Wikitech

Parsoid

Parsoid is a service that converts between wikitext and HTML. The HTML contains additional metadata that allows it to be converted back ("round-tripped") to wikitext. Parsoid operates as a stateless HTTP server running on port 8000.

Uses

  • VisualEditor fetches the HTML for a given page from Parsoid, edits it, then delivers the modified HTML to Parsoid, which converts it back to wikitext.
  • Flow (as configured on WMF wikis with $wgFlowContentFormat = 'html') works the other way around. When a user creates a post Flow uses Parsoid to convert the wikitext to HTML and Flow stores the HTML in ExternalStore. If someone later edits a post Flow uses Parsoid to convert the HTML back to wikitext for editing.

Monitoring

Machine overview

These are the machines involved in a Parsoid deploy:

  • In the beta/wmflabs cluster:
    • deployment-deploy01.deployment-prep.eqiad.wmflabs: staging host in beta; no longer used.
    • deployment-parsoid12.deployment-prep.eqiad.wmflabs: parsoid server in beta
    • deployment-restbase02.deployment-prep.eqiad.wmflabs: restbase server in beta
  • In the production cluster:
    • deployment.eqiad.wmnet: staging host in production; no longer used
    • parse1xxx: parsoid servers in eqiad cluster
    • restbase1xxx: restbase servers in eqiad cluster
    • parse2xxx: parsoid servers in codfw cluster
    • restbase2xxx: restbase servers in codfw cluster
    • scandium.eqiad.wmnet: Parsoid testing host, has read-only access to the production database.

Deploying changes

Parsoid is deployed as part of the MediaWiki train. See How to deploy code for an overview, Heterogeneous deployment for a more technical description of the directory structures involved, and Heterogeneous deployment/Train deploys for the steps to do a train deploy. When code changes outside the train schedule are required, a Backport windows will be required. Generally Parsing team members won't be doing train deploys or Backport deploys directly; we will tag a Parsoid version (which releases it to packagist to make it available via composer) and merge a version bump into the mediawiki/vendor repository. Once the patch is merged into vendor, the new version of Parsoid goes live in beta (almost) immediately; it will then be rolled out to production on the next train.

Deploying Parsoid

Communicate changes

If there are changes to generated HTML or accepted wikitext, please see the communication plan for the Parsing team to ensure they have been appropriately announced.

Test the version you hope to deploy

  • See mw:Parsoid/Round-trip testing for details.
  • Check http://parsoid-rt-tests.wikimedia.org/regressions/between/{from}/{to} where {from} is the last deployed hash from mw:Parsoid/Deployments and {to} is the latest tested commit (which we're about to deploy)
    • http://parsoid-rt-tests.wikimedia.org/commits gives you a nice radio-button interface to create this URL
    • BEWARE: if you get the output total regressions between selected revisions: 0, it is extremely likely that you mistyped the hash or that we didn't actually run round-trip tests for that particular hash. (This is a bug, we should probably give a better message in this case.)
    • Since we are using current revision of titles in round-trip testing, edits to pages can show up as false regressions. tools/regression-testing.php in the Parsoid repo is useful in filtering those out. Running it with the right parameters (use --help for usage) will get a list of pages to look more closely, if necessary.
  • Check that there are no concerning notices or errors in logstash from the rt run

Prepare the vendor patch

THIS PROCESS HAS CHANGED.

The new process is: 

$ tools/prepare_vendor_patch.sh v0.20.0-a{N-1} v0.20.0-a{N} <phab task id> <git hash for v0.20.0-a{N}> /path/to/mediawiki-vendor /path/to/mediawiki-core

Note that the v0.20.0-a{N} tag does not need to have been created yet. The <phab task id> refers to Content Transform Team chore task for the release.

OLDER PROCESS BELOW.

Here is a concise summary of steps in the common case. Detailed explanation follows.

cd PARSOID_REPO
git checkout <git-sha-of-patch-to-tag>
git tag v0.{version}.0-a{N}
git push origin v0.{version}.0-a{N}
tools/gen_deploy_log.sh v0.{version}.0-a{N-1} v0.{version}.0-a{N}
.. copy that log over to https://www.mediawiki.org/wiki/Parsoid/Deployments ..
cd VENDOR_REPO
.. edit composer.json and bump version number of wikimedia/parsoid as above ..
composer update --no-dev
.. ensure all files are added and git commit (see below for what to include in commit message) ..
git review -u
.. add reviewers and get it reviewed ..
.. post-merge, verify it landed on the beta cluster and works fine ..
Details

