Every Fluentd event begets a tag with an input.

Apache log

Fluentd

tag=apache

Fluentd matches the tag against different outputs

Apache log

Fluentd

tag=web.access

• web.access?• web.error?• syslog?

Fluentd then sends the event to the matched output.

Apache log

Fluentd

tag=web.access

• web.access?• web.error?• syslog?

MongoDB

Fluentd supports multiple data sources and destinations

Apache log

Fluentd

tag=web.access

• web.access?• web.error?• syslog?

MongoDBElasticsearch

tag=syslog

syslog

Apache log

Fluentd

tag=web.access

• web.access?• web.error?• syslog?

MongoDBElasticsearch

tag=syslog

syslog

Filter

!Fluentd can re-emit events back to Fluentd with a new tag. This is how filtering works.