Metric Reporters

Fluss allows reporting metrics to external system. Metrics can be exposed to an external system by configuring one or several reporters in conf/server.yaml. These reporters will be instantiated on each CoordinatorServer and TabletServers when they started.

Example reporter configuration that specifies multiple reporters:

metrics.reporters: jmx,prometheus

Push vs. Pull

Metrics are exported either via pushes or pulls.

Push-based reporters usually implement the Scheduled interface and periodically send a summary of current metrics to an external system.

Pull-based reporters are queried from an external system instead.

Reporters

The following sections list the supported reporters currently.

JMX

Type: pull

Parameters:

• port - (optional) the port on which JMX listens for connections. In order to be able to run several instances of the reporter on one host (e.g. when one TabletServer is co-located with the CoordinatorServer) it is advisable to use a port range like 9250-9260. When a range is specified the actual port is shown in the relevant server log. If this setting is set, Fluss will start an extra JMX connector for the given port/range. Metrics are always available on the default local JMX interface.

Example configuration:

metrics.reporters: jmx
metrics.reporter.jmx.port: 9250-9260

Metrics exposed through JMX are identified by a domain and a list of key-properties, which together form the object name.

The domain always begins with com.alibaba.fluss followed by a generalized metric identifier. An example for such a domain would be com.alibaba.fluss.tabletserver.replicaCount.

The key-property list contains the values for all variables, that are associated with a given metric. An example for such a list would be cluster_id=fluss1,host=localhost,server_id=1.

The domain thus identifies a metric class, while the key-property list identifies one (or multiple) instances of that metric.

Prometheus

Type: pull

Parameters:

• metrics.reporter.prometheus.port - (optional) the port the Prometheus exporter listens on, defaults to 9249. In order to be able to run several instances of the reporter on one host (e.g. when one TabletServer is co-located with the CoordinatorServer) it is advisable to use a port range like 9250-9260.

Example configuration:

metrics.reporters: prometheus
metrics.reporter.prometheus.port: 9250

Fluss metric types are mapped to Prometheus metric types as follows:

Fluss	Prometheus	Note
Counter	Gauge	Prometheus counters cannot be decremented.
Gauge	Gauge	Only numbers and booleans are supported.
Histogram	Summary	Quantiles .5, .75, .95, .98, .99 and .999
Meter	Gauge	The gauge exports the meter's rate.