Wikidata Query Service
Wikidata Query Service is the Wikimedia implementation of SPARQL server, based on the Blazegraph engine, to service queries for Wikidata and other data sets. Please see more detailed description in the User Manual.
More information on technical interactions with Query Services is available.
You will need java and maven, java can be installed from: https://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html
The source code is in gerrit project
wikidata/query/rdf. In order to start working on Wikidata Query Service codebase, clone this repository:
or GitHub mirror:
or if you want to push changes and have a Gerrit account:
After update submodules:
$ cd wikidata-query-rdf [../wikidata_query_rdf]$ git submodule update --init Submodule 'gui' (https://gerrit.wikimedia.org/r/wikidata/query/gui) registered for path 'gui'
Then you can build the distribution package by running:
cd wikidata-query-rdf ./mvnw package
and the package will be in the
dist/target directory. Or, to run Blazegraph service from the development environment (e.g. for testing) use:
-d" option to run it in debug mode. If your build is failing cause your version of maven is a different one you can:
mvn package -Denforcer.skip=true
In order to run Updater, use:
The build relies on Blazegraph packages which are stored in Archiva, and the source is in
wikidata/query/blazegraph gerrit repository. See instructions on Mediawiki for the case where dependencies need to be rebuilt.
See also documentation in the source for more instructions.
SPARQL endpoint is available under
/sparql path, which internally redirects to
If there are changes needed to Blazegraph source, they should be checked into
wikidata/query/blazegraph repo. After that, the new Blazegraph sub-version should be built and WDQS should switch to using it. The procedure to follow:
- Commit fixes (watch for extra whitespace changes!)
README.wmfwith descriptions of which changes were done against mainstream
- Blazegraph source in master branch will be on snapshot version, e.g.
2.1.5-wmf.4-SNAPSHOT- set it to non-snapshot:
mvn versions:set -DnewVersion=2.1.5-wmf.4
- Make local build:
mvn clean; bash scripts/mavenInstall.sh; mvn -f bigdata-war/pom.xml install -DskipTests=true
- Switch Blazegraph version in maim pom.xml of WDQS repo to
2.1.5-wmf.4(do not push it yet!). Build and verify everything works as intended.
- Commit the version change in Blazegraph, push it to the main repo. Tag it with the same version and push the tag too.
- Run to deploy:
mvn -f pom.xml -P deploy-archiva deploy -P Development; mvn -f bigdata-war/pom.xml -P deploy-archiva deploy -P Development; mvn -f blazegraph-war/pom.xml -P deploy-archiva deploy -P Development
- Commit the version change in WDQS, and push to gerrit. Ensure the tests pass (this would also ensure Blazegraph deployment to Archiva worked properly).
- After merging the WDQS change, follow the procedure below to deploy new WDQS version.
- Bump Blazegraph master version back to snapshot -
mvn versions:set -DnewVersion=2.1.5-wmf.5-SNAPSHOT- and commit/push it.
We're currently running on the following servers:
- public cluster, eqiad:
- public cluster, codfw:
- internal cluster, eqiad:
- internal cluster, codfw:
These clusters are in active/active mode (traffic is sent to both), but due to how we route traffic with GeoDNS, the primary cluster (usually
eqiad) sees most of the traffic.
Server specs are similar to the following:
- CPU: dual Intel(R) Xeon(R) CPU E5-2620 v3
- Disk: 1600GB raw raided space SSD
- RAM: 128GB
Grafana dashboard: https://grafana.wikimedia.org/d/000000489/wikidata-query-service
Grafana frontend dashboard: https://grafana.wikimedia.org/d/000000522/wikidata-query-service-frontend
I've got a new WDQS host, how do I get it ready for production?
This section explains how to go from a racked server with an OS, to a production WDQS server.
Create and Commit Puppet code
When a server is racked by DC Ops, they will add it to the Puppet repo's site.pp. See the Server Lifecycle page for more details on DC Ops' process.
Apply puppet role (Puppet patch 1)
Once DC Ops hands over the server, our first step is to move the server into one of the available wdqs puppet roles. As of this writing, the roles are
wdqs::test , but you can see an up-to-date list by searching for 'wdqs' in the Puppet repo's site.pp file.
Suppress Alerts (Puppet patch 2)
Until the host is ready, you can suppress alerts by setting the hiera key profile::query_service::blazegraph::monitoring_enabled: false . See this patch for an example.
