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# Analytics/Systems/AQS: Difference between revisions

The Analytics Query Service (AQS) is a public facing API that serves analytics data from both a Cassandra and a Druid backend. It is how Wikistats (stats.wikimedia.org) gets data to visualize.

Data generated by a wiki goes through two main data pipelines before it ends up in AQS. Readership data flows from our varnish caches, through Kafka, into private and public datasets. The public pageviews data ends up in the Pageview API, served by AQS from Cassandra. Editing data flows slower through monthly whole-history loads from mediawiki database replicas. This ends up in Druid as mediawiki_history_reduced and is also served by AQS. (TODO: linkify all this)

To add a new wiki, you need to edit the include lists for these two pipelines:

## Hosted API

More and up to date info in: https://wikimedia.org/api/rest_v1/?doc#/

## Monitoring

Grafana dashboards:

## Throttling

### 2016-05-26

Sum up:Throttling is enforced at the restbase/AQS layer thus requests that are served by varnish are not throttled. This is an important point. It means that the throughput of the API in the top endpoints is real high as the same data is requested over and over as on those endpoints we mostly serve"daily top" data. Throttling is done per (IP/endpoint/second) and if a client breaks throttling limits it will receive a 429 response code to its http request.

At the time of this writing throttling is set to trigger at reqs per (IP/endpoint/second) and thus far we are only logging when limits are breached, we are not enforcing throttling quite yet. Why? Cause if we get more that 30 concurrent requests in cassandra at any one time cassandra lookups time out. This, likely, will not be true after we finish our work in scaling the storage layer of the API.

Ticket in which we discussed throttling: [1]

Throttling limits breached are logged in to: https://logstash.wikimedia.org/#/dashboard/temp/AVTsUtpi_LTxu7wlBfI-

Config for throttling is at: https://github.com/wikimedia/restbase/blob/master/v1/metrics.yaml

### 2016-09-21

Bumping up throttling limits after scaling work to 400 requests per second, after our load tests. See: Analytics/AQS/Scaling#Load_testing

## Developing a New Endpoint

This is roughly how writing a new AQS endpoint goes. Note that some endpoints may use Druid rather than Cassandra, so that process may be different:

• Development
• Write the Oozie job to move data from Hadoop to Cassandra; Verify the output is correct by outputting to plain JSON/test Hive table; The Oozie job will be unable to load into Wikimedia Cloud Cassandra instances (You just have to hope that the loading works)
• Write the AQS endpoint, which includes the table schema spec and unit tests
• Testing
• Tunnel to any of the aqs-test Cassandra instances (i.e., aqs-test1001.analytics.eqiad1.wikimedia.cloud, ..., aqs-test1010.analytics.eqiad1.wikimedia.cloud)
• Create a keyspace in this cloud Cassandra instance of the same name as is detailed in the Oozie job properties file; Insert some data into the table
• From any of the aqs-test machines, run your version of AQS with the new endpoint, pointing to one of the Cassandra instances (e.g., 172.16.4.205); Test by manually running queries against your local instance (i.e., localhost:7231)
• Productionize
• Deploy the Oozie job, but don't run it
• Deploy AQS to point to the new data; Once it is running, it will automatically create the relevant keyspace in the production Cassandra instance
• Manually run a few queries against the new AQS endpoint (i.e., aqs1010; localhost:7232), and ensure that they all respond with 404 (because no data is loaded into Cassandra yet)
• Run the Oozie job to load the data into Cassandra
• Manually run a few queries against the new AQS endpoint, and ensure that they all respond with the proper responses, as the data should now be loaded into Cassandra
• Submit a pull request for the restbase repository on GitHub with the schema of the new endpoint added; Now the endpoint should be publicly accessible!
• Update all relevant documentation

## Deployment

This step-by-step serves for deploying to both staging (beta) and production. Watch out for specific differences between beta and prod in each step of this section.

### Step 0: Testing AQS locally

#### With cassandra

Testing your change in our staging environment (beta) requires either having a stable patch merged in AQS and deployed through scap, or a lot of git black magic and messing around that you shouldn't do. A good solution for quick testing is setting up your own mini AQS in your local machine where you can make changes to the APIs instantly, update dependencies, load data... without switching between machines or sending gerrit patches.

