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SOLR-14683: move "Missing Metrics" section down to config section; add short blurb to intro text

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Cassandra Targett 2020-11-17 11:57:40 -06:00
parent 02514e5bd6
commit 2b5b0f999c
1 changed files with 43 additions and 39 deletions
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solr/solr-ref-guide/src/metrics-reporting.adoc
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@ -26,51 +26,16 @@ Internally this feature uses the http://metrics.dropwizard.io[Dropwizard Metrics
* *timers* - measure the number and duration of events. They provide a count and histogram of timings. * *timers* - measure the number and duration of events. They provide a count and histogram of timings.
* *gauges* - offer instantaneous reading of a current value, e.g., current queue depth, current number of active connections, free heap size. * *gauges* - offer instantaneous reading of a current value, e.g., current queue depth, current number of active connections, free heap size.
Some of these meters may be missing or empty for any number of valid reasons.
In these cases, missing values of any type will be returned as `null` by default so empty values won't impact averages or histograms.
This is configurable for several types of missing values; see the <<The <metrics> <missingValues> Element>> section below.
Each group of related metrics with unique names is managed in a *metric registry*. Solr maintains several such registries, each corresponding to a high-level group such as: `jvm`, `jetty`, `node`, and `core` (see <<Metric Registries>> below). Each group of related metrics with unique names is managed in a *metric registry*. Solr maintains several such registries, each corresponding to a high-level group such as: `jvm`, `jetty`, `node`, and `core` (see <<Metric Registries>> below).
For each group (and/or for each registry) there can be several *reporters*, which are components responsible for communication of metrics from selected registries to external systems. Currently implemented reporters support emitting metrics via JMX, Ganglia, Graphite and SLF4J. For each group (and/or for each registry) there can be several *reporters*, which are components responsible for communication of metrics from selected registries to external systems. Currently implemented reporters support emitting metrics via JMX, Ganglia, Graphite and SLF4J.
There is also a dedicated `/admin/metrics` handler that can be queried to report all or a subset of the current metrics from multiple registries. There is also a dedicated `/admin/metrics` handler that can be queried to report all or a subset of the current metrics from multiple registries.
=== Missing metrics
Long-lived metrics values are still reported when the underlying value is unavailable (eg. "INDEX.sizeInBytes" when
IndexReader is closed). Short-lived transient metrics (such as cache entries) that are properties of complex gauges
(internally represented as `MetricsMap`) are simply skipped when not available, and neither their names nor values
appear in registries (or in /admin/metrics reports).
When a missing value is encountered by default it's reported as null value, regardless of the metrics type.
This can be configured in the `solr.xml:/solr/metrics/missingValues` element, which recognizes the following child elements
(for string elements a JSON payload is supported):
`nullNumber`::
value to use when a missing (null) numeric metrics value is encountered.
`notANumber`::
value to use when an invalid numeric value is encountered.
`nullString`::
value to use when a missing (null) string metrics is encountered.
`nullObject`::
value to use when a missing (null) complex object is encountered.
Example configuration that returns null for missing numbers, -1 for
invalid numeric values, empty string for missing strings, and a Map for missing
complex objects:
[source,xml]
----
<metrics>
<missingValues>
<null name="nullNumber"/>
<int name="notANumber">-1</int>
<str name="nullString"></str>
<str name="nullObject">{"value":"missing"}</str>
</missingValues>
</metrics>
----
== Metric Registries == Metric Registries
Solr includes multiple metric registries, which group related metrics. Solr includes multiple metric registries, which group related metrics.
@ -202,6 +167,45 @@ As an example of a section of `solr.xml` that defines some of these custom param
</metrics> </metrics>
---- ----
=== The <metrics> <missingValues> Element
Long-lived metrics values are still reported when the underlying value is unavailable (e.g., "INDEX.sizeInBytes" when
IndexReader is closed). Short-lived transient metrics (such as cache entries) that are properties of complex gauges
(internally represented as `MetricsMap`) are simply skipped when not available, and neither their names nor values
appear in registries (or in `/admin/metrics` reports).
When a missing value is encountered by default it's reported as null value, regardless of the metrics type.
This can be configured in the `solr.xml:/solr/metrics/missingValues` element, which recognizes the following child elements
(for string elements a JSON payload is supported):
`nullNumber`::
The value to use when a missing (null) numeric metrics value is encountered.
`notANumber`::
The value to use when an invalid numeric value is encountered.
`nullString`::
The value to use when a missing (null) string metrics is encountered.
`nullObject`::
The value to use when a missing (null) complex object is encountered.
Example configuration that returns null for missing numbers, -1 for
invalid numeric values, empty string for missing strings, and a Map for missing
complex objects:
[source,xml]
----
<metrics>
<missingValues>
<null name="nullNumber"/>
<int name="notANumber">-1</int>
<str name="nullString"></str>
<str name="nullObject">{"value":"missing"}</str>
</missingValues>
</metrics>
----
== Reporters == Reporters
Reporter configurations are specified in `solr.xml` file in `<metrics><reporter>` sections, for example: Reporter configurations are specified in `solr.xml` file in `<metrics><reporter>` sections, for example: