docs/HotKeys.md
The HOTKEYS command allows for server-side profiling of CPU and network usage by key. It is available in Redis 8.6 and later.
This command is available via the IServer.HotKeys* methods:
// Get the server instance.
IConnectionMultiplexer muxer = ... // connect to Redis 8.6 or later
var server = muxer.GetServer(endpoint); // or muxer.GetServer(key)
// Start the capture; you can specify a duration, or manually use the HotKeysStop[Async] method; specifying
// a duration is recommended, so that the profiler will not be left running in the case of failure.
// Optional parameters allow you to specify the metrics to capture, the sample ratio, and the key slots to include;
// by default, all metrics are captured, every command is sampled, and all key slots are included.
await server.HotKeysStartAsync(duration: TimeSpan.FromSeconds(30));
// Now either do some work ourselves, or await for some other activity to happen:
await Task.Delay(TimeSpan.FromSeconds(35)); // whatever happens: happens
// Fetch the results; note that this does not stop the capture, and you can fetch the results multiple times
// either while it is running, or after it has completed - but only a single capture can be active at a time.
var result = await server.HotKeysGetAsync();
// ...investigate the results...
// Optional: discard the active capture data at the server, if any.
await server.HotKeysResetAsync();
The HotKeysResult class (our result value above) contains the following properties:
Metrics: The metrics captured during this profiling session.TrackingActive: Indicates whether the capture currently active.SampleRatio: Profiling frequency; effectively: measure every Nth command. (also: IsSampled)SelectedSlots: The key slots active for this profiling session.CollectionStartTime: The start time of the capture.CollectionDuration: The duration of the capture.AllCommandsAllSlotsTime: The total CPU time measured for all commands in all slots, without any sampling or filtering applied.AllCommandsAllSlotsNetworkBytes: The total network usage measured for all commands in all slots, without any sampling or filtering applied.When slot filtering is used, the following properties are also available:
AllCommandsSelectedSlotsTime: The total CPU time measured for all commands in the selected slots.AllCommandsSelectedSlotsNetworkBytes: The total network usage measured for all commands in the selected slots.When slot filtering and sampling is used, the following properties are also available:
SampledCommandsSelectedSlotsTime: The total CPU time measured for the sampled commands in the selected slots.SampledCommandsSelectedSlotsNetworkBytes: The total network usage measured for the sampled commands in the selected slots.If CPU metrics were captured, the following properties are also available:
TotalCpuTimeUser: The total user CPU time measured in the profiling session.TotalCpuTimeSystem: The total system CPU time measured in the profiling session.TotalCpuTime: The total CPU time measured in the profiling session.CpuByKey: Hot keys, as measured by CPU activity; for each:
Key: The key observed.Duration: The time taken.If network metrics were captured, the following properties are also available:
TotalNetworkBytes: The total network data measured in the profiling session.NetworkBytesByKey: Hot keys, as measured by network activity; for each:
Key: The key observed.Bytes: The network activity, in bytes.Note: to use slot-based filtering, you must be connected to a Redis Cluster instance. The
IConnectionMultiplexer.HashSlot(RedisKey) method can be used to determine the slot for a given key. The key
can also be used in place of an endpoint when using GetServer(...) to get the IServer instance for a given key.