Event Forwarding

Event forwarding is a BETA feature. You should test it before relying on it in production. It is not yet available on Humio Cloud.

Event forwarding is used to forward events that are ingested into Humio to other systems that require parts of the data for e.g. Machine Learning, while still logging everything in a central place. Currently, forwarding is done using Kafka.

Figure 1, Event Forwarding

When data is shipped into Humio, it is first parsed. Then it is stored in a repository in Humio and sent through any event forwarding rules on the repository, which can filter and transform the events before forwarding them to an external system through an event forwarder.

If you ingest events with timestamps older than your retention policy allows, the data will be forwarded without being stored in Humio.

Configuring Event Forwarding

Event forwarding is configured in two steps. First, an event forwarder is created that defines a Kafka server and topic to forward the events to. Second, one or more event forwarding rules are configured on the repositories, where events should be forwarded from, and connected to the event forwarders.

You need to enable event forwarding in the configuration using ENABLE_EVENT_FORWARDING.


Events are sent as one event per message. The format is JSON where every field is a top-level element, and all field values are returned as JSON strings, except for @timestamp, which is returned as a number representing time as Unix time in milliseconds (UTC/Zulu time).

Error Handling

There are no delivery guarantees on event forwarding. This means that if forwarding an event fails, Humio will neither retry later nor fail the ingest. This is done in order to not impact ingest.

Note that a failure during parsing does not necessarily mean a failure during forwarding. As described in the parser error documentation, this will simply set a number of fields to error values, such as @event_parsed = false. Unless filtered out by the forwarding rule (using e.g. @event_parsed != false), these events will still be forwarded.

Humio will only log that event forwarding failed if multiple events fail to be forwarded, in order not to spam the logs. The number of events that failed to be forwarded can be seen in the metric event-forwarding-errors, see metrics.

Humio uses circuit breakers to prevent event forwarding errors from affecting the performance and stability of Humio. The circuit breakers can be configured using the configuration options that have the FORWARDING_BREAKER_ prefix.

Humio also enforces a limit on the number of events concurrently waiting to be forwarded. This is to prevent events exhausting memory due to a stuck/blocked forwarder. This limit can be changed by setting FORWARDING_MAX_CONCURRENCY.