Once these change are merged, run puppet agent on the host and it should be close to being ready.
Manual Steps (Likely to Change Frequently)
Once Puppet runs, there are a few manual steps required. These are temporary and subject to change. See this Phab ticket for more context .
- Remove /srv/deployment/wdqs/* and do a forced scap deploy
- Run data-transfer cookbook
Needed to get the actual Blazegraph data onto the server. As of this writing, the cookbook takes about 90 minutes to transfer all data ~(1.2TB) from another host in the same DC
Monitor lag using the WDQS dashboard . If it's not dropping, check the updater service again.
- Manually start the load-dcatap-weekly.service
Additional context at T342361
- Remove the alert suppression you configured in "Puppet patch 2".
- Wait 30 minutes and confirm no alerts in AlertManager/Icinga.
The deployment version of the query service is in the Gerrit project
with the deployment version of the GUI,
production branch), as a submodule.
Note that currently deployment is via git-fat (see below) which may require some manual steps after checkout. This can be done as follows:
- Check out
wikidata/query/deployrepository and update
guisubmodule to current
git submodule update).
git-fat pullto instantiate the binaries if necessary.
- rsync the files to deploy directory (
role::wdqs::labs for installing WDQS. You may also want to enable
role::labs::lvm::srv to provide adequate diskspace in
Command sequence for manual install:
git clone https://gerrit.wikimedia.org/r/wikidata/query/deploy cd deploy git fat init git fat pull git submodule init git submodule update sudo rsync -av --exclude .git\* --exclude scap --delete . /srv/wdqs/blazegraph
Production deployment is done via git deployment repository
wikidata/query/deploy. The procedure is as follows:
Preferred option: from Jenkins
- Log into Jenkins
- Go to https://integration.wikimedia.org/ci/job/wikidata-query-rdf-maven-release-docker-wdqs/
- Select build with parameters
Note: If the job fails, the archiva credentials could have changed, see here: https://wikitech.wikimedia.org/wiki/Analytics/Systems/Cluster/Deploy/Refinery-source#Changing_the_archiva-ci_password
Fallback option: from your own machine
./mvnw -Pdeploy-archiva release:preparein the source repository which updates the version numbers. If your system username is different that the one in scm, use
./mvnw -Pdeploy-archiva release:performin the source repository - this deploys the artifacts to archiva.
Note that for the above you will need repositories
archiva.snapshots configured in
~/.m2/settings.xml with archiva username/password. You will also need to have a gpg key setup.
Further required preparation
Prepare and submit the patch containing the new code updates:
deploy-prepare.sh <target version>script - it will create a commit with newest version of jars.
- Using the commit generated by the above, open up a patch, and get it approved and merged.
Test that the service is working as expected before we mutate it with a deploy, so that we can compare properly:
- Open up a tunnel to the current wdqs canary instance via
ssh -L 9999:localhost:80 wdqs1003.eqiad.wmnet(check that wdqs1003 is still the canary)
- Canary is defined in the deploy repo within
scap/scap.cfgas the wdqs-canary dsh group.
- This dsh group is defined within the same repo in the file
scap/wdqs-canarywith one host per line.
- Canary is defined in the deploy repo within
- Run the test script through the tunnel: from the
cd queries && ./test.sh -s http://localhost:9999/
- You may also want to navigate to http://localhost:9999 and run an example query.
Now we're ready for the actual deploy!
The actual code deploy
On the deployment server (
cd /srv/deployment/wdqs/wdqs. First we'll get the repo into the desired state, then do the actual deploy.
git fetch, then glance at
git log HEAD...origin/masterand manually verify the expected commits are there, then
git rebase && git fat pull
- Now that the repo is in the desired state, sanity check with
ls -lahthat you see the
.warfile and that it doesn't seem absurdly small
scap deploy '<the latest version number>'to deploy the new build. After canary deployment will be done (scap will ask for confirmation to proceed), please test the service. You can do that by ssh tunneling access to
wdqs1003.eqiad.wmnet and running
./tests.sh -s localhost:<tunneled_port> script from `queries` subdirectory
- Validation #1: In a separate pane or tab, navigate to
/srv/deployment/wdqs/wdqsand run/look at
- Validation #2: In yet another separate pane, tail the logs on the wdqs canary via
tail -f /var/log/wdqs/wdqs-updater.log -f /var/log/wdqs/wdqs-blazegraph.log(Note we're tailing two log files at once so results will be interleaved)
- Once the canary deployment looks good, proceed to the rest of the fleet by pressing
Post code-deploy operational steps
These steps have been separated into a separate subsection from the actual code deploy, but these steps are a mandatory part of the deploy, just to be clear.
