Metrics - Impressions

Unlaunch SDKs regularly send metrics to Unlaunch servers. These are useful for statistics and debugging purposes.

Metrics are a type of an event. Metric events are automatically generated when feature flags are evaluated on SDKs. Unlaunch SDKs keep a separate queue for metrics and allow fine-grained control over how frequently metrics are submitted to the server, separate from other types of events.

When a feature flag is evaluated on the SDK, an impression capturing the details of the evaluation is generated and recorded by the SDK in a queue. This queue is periodically flushed and events are sent to Unlaunch servers. This information includes the flag details, evaluation results, user information, timestamp etc. These events are then stored in a database. You can view these events in real-time using Live Tail.

Impression Event fields

Every impression event contains the following fields:

Key Description
Key The feature flag key that was evaluated
User Id User Id for which the event was evaluated
Variation Key The variation that was returned
Evaluation Reason Why the particular variation was evaluated e.g. Targeting Rule matched, etc.
Flag Status Whether the flag was enabled or disabled
Machine name Hostname of the machine where feature flag was evaluated
SDK Name & Version The name and version of the SDK

Adjusting Flush Interval and Queue Size

Server side SDKs send impression events periodically to Unlaunch servers. You can control how often these are sent to the server by setting the metricsFlushInterval() or metricsQueueSize() methods when building the client.