1. Install Zookeeper (brew install zookeeper on mac).
2. Install Cassandra (brew install cassandra@2.2 on mac. Be aware that without the @2.2, brew will install version 3, which we don't have yet in production).
3. Make sure you're using the right Java version (8). Cassandra will complain a lot about Java 9 and 10, so make sure that your JAVA_HOME environment variable points to your Java 8 installation (/usr/libexec/java_home -V will show the versions currently installed). To do that, set export JAVA_HOME=/usr/libexec/java_home -v 1.8
4. Once the Cassandra service is running, start AQS by running the server with the default config provided on the repo: ./server.js -c config.example.wikimedia.yaml
5. To load data or make changes in Cassandra, run cqlsh

#### With druid

The easiest to test AQS druid integration is to use the production druid cluster (AQS can only query druid, no data loss is possible). This is doable by following those steps:

1. Start an SSH tunnel between your machine and the druid-public broker : ssh -N druid1010.eqiad.wmnet -L 8082:druid-public-broker.svc.eqiad.wmnet:8082
2. Start AQS locally with the appropriate configuration, as suggested in this gerrit patch (WARNING: Update the datasources: mediawiki_history to the correct value for testing).
3. You should be able to query your local AQS for druid-oriented queries (for instance: http://localhost:7231/analytics.wikimedia.org/v1/edits/aggregate/all-projects/all-editor-types/all-page-types/monthly/20180101/20190101)

### Step 1: Update the AQS deploy repository

Note: Be aware that this process requires having Docker installed as an instantiation of docker is done when building.

Note: Even if you're deploying to staging (beta), the code you want to deploy should be merged to master. Otherwise, the whole deployment process won't work.

