Parsoid/Round-trip testing

The Parsoid code includes a round-trip testing system that tests code changes, composed of a server that gives out tasks and presents results and clients that do the testing and report back to the server. The code is in the testreduce repo which is an automatic mirror of the repo in gerrit. The roundtrip testing code on scandium has been fully puppetized.

There's a private instance of the server on scandium that currently tests a representative (~160000) set of pages from different wikipedia languages. You can access by setting up a ssh tunnel to scandium as follows:  will let you access the web service at http://localhost:8003 locally on your computer.

Private setup
The instructions to set up a private instance of the round-trip test server can be found here. A MySQL database is needed to keep the set of pages and the testing results.

RT-testing setup
Coordinator runs on scandium. RT-testing clients run on scandium and commit suicide when the revision of that checkout changes. You need access to bastion on wikimedia.org to access scandium.

The clients are managed/restarted by systemd and the config is in. Please do not modify the config on scandium directly (they will be overwritten by puppet runs every 30 minutes). Any necessary changes should be made in puppet and deployed.

To {stop,restart,start} all clients on a VM (not normally needed):

Client logs are in systemd journals and can be accessed as: In the current setup, the testreduce clients talk to a global parsoid service that runs on scandium. So, look at the logs of the parsoid service to find problems / bugs with the parsoid code being tested. These logs are also mirrored to Kibana which you can find on this dashboard.

Updating the code to test (and being run by the clients)
To update rt-testing code, run the following on scandium:

This updates the parsoid checkout, restarts the parsoid service, and the parsoid-rt-client service.

In order to kick off a new round of testing, first go to  and verify the current checked-out commit is the one you want to test. Then edit  and add a new line to the top of the file with a new entry. To ensure the test run starts right away (vs after the clients notice the change), you can. Then watch the logs for parsoid-rt service (see the intro in this section with info about logs).

BE CAREFUL: the entry you add to  is an identifer *only*. The code which is going to run for the test run is whatever is currently checked out in. Don't add a line to  without first verifying that   is currently sitting at that commit!

Updating the round-trip server code
The rt-server code lives in  and runs off the ruthenium branch.

After review/merge on master, checkout the ruthenium branch locally. Merge master into scandium. If you need to update node_modules/ do that as well, and commit it, then push the branch to gerrit (you should have push rights).

Running the regression script
After an rt run, we compare diffs with previous runs to determine if we've introduced some new semantic differences. However, since the runs happen on different dates and the production data is used, there's going to be some natural churn to account for. The regression script automates the process of rerunning the rt script on a handful of pages to determine if there are any true positives Note that the script will checkout the specified commits while running but that it doesn't do anything for dependencies. So, at present, it isn't appropriate when bumping dependency versions in between commits.

Crashers prevent the script from running and may need to be pruned. They can then be tested individually as follows. It's also a good idea to check on the parsoid-tests dashboard for notices and errors.

Running Parsoid tools on scandium
Parsoid will run in integrated mode on scandium from  but it requires use of the   wrapper in order to configure   properly. More information on  is at Extension:MediaWikiFarm/Scripts. A sample command would look like: Parts of that command are often abbreviated as an helper alias  in your shell to make invocations easier.

Todo / Roadmap
Please look at the general Parsoid roadmap.

Server UI and other usability improvements
We recently changed the server to use a templating system to separate the code from the presentation. Now other improvements could be done on the presentation itself.

Ideas for improvement:

 * Improve pairwise regressions/fixes interface on commits list . Done!
 * Flag certain types of regressions that we currently search for by eye: create views with
 * Regressions introducing exactly one semantic/syntactic diff into a perfect page, and
 * Other introductions of semantic diffs to pages that previously had only syntactic diffs.
 * Improve diffing in results views:
 * Investigate other diffing libraries for speed,
 * Apply word based diffs on diffed lines,
 * Diff results pages between revisions to detect new semantic/syntactic errors,
 * Currently new diff content appears before old, which is confusing; change this.