Auto merge of #22424 - servo:tc-docs, r=Manishearth

Add documentation on Treeherder

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etc/taskcluster/README.md

@@ -193,8 +193,7 @@ daily tasks are indexed under the [`project.servo.servo.daily`] namespace.
 
 ## AWS EC2 workers
 
-As of this writing, Servo on Taskcluster can only use the `servo-docker-worker` worker type.
-Tasks scheduled with this worker type run in a Linux environment,
+Tasks scheduled with the `servo-docker-worker` worker type run in a Linux environment,
 in a Docker container, on an AWS EC2 virtual machine.
 
 These machines are short-lived “spot instances”.
@@ -213,6 +212,20 @@ in particular with the types of EC2 instances to be used.
 [worker type definition]: https://tools.taskcluster.net/aws-provisioner/servo-docker-worker/view
 
 
+## Other worker types
+
+See respective `README.md` files for:
+
+* [Windows](windows/README.md), also short-lived workers on EC2
+* [macOS](macos/README.md), Mac Minis hosted by Macstadium
+* [Non-virtualized Linux](packet.net/README.md), hosted by Packet.net
+
+
+## Taskcluster − Treeherder integration
+
+See [`treeherder.md`](treeherder.md).
+
+
 ## Self-service, Bugzilla, and IRC
 
