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Version: Python

Performance tables cheat sheet

Deephaven makes several performance log tables available.


The word "log" in this context refers to the append-only nature of these tables, not to log files in the traditional sense.

These tables track various metrics across Deephaven, and in normal circumstances will be populated with raw performance data pertaining to your running queries and server state.

import deephaven.perfmon as pm

upl = pm.update_performance_log()
qopl = pm.query_operation_performance_log()
qpl = pm.query_performance_log()
pml = pm.process_metrics_log()
pil = pm.process_info_log()
ssl = pm.server_state_log()

Several derived tables are defined on top of them, typically by removing the suffix _log from the name; these derived tables accumulate data and present it in more user-friendly column types (e.g., time units in fractional seconds instead of nanoseconds for CPU time metrics), and as such are more useful for dashboards, where the _log tables are more useful as sources of raw data for user-defined computation of performance statistics. For the derived tables in the list below that are related to query performance, the functions that create them take one query evaluation number id as a parameter to show results for a particular query (where the _log tables show data for all queries).

import deephaven.perfmon as pm

qup = pm.query_update_performance(1)
qp = pm.query_performance(1)
qop = pm.query_operation_performance(1)
ss = pm.server_state()

Barrage Performance

Barrage is the name of our IPC table transport. There are two sets of statistics. The subscription metrics are recorded for ticking subscriptions. The snapshot metrics are recorded for one-off requests such as via an Arrow Flight DoGet.

Tables are identified by their TableId and TableKey. The TableId is determined by the source table's System.identityHashCode(). The TableKey defaults to Table#getDescription() but can be overridden by setting a table attribute (withAttributes)

import jpy
from deephaven import empty_table

t = empty_table(0)
table = jpy.get_type("io.deephaven.engine.table.Table")
attr_table = t.with_attributes({ table.BARRAGE_PERFORMANCE_KEY_ATTRIBUTE: "MyTableKey" })

The web client applies transformations to every table that it subscribes to. If a table is also subscribed by a non-web client then statistics for the original table and the transformed table will both appear in the metrics table. Their TableId will differ. Most transformations clear the TableKey attribute, such as when a column is sorted or filtered by the user through the GUI.

Here are server-side flags that change the behavior of barrage metrics.

  • -DBarragePerformanceLog.enableAll: record metrics for tables that do not have an explicit TableKey (default: true)
  • -DBarragePerformanceLog.cycleDurationMillis: the interval to flush aggregated statistics (default: 60000 - once per minute)

You can access these tables as follows:

import jpy

bpl = jpy.get_type("io.deephaven.extensions.barrage.BarragePerformanceLog").getInstance()
subs = bpl.getSubscriptionTable()
snaps = bpl.getSnapshotTable()