Reference doc update for mongodb

docs/modules/ROOT/nav.adoc

@@ -42,6 +42,7 @@
 ** xref:reference/httpcomponents.adoc[HttpComponents Client]
 ** xref:reference/jetty.adoc[Jetty and Jersey]
 ** xref:reference/jvm.adoc[JVM]
+** xref:reference/mongodb.adoc[MongoDB]
 ** xref:reference/netty.adoc[Netty]
 ** xref:reference/okhttpclient.adoc[OkHttpClient]
 * xref:guides.adoc[Guides]

docs/modules/ROOT/pages/reference/mongodb.adoc

@@ -0,0 +1,30 @@
+[[overview]]
+= MongoDB Metrics Instrumentation
+
+https://www.mongodb.com/[MongoDB] is a modern database that supports transactional, search, analytics, and mobile use cases with a flexible document data model and a unified query interface.
+
+Below you can find an example of how to instrument MongoDb with Micrometer.
+
+TIP: To add more capabilities such as distributed tracing, please consider using https://docs.spring.io/spring-data/mongodb/reference/observability/observability.html[Spring Data MongoDb] which uses https://docs.micrometer.io/micrometer/reference/observation.html[Micrometer Observation] under the hood.
+
+Below you can find an example of metrics for command execution.
+
+[source,java,subs=+attributes]
+-----
+// Setting up instrumentation
+include::{include-core-test-java}/io/micrometer/core/instrument/binder/mongodb/MongoMetricsCommandListenerTest.java[tags=setup, indent=0]
+
+// Usage example
+include::{include-core-test-java}/io/micrometer/core/instrument/binder/mongodb/MongoMetricsCommandListenerTest.java[tags=example, indent=0]
+-----
+
+Below you can find an example of metrics of the connection pool.
+
+[source,java,subs=+attributes]
+-----
+// Setting up instrumentation
+include::{include-core-test-java}/io/micrometer/core/instrument/binder/mongodb/MongoMetricsConnectionPoolListenerTest.java[tags=setup, indent=0]
+
+// Usage example
+include::{include-core-test-java}/io/micrometer/core/instrument/binder/mongodb/MongoMetricsConnectionPoolListenerTest.java[tags=example, indent=0]
+-----

micrometer-core/src/test/java/io/micrometer/core/instrument/binder/mongodb/MongoMetricsCommandListenerTest.java

@@ -56,8 +56,9 @@ class MongoMetricsCommandListenerTest extends AbstractMongoDbTest {
 
     @BeforeEach
     void setup() {
-        registry = new SimpleMeterRegistry();
         clusterId = new AtomicReference<>();
+        // tag::setup[]
+        registry = new SimpleMeterRegistry();
         MongoClientSettings settings = MongoClientSettings.builder()
             .addCommandListener(new MongoMetricsCommandListener(registry))
             .applyToClusterSettings(builder -> builder.hosts(singletonList(new ServerAddress(host, port)))
@@ -69,15 +70,18 @@ public void clusterOpening(ClusterOpeningEvent event) {
                 }))
             .build();
         mongo = MongoClients.create(settings);
+        // end::setup[]
     }
 
     @Test
     void shouldCreateSuccessCommandMetric() {
+        // tag::example[]
         mongo.getDatabase("test").getCollection("testCol").insertOne(new Document("testDoc", new Date()));
 
         Tags tags = Tags.of("cluster.id", clusterId.get(), "server.address", String.format("%s:%s", host, port),
                 "command", "insert", "collection", "testCol", "status", "SUCCESS");
         assertThat(registry.get("mongodb.driver.commands").tags(tags).timer().count()).isEqualTo(1);
+        // end::example[]
     }
 
     @Test

micrometer-core/src/test/java/io/micrometer/core/instrument/binder/mongodb/MongoMetricsConnectionPoolListenerTest.java

@@ -79,8 +79,9 @@ public void clusterOpening(ClusterOpeningEvent event) {
 
     @Test
     void shouldCreatePoolMetricsWithCustomTags() {
-        MeterRegistry registry = new SimpleMeterRegistry();
         AtomicReference<String> clusterId = new AtomicReference<>();
+        // tag::setup[]
+        MeterRegistry registry = new SimpleMeterRegistry();
         MongoMetricsConnectionPoolListener connectionPoolListener = new MongoMetricsConnectionPoolListener(registry,
                 e -> Tags.of("cluster.id", e.getServerId().getClusterId().getValue(), "server.address",
                         e.getServerId().getAddress().toString(), "my.custom.connection.pool.identifier", "custom"));
@@ -96,7 +97,9 @@ public void clusterOpening(ClusterOpeningEvent event) {
                 }))
             .build();
         MongoClient mongo = MongoClients.create(settings);
+        // end::setup[]
 
+        // tag::example[]
         mongo.getDatabase("test").createCollection("testCol");
 
         Tags tags = Tags.of("cluster.id", clusterId.get(), "server.address", String.format("%s:%s", host, port),
@@ -107,6 +110,7 @@ public void clusterOpening(ClusterOpeningEvent event) {
         assertThat(registry.get("mongodb.driver.pool.waitqueuesize").gauge().value()).isZero();
 
         mongo.close();
+        // end::example[]
 
         assertThat(registry.find("mongodb.driver.pool.size").tags(tags).gauge())
             .describedAs("metrics should be removed when the connection pool is closed")