From 8bda91d20ab248a0d262d396646861113195f3ed Mon Sep 17 00:00:00 2001
From: Akira Ajisaka <aajisaka@apache.org>
Date: Wed, 31 Jul 2019 10:11:36 -0700
Subject: [PATCH] HADOOP-16398. Exports Hadoop metrics to Prometheus (#1170)

---
 .../fs/CommonConfigurationKeysPublic.java     |   8 ++
 .../org/apache/hadoop/http/HttpServer2.java   |  26 ++++
 .../apache/hadoop/http/PrometheusServlet.java |  47 +++++++
 .../metrics2/sink/PrometheusMetricsSink.java  | 115 ++++++++++++++++++
 .../src/main/resources/core-default.xml       |  10 ++
 .../sink/TestPrometheusMetricsSink.java       | 111 +++++++++++++++++
 .../hadoop/hdds/server/BaseHttpServer.java    |   6 +
 7 files changed, 323 insertions(+)
 create mode 100644 hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/http/PrometheusServlet.java
 create mode 100644 hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/sink/PrometheusMetricsSink.java
 create mode 100644 hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/sink/TestPrometheusMetricsSink.java

diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeysPublic.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeysPublic.java
index 0fa78c2f2ae..7e3e47c80d6 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeysPublic.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeysPublic.java
@@ -961,5 +961,13 @@ public class CommonConfigurationKeysPublic {
   /** Default shutdown hook timeout: {@value} seconds. */
   public static final long SERVICE_SHUTDOWN_TIMEOUT_DEFAULT = 30;
 
+  /**
+   * @see
+   * <a href="{@docRoot}/../hadoop-project-dist/hadoop-common/core-default.xml">
+   * core-default.xml</a>
+   */
+  public static final String HADOOP_PROMETHEUS_ENABLED =
+      "hadoop.prometheus.endpoint.enabled";
+  public static final boolean HADOOP_PROMETHEUS_ENABLED_DEFAULT = false;
 }
 
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/http/HttpServer2.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/http/HttpServer2.java
index 7825e08dac5..82d7b59dc7d 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/http/HttpServer2.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/http/HttpServer2.java
@@ -61,8 +61,11 @@
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.conf.Configuration.IntegerRanges;
 import org.apache.hadoop.fs.CommonConfigurationKeys;
+import org.apache.hadoop.fs.CommonConfigurationKeysPublic;
 import org.apache.hadoop.jmx.JMXJsonServlet;
 import org.apache.hadoop.log.LogLevel;
+import org.apache.hadoop.metrics2.lib.DefaultMetricsSystem;
+import org.apache.hadoop.metrics2.sink.PrometheusMetricsSink;
 import org.apache.hadoop.security.AuthenticationFilterInitializer;
 import org.apache.hadoop.security.SecurityUtil;
 import org.apache.hadoop.security.UserGroupInformation;
@@ -191,6 +194,11 @@ public final class HttpServer2 implements FilterContainer {
   private static final String X_FRAME_OPTIONS = "X-FRAME-OPTIONS";
   private static final Pattern PATTERN_HTTP_HEADER_REGEX =
           Pattern.compile(HTTP_HEADER_REGEX);
+
+  private boolean prometheusSupport;
+  protected static final String PROMETHEUS_SINK = "PROMETHEUS_SINK";
+  private PrometheusMetricsSink prometheusMetricsSink;
+
   /**
    * Class to construct instances of HTTP server with specific options.
    */
@@ -612,6 +620,19 @@ private void initializeWebServer(String name, String hostName,
     }
 
     addDefaultServlets();
+    addPrometheusServlet(conf);
+  }
+
+  private void addPrometheusServlet(Configuration conf) {
+    prometheusSupport = conf.getBoolean(
+        CommonConfigurationKeysPublic.HADOOP_PROMETHEUS_ENABLED,
+        CommonConfigurationKeysPublic.HADOOP_PROMETHEUS_ENABLED_DEFAULT);
+    if (prometheusSupport) {
+      prometheusMetricsSink = new PrometheusMetricsSink();
+      getWebAppContext().getServletContext()
+          .setAttribute(PROMETHEUS_SINK, prometheusMetricsSink);
+      addServlet("prometheus", "/prom", PrometheusServlet.class);
+    }
   }
 
