Add instrumentation for pools of Apache HttpComponents HttpClient (mi…

…crometer-metrics#1223)

Provides metrics for the underlying connection pool total stats.

See micrometer-metrics#533

micrometer-core/src/main/java/io/micrometer/core/instrument/binder/httpcomponents/PoolingHttpClientConnectionManagerMetricsBinder.java

@@ -0,0 +1,128 @@
+/*
+ * Copyright 2019 Pivotal Software, Inc.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micrometer.core.instrument.binder.httpcomponents;
+
+import io.micrometer.core.instrument.*;
+import io.micrometer.core.instrument.binder.MeterBinder;
+import io.micrometer.core.lang.NonNull;
+import org.apache.http.conn.HttpClientConnectionManager;
+import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
+
+/**
+ * Collects metrics from a {@link PoolingHttpClientConnectionManager}.
+ *
+ * It monitors the overall connection pool state.
+ *
+ * @author Benjamin Hubert ([email protected])
+ * @since 1.3.0
+ */
+public class PoolingHttpClientConnectionManagerMetricsBinder implements MeterBinder {
+
+    private static final String METER_TOTAL_MAX_DESC = "The configured maximum number of allowed persistent connections for all routes.";
+    private static final String METER_TOTAL_MAX = "httpcomponents.httpclient.pool.total.max";
+    private static final String METER_TOTAL_CONNECTIONS_DESC = "The number of persistent and leased connections for all routes.";
+    private static final String METER_TOTAL_CONNECTIONS = "httpcomponents.httpclient.pool.total.connections";
+    private static final String METER_TOTAL_PENDING_DESC = "The number of connection requests being blocked awaiting a free connection for all routes.";
+    private static final String METER_TOTAL_PENDING = "httpcomponents.httpclient.pool.total.pending";
+    private static final String METER_DEFAULT_MAX_PER_ROUTE_DESC = "The configured default maximum number of allowed persistent connections per route.";
+    private static final String METER_DEFAULT_MAX_PER_ROUTE = "httpcomponents.httpclient.pool.route.max.default";
+    private static final String TAG_CONNECTIONS_STATE = "state";
+
+    private final PoolingHttpClientConnectionManager connectionManager;
+    private final Iterable<Tag> tags;
+
+    /**
+     * Creates a metrics binder for the given pooling connection manager.
+     *
+     * For convenience this constructor will take care of casting the given
+     * {@link HttpClientConnectionManager} to the required {@link
+     * PoolingHttpClientConnectionManager}. An {@link IllegalArgumentException}
+     * is thrown, if the given {@code connectionManager} is not an instance of
+     * {@link PoolingHttpClientConnectionManager}.
+     *
+     * @param connectionManager The connection manager to monitor.
+     * @param name Name of the connection manager. Will be added as tag with the
+     *             key "httpclient".
+     * @param tags Tags to apply to all recorded metrics. Must be an even number
+     *             of arguments representing key/value pairs of tags.
+     */
+    @SuppressWarnings("WeakerAccess")
+    public PoolingHttpClientConnectionManagerMetricsBinder(HttpClientConnectionManager connectionManager, String name, String... tags) {
+        this(connectionManager, name, Tags.of(tags));
+    }
+
+    /**
+     * Creates a metrics binder for the given pooling connection manager.
+     *
+     * For convenience this constructor will take care of casting the given
+     * {@link HttpClientConnectionManager} to the required {@link
+     * PoolingHttpClientConnectionManager}. An {@link IllegalArgumentException}
+     * is thrown, if the given {@code connectionManager} is not an instance of
+     * {@link PoolingHttpClientConnectionManager}.
+     *
+     * @param connectionManager The connection manager to monitor.
+     * @param name Name of the connection manager. Will be added as tag with the
+     *             key "httpclient".
+     * @param tags Tags to apply to all recorded metrics.
+     */
+    @SuppressWarnings("WeakerAccess")
+    public PoolingHttpClientConnectionManagerMetricsBinder(HttpClientConnectionManager connectionManager, String name, Iterable<Tag> tags) {
+        if (!(connectionManager instanceof PoolingHttpClientConnectionManager)) {
+            throw new IllegalArgumentException("The given connectionManager is not an instance of PoolingHttpClientConnectionManager.");
+        }
+        this.connectionManager = (PoolingHttpClientConnectionManager) connectionManager;
+        this.tags = Tags.concat(tags, "httpclient", name);
+    }
+
+    @Override
+    public void bindTo(@NonNull MeterRegistry registry) {
+        registerTotalMetrics(registry);
+    }
+
+    private void registerTotalMetrics(MeterRegistry registry) {
+        Gauge.builder(METER_TOTAL_MAX,
+            connectionManager,
+            (connectionManager) -> connectionManager.getTotalStats().getMax())
+            .description(METER_TOTAL_MAX_DESC)
+            .tags(tags)
+            .register(registry);
+        Gauge.builder(METER_TOTAL_CONNECTIONS,
+            connectionManager,
+            (connectionManager) -> connectionManager.getTotalStats().getAvailable())
+            .description(METER_TOTAL_CONNECTIONS_DESC)
+            .tags(tags).tag(TAG_CONNECTIONS_STATE, "available")
+            .register(registry);
+        Gauge.builder(METER_TOTAL_CONNECTIONS,
+            connectionManager,
+            (connectionManager) -> connectionManager.getTotalStats().getLeased())
+            .description(METER_TOTAL_CONNECTIONS_DESC)
+            .tags(tags).tag(TAG_CONNECTIONS_STATE, "leased")
+            .register(registry);
+        Gauge.builder(METER_TOTAL_PENDING,
+            connectionManager,
+            (connectionManager) -> connectionManager.getTotalStats().getPending())
+            .description(METER_TOTAL_PENDING_DESC)
+            .tags(tags)
+            .register(registry);
+        Gauge.builder(METER_DEFAULT_MAX_PER_ROUTE,
+            connectionManager,
+            PoolingHttpClientConnectionManager::getDefaultMaxPerRoute)
+            .description(METER_DEFAULT_MAX_PER_ROUTE_DESC)
+            .tags(tags)
+            .register(registry);
+    }
+
+}

