion battery rechargeable via microUSB once a year or so) and put that on a shelf. I secured it with some double-sided tape after the cat got to it once and played some hockey while I was away. The temperature sensor immediately showed up in the Web UI and I could assign it to a room.
The regulator installation was the most complex bit, but it was trivial as well all I had to do was insert some AA batteries (helpfully included in the box, should last a couple years by their estimates), then go outside to the newly installed inlet valve, put this thing on, screw the thread with my hands and then push and hold a button for 10 seconds. After that the controller came to life, connected with the base station and started spinning the valve, testing its operational range I presume. The range is very good you can see 13% signal in the screenshots that is across the whole of the apartment, trough 3 solid walls and another 5 meters out in the hallway inside another wall.
As soon as that was done, the Web UI showed the controller and asked my to assign it to a room. So now I have 1 room defined with 1 temperature sensor and one controller. That is all that is needed.
From the charts I have already found out that at current inside/outside temperatures my apartment cools down at around 0.3 degrees C per hour and with current radiator settings it heats up by around 1 degree C per hour. I should turn the radiators up a bit thus increasing the rate at which the system is able to heat things up. Also I should try to re-inspect all possible cold spots to see why the cooldown speed is so high. I expected it to be lower. At least now I have real data to compare things.
At this point you can either fire up your web browser or a Android/iOS client on you mobile device to monitor and control the temperature of the apartment. But that was not enough for me I opted for the PRO upgrade which includes the ability to program a weekly cycle of desired temperatures. The programming is limited and thus simple to do there are three temperature modes: day, night and eco. The idea is that you have the night mode every night, then at some time during the day, you have the day mode (to wake up), then you switch to eco mode (when noone is home) and then in the evening you go back to day mode and later to night mode. There are separate sliders for each day of the week and temperature settings for each of the modes for every programmed room.
Total investment so far 210 Ls (or around 3 months worth of just heating bills). The experience of other users tells of 30-50% heating bill reduction, so this should pay for itself in 2-3 years. In addition I get a more stable and predictable temperature at home and some more geeky stuff to brag about yay!
These guys have their work cut out for them I have no idea how/of they do international orders, I would definately like to see more information in the web site about how my system is working (more temperature history, valve state history, wireless signal and battery history, mobile apps are a bit wonky it feels like the mobile app does not respect the temperature set over the web and tries to reassert itself when opened and it often shows out-of-date temperature data with no indication that it is out-of-date + the mobile apps are missing charts.
All in all this is a great start: easy, quite cheap and stylish home heating automation. Good work!
P.S. I am pretty sure they use Linux, but it is so packaged, that there is basically no way to confirm or deny that.
P.P.S. Also check out this overnight chart, there is definitely some mode switch anticipation going on 
I will be speaking at the 
This will need more work since some of the sliders look a bit a awkward
now so any enhancements will be greatly appreciated. The docs for GTK3's
CSS are 
I am in some way flattered (en_FR?) that some people think that I should stand
as DPL candidate (
Soile, my beloved, is running a second Kickstarter campaign to
fund her first feature-length movie, Maria Eveliina.
This time, she and her producer are seeking funding to pay an
editor to do the final, professional cut of the movie. They've
found a professional editor who'd like to work on the project,
but need some payment.
The 
For some reason that is not very important, I was looking for a better
solution for GPSes with maps.
Side-note: if you ask why Android is not good enough , here's the
story: last year, knowing that Google Maps supports caching (finally),
I upgraded Maps, preloaded London, and went on a trip. Only to exit
the Victoria underground station and to stare ~20 minutes in light
rain at my phone, wondering why it doesn't get a fix. I gave up in the
end, and used the cached maps for getting around. Later I learned the
reason: Maps was not broken, but without data, Android can't get a
lock easily; and more-over, the recent Maps update without GPS active
even once afterwards, to do whatever it needed, meant I couldn't get a
lock until back in Switzerland.
Or, alternatively: while on a trip to Japan, it turns out that Google
Maps caching is not supported there, probably because of rights over
mapping data. So I had location, but only temporary cached maps (from
the wifi in the hotels).
Due to this kind of problems makes I consider Android maps a toy, so I
wanted a GPS device with proper maps (on the device, not in the
cloud), and with good GPS capabilities (no fancy A-GPS or anything,
just plain good standalone GPS).
Having had good experiences with the sport line of Garmin (but which
doesn't have maps, so it's out of the question), I looked at
Garmin. Many people complained about some things (same all over the
place):
Garmin's tag line: Big and Tough Goes anywhere, everywhere . I tend
to agree 
* Inspired by 
As you have probably already noticed, Google Summer of Code 2013 has been officially announced. As usual, we want to participate with 
I wrote that I would 
Recently, I've worked on the cloud utilities that are provided as standard
in Ubuntu, and I ported them to Debian. Let's see how that brings Debian to
the cloud!
Basics of a cloud image
When starting an instance on a IaaS platform, your instance image is raw,
un-configured. Therefore, you need to have a way to configure it
automagically at boot time, based on what you want to do with it. Usually,
IaaS platforms provides for this a metadata server, like
Hey y all,
As some may have seen, I ve taken a shine to a project called 
What is this?
One of the thing CDBS provides is support for verifying / generating
debian/copyright file. This feature will be help full if new files
show up in newer releases. It can also be helpful to generate the
first version of copyright file. But don't blindly follow this
feature, you need to cross verify the things it generates.
To use this feature add the following line to your debian/rules file
first