   private void addListener(ServerConnector connector) {
@@ -1133,6 +1154,11 @@ public void start() throws IOException {
       try {
         openListeners();
         webServer.start();
+        if (prometheusSupport) {
+          DefaultMetricsSystem.instance()
+              .register("prometheus", "Hadoop metrics prometheus exporter",
+                  prometheusMetricsSink);
+        }
       } catch (IOException ex) {
         LOG.info("HttpServer.start() threw a non Bind IOException", ex);
         throw ex;
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/http/PrometheusServlet.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/http/PrometheusServlet.java
new file mode 100644
index 00000000000..abcc088a031
--- /dev/null
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/http/PrometheusServlet.java
@@ -0,0 +1,47 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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 org.apache.hadoop.http;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+import org.apache.hadoop.metrics2.lib.DefaultMetricsSystem;
+import org.apache.hadoop.metrics2.sink.PrometheusMetricsSink;
+
+/**
+ * Servlet to publish hadoop metrics in prometheus format.
+ */
+public class PrometheusServlet extends HttpServlet {
+
+  public PrometheusMetricsSink getPrometheusSink() {
+    return
+        (PrometheusMetricsSink) getServletContext().getAttribute(
+            HttpServer2.PROMETHEUS_SINK);
+  }
+
+  @Override
+  protected void doGet(HttpServletRequest req, HttpServletResponse resp)
+      throws ServletException, IOException {
+    DefaultMetricsSystem.instance().publishMetricsNow();
+    getPrometheusSink().writeMetrics(resp.getWriter());
+    resp.getWriter().flush();
+  }
+}
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/sink/PrometheusMetricsSink.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/sink/PrometheusMetricsSink.java
new file mode 100644
index 00000000000..291cfe3295a
--- /dev/null
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/sink/PrometheusMetricsSink.java
@@ -0,0 +1,115 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.hadoop.metrics2.sink;
+
+import org.apache.commons.configuration2.SubsetConfiguration;
+import org.apache.hadoop.metrics2.AbstractMetric;
+import org.apache.hadoop.metrics2.MetricType;
+import org.apache.hadoop.metrics2.MetricsRecord;
+import org.apache.hadoop.metrics2.MetricsSink;
+import org.apache.hadoop.metrics2.MetricsTag;
+
+import java.io.IOException;
+import java.io.Writer;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.regex.Pattern;
+
+import org.apache.commons.lang3.StringUtils;
+
+/**
+ * Metrics sink for prometheus exporter.
+ * <p>
+ * Stores the metric data in-memory and return with it on request.
+ */
+public class PrometheusMetricsSink implements MetricsSink {
+
+  /**
+   * Cached output lines for each metrics.
+   */
+  private Map<String, String> metricLines = new HashMap<>();
+
+  private static final Pattern SPLIT_PATTERN =
+      Pattern.compile("(?<!(^|[A-Z_]))(?=[A-Z])|(?<!^)(?=[A-Z][a-z])");
+
+  public PrometheusMetricsSink() {
+  }
+
+  @Override
+  public void putMetrics(MetricsRecord metricsRecord) {
+    for (AbstractMetric metrics : metricsRecord.metrics()) {
+      if (metrics.type() == MetricType.COUNTER
+          || metrics.type() == MetricType.GAUGE) {
+
+        String key = prometheusName(
+            metricsRecord.name(), metrics.name());
+
+        StringBuilder builder = new StringBuilder();
+        builder.append("# TYPE " + key + " " +
+            metrics.type().toString().toLowerCase() + "\n");
+        builder.append(key + "{");
+        String sep = "";
+
+        //add tags
+        for (MetricsTag tag : metricsRecord.tags()) {
+          String tagName = tag.name().toLowerCase();
+
+          //ignore specific tag which includes sub-hierarchy
+          if (!tagName.equals("numopenconnectionsperuser")) {
+            builder.append(
+                sep + tagName + "=\"" + tag.value() + "\"");
+            sep = ",";
+          }
+        }
+        builder.append("} ");
+        builder.append(metrics.value());
+        metricLines.put(key, builder.toString());
+
+      }
+    }
+  }
+
+  /**
+   * Convert CamelCase based names to lower-case names where the separator
+   * is the underscore, to follow prometheus naming conventions.
+   */
+  public String prometheusName(String recordName,
+                               String metricName) {
+    String baseName = StringUtils.capitalize(recordName)
+        + StringUtils.capitalize(metricName);
+    baseName = baseName.replace('-', '_');
+    String[] parts = SPLIT_PATTERN.split(baseName);
+    return String.join("_", parts).toLowerCase();
+  }
+
+  @Override
+  public void flush() {
+
+  }
+
+  @Override
+  public void init(SubsetConfiguration subsetConfiguration) {
+
+  }
+
+  public void writeMetrics(Writer writer) throws IOException {
+    for (String line : metricLines.values()) {
+      writer.write(line + "\n");
+    }
+  }
+}