• If it's the first time you deploy:
• Get the deploy repository: git clone ssh://$USER@gerrit.wikimedia.org:29418/analytics/aqs/deploy . • Make sure AQS source git repo has the deploy.dir config variable set (see Services/FirstDeployment#Local Git). • Run npm install in the source repository and make sure that no error is returned. Do also the same thing with npm test • Are you deploying a new endpoint? You need to add a bit of code to the fake data script that matches the x-amples definition in AQS's v1 yaml. Otherwise endpoint checks will fail on deployment. An alternative is to set x-monitor to false, in which case your new endpoints won't get checked (tip: while this fixes the deploy, not testing the endpoint is not advised). • Then (regardless if first time or not): • Make sure both aqs-deploy and aqs repositories are on master, have latest, are clean, including submodules updated • Follow Services/Deployment#Preparing_the_Deploy_Repository (basically, run ./server.js build --deploy-repo --force --review -c config.test.yaml in the source folder). • Check that src's sha1 in the review corresponds to the code you want to deploy). • Merge the newly created change to aqs deploy repo to master. #### Issues with "src" path Remove src path from deploy repo. (We're not sure why this was added to the docs, we should discuss and explain or remove.) #### Issues with git review It uses git review only if you pass it the --review param, omit it and it will not try to submit patch, it will commit it but it will not be pushed. Sometimes the build hangs. In this case, check the sync-repo branch of the deploy repository. It should have the commit in there and that can be pushed to gerrit. It's ok to kill the build if it's been hanging for a while. #### NPM vulnerabilities Whenever possible, it is convenient to run npm audit and make sure that no dependencies pose a threat to the service. Most vulnerabilities will be solved by upgrading packages, but in some cases they will correspond to a second or third-level dependency that can only be upgraded by forcing versions in package-lock.json . Forcing versions can be avoided if you are certain that the code carrying the vulnerability will not be run by AQS (task T207945 is an example of this). If this is not the case, you can enforce the new version by editing package-lock.json and making sure that the version change doesn't break tests. See note about hoek npm vulnerability here: https://phabricator.wikimedia.org/T206474 NPM has more information about dealing with vulnerabilities here. ### Step 2: Deploy using scap • Tell the #wikimedia-analytics and #wikimedia-operations IRC channels that you are deploying (use !log for instance) • Ssh into the deployment machine that suits your needs: • For staging (beta) use: deployment-deploy01.deployment-prep.eqiad1.wikimedia.cloud. • For production use: deployment.eqiad.wmnet . • Execute scap: • cd /srv/deployment/analytics/aqs/deploy • git pull • git submodule update --init • scap deploy "YOUR DEPLOYMENT MESSAGE" • [optional] To see more detailed error logs during deployment, run scap deploy-log from /srv/deployment/analytics/aqs/deploy while you deploy. Note: after T156049 scap will deploy only to aqs1010 (or deployment-aqs01 in case of beta) as first step (canary) and it will ask for confirmation before proceeding to the rest of the cluster. After that, it will deploy to one host at the time serially. You can force scap to ask for confirmation after each host or not, but telling him to proceed to all the other hosts (after the canary) will not cause a deployment to all of them at the same time, since the previously mentioned constraint will hold. Each host will be de-pooled from the load-balancer before the aqs restart, and re-pooled after that. ### Step 3: Test #### Staging (beta) Beta thus far just has a modest dataset with pageviews to Barack Obama page in 2016 from es.wikipedia, en.wikipedia and de.wikipedia You can run some queries like the following to see that aqs is running well:  wget http://localhost:7232/analytics.wikimedia.org/v1/pageviews/   curl http://localhost:7232/analytics.wikimedia.org/v1/pageviews/per-article/de.wikipedia/all-access/all-agents/Barack_Obama/daily/2016010100/2016020200  Should return daily records curl http://localhost:7232/analytics.wikimedia.org/v1/pageviews/per-article/de.wikipedia/all-access/all-agents/Barack_Obama/monthly/2016010100/2016020200  Should return monthly records curl http://localhost:7232/analytics.wikimedia.org/v1/pageviews/aggregate/en.wikipedia/all-access/all-agents/daily/2015100100/2016103100  Should return aggreggate data for en.wikipedia, if any curl http://localhost:7232/analytics.wikimedia.org/v1/pageviews/aggregate/es.wikipedia/all-access/all-agents/monthly/2015100100/2016103100  Should return monthly aggreggate data for en.wikipedia #### Production From (one of) the deployed machine, run /srv/deployment/analytics/aqs/deploy/test/test_local_aqs_urls.sh. ### Troubleshooting Deployment #### Issues with deployment to labs deploy had to: SSH_AUTH_SOCK=/run/keyholder/proxy.sock ssh -l deploy-service deployment-aqs01.deployment-prep.eqiad1.wikimedia.cloud  #### Issues with scap • Depool machine • Delete deployment directory • Run puppet • Try to deploy again. #### Check deploy logs: scap deploy-log -v  #### Check AQS logs: sudo journalctl -u aqs  Journalctl might not have a lot of information since by default Restbase is configured to push logs to logstash. So in order to disable this behavior, remove the following from the AQS configuration file under /etc: logging: name: aqs level: warn streams: - # XXX: Use gelf-stream -> logstash - - type: gelf - host: localhost - port: 12201  Manual AQS restart: sudo systemctl restart aqs  ## Administration ### Cassandra CLI Cqlsh is a python-based CLI for executing Cassandra Query Language commands. To start cqlsh in beta (password is public, this is labs): cqlsh -u cassandra -p cassandra 172.16.4.205  ### Load data into cassandra in beta 1. Generate a CSV with the data you want to load. You have basically 2 options: • Generate it via a query to production cassandra: cqlsh -u user -p pwd aqs1004-a -e "select <<see below for column list>> from \"local_group_default_T_pageviews_per_article_flat\".data where article='Barack_Obama' and timestamp >'2016010100' and timestamp <'2017012000' and project in ('en.wikipedia', 'de.wikipedia' , 'jp.wikipedia', 'es.wikipedia') and granularity='daily' and \"_domain\"='analytics.wikimedia.org' " > out.csv • This will generate a file separated by | with a header and footer, so you have to adjust it manually. • Generate it yourself. If you do this, take the following into account: • You have to include the underscore-prefixed columns of your table, i.e. _domain or _tid. Look at the table description to get them. • The _tid column needs to have valid timeuuid values. You can grab an existing _tid value from the data that is already loaded in another table. It's OK for testing purposes to give the same _tid value to all rows. • The column _del (that exists in all tables) must be left out. It should not be populated, otherwise the table will interpret the record as deleted. • Be careful with the values you insert. The COPY command checks for data types, but not for value correctness (as an insert statement would). So if you insert values that do not match the possible options for that column, your queries may not find the data. Example: If a column accepts a string among (a, b, c), and you give it d, the COPY command will not complain, but you'll not be able to find any data with your queries. • The CSV should have no header. 2. move data into beta (deployment-aqs01.deployment-prep.eqiad1.wikimedia.cloud) 3. load data into beta using cqlsh COPY command: cqlsh -u cassandra -p cassandra 172.16.4.205 • Generate INSERT statements like the following: insert into "local_group_default_T_pageviews_per_article_flat".data ("_domain", project, article, granularity, timestamp, "_tid", aa, ab, as, au, da, db, ds, du, maa, mab, mas, mau, mwa, mwb, mws, mwu) VALUES ('analytics.wikimedia.org','de.wikipedia','Barack_Obama','daily','2016010200', 13814000-1dd2-11b2-8080-808080808080,null,3527,null,28,3499,1398,null,22,1376,145,null,null,145,1984,null,6,1978); copy "local_group_default_T_pageviews_per_article_flat".data ("_domain", "project", "article", "granularity", "timestamp", "_tid", "aa", "ab", "as", "au", "da", "db", "ds", "du", "maa", "mab", "mas", "mau", "mwa", "mwb", "mws", "mwu") from '/home/your_user/cassandra_test_input.csv'; ### Restbase status On the host to check live requests: elukey@aqs1003:~$ sudo httpry -i eth0 tcp


