This change modifies the Nomad job register and deregister RPCs to
accept an updated option set which includes eval priority. This
param is optional and override the use of the job priority to set
the eval priority.
In order to ensure all evaluations as a result of the request use
the same eval priority, the priority is shared to the
allocReconciler and deploymentWatcher. This creates a new
distinction between eval priority and job priority.
The Nomad agent HTTP API has been modified to allow setting the
eval priority on job update and delete. To keep consistency with
the current v1 API, job update accepts this as a payload param;
job delete accepts this as a query param.
Any user supplied value is validated within the agent HTTP handler
removing the need to pass invalid requests to the server.
The register and deregister opts functions now all for setting
the eval priority on requests.
The change includes a small change to the DeregisterOpts function
which handles nil opts. This brings the function inline with the
RegisterOpts.
Fix deployment watchers to avoid creating unnecessary deployment watcher goroutines and blocking queries. `deploymentWatcher.getAllocsCh` creates a new goroutine that makes a blocking query to fetch updates of deployment allocs.
## Background
When operators submit a new or updated service job, Nomad create a new deployment by default. The deployment object controls how fast to place the allocations through [`max_parallel`](https://www.nomadproject.io/docs/job-specification/update#max_parallel) and health checks configurations.
The `scheduler` and `deploymentwatcher` package collaborate to achieve deployment logic: The scheduler only places the canaries and `max_parallel` allocations for a new deployment; the `deploymentwatcher` monitors for alloc progress and then enqueues a new evaluation whenever the scheduler should reprocess a job and places the next `max_parallel` round of allocations.
The `deploymentwatcher` package makes blocking queries against the state store, to fetch all deployments and the relevant allocs for each running deployments. If `deploymentwatcher` fails or is hindered from fetching the state, the deployments fail to make progress.
`Deploymentwatcher` logic only runs on the leader.
## Why unnecessary deployment watchers can halt cluster progress
Previously, `getAllocsCh` is called on every for loop iteration in `deploymentWatcher.watch()` function. However, the for-loop may iterate many times before the allocs get updated. In fact, whenever a new deployment is created/updated/deleted, *all* `deploymentWatcher`s get notified through `w.deploymentUpdateCh`. The `getAllocsCh` goroutines and blocking queries spike significantly and grow quadratically with respect to the number of running deployments. The growth leads to two adverse outcomes:
1. it spikes the CPU/Memory usage resulting potentially leading to OOM or very slow processing
2. it activates the [query rate limiter](abaa9c5c5b/nomad/deploymentwatcher/deployment_watcher.go (L896-L898)), so later the watcher fails to get updates and consequently fails to make progress towards placing new allocations for the deployment!
So the cluster fails to catch up and fails to make progress in almost all deployments. The cluster recovers after a leader transition: the deposed leader stops all watchers and free up goroutines and blocking queries; the new leader recreates the watchers without the quadratic growth and remaining under the rate limiter. Well, until a spike of deployments are created triggering the condition again.
### Relevant Code References
Path for deployment monitoring:
* [`Watcher.watchDeployments`](abaa9c5c5b/nomad/deploymentwatcher/deployments_watcher.go (L164-L192)) loops waiting for deployment updates.
* On every deployment update, [`w.getDeploys`](abaa9c5c5b/nomad/deploymentwatcher/deployments_watcher.go (L194-L229)) returns all deployments in the system
* `watchDeployments` calls `w.add(d)` on every active deployment
* which in turns, [updates existing watcher if one is found](abaa9c5c5b/nomad/deploymentwatcher/deployments_watcher.go (L251-L255)).
* The deployment watcher [updates local local deployment field and trigger `deploymentUpdateCh` channel]( abaa9c5c5b/nomad/deploymentwatcher/deployment_watcher.go (L136-L147))
* The [deployment watcher `deploymentUpdateCh` selector is activated](abaa9c5c5b/nomad/deploymentwatcher/deployment_watcher.go (L455-L489)). Most of the time the selector clause is a no-op, because the flow was triggered due to another deployment update
* The `watch` for-loop iterates again and in the previous code we create yet another goroutine and blocking call that risks being rate limited.
Co-authored-by: Tim Gross <tgross@hashicorp.com>
In a deployment with two groups (ex. A and B), if group A's canary becomes
healthy before group B's, the deadline for the overall deployment will be set
to that of group A. When the deployment is promoted, if group A is done it
will not contribute to the next deadline cutoff. Group B's old deadline will
be used instead, which will be in the past and immediately trigger a
deployment progress failure. Reset the progress deadline when the job is
promotion to avoid this bug, and to better conform with implicit user
expectations around how the progress deadline should interact with promotions.
Fixes#9017
The ?resources=true query parameter includes resources in the object
stub listings. Specifically:
- For `/v1/nodes?resources=true` both the `NodeResources` and
`ReservedResources` field are included.
- For `/v1/allocations?resources=true` the `AllocatedResources` field is
included.
The ?task_states=false query parameter removes TaskStates from
/v1/allocations responses. (By default TaskStates are included.)
The field name `Deployment.TaskGroups` contains a map of `DeploymentState`,
which makes it a little harder to follow state updates when combined with
inconsistent naming conventions, particularly when we also have the state
store or actual `TaskGroup`s in scope. This changeset changes all uses to
`dstate` so as not to be confused with actual TaskGroups.
* `nextRegion` should take status parameter
* thread Deployment/Job RPCs thru `nextRegion`
* add `nextRegion` calls to `deploymentwatcher`
* use a better description for paused for peer
Fix an issue in which the deployment watcher would fail the deployment
based on the earliest progress deadline of the deployment regardless of
if the task group has finished.
Further fix an issue where the blocked eval optimization would make it
so no evals were created to progress the deployment. To reproduce this
issue, prior to this commit, you can create a job with two task groups.
The first group has count 1 and resources such that it can not be
placed. The second group has count 3, max_parallel=1, and can be placed.
Run this first and then update the second group to do a deployment. It
will place the first of three, but never progress since there exists a
blocked eval. However, that doesn't capture the fact that there are two
groups being deployed.
Fixes three issues:
1. Retrieving the latest evaluation index was not properly selecting the
greatest index. This would undermine checks we had to reduce the number
of evaluations created when the latest eval index was greater than any
alloc change
2. Fix an issue where the blocking query code was using the incorrect
index such that the index was higher than necassary.
3. Special case handling of blocked evaluation since the create/snapshot
index is no particularly useful since they can be reblocked.