wdqs-updaterafter the deployment is complete:
sudo -E cumin -b 4 'A:wdqs-all' 'systemctl restart wdqs-updater'(Note that wdqs-updater can be safely restarted without user impact)
wdqs-categoriesone in-service node at a time (restarting it on a pooled node impacts users and thus requires depooling), like so:
sudo -E cumin -b 1 'A:wdqs-all and not A:wdqs-test' 'depool && sleep 45 && systemctl restart wdqs-categories && sleep 45 && pool'
- Restart the remaining wdqs-test nodes, which aren't pooled and therefore we can't use the above command:
sudo -E cumin 'A:wdqs-test' 'systemctl restart wdqs-categories'
- Run a basic test query on query.wikidata.org
- Check icinga - wdqs to verify there's no new warning/critical/unknown, and also check grafana to make sure everything looks good.
- Verify the commit hash for the new deploy matches the correct commit hash from the deploy repo:
sudo -E cumin -b 4 'A:wdqs-all' 'ls -ld /srv/deployment/wdqs/wdqs'expected output:
General puppet note (nothing to do here for a deploy): The puppet role that needs to be enabled for the service is
It is recommended to test deployment checkout on beta before deploying it in production.
The test script is located at rdf/query/test.sh.
GUI deployment general notes
GUI deployment files are in repository
production. The GUI is deployed as a microsite.
A new deployment GUI version can be built by
WDQSGuiBuilder from the latest master in the
wikidata/query/gui repo by issuing a rebuild of the wikidata-query-gui-build Jenkins job; after the change has been uploaded (query), it needs to be manually +2ed (both “code review” and “verified”) and submitted. You can also run
grunt deploy in the GUI directory to generate such a patch by hand (which still needs to be merged manually). Either way, after the gui-deploy repo has been updated, the microsite should update itself with the next Puppet run (after at most 30 minutes as of 2022-02-10).
Data reload procedure (SRE-level access required)
Reloading data is a time-consuming (~17 days) and fragile process. When possible, transfer data instead of reloading. As of this writing, it is not possible to complete a reload from codfw due to NFS issues, so be sure to use eqiad datacenter only. You can then use the data transfer process to send the data from eqiad to codfw.
Ensure clouddumps1001.wikimedia.org is mounted via NFS on the target host
Eventually we will move to rsync, but for now, you'll have to update puppet to mount the clouddumps hosts via NFS on your target server. Example PRs for mounting and opening the software firewall . You can combine your changes as a single PR, we just screwed it up on those two ;) .
Run the data-reload cookbook
Use the data-reload cookbook from cumin. Note that the process takes around 17 days to complete. Bugs in Blazegraph can cause the reload to corrupt itself. If that happens, you have to start the process over again.
The manual process is not used anymore, but is documented in this page's history just in case.
Data transfer procedure
Transferring data from between nodes is typically faster than recovering from a dump. The port
9876 is opened between the wdqs nodes of the same cluster for that purpose. Across different clusters, that port needs to be opened manually (and closed after the opertation). The procedure is automated in a cookbook (text in BOLD needs to be adapted):
- on the destination node, open a port if needed:
sudo iptables -A INPUT -p tcp -s wdqs1010.eqiad.wmnet --dport 9876 -j ACCEPT
- copy the main data:
sudo -i cookbook sre.wdqs.data-transfer --source wdqs1010.eqiad.wmnet --dest wdqs2007.codfw.wmnet --without-lvs --blazegraph_instance blazegraph --reason "reloading data from wdqs1010 to wdqs2007 - some reason" --task-id T246343
- copy the categories data:
sudo -i cookbook sre.wdqs.data-transfer --source wdqs1010.eqiad.wmnet --dest wdqs2007.codfw.wmnet --without-lvs --blazegraph_instance categories --reason "reloading data from wdqs1010 to wdqs2007 - some reason" --task-id T246343
- on the destination node, close the port if needed:
sudo iptables -D INPUT -p tcp -s wdqs1010.eqiad.wmnet --dport 9876 -j ACCEPT
By default the cookbook will depool / pool nodes automatically. The
--without-lvs argument prevents this. This affects both source and destination, so in the case where the source is not behind LVS but the destination is, depooling / pooling must be done manually.