(This process was hashed out in phab:T240055)

  • Pull the latest version of master into your master branch of Parsoid and do remote update thereafter
  • Tag a new version of Parsoid and push the tag: (hint use: git tag -l to show existing tags)
  • Create a short deployment summary on mw:Parsoid/Deployments.
    • In Parsoid repository, tools/gen_deploy_log.sh v0.20.0-a{from} v0.20.0-a{to} (for appropriate values of {from} and {to}) will generate wikitext you can cut-and-paste into mw:Parsoid/Deployments (improvements to this script are welcome!)
    • In mw:Parsoid/Deployments, copy previous release header line, edit the dates and version info and delete "done" template and insert "In progress" template
    • The manual way is/was to start from git log --cherry-pick {from}...{to}. Don't include all commits, but only notable fixes and changes (ignore rt-test fixes, code cleanup updates, parser test updates, etc). (The above command will do the right thing if {from} was on a branch and had patches cherry-picked from {to}, although if there were conflicts during the cherry-pick to {from} the patch will still appear in the log for {to}.)
  • Checkout mediawiki/vendor.git master branch into its own working directory. (hint: $ git clone "https://gerrit.wikimedia.org/r/mediawiki/vendor")
    • Make a new branch in that repo: (hint: git branch deploy; get checkout deploy)
    • In that repo: Update composer.json to include "wikimedia/parsoid": "0.20.0-aN", (for your version {N}; note no leading "v")
    • Ensure you're running the version of composer listed in the README for the vendor repo. At time of writing this is 2.6.4. composer --version will tell you what version you're running and (usually) composer self-update will bring you up-to-date. If you use an old composer, you will create unrelated diffs to non-parsoid code when you do the next step.
    • Do composer update --no-dev (which should only update parsoid)
      • If composer complains "The requested package wikimedia/parsoid 0.20.0-aN exists as [...long list not including 0.20.0-aN...]" then composer's local cache hasn't been updated to include the new version available from packagist.org yet. Wait 15 minutes and try again. The --no-cache option to composer *might* help... but it might not (it probably won't). Apparently composer 2.x sped this up? :)
    • Add the changed files to git, commit and provide a detailed commit message as described below, and then upload to gerrit:
git add wikimedia/parsoid composer.lock composer.json composer # & etc, if needed
git commit
git review
  • Use a commit message that (1) names the new parsoid tag, (2) includes the git hash of the new parsoid version (we've stopped including this for the most part because the hash is given by the parsoid tag in part 1), and (3) references key bug #s from the deployment summary so the deploy gets linked to phab ( Tip: git log v0.20.0-a$PREV..v0.20.0-a$NEW | grep Bug: | sort -u). For example:
Bump wikimedia/parsoid to 0.20.0-aN

Bug: T111111
Bug: T222222
  • Review the generated patch (either via git show or on gerrit), looking specifically for unexpected changes. The code in wikimedia/parsoid should change in roughly the ways you expect from the deploy summary, there should be a change to the version number in composer.json and changes to some hashes, timestamps, and versions in composer.lock ,composer/installed.json and composer/installed.php but there should be no other changes. See this patch set for an example where an old version of composer was used, resulting in spurious changes to other files in composer/.
  • If jenkins fails on gerrit with the same "The requested package wikimedia/parsoid 0.20.0-aN exists as..." message described above, the reason is the as that described for the composer update --no-dev step above: composer's cache on jenkins still doesn't have your new version yet. Wait a minute and comment "recheck" to re-run the jenkins tests.
  • Review and C+2 on gerrit. This will go live on beta cluster pretty quickly (within 30 minutes).
  • If you were late and just missed the train branch, be sure to check the "If the train branch has already been cut" section below.

Verify deployment version on beta after the vendor patch is merged

$ ssh deployment-parsoid12.deployment-prep.eqiad.wmflabs
user@deployment-parsoid12$ curl -x deployment-parsoid12:80 'http://en.wikipedia.beta.wmflabs.org/wiki/Special:Version' | fgrep wikimedia/parsoid -C0

Be around on IRC

  • Add yourself to the "deployer" field of Deployments if you're not already there
  • Be online in the libera.chat IRC channel #wikimedia-operations connect (and stay online through the deployment window)

Logs to monitor

Post-deploy checks

  • Test VE editing on enwiki and non-latin wikis
    • For example, open it:Luna (or other complex page), start the visual editor, make some random vandalism, click save -> review changes, then verify that the wikitext reflects your changes and was not corrupted. Hit cancel to abort the edit.
    • Reading through the recent edits (frwiki, enwiki) can also be a good check.