micrometer-core/src/test/java/io/micrometer/core/instrument/binder/httpcomponents/PoolingHttpClientConnectionManagerMetricsBinderTest.java

@@ -0,0 +1,113 @@
+/*
+ * Copyright 2017 Pivotal Software, Inc.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micrometer.core.instrument.binder.httpcomponents;
+
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.MockClock;
+import io.micrometer.core.instrument.simple.SimpleConfig;
+import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
+import org.apache.http.conn.HttpClientConnectionManager;
+import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
+import org.apache.http.pool.PoolStats;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+/**
+ * Unit tests for {@link PoolingHttpClientConnectionManagerMetricsBinder}.
+ *
+ * @author Benjamin Hubert ([email protected])
+ */
+class PoolingHttpClientConnectionManagerMetricsBinderTest {
+
+    private MeterRegistry registry = new SimpleMeterRegistry(SimpleConfig.DEFAULT, new MockClock());
+    private PoolingHttpClientConnectionManager connectionManager;
+    private PoolingHttpClientConnectionManagerMetricsBinder binder;
+
+    @BeforeEach
+    void setup() {
+        connectionManager = mock(PoolingHttpClientConnectionManager.class);
+        binder = new PoolingHttpClientConnectionManagerMetricsBinder(connectionManager, "test");
+        binder.bindTo(registry);
+    }
+
+    @Test
+    void creationWithNonPoolingHttpClientThrowsException() {
+        assertThrows(IllegalArgumentException.class, () -> {
+            HttpClientConnectionManager connectionManager = mock(HttpClientConnectionManager.class);
+            new PoolingHttpClientConnectionManagerMetricsBinder(connectionManager, "test");
+        });
+    }
+
+    @Test
+    void creationWithPoolingHttpClientIsOk() {
+        HttpClientConnectionManager connectionManager = mock(PoolingHttpClientConnectionManager.class);
+        new PoolingHttpClientConnectionManagerMetricsBinder(connectionManager, "test");
+    }
+
+    @Test
+    void totalMax() {
+        PoolStats poolStats = mock(PoolStats.class);
+        when(poolStats.getMax()).thenReturn(13);
+        when(connectionManager.getTotalStats()).thenReturn(poolStats);
+        assertThat(registry.get("httpcomponents.httpclient.pool.total.max")
+            .tags("httpclient", "test")
+            .gauge().value()).isEqualTo(13.0);
+    }
+
+    @Test
+    void totalAvailable() {
+        PoolStats poolStats = mock(PoolStats.class);
+        when(poolStats.getAvailable()).thenReturn(17);
+        when(connectionManager.getTotalStats()).thenReturn(poolStats);
+        assertThat(registry.get("httpcomponents.httpclient.pool.total.connections")
+            .tags("httpclient", "test", "state", "available")
+            .gauge().value()).isEqualTo(17.0);
+    }
+
+    @Test
+    void totalLeased() {
+        PoolStats poolStats = mock(PoolStats.class);
+        when(poolStats.getLeased()).thenReturn(23);
+        when(connectionManager.getTotalStats()).thenReturn(poolStats);
+        assertThat(registry.get("httpcomponents.httpclient.pool.total.connections")
+            .tags("httpclient", "test", "state", "leased")
+            .gauge().value()).isEqualTo(23.0);
+    }
+
+    @Test
+    void totalPending() {
+        PoolStats poolStats = mock(PoolStats.class);
+        when(poolStats.getPending()).thenReturn(37);
+        when(connectionManager.getTotalStats()).thenReturn(poolStats);
+        assertThat(registry.get("httpcomponents.httpclient.pool.total.pending")
+            .tags("httpclient", "test")
+            .gauge().value()).isEqualTo(37.0);
+    }
+
+    @Test
+    void routeMaxDefault() {
+        when(connectionManager.getDefaultMaxPerRoute()).thenReturn(7);
+        assertThat(registry.get("httpcomponents.httpclient.pool.route.max.default")
+            .tags("httpclient", "test")
+            .gauge().value()).isEqualTo(7.0);
+    }
+
+}