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Atomic eval insertion with job (de-)registration #8435

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merged 5 commits into from
Jul 15, 2020
Merged

Atomic eval insertion with job (de-)registration #8435

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97c69ee
Atomic eval insertion with job (de-)registration
Jul 10, 2020
6a082ad
time.Now().UTC().UnixNano() -> time.Now().UnixNano()
Jul 15, 2020
a6a96c4
only set args.Eval after all servers upgrade
Jul 15, 2020
921a42b
no need to handle duplicate evals anymore
Jul 15, 2020
37ad947
comment compat concern in fsm.go
Jul 15, 2020
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32 changes: 29 additions & 3 deletions nomad/fsm.go
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Original file line number Diff line number Diff line change
Expand Up @@ -555,6 +555,13 @@ func (n *nomadFSM) applyUpsertJob(buf []byte, index uint64) interface{} {
}
}

if req.Eval != nil {
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req.Eval.JobModifyIndex = index
if err := n.upsertEvals(index, []*structs.Evaluation{req.Eval}); err != nil {
return err
}
}

return nil
}

Expand All @@ -565,14 +572,30 @@ func (n *nomadFSM) applyDeregisterJob(buf []byte, index uint64) interface{} {
panic(fmt.Errorf("failed to decode request: %v", err))
}

return n.state.WithWriteTransaction(func(tx state.Txn) error {
if err := n.handleJobDeregister(index, req.JobID, req.Namespace, req.Purge, tx); err != nil {
err := n.state.WithWriteTransaction(func(tx state.Txn) error {
err := n.handleJobDeregister(index, req.JobID, req.Namespace, req.Purge, tx)

if err != nil {
n.logger.Error("deregistering job failed", "error", err)
return err
}

return nil
})

// always attempt upsert eval even if job deregister fail
if req.Eval != nil {
req.Eval.JobModifyIndex = index
if err := n.upsertEvals(index, []*structs.Evaluation{req.Eval}); err != nil {
return err
}
}
Comment on lines +590 to +596
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Note that here we attempt to insert the eval even if the job deregistration fails. I find this behavior very odd but it's explicitly tested in

nomad/nomad/job_endpoint_test.go

Line 2969 in 97c69ee

func TestJobEndpoint_Deregister_Nonexistent(t *testing.T) {
- with it insuring that the resulting eval is populated and have JobModifyIndex set ?! I kept the behavior the same

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Maybe this was intended to protect against the previous non-atomic behavior? Ex. if you deregister but the eval wasn't persisted, but then tried to deregister again, the job would be potentially gone but you'd still want an eval to clean it up?

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This actually seems like a bug to me, but I think one that does not impact correctness (only waste some work doing nothing).

From peeking around generic_sched.go and reconcile.go, I'm not seeing us check if the evaluation is a Deregister. We always seem to checked if Job.Stopped is true! This means if we fail to update the statestore with the stopped Job, the Deregister evaluation will be the same as any other evaluation and end up being a noop for the job as it is not stopped and presumably already scheduled/allocated.

I suspect that @tgross is correct and that the test is merely asserting the non-atomic behavior existed: #981

Since we're making Job+Eval submissions atomic, I think we should at least trying to make this section atomic as well. I can't figure out where a Deregister eval for a non-Stopped job would have a desirable affect, but perhaps somebody else can find a case?

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I'm inclined to let the current behavior stand as-is, as stopping making an eval is a user visible change. Will follow up in another PR and we can discuss this issue further there.

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I'm inclined to let the current behavior stand as-is, as stopping making an eval is a user visible change.

I don't find this reason sufficient to keep it since the eval in question is a dereg but the effect would be a noop. If that's the behavior I feel like we're emitting a useless and actively misleading eval which should be treated like a bug and removed. There's no benefit to leaving it in place as anyone observing it would only be confused by its lack of affect.

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I agree that it should be changed - but I believe such a user-visible behavior (albeit a small one) change is outside the scope of this PR, so I will follow up in another PR.


if err != nil {
return err
}

return nil
}

func (n *nomadFSM) applyBatchDeregisterJob(buf []byte, index uint64) interface{} {
Expand Down Expand Up @@ -663,7 +686,10 @@ func (n *nomadFSM) applyUpdateEval(buf []byte, index uint64) interface{} {
}

func (n *nomadFSM) upsertEvals(index uint64, evals []*structs.Evaluation) error {
if err := n.state.UpsertEvals(index, evals); err != nil {
if err := n.state.UpsertEvals(index, evals); len(evals) == 1 && err == state.ErrDuplicateEval {
// the request is a duplicate, ignore processing it
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return nil
} else if err != nil {
n.logger.Error("UpsertEvals failed", "error", err)
return err
}
Expand Down
160 changes: 91 additions & 69 deletions nomad/job_endpoint.go
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Original file line number Diff line number Diff line change
Expand Up @@ -312,10 +312,31 @@ func (j *Job) Register(args *structs.JobRegisterRequest, reply *structs.JobRegis
return err
}