Check Restbase status:

elukey@aqs1003:~$systemctl status aqs ● aqs.service - "aqs service" Loaded: loaded (/lib/systemd/system/aqs.service; enabled) Active: active (running) since Tue 2016-05-17 15:45:58 UTC; 1 day 21h ago Main PID: 25226 (firejail) CGroup: /system.slice/aqs.service ├─25226 /usr/bin/firejail --blacklist=root --blacklist=/home/* --tmpfs=/tmp --caps --seccomp /usr/bin/nodejs src/server.js -c /etc/aqs/config.yaml ├─25227 /usr/bin/nodejs src/server.js -c /etc/aqs/config.yaml ├─25254 /usr/bin/nodejs /srv/deployment/analytics/aqs/deploy-cache/revs/a38e4d78718b072a70514477c3b268baaf8e1d29/src/server.js -c /etc/aqs/config.yaml [...] ├─25493 /usr/bin/nodejs /srv/deployment/analytics/aqs/deploy-cache/revs/a38e4d78718b072a70514477c3b268baaf8e1d29/src/server.js -c /etc/aqs/config.yaml └─25504 /usr/bin/nodejs /srv/deployment/analytics/aqs/deploy-cache/revs/a38e4d78718b072a70514477c3b268baaf8e1d29/src/server.js -c /etc/aqs/config.yaml  ### Cassandra status Check Cassandra cluster status (UN == Up Normal): # Please note the -a suffix, there is also another instance that can be inspected using -b elukey@aqs1004:~$ nodetool-a status
=================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
UN  10.64.48.148  1.6 TB     256          24.5%             ec437eff-af17-4863-b6ff-42f87ea86557  rack3
UN  10.64.0.213   1.8 TB     256          23.1%             c1fcaa1e-fc38-4597-8794-a37d9831df74  rack1
UN  10.64.48.149  1.58 TB    256          24.4%             4d24db1d-fc2a-4ec9-9d43-3952d480ff7e  rack3
UN  10.64.16.74   1.67 TB    256          24.9%             7d8443d7-3b81-401a-a46e-d15316d69a56  rack2
UN  10.64.48.122  1.81 TB    256          26.1%             c1e9333f-2e7a-48cc-a0cc-c4db53930c22  rack3
UN  10.64.48.123  1.68 TB    256          25.0%             a4cade35-16cd-427c-ac77-a51d3d12c3a3  rack3
UN  10.64.32.189  1.59 TB    256          24.1%             de1f9797-9ee0-472f-9713-e9bc3c8a1949  rack2
UN  10.64.0.237   1.83 TB    256          26.8%             7f25e4fb-e1b5-4ae3-916d-446f94f4cca9  rack1
UN  10.64.32.190  1.64 TB    256          24.5%             38b46448-a547-4a4f-9e96-35a0e28ee796  rack2
UN  10.64.16.78   1.82 TB    256          26.6%             ab0da954-4db8-4e68-8a84-7bca0cf7e8c4  rack2
UN  10.64.0.126   1.77 TB    256          25.7%             a6c7480a-7f94-4488-a925-0cff98c5841a  rack1
UN  10.64.0.127   1.61 TB    256          24.3%             ed33d9e1-a654-4ca6-a232-bf97f32206ba  rack1

