Dynamic Stats

Rsyslog produces runtime-stats to allow user to study service health, performance, bottlenecks etc. Runtime-stats counters that Rsyslog components publish are statically defined.

Dynamic Stats (called dyn-stats henceforth) component allows user to configure stats-namespaces (called stats-buckets) and increment counters within these buckets using Rainerscript function call.

The metric-name in this case can be a message-property or a sub-string extracted from message etc.

Dyn-stats configuration

Dyn-stats configuration involves a two part setup.

dyn_stats(name=”<bucket>”...) (object)

Defines the bucket(identified by the bucket-name) and allows user to set some properties that control behavior of the bucket.


name <string litteral, mandatory> : Name of the bucket.

resettable <on|off, default: on> : Whether or not counters should be reset every time they are reported

maxCardinality <number, default: 2000> : Maximum number of unique counter-names to track.

unusedMetricLife <number, default: 3600> : Interval between full purges (in seconds). This prevents unused counters from occupying resources forever.

A definition setting all the parameters looks like:

dyn_stats(name="msg_per_host" resettable="on" maxCardinality="3000" unusedMetricLife="600")

dyn_inc(“<bucket>”, <expr>) (function)

Increments counter identified by value of variable in bucket identified by name.


name <string litteral, mandatory> : Name of the bucket

expr <expression resulting in a string> : Name of counter (this name will be reported by impstats to identify the counter)

A dyn_inc call looks like:

set $.inc = dyn_inc("msg_per_host", $hostname);

if ($.inc != 0) then {


global: origin=dynstats msg_per_host.ops_overflow=1 msg_per_host.new_metric_add=3 msg_per_host.no_metric=0 msg_per_host.metrics_purged=0 msg_per_host.ops_ignored=0
msg_per_host: origin=dynstats.bucket foo=2 bar=1 baz=1


global: origin=dynstats:

ops_overflow: Number of operations ignored because number-of-counters-tracked has hit configured max-cardinality.

new_metric_add: Number of “new” metrics added (new counters created).

no_metric: Counter-name given was invalid (length = 0).

metrics_purged: Number of counters discarded at discard-cycle (controlled by unusedMetricLife).

ops_ignored: Number of operations ignored due to potential performance overhead. Dyn-stats subsystem ignores operations to avoid performance-penalty if it can’t get access to counter without delay(lock acquiring latency).

purge_triggered: Indicates that a discard was performed (1 implies a discard-cycle run).

msg_per_host: origin=dynstats.bucket:
<metric_name>: Value of counter identified by <metric-name>.