// Create a new evaluation
now := time.Now().UTC().UnixNano()
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submittedEval := false

// Set the submit time
args.Job.SubmitTime = time.Now().UTC().UnixNano()
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// If the job is periodic or parameterized, we don't create an eval.
if !(args.Job.IsPeriodic() || args.Job.IsParameterized()) {
args.Eval = &structs.Evaluation{
ID: uuid.Generate(),
Namespace: args.RequestNamespace(),
Priority: args.Job.Priority,
Type: args.Job.Type,
TriggeredBy: structs.EvalTriggerJobRegister,
JobID: args.Job.ID,
Status: structs.EvalStatusPending,
CreateTime: now,
ModifyTime: now,
}
reply.EvalID = args.Eval.ID
}

// Check if the job has changed at all
if existingJob == nil || existingJob.SpecChanged(args.Job) {
// Set the submit time
args.Job.SetSubmitTime()

// Commit this update via Raft
fsmErr, index, err := j.srv.raftApply(structs.JobRegisterRequestType, args)
Expand All @@ -328,52 +349,51 @@ func (j *Job) Register(args *structs.JobRegisterRequest, reply *structs.JobRegis
return err
}

submittedEval = true

// Populate the reply with job information
reply.JobModifyIndex = index
reply.Index = index

if args.Eval != nil {
reply.EvalCreateIndex = index
}

} else {
reply.JobModifyIndex = existingJob.JobModifyIndex
}

// used for multiregion start
args.Job.JobModifyIndex = reply.JobModifyIndex

// If the job is periodic or parameterized, we don't create an eval.
if args.Job.IsPeriodic() || args.Job.IsParameterized() {
if args.Eval == nil {
return nil
}

// Create a new evaluation
now := time.Now().UTC().UnixNano()
eval := &structs.Evaluation{
ID: uuid.Generate(),
Namespace: args.RequestNamespace(),
Priority: args.Job.Priority,
Type: args.Job.Type,
TriggeredBy: structs.EvalTriggerJobRegister,
JobID: args.Job.ID,
JobModifyIndex: reply.JobModifyIndex,
Status: structs.EvalStatusPending,
CreateTime: now,
ModifyTime: now,
}
update := &structs.EvalUpdateRequest{
Evals: []*structs.Evaluation{eval},
WriteRequest: structs.WriteRequest{Region: args.Region},
}
// COMPAT(1.1.0): Remove the ServerMeetMinimumVersion check.
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// 0.12.1 introduced atomic eval job registration
if args.Eval != nil &&
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@tgross tgross Jul 14, 2020 •
edited

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I think this args.Eval != nil is always true; we're returning early from checking args.Eval == nil right above it.

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Actually, do we need to remove the returning early above for multi region deployment? Returning early means that periodic/dispatch jobs will not be handled by multiregionStart? This PR doesn't change the behavior, but just noticed the MRD call.

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@tgross tgross Jul 14, 2020 •
edited

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Periodic and dispatch jobs get kicked off with their normal dispatch mechanisms in MRD. We special case them in schedule/reconcile.go, rather than running them through the MRD in deploymentwatcher. (There might be future work there but that's a later phase of work.)

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In that case, I'm tempted to remove the early return and somehow make it more multiregionStart that doesn't apply to paramterized/periodic jobs.

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Not a bad idea. There's a big blog of return nil at the top of the ENT functionality where we return early when we don't need it.

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Actually, I'll follow up in another PR - I'm a bit confused about the interaction and would love to do more testing.