Testing a version bump

If the deployed version of Parsoid updates the Parsoid DOM version and/or will exercises the html2html "down convert" endpoint, the following test procedure will ensure that clients are getting the appropriate DOM version:

  • First and foremost, mocha tests should already be present that cover both downgrading the HTML and serializing it with and without selser.
  • Create a test page on the beta cluster containing the features that merited the major version bump.
  • Deploy the desired commit to the beta cluster and, as a sanity check, make requests for the above test page from Parsoid directly (via deployment-parsoid12.deployment-prep.eqiad.wmflabs) accepting the various specs that are available. The inline meta tag and aforementioned features should indicate that it worked. Example requests might be,
  • Confirm that VE on the beta cluster is still tied to the older content version and will be needing a downgrade (see the commit in Special:Version for the extension and compare with the header defined in includes/ApiVisualEditor.php)
  • At this point, two scenarios need to be tested: an edit starting from the older content version stored in RESTBase (which won't require a downgrade) and one starting from the new content version, which will.
    • Note that, for extra points, there are potentially several versions numbers stored in RESTBase that satisfy the VE request based on caret semantics and it might be worthwhile to confirm that edits starting from those versions work as well.
    • Once you've found stored content in RESTBase with an appropriate version for your test it's prudent to confirm that VE is actually editing what you expect. This can be achieved by dumping the various DOMs: the original copy(ve.init.target.doc.body.outerHTML) and the edited copy(ve.init.target.docToSave.body.outerHTML)
  • In each case, try to confirm that the features can be edited directly as well as being ignored by selser (usually because no normalizations occur). Unfortunately, testing here is a bit more art than science.
  • Finally, open up the various testing dashboards for logging and metrics to verify that no unexpected errors are present and that the downgrades are accounted for.

Testing on scandium

When on scandium, use this command to test Parsoid directly: 

NO_PROXY="" no_proxy="" curl -x scandium.eqiad.wmnet:80 http://<domain>/w/rest.php/<domain>/v3/page/html/<title>/<revid>

Note: yes, it's really http and not https.

The NO_PROXY="" no_proxy="" business is to ignore the environment variables that are set, which override the explicit proxy from -x.

Testing LanguageConverter

LanguageConverter can be tested on beta in a manner similar to testing a version bump.

  • Create a test page on the beta cluster containing the language converter features you wish to touch. Either the page language for the article must be set to a language w/ variants, or else the article must take place on a wiki where the main language has variants. We'll use the SrTest page on beta srwiki in our examples below.
  • Deploy the desired commit to the beta cluster and, as a sanity check, make requests for the above test page from Parsoid directly (via ssh to deployment-parsoid12.deployment-prep.eqiad.wmflabs) specifying the desired variant language. Verify that the result has been converted appropriately. Example requests might be,

See https://phabricator.wikimedia.org/T241146#5810424 for some more examples.

Deploying a cherry-picked patch

One way to do this is to create a new branch in the Parsoid repo and cherry-pick your patches to that. For example: 

git checkout v0.19.0-a3 # this is the commit on the master branch that you want to cherry pick on top of
git checkout -b deploy-20230528 # give it a name (go ahead and use the date of your deploy)
git cherry-pick f274c3f54f385a6ac159a47209d279b9040a161c # patch number 1
git cherry-pick de087b106be48fc6e97f2ebc4644f9d297ecdfed # patch number 2
git push gerrit deploy-20230528:deploy-20230528 # create the branch in gerrit (DON'T USE SLASHES HERE)

Now do the usual steps to tag a release and prepare a vendor branch patch (see above) using the next available release version number (v0.19.0-a4 in the example below): 

git tag v0.19.0-a4 # this is the next available release number
git push origin v0.19.0-a4

Switch to the mediawiki/vendor repository: 

git checkout master ; git pull origin master
edit composer.json # set wikimedia/parsoid to v0.19.0-a4
composer update --no-dev
git add -u
git commit -m "Bump wikimedia/parsoid to v0.19.0-a4"
git review -u

Note that the automated push to beta will fail if your gerrit branch name contains a slash. This is probably just because some ancient version of git is being used, and will eventually be fixed. But in the meantime, use dashes instead of slashes.

When this is merged into mediawiki-vendor it will (shortly) go live on beta; you should verify that everything looks good there. See #Verify deployment version on beta after the vendor patch is merged. If you want this cherry-pick to shortcut the train (instead of waiting to ride the next one) keep going into the next section, "If the train branch has already been cut".

