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imported>C. Scott Ananian
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=== Testing on scandium ===
=== Testing on scandium ===
When on scandium, use this command to test Parsoid directly:
When on scandium, use this command to test Parsoid directly:
<syntaxhighlight lang="bash">
curl -x scandium.eqiad.wmnet:80 http://<domain>/w/rest.php/<domain>/v3/page/html/<title>/<revid>
curl -x scandium.eqiad.wmnet:80 http://<domain>/w/rest.php/<domain>/v3/page/html/<title>/<revid>
=== Testing LanguageConverter ===
=== Testing LanguageConverter ===
LanguageConverter can be tested on beta in a manner similar to testing a version bump.
LanguageConverter can be tested on beta in a manner similar to testing a version bump.

Revision as of 22:32, 18 January 2020

Parsoid is a service that parses converts between wikitext and HTML. The HTML contains additional metadata that allows it to be converted back ("round-tripped") to wikitext.

  • 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. Parsoid is a stateless HTTP server running on port 8000.
  • 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.


Deploying changes

Parsoid is deployed using scap3. Doing deployments with scap3 is very easy. You just run scap deploy, which pushes the new state to all backends and restarts them. You should have deploy access and be a member of the deploy-service group puppet group.

Pre-deploy checks

Prepare the deploy patch

  • Check{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)
    • 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.js is useful in filtering those out. Grab the wiki:title pairs that show up as regressions in the regressions url, save it to a file and feed it to the regressions tool and you will get a list of pages to look more closely, if necessary.
  • Create a short deployment summary on mw:Parsoid/Deployments 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}.)
  • Prepare a deploy repo commit and push for +2
    • Roughly: cd deploy ; git checkout master ; git pull origin master ; git submodule update ; cd src ; git checkout {to} ; cd .. ; git add -u ; git commit -m "Bump src to {to} for deploy" ; git review

Verify deployment version on beta after the deploy patch is merged

  • Deploy code (if not already there) to the beta cluster (same instructions as below but ssh to deployment-deploy01.deployment-prep.eqiad.wmflabs)
  • If beta cluster is down or visual editor is down in beta cluster, do not continue with routine deployments.
  • On beta cluster (eg, perform manual VisualEditor editing tests. This requires you to have an account on the beta cluster wiki. Test with non-ASCII content too to catch encoding issues. Check parsoid logs, if necessary.

Be around on IRC

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

Deploying the latest version of Parsoid

Before you begin, note that Parsoid caches its git version string. So you may wish to do:

ssh deployment.eqiad.wmnet
tin$ for wtp in `grep wtp /etc/dsh/group/parsoid`; do echo -n "Querying $wtp: "; \
   curl "http://$wtp:8000/_version"; echo; done;

to ensure that the "old" version string is cached, so that you will be able to tell when parsoid restarts with its "new" version below.

Now to do the deploy:

ssh deployment.eqiad.wmnet
tin$ cd /srv/deployment/parsoid/deploy
tin$ git pull
tin$ git submodule update --init
tin$ scap deploy 'Updating Parsoid to <new hash> (T<bug number>, T<bug number>)'

The argument in the scap command will appear in the Server Admin Log as scap runs. List the hash of the deployed Parsoid version as well as any bug numbers referenced in the deploy log. This will create cross-references in the listed bugs to the SAL.

First, the canary group is deployed to (wtp{1025,1026}.eqiad and wtp{2001,2002}.codfw). Watch the canary machines on grafana for eqiad and codfw for a while to ensure there aren't any sudden load changes, and check the logs in logstash to ensure they are not being spammed with some new error. If everything is OK, scap will ask you whether you want to continue to the next group or do all groups. It is safe to use c to tell it to do all groups without asking.

Scap will log the completion of the deploy, but if you want to add additional information to the SAL, make a comment in #wikimedia-operations with something like

!log Attempted Parsoid deploy, but rolled back to version <new hash> (T<bug number>)

As with the argument to scap, mentioning bug numbers will create cross-references to the SAL.