diff --git a/hadoop-common-project/hadoop-common/src/main/resources/core-default.xml b/hadoop-common-project/hadoop-common/src/main/resources/core-default.xml
index 7d9862d6f1f..3f4608d91c5 100644
--- a/hadoop-common-project/hadoop-common/src/main/resources/core-default.xml
+++ b/hadoop-common-project/hadoop-common/src/main/resources/core-default.xml
@@ -3494,4 +3494,14 @@
       the right KMS for encrypted files.
     </description>
   </property>
+
+  <property>
+    <name>hadoop.prometheus.endpoint.enabled</name>
+    <value>false</value>
+    <description>
+      If set to true, prometheus compatible metric page on the HTTP servers
+      is enabled via '/prom' endpoint.
+    </description>
+  </property>
+
 </configuration>
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/sink/TestPrometheusMetricsSink.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/sink/TestPrometheusMetricsSink.java
new file mode 100644
index 00000000000..f9649a6bfdd
--- /dev/null
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/sink/TestPrometheusMetricsSink.java
@@ -0,0 +1,111 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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 org.apache.hadoop.metrics2.sink;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.OutputStreamWriter;
+
+import org.apache.hadoop.metrics2.MetricsSystem;
+import org.apache.hadoop.metrics2.annotation.Metric;
+import org.apache.hadoop.metrics2.annotation.Metrics;
+import org.apache.hadoop.metrics2.lib.DefaultMetricsSystem;
+import org.apache.hadoop.metrics2.lib.MutableCounterLong;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+/**
+ * Test prometheus Sink.
+ */
+public class TestPrometheusMetricsSink {
+
+  @Test
+  public void testPublish() throws IOException {
+    //GIVEN
+    MetricsSystem metrics = DefaultMetricsSystem.instance();
+
+    metrics.init("test");
+    PrometheusMetricsSink sink = new PrometheusMetricsSink();
+    metrics.register("Prometheus", "Prometheus", sink);
+    TestMetrics testMetrics = metrics
+        .register("TestMetrics", "Testing metrics", new TestMetrics());
+
+    metrics.start();
+    testMetrics.numBucketCreateFails.incr();
+    metrics.publishMetricsNow();
+    ByteArrayOutputStream stream = new ByteArrayOutputStream();
+    OutputStreamWriter writer = new OutputStreamWriter(stream, UTF_8);
+
+    //WHEN
+    sink.writeMetrics(writer);
+    writer.flush();
+
+    //THEN
+    String writtenMetrics = stream.toString(UTF_8.name());
+    System.out.println(writtenMetrics);
+    Assert.assertTrue(
+        "The expected metric line is missing from prometheus metrics output",
+        writtenMetrics.contains(
+            "test_metrics_num_bucket_create_fails{context=\"dfs\"")
+    );
+
+    metrics.stop();
+    metrics.shutdown();
+  }
+
+  @Test
+  public void testNamingCamelCase() {
+    PrometheusMetricsSink sink = new PrometheusMetricsSink();
+
+    Assert.assertEquals("rpc_time_some_metrics",
+        sink.prometheusName("RpcTime", "SomeMetrics"));
+
+    Assert.assertEquals("om_rpc_time_om_info_keys",
+        sink.prometheusName("OMRpcTime", "OMInfoKeys"));
+
+    Assert.assertEquals("rpc_time_small",
+        sink.prometheusName("RpcTime", "small"));
+  }
+
+  @Test
+  public void testNamingPipeline() {
+    PrometheusMetricsSink sink = new PrometheusMetricsSink();
+
+    String recordName = "SCMPipelineMetrics";
+    String metricName = "NumBlocksAllocated-"
+        + "RATIS-THREE-47659e3d-40c9-43b3-9792-4982fc279aba";
+    Assert.assertEquals(
+        "scm_pipeline_metrics_"
+            + "num_blocks_allocated_"
+            + "ratis_three_47659e3d_40c9_43b3_9792_4982fc279aba",
+        sink.prometheusName(recordName, metricName));
+  }
+
+  /**
+   * Example metric pojo.
+   */
+  @Metrics(about = "Test Metrics", context = "dfs")
+  private static class TestMetrics {
+
+    @Metric
+    private MutableCounterLong numBucketCreateFails;
+  }
+}
\ No newline at end of file
diff --git a/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/server/BaseHttpServer.java b/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/server/BaseHttpServer.java
index 9a1d4b3c779..906790f8dea 100644
--- a/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/server/BaseHttpServer.java
+++ b/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/server/BaseHttpServer.java
@@ -70,6 +70,12 @@ public BaseHttpServer(Configuration conf, String name) throws IOException {
       this.httpAddress = getHttpBindAddress();
       this.httpsAddress = getHttpsBindAddress();
       HttpServer2.Builder builder = null;
+
+      // Avoid registering o.a.h.http.PrometheusServlet in HttpServer2.
+      // TODO: Replace "hadoop.prometheus.endpoint.enabled" with
+      // CommonConfigurationKeysPublic.HADOOP_PROMETHEUS_ENABLED when possible.
+      conf.setBoolean("hadoop.prometheus.endpoint.enabled", false);
+
       builder = DFSUtil.httpServerTemplateForNNAndJN(conf, this.httpAddress,
           this.httpsAddress, name, getSpnegoPrincipal(), getKeytabFile());