MetricsConfig — Metrics System Configuration

MetricsConfig is the configuration of the MetricsSystem (i.e. metrics sources and sinks).

MetricsConfig uses metrics.properties as the default metrics configuration file that can however be changed using spark.metrics.conf property. The file is first loaded from the path directly before using Spark’s CLASSPATH.

MetricsConfig lets you also configure the metrics configuration using spark.metrics.conf.-prefixed Spark properties.

MetricsConfig makes sure that the default metrics properties are always defined.

Table 1. MetricsConfig’s Default Metrics Properties
Name Description

*.sink.servlet.class

org.apache.spark.metrics.sink.MetricsServlet

*.sink.servlet.path

/metrics/json

master.sink.servlet.path

/metrics/master/json

applications.sink.servlet.path

/metrics/applications/json

Note

The order of precedence of metrics configuration settings is as follows:

  1. Default metrics properties

  2. spark.metrics.conf or metrics.properties configuration file

  3. spark.metrics.conf.-prefixed Spark properties

MetricsConfig is created when MetricsSystem is created.

Table 2. MetricsConfig’s Internal Registries and Counters
Name Description

properties

java.util.Properties

Used when…​FIXME

perInstanceSubProperties

FIXME

Used when…​FIXME

Creating MetricsConfig Instance

MetricsConfig takes the following when created:

MetricsConfig initializes the internal registries and counters.

Initializing MetricsConfig — initialize Method

initialize(): Unit

initialize takes all Spark properties that start with spark.metrics.conf. prefix from SparkConf and adds them to properties (without the prefix).

In the end, initialize splits configuration per Spark subsystem with the default configuration (denoted as *) assigned to the configured subsystems afterwards.

Note
initialize accepts * (star) for the default configuration or any combination of lower- and upper-case letters for Spark subsystem names.
Note
initialize is used exclusively when MetricsSystem is created.

setDefaultProperties Internal Method

setDefaultProperties(prop: Properties): Unit

setDefaultProperties sets the default properties (in the input prop).

Note
setDefaultProperties is used exclusively when MetricsConfig is initialized.

Loading Custom Metrics Configuration File or metrics.properties — loadPropertiesFromFile Method

loadPropertiesFromFile(path: Option[String]): Unit

loadPropertiesFromFile tries to open the input path file (if defined) or the default metrics configuration file metrics.properties (on CLASSPATH).

If either file is available, loadPropertiesFromFile loads the properties (to properties registry).

In case of exceptions, you should see the following ERROR message in the logs followed by the exception.

ERROR Error loading configuration file [file]
Note
loadPropertiesFromFile is used when MetricsConfig is initialized.

Grouping Properties Per Subsystem — subProperties Method

subProperties(prop: Properties, regex: Regex): mutable.HashMap[String, Properties]

subProperties takes prop properties and destructures keys given regex. subProperties takes the matching prefix (of a key per regex) and uses it as a new key with the value(s) being the matching suffix(es).

driver.hello.world => (driver, (hello.world))
Note
subProperties is used when MetricsConfig is initialized (to apply the default metrics configuration) and when MetricsSystem registers metrics sources and sinks.

Settings

Table 3. Spark Properties
Spark Property Default Value Description

spark.metrics.conf

metrics.properties

The metrics configuration file.

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