elukey@aqs1004:~$nodetool-a info ID : a6c7480a-7f94-4488-a925-0cff98c5841a Gossip active : true Thrift active : false Native Transport active: true Load : 1.77 TB Generation No : 1606380190 Uptime (seconds) : 684961 Heap Memory (MB) : 8855.14 / 16384.00 Off Heap Memory (MB) : 3331.05 Data Center : eqiad Rack : rack1 Exceptions : 0 Key Cache : entries 977802, size 400 MB, capacity 400 MB, 29643458 hits, 58426030 requests, 0.507 recent hit rate, 14400 save period in seconds Row Cache : entries 0, size 0 bytes, capacity 200 MB, 0 hits, 0 requests, NaN recent hit rate, 0 save period in seconds Counter Cache : entries 0, size 0 bytes, capacity 50 MB, 0 hits, 0 requests, NaN recent hit rate, 7200 save period in seconds Token : (invoke with -T/--tokens to see all 256 tokens)  ### Cassandra logs Most useful one is /var/log/cassandra/system.log, that becomes -a and -b on aqs100[456] since we have two cassandra instances running: elukey@aqs1004:/var/log/cassandra$ ls
gc-a.log.0.current  gc-b.log.0.current	system-a.log  system-b.log  system.log


### Network Configuration

The AQS IPs are deployed in the Production network, meanwhile the Hadoop IPs are running in the Analytics network. The traffic flow is guarded by ACLs on switches/routers that needs to be updated if you need to connect new AQS IPs to the Analytics network. For example, this is the error that we were getting from analytics1* hosts while trying to upload data to the aqs1010-a.eqiad.wmnet Cassandra instance:

Caused by: com.datastax.driver.core.exceptions.NoHostAvailableException:
All host(s) tried for query failed


To solve the issue ops extended the existing ACL for aqs100[123].eqiad.wmnet to allow all the Cassandra Instances IPs too.

### Deploy new History snapshot for Wikistats Backend

As of Q4 2018 every snapshot of mediawiki history we load into druid is a new datasource named after the snapshot. For example: "mediawiki-2021-10" AQS will not serve this data until told to do so (this is so we can actually rollback to a prior snapshot easily). In order to enable a new snapshot you need to change the hiera config for AQS that points to the active snapshot. See patch for example:

https://gerrit.wikimedia.org/r/c/operations/puppet/+/736542 (note the two files you need to change it in). Once merged and applied, you'll need to restart the aqs servers to have it take effect, and the safest way to do it is to ask an SRE to run the following from one of the cluster management hosts (cumin1001.eqiad.wmnet, cumin2002.codfw.wmnet):

# Ensure that the new config is deployed on all hosts
elukey@cumin1001:~$sudo cumin 'A:aqs' 'run-puppet-agent' # Roll restart the aqs nodejs daemon elukey@cumin1001:~$ sudo cookbook sre.aqs.roll-restart aqs


The cookbook does the following:

• depool the aqs-canary (aqs1010 currently) from LVS, restarts aqs and wait for an input before proceeding. This step is needed to allow people to test the new AQS settings before proceeding.
• To test aqs on the canary, ssh onto aqs1010 and make a request to access new data by changing the end date to be in the future, for example:
curl http://localhost:7232/analytics.wikimedia.org/v1/edits/aggregate/all-projects/all-editor-types/all-page-types/monthly/$(date --date "last month" "+%Y%m0100")/$(date "+%Y%m0100")

• repools the aqs canary, and then roll restart all the nodes (depool/restart/repool).

For SREs: in case something is wrong when testing the canary, you can simply control+c the cookbook. After that, rollback the config, run puppet and the repool the aqs node (there are various ways to do it but the quickest is to run sudo -i pool on the node itself).

A quick note on caching. After deploying a new snapshot, you can check the data by hitting AQS directly with curl:

https://wikimedia.org/api/rest_v1/metrics/edits/aggregate/all-projects/all-editor-types/all-page-types/monthly/2017060100/2019070500

Real people out in the world won't see the new data until they also clear cache or it expires (14400 seconds / 4 hours).

### Useful comands

See: /etc/aqs/config.yaml

See table schema:

cassandra@cqlsh> describe table "local_group_default_T_pageviews_per_article_flat".data


### Add fake data to Cassandra after wiping the cluster

cqlsh -u cassandra -p cassandra aqs1004-a -f /srv/deployment/analytics/aqs/deploy/scripts/insert_monitoring_fake_data.cql


This commands will ensure that no AQS related alarm will fire.