 Taskcluster is designed to be “self-service” as much as possible,

etc/taskcluster/macos/README.md

@@ -15,6 +15,18 @@ cd etc/taskcluster/macos
 ./salt-ssh '*' state.apply test=True
 ```
 
+## Troubleshooting
+
+SSH into `servo-tc-mac1.servo.org`.
+`generic-worker` logs are in `less /Users/worker/stderr.log`.
+
+If the worker seems stuck but nothing seems wrong in the log,
+try running `launchctl stop net.generic.worker`.
+(It is configured to restart automatically.)
+This issue is tracked at
+[generic-worker#133](https://github.com/taskcluster/generic-worker/issues/133).
+
+
 ## (Re)deploying a server
 
 * Place an order or file a ticket with MacStadium to get a new hardware or reinstall an OS.

etc/taskcluster/treeherder.md

@@ -0,0 +1,105 @@
+# Treeherder for Servo
+
+Treeherder is tool for visualizing the status of “trees”,
+meaning branches in various source repositories.
+It shows each push to the repository with the corresponding commits
+as well as the CI jobs that were started for that push.
+While it is possible to write other tools that submit job data,
+CI integration is easiest with Taskcluster.
+
+* [Production instance](https://treeherder.mozilla.org/)
+* [Staging instance](https://treeherder.allizom.org/)
+* [Source code](https://github.com/mozilla/treeherder/)
+
+
+## Trees / repositories / branches
+
+Treeherders knows a about a number of *repostories*.
+Mercurial on Mozilla’s servers and git on GitHub are supported.
+Despite the name, in the GitHub case
+each Treeherder repository maps to one branch in a git repository.
+They are configured in the [`repository.json`] file.
+As of this writing there are four for `github.com/servo/servo`,
+named after the corresponding branch:
+
+[`repository.json`]: https://github.com/mozilla/treeherder/blob/master/treeherder/model/fixtures/repository.json
+
+* [`servo-master`](https://treeherder.mozilla.org/#/jobs?repo=servo-master)
+* [`servo-auto`](https://treeherder.mozilla.org/#/jobs?repo=servo-auto)
+* [`servo-try`](https://treeherder.mozilla.org/#/jobs?repo=servo-try)
+* [`servo-try-taskcluster`](https://treeherder.mozilla.org/#/jobs?repo=servo-try-taskcluster)
+
+In the UI, the “Repos” button near the top right corner allows switching.
+
+`servo-auto` is the relevant one when a pull request is approved with Homu for landing,
+since the `auto` branch is where it pushes a merge commit for testing.
+
+
+## Data flow / how it all works
+
+(This section is mostly useful for future changes or troubleshooting.)
+
+Changes to the Treeherder repository are deployed to Staging
+soon (minutes) after they are merged on GitHub,
+and to Production manually at some point later.
+See [current deployment status](https://whatsdeployed.io/s-dqv).
+
+Once a configuration change with a new repository/branch is deployed,
+Treeherder will show it in its UI and start recording push and job data in its database.
+This data comes from [Pulse], Mozilla’s shared message queue that coordinates separate services.
+The [Pulse Inspector] shows messages as they come (though not in the past),
+which can be useful for debugging.
+Note that you need to add at least one “Binding”,
+or the “Start Listening” button won’t do anything.
+
+[Pulse]: https://wiki.mozilla.org/Auto-tools/Projects/Pulse
+[Pulse Inspector]: https://tools.taskcluster.net/pulse-inspector
+
+
+### Push data
+
+When [taskcluster-github] is [enabled] on a repository,
+it recieves [webhooks] from GitHub for various events
+such as a push to a branch of the repository.
+
+In addition to starting Taskcluster tasks based on `.taskcluster.yml` in the repository,
+in [`api.js`] it creates [Pulse messages] corresponding to those events.
+Treeherder consumes messages from the `exchange/taskcluster-github/v1/push` exchange
+(among others) in [`push_loader.py`].
+In Pulse Inspector, these messages for the Servo repository can be seen
+by specifying the [`primary.servo.servo`] routing key pattern.
+
+[taskcluster-github]: https://github.com/taskcluster/taskcluster-github
+[enabled]: https://github.com/apps/taskcluster
+[webhooks]: https://developer.github.com/webhooks/
+[Pulse messages]: https://docs.taskcluster.net/docs/reference/integrations/taskcluster-github/references/events
+[`api.js`]: https://github.com/taskcluster/taskcluster-github/blob/master/src/api.js
+[`push_loader.py`]: https://github.com/mozilla/treeherder/blob/master/treeherder/etl/push_loader.py
+[`primary.servo.servo`]: https://tools.taskcluster.net/pulse-inspector?bindings%5B0%5D%5Bexchange%5D=exchange%2Ftaskcluster-github%2Fv1%2Fpush&bindings%5B0%5D%5BroutingKeyPattern%5D=primary.servo.servo
+
+
+### (Taskcluster) job data
+
+The Taskcluster Queue generates a number of [Pulse messages about tasks].
+Each value of the `routes` array in the task definition, with a `route.` prefix prepended,
+is additional routing key for those messages.
+
+The [taskcluster-treeherder] integration service reads those messages
+if they have an appropriate route ([see in Pulse inspector][inspector1]),
+and converts them into [other messages] ([see in Pulse inspector][inspector2]).
+However, it will drop an incoming message
+if the `extra.treeherder` object in the task definition doesn’t conform to the [schema].
+Such schema validation errors are logged, but those logs are not easy to access.
+Ask on IRC on `#taskcluster`.
+
+Finally, Treeherder reads that latter kind of message in [`job_loader.py`].
+
+
+
+[Pulse messages about tasks]: https://docs.taskcluster.net/docs/reference/platform/taskcluster-queue/references/events
+[taskcluster-treeherder]: https://github.com/taskcluster/taskcluster-treeherder/
+[other messages]: https://docs.taskcluster.net/docs/reference/integrations/taskcluster-treeherder#job-pulse-messages
+[schema]: https://schemas.taskcluster.net/treeherder/v1/task-treeherder-config.json
+[`job_loader.py`]: https://github.com/mozilla/treeherder/blob/master/treeherder/etl/job_loader.py
+[inspector1]: https://tools.taskcluster.net/pulse-inspector?bindings%5B0%5D%5Bexchange%5D=exchange%2Ftaskcluster-queue%2Fv1%2Ftask-defined&bindings%5B0%5D%5BroutingKeyPattern%5D=route.tc-treeherder.%23
+[inspector2]: https://tools.taskcluster.net/pulse-inspector?bindings%5B0%5D%5Bexchange%5D=exchange%2Ftaskcluster-treeherder%2Fv1%2Fjobs&bindings%5B0%5D%5BroutingKeyPattern%5D=tc-treeherder.servo-auto._

etc/taskcluster/windows/README.md

@@ -1,4 +1,8 @@
-# Windows AMIs for Servo on Taskcluster
+# Windows workers for Servo on Taskcluster
+
+The `servo-win2016` worker type runs short-lived Windows 2016 workers on EC2.
+
+## AMIs
 
 Unlike Linux tasks on `docker-worker` where each tasks is executed in a container
 based on a Docker image provided with the task,