Potential improvements to the cookbook:
- open and close ports automatically
- iterate over multiple destination servers
- iterate over multiple data files (blazegraph / categories)
- supports different depooling strategies for source and destination
- wait for server to catchup on lag before repooling / terminating the cookbook
Updating federation whitelist
- Add endpoint to
wikidata-query-deployrepo. Commit & push the repo.
- After deploy, document on https://www.mediawiki.org/wiki/Wikidata_Query_Service/User_Manual/SPARQL_Federation_endpoints
- Update https://www.wikidata.org/wiki/Wikidata:SPARQL_query_service/Copyright
- If it was requested on https://www.wikidata.org/wiki/Wikidata:SPARQL_federation_input, move request to archive
- Check https://www.wikidata.org/wiki/Wikidata:SPARQL_query_service/Federation_report for signs of trouble periodically.
Manually updating entities
It is possible to update single entity or a number of entities on each server, in case data gets out of sync. The command to do it is:
cd /srv/deployment/wdqs/wdqs; bash runUpdate.sh -n wdq -N -S -- -b 500 --ids Q1234 Q5678 ...
In order to do it on all servers at once, commands like
pssh can be used:
pssh -t 0 -p 20 -P -o logs -e elogs -H "$SERVERS" "cd /srv/deployment/wdqs/wdqs; bash runUpdate.sh -n wdq -N -S -- -b 500 --ids $*"
$SERVERS would contain the list of servers updated. Note that since it is done via command line, updating larger batches of IDs will need some scripting to split them into manageable chunks. Doing bigger updates at moderate pace, with pauses to not interfere with regular updates, is recommended.
Updating IDs by timeframe
Sometimes, due to some malfunction, a segment of updates for certain time period gets lost. If it's a recent segment, updater can be reset to start with certain timestamp by using
--start TIMESTAMP --init (you have to shut down regular updater, reset the timestamp, and then start it again). If the missed segment is in the past, the best way is to fetch IDs that were updated in that time period, using Wikidata recentchanges API, and then update these IDs as described above.
Example of such script can be found here: https://phabricator.wikimedia.org/P8919. The output should be filtered and duplicates removed, then fed to a script calling to update script as per above.
Updating value or reference nodes
Since value (
wdv:hash) and reference (
wdref:hash) nodes are supposed to be immutable,
they will not be touched by updates to items that use them.
To fix these nodes, you need to delete all triples with these nodes as the subject (SPARQL
DELETE through production access),
then trigger an update (as above) for items which reference these nodes (so they will be recreated; only one item per node necessary).
Notes about running the service on non-WMF infrastructure
This project has been designed to support wikidata and commons mediainfo and thus it's not rare to stumble upon features where this assumption has been hardcoded either directly in the code or as default values. Here are few notes that may help if you are running this service for your own wikibase installation.
- blazegraph enpoint options:
scheme:blazegraph_host:port: blazegraph_host:port to write to (defaults to
url path: the context part (defaults to
url path: the blazegraph namespace (defaults to
seconds: timeout in seconds for the update in blazegraph to happen (defaults
-1: to no timeout)
- -s: skip site links (defaults keep site links)
- Updater specific options must be added after
wikibase_url: the wikibase URL the updater will connect to to fetch updates (defaults to
concept uris: The URI used to identify concepts, this should be the value set in
baseUriwith one path stripped out, defaults to (
namespace ids: comma separated list of namespace ids (defaults to 0,120)
Example: for a wikibase available on
https://mywikibase.local/ whose config is set with something
$wgWBRepoSettings['conceptBaseUri'] = "https://myentities.local/entity/";
and using default blazegraph options:
- Data drift: The update process is imperfect, data might drift over time as updates are missed. Different servers might have slightly different data sets. This is mitigated by reloading the full data set periodically. If you identify a specific entity that has drifted, please open a Phabricator task with the entity (or list of entities) that need to be reloaded.
If you need more info, talk to anybody on the mw:Wikimedia_Search_Platform team.