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fix: move pubsub publishing out of database transactions to avoid conn exhaustion #17648

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Merged
merged 7 commits into from
May 5, 2025
Merged

fix: move pubsub publishing out of database transactions to avoid conn exhaustion #17648

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ba2f90a
fix: move pubsub publishing out of database transactions to avoid con…
dannykopping May 1, 2025
74f5dd7
chore: commentary
dannykopping May 2, 2025
f6909ff
chore: polish
dannykopping May 2, 2025
1c84fac
chore: augment reconciler test to validate that broken publish does n…
dannykopping May 2, 2025
5117a5e
Merge branch 'main' of github.com:/coder/coder into dk/notify-outside-tx
dannykopping May 2, 2025
42cc3f5
chore: make lint
dannykopping May 2, 2025
9ddad0b
fix: only break pubsub after dbgen setup
dannykopping May 5, 2025
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61 changes: 46 additions & 15 deletions enterprise/coderd/prebuilds/reconcile.go
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Original file line number Diff line number Diff line change
Expand Up @@ -40,10 +40,11 @@ type StoreReconciler struct {
registerer prometheus.Registerer
metrics *MetricsCollector

cancelFn context.CancelCauseFunc
running atomic.Bool
stopped atomic.Bool
done chan struct{}
cancelFn context.CancelCauseFunc
running atomic.Bool
stopped atomic.Bool
done chan struct{}
provisionNotifyCh chan database.ProvisionerJob
}

var _ prebuilds.ReconciliationOrchestrator = &StoreReconciler{}
Expand All @@ -56,13 +57,14 @@ func NewStoreReconciler(store database.Store,
registerer prometheus.Registerer,
) *StoreReconciler {
reconciler := &StoreReconciler{
store: store,
pubsub: ps,
logger: logger,
cfg: cfg,
clock: clock,
registerer: registerer,
done: make(chan struct{}, 1),
store: store,
pubsub: ps,
logger: logger,
cfg: cfg,
clock: clock,
registerer: registerer,
done: make(chan struct{}, 1),
provisionNotifyCh: make(chan database.ProvisionerJob, 10),
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Thumb-suck; I want to protect against temporary network/database blips but also don't want to accumulate too many messages.

}

reconciler.metrics = NewMetricsCollector(store, logger, reconciler)
Expand Down Expand Up @@ -100,6 +102,29 @@ func (c *StoreReconciler) Run(ctx context.Context) {
// NOTE: without this atomic bool, Stop might race with Run for the c.cancelFn above.
c.running.Store(true)

// Publish provisioning jobs outside of database transactions.
// A connection is held while a database transaction is active; PGPubsub also tries to acquire a new connection on
// Publish, so we can exhaust available connections.
//
// A single worker dequeues from the channel, which should be sufficient.
// If any messages are missed due to congestion or errors, provisionerdserver has a backup polling mechanism which
// will periodically pick up any queued jobs (see poll(time.Duration) in coderd/provisionerdserver/acquirer.go).
go func() {
for {
select {
case <-c.done:
return
case <-ctx.Done():
return
case job := <-c.provisionNotifyCh:
err := provisionerjobs.PostJob(c.pubsub, job)
if err != nil {
c.logger.Error(ctx, "failed to post provisioner job to pubsub", slog.Error(err))
}
}
}
}()

for {
select {
// TODO: implement pubsub listener to allow reconciling a specific template imperatively once it has been changed,
Expand Down Expand Up @@ -571,10 +596,16 @@ func (c *StoreReconciler) provision(
return xerrors.Errorf("provision workspace: %w", err)
}

err = provisionerjobs.PostJob(c.pubsub, *provisionerJob)
if err != nil {
// Client probably doesn't care about this error, so just log it.
c.logger.Error(ctx, "failed to post provisioner job to pubsub", slog.Error(err))
if provisionerJob == nil {
return nil
}

// Publish provisioner job event outside of transaction.
select {
case c.provisionNotifyCh <- *provisionerJob:
default: // channel full, drop the message; provisioner will pick this job up later with its periodic check, though.
c.logger.Warn(ctx, "provisioner job notification queue full, dropping",
slog.F("job_id", provisionerJob.ID), slog.F("prebuild_id", prebuildID.String()))
}

c.logger.Info(ctx, "prebuild job scheduled", slog.F("transition", transition),
Expand Down
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