How to use Barrage metrics for performance monitoring
Barrage is the name of our IPC table transport. This is a guide of what statistics are recorded and how to access them.
Accessing the Metrics Table
You can access these tables as follows:
bpl = jpy.get_type("io.deephaven.extensions.barrage.BarragePerformanceLog").getInstance()
subs = bpl.getSubscriptionTable()
snaps = bpl.getSnapshotTable()
This is what the subscription table looks like when there are live subscriptions:
This is what the snapshot table looks like after processing a few requests:
Barrage Subscription Metrics Summary
Subscription statistics are presented in percentiles bucketed over a time period.
Here are the various metrics that are recorded by the deephaven-core server:
| Stat Type | Sender / Receiver | Description |
|---|---|---|
| EnqueueMillis | Sender | The time it took to record changes that occurred during a single update graph cycle |
| AggregateMillis | Sender | The time it took to aggregate multiple updates within the same interval |
| PropagateMillis | Sender | The time it took to deliver an aggregated message to all subscribers |
| SnapshotMillis | Sender | The time it took to snapshot data for a new or changed subscription |
| UpdateJobMillis | Sender | The time it took to run one full cycle of the off-thread propagation logic |
| WriteMillis | Sender | The time it took to write the update to a single subscriber |
| WriteMegabits | Sender | The payload size of the update in megabits |
| DeserializationMillis | Receiver | The time it took to read and deserialize the update from the wire |
| ProcessUpdateMillis | Receiver | The time it took to apply a single update during the update graph cycle |
| RefreshMillis | Receiver | The time it took to apply all queued updates during a single udpate graph cycle |
Barrage Snapshot Metrics Summary
Snapshot statistics are presented once per request.
| Stat Type | Description |
|---|---|
| QueueMillis | The time it took waiting for a thread to process the request |
| SnapshotMillis | The time it took to construct a consistent snapshot of the source table |
| WriteMillis | The time it took to write the snapshot |
| WriteMegabits | The payload size of the snapshot in megabits |