Making a stable release

Forking for the major release

For a major release from (for example) 0.19 to 0.20, corresponding to MW 1.42 and 1.43:

  • (If necessary:) Tag the branch point, aka 0.19.0-a21 (ie, if you want to get an extra patch or two into the release branch that weren't tagged in the previous week's train deploy); also update mw:Parsoid/Deployments. 
    git tag v0.19.0-a21 <some hash>
git push origin v0.19.0-a21
tools/gen_deploy_log.sh v0.19.0-a20 v0.19.0-a21
  • Create a new REL1_42 parsoid branch, corresponding to the mediawiki-core release version. 
    git branch REL1_42 v0.19.0-a21
git push origin REL1_42
  • (If necessary:) Bump mediawiki-vendor:composer.json on the REL1_42 branch with the new 0.19.0-a21 tag. 
    cd ..../mediawiki-vendor
git checkout REL1_42 ; git pull origin
.. edit composer.json ..
composer update --no-dev
.. git add, git commit etc ..
git review -u
  • Bump the parsoid version number; also update mw:Parsoid/Deployments. 
    git tag v0.20.0-a1 <this week's release hash>
git push origin v0.20.0-a1
tools/gen_deploy_log.sh v0.19.0-a29 v0.20.0-a1
  • Bump mediawiki-vendor:composer.json on the main/master branch with the new 0.20.0-a1 tag. 
    cd ..../mediawiki-vendor
git checkout origin/master ; git pull origin
.. edit composer.json ..
composer update --no-dev
.. git add, git commit etc ..
git review -u
  • (IMPORTANT) Bump mediawiki-core:composer.json in mediawiki-core to "0.20.0-a1" and make this patch Depends-On: <change-id-for-mediawiki-vendor-patch>.
    cd ..../mediawiki-core
git checkout origin/master ; git pull origin
.. edit composer.json ..
git add composer.json
git commit # INCLUDE THE DEPENDS-ON
git review -u
  • Update mw:Parsoid/Releases to include the new "not yet released" branch.
    • Probably no one will have remembered to update this page when the last ".0" version of the previous release was tagged, so check the history of the REL1_41 branch (aka current release minus one) to see what non-alpha versions of parsoid were released and update the releases page accordingly; you can use the date of the mediawiki-vendor patch as the "release date".

Making the first/another minor release

In the early stages of the release cycle, you'll probably keep cherry-picking patches back onto your REL1_42 branch -- you might even make new alpha releases in the 0.19 series. But around the time of the -rc1 or -rc2 release of the new MediaWiki version, you're going to want to tag a non-alpha .0 version. Continuing the example above, we'll want to tag v0.19.0 on the REL1_42 branch. This may end up identical to one of the pre-existing alpha tags, or it might have an extra patch or two. The process for tagging and releasing a non-alpha version is very similar to the above, but we're going to be working on the REL1_42 branch exclusively, for both the parsoid tag as well as the mediawiki-vendor and mediawiki-core patches. And if you need to release a bug fix v0.19.1, you'll use this same process for that as well.

  • (If necessary:) Tag the branch point, aka 0.19.0. 
    git tag v0.19.0 <some hash>
git push origin v0.19.0
  • Bump mediawiki-vendor:composer.json on the REL1_42 branch with the new 0.19.0 tag. 
    cd ..../mediawiki-vendor
git checkout REL1_42 ; git pull origin
.. edit composer.json ..
composer update --no-dev
.. git add, git commit etc ..
git review -u
  • Bump mediawiki-core:composer.json in mediawiki-core to "0.19.0" (note no caret) and make this patch Depends-On: <change-id-for-mediawiki-vendor-patch>.
    cd ..../mediawiki-core
git checkout REL1_42 ; git pull origin
.. edit composer.json ..
git add composer.json
git commit # INCLUDE THE DEPENDS-ON
git review -u
  • Update mw:Parsoid/Releases to include the new ".0" version.