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.
  • Verify all Parsoid servers are running the same version with:
    ssh deployment.eqiad.wmnet
    tin$ for wtp in `grep wtp /etc/dsh/group/parsoid`; do echo -n "Querying $wtp: "; \
       curl "http://$wtp:8000/_version"; echo; done;

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-parsoid09.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( and the edited copy(
  • 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:

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

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-parsoid09.deployment-prep.eqiad.wmflabs) specifying the desired variant language. Verify that the result has been converted appropriately. Example requests might be,

See 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 497da30e # this is the commit on the master branch that you want to cherry pick on top of
git checkout -b deploy-20150528 # 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-20150528:deploy-20150528 # create the branch in gerrit (DON'T USE SLASHES HERE)

Now do the usual steps to prepare a deploy repo (see below) using the hash of your branch commit (73445bfd in the example below):

cd deploy
git checkout master ; git pull origin master ; git submodule update ; cd src ; git checkout 73445bfddded9f0baa6afe548c98880f4401fb7b # your branch commit
cd .. ; git add -u ; git commit -m "Bump src to 73445bfd (deploy-20150528 branch) for deploy"
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.

Cherry-picking directly from the deployment server and deploying it

In many situations, a hotfix might need to be pushed quickly. One way to do that is to cherry-pick the patch on the deployment server (aka deployment.eqiad.wmnet) and sync it.

### Verify that you have the most recently deployed code that you want to cherry-pick on top of
tin$ cd /srv/deployment/parsoid/deploy (verify via git log)
tin$ cd src (verify via git log)

### Create a hotfix branch
tin$ git checkout -b hotfix_<some_unique_tag>

### Get latest code from master you want to cherry-pick from
tin$ git checkout master; git pull

### Check out the hotfix branch and cherry-pick
tin$ git checkout hotfix_<some_unique_tag>
tin$ git cherry-pick <commit-from-master>

### Create a deploy-repo patch
tin$ cd ..; git commit -a -m "Bump src to whatever-git-sha-it-is for hotfix"

### The usual deployment steps
tin$ scap deploy
... verify deployment ...


In case you need to restart Parsoid without any deployments (for example, to reload mediawiki configs from config or other deployments),

  • Restart parsoid hosts, from deployment.eqiad.wmnet (production) or deployment-deploy01.deployment-prep.eqiad.wmflabs (beta)
    cd /srv/deployment/parsoid/deploy && scap deploy --service-restart

Converting a Parsoid/JS to a Parsoid/PHP server

A conventional parsoid/JS (wtp*) server can be switched to a parsoid/PHP server by setting the parameter "$use_php" to "true" in Hiera. It is a parameter of the class profile::parsoid and defaults to false. Setting this to true will mean a number of profile::mediawiki:: classes will be included turning it into a MediaWiki appserver-like server effectively.

After doing so a couple Hiera keys are needed to configure PHP and related things. See below and compare to the values in hieradata/role/common/parsoid.yaml.

# switch Parsoid/JS-server to Parsoid/PHP-MW-appserver
profile::parsoid::use_php: true
has_lvs: true

profile::mediawiki::php::php_version: "7.2"
profile::mediawiki::webserver::has_tls: true

nutcracker::verbosity: "4" 
# Bump the connections per backend to 5 in mcrouter, see T203786
profile::mediawiki::mcrouter_wancache::num_proxies: 5
profile::mediawiki::httpd::logrotate_retention: 12
profile::mediawiki::vhost_feature_flags: {}
# bail out in case a long-lasting C function is called and 
# excimer can't throw its exception
profile::mediawiki::php::request_timeout: 201 
profile::mediawiki::apc_shm_size: 4096M
profile::mediawiki::php::enable_fpm: true
  opcache.interned_strings_buffer: 96
  opcache.memory_consumption: 1024
  apc.ttl: 10
# Configure php-fpm restarts
profile::mediawiki::php::restarts::ensure: present
# We set the restart watermark at 200 MB, which is approximately how much
# opcache one full day of deployments consume.
profile::mediawiki::php::restarts::opcache_limit: 200 

When something goes wrong

Reverting a Parsoid deployment


ssh deployment.eqiad.wmnet
cd /srv/deployment/parsoid/deploy
scap deploy --rev <sha>

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)                 |
                                                           | +---------------------------------+