!(submittedEval && ServersMeetMinimumVersion(j.srv.Members(), minJobRegisterAtomicEvalVersion, false)) {
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args.Eval.JobModifyIndex = reply.JobModifyIndex
update := &structs.EvalUpdateRequest{
Evals: []*structs.Evaluation{args.Eval},
WriteRequest: structs.WriteRequest{Region: args.Region},
}

// Commit this evaluation via Raft
// XXX: There is a risk of partial failure where the JobRegister succeeds
// but that the EvalUpdate does not.
_, evalIndex, err := j.srv.raftApply(structs.EvalUpdateRequestType, update)
if err != nil {
j.logger.Error("eval create failed", "error", err, "method", "register")
return err
}
// Commit this evaluation via Raft
// There is a risk of partial failure where the JobRegister succeeds
// but that the EvalUpdate does not, before 0.12.1
_, evalIndex, err := j.srv.raftApply(structs.EvalUpdateRequestType, update)
if err != nil {
j.logger.Error("eval create failed", "error", err, "method", "register")
return err
}

// Populate the reply with eval information
reply.EvalID = eval.ID
reply.EvalCreateIndex = evalIndex
reply.Index = evalIndex
if !submittedEval {
reply.EvalCreateIndex = evalIndex
reply.Index = evalIndex
}
}

// Kick off a multiregion deployment (enterprise only).
if isRunner {
Expand Down Expand Up @@ -766,6 +786,25 @@ func (j *Job) Deregister(args *structs.JobDeregisterRequest, reply *structs.JobD
}
}

// The job priority / type is strange for this, since it's not a high
// priority even if the job was.
now := time.Now().UTC().UnixNano()
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// If the job is periodic or parameterized, we don't create an eval.
if job == nil || !(job.IsPeriodic() || job.IsParameterized()) {
args.Eval = &structs.Evaluation{
ID: uuid.Generate(),
Namespace: args.RequestNamespace(),
Priority: structs.JobDefaultPriority,
Type: structs.JobTypeService,
TriggeredBy: structs.EvalTriggerJobDeregister,
JobID: args.JobID,
Status: structs.EvalStatusPending,
CreateTime: now,
ModifyTime: now,
}
reply.EvalID = args.Eval.ID
}

// Commit the job update via Raft
_, index, err := j.srv.raftApply(structs.JobDeregisterRequestType, args)
if err != nil {
Expand All @@ -775,6 +814,8 @@ func (j *Job) Deregister(args *structs.JobDeregisterRequest, reply *structs.JobD

// Populate the reply with job information
reply.JobModifyIndex = index
reply.EvalCreateIndex = index
reply.Index = index

// Make a raft apply to release the CSI volume claims of terminal allocs.
var result *multierror.Error
Expand All @@ -783,44 +824,25 @@ func (j *Job) Deregister(args *structs.JobDeregisterRequest, reply *structs.JobD
result = multierror.Append(result, err)
}

// If the job is periodic or parameterized, we don't create an eval.
if job != nil && (job.IsPeriodic() || job.IsParameterized()) {
return nil
}

// Create a new evaluation
// XXX: The job priority / type is strange for this, since it's not a high
// priority even if the job was.
now := time.Now().UTC().UnixNano()
eval := &structs.Evaluation{
ID: uuid.Generate(),
Namespace: args.RequestNamespace(),
Priority: structs.JobDefaultPriority,
Type: structs.JobTypeService,
TriggeredBy: structs.EvalTriggerJobDeregister,
JobID: args.JobID,
JobModifyIndex: index,
Status: structs.EvalStatusPending,
CreateTime: now,
ModifyTime: now,
}
update := &structs.EvalUpdateRequest{
Evals: []*structs.Evaluation{eval},
WriteRequest: structs.WriteRequest{Region: args.Region},
}
// COMPAT(1.1.0) - 0.12.1 introduced atomic job deregistration eval
if args.Eval != nil &&
!ServersMeetMinimumVersion(j.srv.Members(), minJobRegisterAtomicEvalVersion, false) {
// Create a new evaluation
args.Eval.JobModifyIndex = index
update := &structs.EvalUpdateRequest{
Evals: []*structs.Evaluation{args.Eval},
WriteRequest: structs.WriteRequest{Region: args.Region},
}

// Commit this evaluation via Raft
_, evalIndex, err := j.srv.raftApply(structs.EvalUpdateRequestType, update)
if err != nil {
result = multierror.Append(result, err)
j.logger.Error("eval create failed", "error", err, "method", "deregister")
return result.ErrorOrNil()
// Commit this evaluation via Raft
_, _, err := j.srv.raftApply(structs.EvalUpdateRequestType, update)
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if err != nil {
result = multierror.Append(result, err)
j.logger.Error("eval create failed", "error", err, "method", "deregister")
return result.ErrorOrNil()
}
}

// Populate the reply with eval information
reply.EvalID = eval.ID
reply.EvalCreateIndex = evalIndex
reply.Index = evalIndex
return result.ErrorOrNil()
}

Expand Down