Edge case deployment scenarios

If the train branch has already been cut

IF THE TRAIN BRANCH HAS ALREADY BEEN CUT (aka the wmf/1.XX.0-wmf.YY branch exists) then after you merge to master of mediawiki-vendor you will also need to cherry-pick a patch to the appropriate branch of mediawiki-vendor, for example wmf/1.42.0-wmf.3. In some cases you can use gerrit to cherry-pick the vendor branch to the branch, but in practice most updates to vendor conflict with each other due to the presence of content hashes, so you'll most likely need to repeat the steps above:

# from mediawiki/vendor
git remote update # if needed
git checkout wmf/1.42.0-wmf.3
edit composer.json # set wikimedia/parsoid to v0.19.0-a21
composer update --no-dev
git add -u
git commit -m "Bump wikimedia/parsoid to v0.19.0-a21"
git review -u

Now, before you merge this cherry-pick onto the branch, you need to check one of three possible cases:

  1. If the train branch is new and the "branch commit" has not yet been merged (it looks like this; here is a gerrit search) -- wait! Do not merge the cherry-pick into mediawiki-vendor until the branch commit has landed, or the git submodules in mediawiki-core will be left out of sync (T259832). You might want to add a Depends-On clause to the cherry-pick patch to enforce this. If you accidentally merged this, see below for how to fix it.
  2. If the branch commit has been merged, but the train has not been deployed anywhere (check Deployments and the status page on versions.toolforge.org), then it's safe to just C+2 the cherry-pick. But be sure to ping #wikimedia-operations connect and get clearance before C+2 and merge, since (a) the deployer may have already checked out the branch in preparation for the train, and (b) since jenkins can take a while to complete the merge and they need to know to wait for it. Probably worth leaving a comment on the phab task for the blocker bug for the train release as well.
  3. If the train has already been deployed, then you will need to backport this cherry-pick; it is considered bad form to leave code committed on the branch which isn't deployed. Don't merge the cherry-pick until the backport window.

If you accidentally merged into vendor before the branch commit has been merged

Merging a patch onto a branch in the mediawiki-vendor repository will automatically update the git submodules in core, but only after the branch commit is in place. See phab:T259832 for details. If you think you might have merged onto vendor before the branch commit was merged, check the appropriate vendor branch history for core, aka https://gerrit.wikimedia.org/g/mediawiki/core/+/refs/heads/wmf/1.42.0-wmf.3. Verify that the submodule hash for vendor corresponds to the tip of the branch of mediawiki-vendor. If it's not correct, after the branch commit has been merged into mediawiki-core you need to manually bump the submodules:

cd .../mediawiki-core
# note that the below will clobber your vendor, extensions, and skins directories
# you might want to use a new clean checkout of core
git checkout wmf/1.42.0-wmf.3
git submodule update --init
git submodule update --remote vendor
git add vendor
git commit -m "Update git submodules"
git review -u

Review and merge that.

Misc stuff

  • To deploy to a single host
    scap deploy --force -l <node>
  • To see which hosts are pooled, from another host
    confctl select dc=.*,cluster=parsoid,service=parsoid get
  • To see the list of parsoid hosts in beta:
    cat /srv/deployment/parsoid/deploy/scap/betacluster
    • See also /srv/deployment/parsoid/deploy/scap/scap.cfg in general
  • To pool/depool a node, from deployment.eqiad.wmnet, run:
    • To depool: SSH_AUTH_SOCK=/run/keyholder/proxy.sock ssh -l deploy-service <node> 'depool service=parsoid'
    • To pool  : SSH_AUTH_SOCK=/run/keyholder/proxy.sock ssh -l deploy-service <node> 'pool service=parsoid'

Data flow

Parsoid runs entirely on an internal subnet, so requests to it are proxied through the ve-parsoid API module. This module is implemented in extensions/VisualEditor/ApiVisualEditor.php and is invoked with a POST request to /w/api.php?action=ve-parsoid. The API module then sends a request to Parsoid, either GET /$prefix/$pagename to get the HTML for a page, or POST /$prefix/$pagename to submit HTML and get wikitext back. Parsoid itself also issues requests to /w/api.php to get the wikitext of the requested page and to do template expansion.

Once the ve-parsoid API module receives a response from Parsoid, it either relays it back to the client (when requesting HTML), or saves the returned wikitext to the page (when submitting HTML). 

                (POST /w/api.php?action=ve-parsoid)          (GET /en/Barack_Obama?oldid=1234)           (requests for page content and template expansions)
Client browser ------------------------------------------> API ---------------------------->  Parsoid -----------------------------------------------------> API
    ^                                                      | ^                                 |   ^                                                          |
    |                  (response)                          | |      (HTML)                     |   |                   (responses)                            |
    +------------------------------------------------------+ +---------------------------------+   +----------------------------------------------------------+


                (POST /w/api.php?action=ve-parsoid)          (POST /en/Barack_Obama; oldid=1234)
Client browser ------------------------------------------> API ---------------------------->  Parsoid
                                                           | ^                                 |
                                               (save page) | |      (wikitext)                 |
                                                           | +---------------------------------+
                                                           |
                                                        Database
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