// file included in the following:
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// assembly-monitoring-proxy.adoc

[id='con-integrating-micrometer-{context}']
= Integrating Micrometer
Kroxylicious integrates with https://micrometer.io/docs[Micrometer] for gathering metrics.

Micrometer provides a simple facade over instrumentation clients for popular observability systems, allowing you to instrument your JVM-based application code without vendor lock-in. 
The following example shows how to define the `CommonTagsHook` and `StandardBindersHook` types to add a label to metrics and register a JVM metrics binder.

.Example proxy configuration for Micrometer integration
[source,yaml]
----
adminHttp:
  endpoints:
    prometheus: {}
micrometer:
  - type: "CommonTagsHook" # <1>
    config:
      commonTags:
        zone: "euc-1a" # <2>
  - type: "StandardBindersHook" # <3>
    config:
      binderNames:
      - "JvmGcMetrics" # <4>
----
<1> Specifies the `CommonTagsHook` type to add common tags to all metrics.
<2> Adds common tag zone `euc-1a` to all metrics in the global registry included with Micrometer, which appears as a label in Prometheus.
<3> Specifies the `StandardBindersHook` type to register standard Micrometer binders.
<4> Registers the `JvmGcMetrics` binder with the global registry.

Prometheus is connected to the Micrometer global registry, so filters can record metrics against it as part of the Prometheus scrape data.

Using the `curl localhost:9190/metrics` command shows metrics as follows:

.Example metrics returned from request
[source,shell]
----
jvm_gc_memory_allocated_bytes_total{zone="euc-1a",} 0.0
----

== Common tags

Add common tags for metrics to appear as labels in the Prometheus scrape.

.Example common tag configuration
[source,yaml]
----
- type: "CommonTagsHook"
  config:
    commonTags:
      zone: "euc-1a"
      owner: "team-a"
----

== Standard binders

Micrometer uses the concept of meter binders to register metrics that provide information about the state of some aspect of the application or its container.
By registering standard binders included with Micrometer, you can expose metrics about the JVM and system, such as JVM memory usage and garbage collection.

.Example binders configuration
[source,yaml]
----
micrometer:
  - type: "StandardBindersHook"
    config:
      binderNames:
      - "JvmGcMetrics"
      - "JvmHeapPressureMetrics"
----

.Standard binders available with Micrometer
[cols="2m,4m",options="header"]
|===
 
| Name | Micrometer class 
| ClassLoaderMetrics | io.micrometer.core.instrument.binder.jvm.ClassLoaderMetrics 
| JvmCompilationMetrics | io.micrometer.core.instrument.binder.jvm.JvmCompilationMetrics 
| JvmGcMetrics | io.micrometer.core.instrument.binder.jvm.JvmGcMetrics 
| JvmHeapPressureMetrics | io.micrometer.core.instrument.binder.jvm.JvmHeapPressureMetrics 
| JvmInfoMetrics | io.micrometer.core.instrument.binder.jvm.JvmInfoMetrics 
| JvmMemoryMetrics | io.micrometer.core.instrument.binder.jvm.JvmMemoryMetrics 
| JvmThreadMetrics | io.micrometer.core.instrument.binder.jvm.JvmThreadMetrics 
| FileDescriptorMetrics | io.micrometer.core.instrument.binder.system.FileDescriptorMetrics 
| ProcessorMetrics | io.micrometer.core.instrument.binder.system.ProcessorMetrics 
| UptimeMetrics | io.micrometer.core.instrument.binder.system.UptimeMetrics 

|===

== Using Micrometer with filters

Use the static methods of https://www.javadoc.io/doc/io.micrometer/micrometer-core/1.10.5/io/micrometer/core/instrument/Metrics.html[Micrometer Metrics^] to register metrics with the global registry. 

Alternatively, use `Metrics.globalRegistry` to get a reference to the global registry. 
Metrics registered this way are automatically available through the Prometheus scrape endpoint.