0001 0.624 connectionReleased
0001 0.624 callEnd
```

The `EventListener.Factory` also makes it possible to limit metrics to a subset of calls. This one captures metrics on a random 10%:

```java
class MetricsEventListener extends EventListener {
  private static final Factory FACTORY = new Factory() {
    @Override public EventListener create(Call call) {
      if (Math.random() < 0.10) {

          ioe: IOException,
        ) = TODO()

        override fun canceled(call: Call) = TODO()
      }
    val none: EventListener = EventListener.NONE
  }

  @Test
  fun eventListenerBuilder() {
    var builder: EventListener.Factory = EventListener.Factory { TODO() }
  }

  @Test
  fun formBody() {
    val formBody: FormBody = FormBody.Builder().build()

	public abstract fun lookup (Ljava/lang/String;)Ljava/util/List;
}

public final class okhttp3/Dns$Companion {
}

public abstract class okhttp3/EventListener {
	public static final field Companion Lokhttp3/EventListener$Companion;
	public static final field NONE Lokhttp3/EventListener;
	public fun <init> ()V
	public fun cacheConditionalHit (Lokhttp3/Call;Lokhttp3/Response;)V
	public fun cacheHit (Lokhttp3/Call;Lokhttp3/Response;)V

    sslSocketFactoryOrNull = sslSocketFactory,
    x509TrustManagerOrNull = x509TrustManager,
    certificateChainCleaner = certificateChainCleaner,
  )

  override val eventListener: EventListener
    get() = call.eventListener

  override val followSslRedirects: Boolean
    get() = call.client.followSslRedirects

  override val followRedirects: Boolean
    get() = call.client.followRedirects

          // $0.05 worth of phone storage in 2020
          maxSize = 50L * 1024L * 1024L // 50 MiB
      ))
      .build()
```

## EventListener events

Cache Events are exposed via the EventListener API.  Typical scenarios are below.

### Cache Hit

In the ideal scenario the cache can fulfill the request without any conditional call to the network.

    val connectionPool: ConnectionPool

    /**
     * Returns a new chain with the specified [ConnectionPool].
     */
    fun withConnectionPool(connectionPool: ConnectionPool): Chain

    val eventListener: EventListener
  }

	public abstract fun lookup (Ljava/lang/String;)Ljava/util/List;
}

public final class okhttp3/Dns$Companion {
}

public abstract class okhttp3/EventListener {
	public static final field Companion Lokhttp3/EventListener$Companion;
	public static final field NONE Lokhttp3/EventListener;
	public fun <init> ()V
	public fun cacheConditionalHit (Lokhttp3/Call;Lokhttp3/Response;)V
	public fun cacheHit (Lokhttp3/Call;Lokhttp3/Response;)V

        var first = true
        client =
          client
            .newBuilder()
            .connectionSpecs(listOf(ConnectionSpec.RESTRICTED_TLS, ConnectionSpec.MODERN_TLS))
            .eventListener(
              object : EventListener() {
                override fun secureConnectEnd(
                  call: Call,
                  handshake: Handshake?,
                ) {
                  if (first) {

  fun connectionIsImmediatelyUnhealthy() {
    val listener: EventListener =
      object : EventListener() {
        override fun connectionAcquired(
          call: Call,
          connection: Connection,
        ) {
          connection.socket().closeQuietly()
        }
      }
    client =
      client
        .newBuilder()
        .eventListener(listener)
        .build()

        }

        @Override
        public <T extends java.util.EventListener> void addListener(T t) {
        }

        @Override
        public void addListener(Class<? extends java.util.EventListener> listenerClass) {
        }

        @Override
        public <T extends java.util.EventListener> T createListener(Class<T> clazz) {
            return null;
        }

        @Override