Notify systemd when Elasticsearch is ready

distribution/build.gradle

@@ -68,6 +68,7 @@ task buildOssNoJdkNotice(type: NoticeTask) {
  *****************************************************************************/
 String ossOutputs = 'build/outputs/oss'
 String defaultOutputs = 'build/outputs/default'
+String systemdOutputs = 'build/outputs/systemd'
 String transportOutputs = 'build/outputs/transport-only'
 
 task processOssOutputs(type: Sync) {
@@ -79,6 +80,10 @@ task processDefaultOutputs(type: Sync) {
   from processOssOutputs
 }
 
+task processSystemdOutputs(type: Sync) {
+  into systemdOutputs
+}
+
 // Integ tests work over the rest http layer, so we need a transport included with the integ test zip.
 // All transport modules are included so that they may be randomized for testing
 task processTransportOutputs(type: Sync) {
@@ -110,6 +115,10 @@ task buildDefaultConfig {
   dependsOn processDefaultOutputs
   outputs.dir "${defaultOutputs}/config"
 }
+task buildSystemdModule {
+  dependsOn processSystemdOutputs
+  outputs.dir "${systemdOutputs}/modules"
+}
 task buildTransportModules {
   dependsOn processTransportOutputs
   outputs.dir "${transportOutputs}/modules"
@@ -186,6 +195,10 @@ ext.restTestExpansions = [
 // we create the buildOssModules task above but fill it here so we can do a single
 // loop over modules to also setup cross task dependencies and increment our modules counter
 project.rootProject.subprojects.findAll { it.parent.path == ':modules' }.each { Project module ->
+  if (module.name == 'systemd') {
+    // the systemd module is only included in the package distributions
+    return
+  }
   File licenses = new File(module.projectDir, 'licenses')
   if (licenses.exists()) {
     buildDefaultNotice.licensesDir licenses
@@ -218,6 +231,8 @@ xpack.subprojects.findAll { it.parent == xpack }.each { Project xpackModule ->
   copyLog4jProperties(buildDefaultLog4jConfig, xpackModule)
 }
 
+copyModule(processSystemdOutputs, project(':modules:systemd'))
+
 // make sure we have a clean task since we aren't a java project, but we have tasks that
 // put stuff in the build dir
 task clean(type: Delete) {
@@ -288,6 +303,9 @@ configure(subprojects.findAll { ['archives', 'packages'].contains(it.name) }) {
             exclude "**/platform/${excludePlatform}-x86_64/**"
           }
         }
+        if (project.path.startsWith(':distribution:packages')) {
+          from(project(':distribution').buildSystemdModule)
+        }
       }
     }
 

distribution/packages/src/common/systemd/elasticsearch.service

@@ -5,11 +5,13 @@ Wants=network-online.target
 After=network-online.target
 
 [Service]
+Type=notify
 RuntimeDirectory=elasticsearch
 PrivateTmp=true
 Environment=ES_HOME=/usr/share/elasticsearch
 Environment=ES_PATH_CONF=${path.conf}
 Environment=PID_DIR=/var/run/elasticsearch
+Environment=ES_SD_NOTIFY=true
 EnvironmentFile=-${path.env}
 
 WorkingDirectory=/usr/share/elasticsearch

modules/systemd/build.gradle

@@ -0,0 +1,25 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch 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.
+ */
+
+esplugin {
+    description 'Integrates Elasticsearch with systemd'
+    classname 'org.elasticsearch.systemd.SystemdPlugin'
+}
+
+integTest.enabled = false

modules/systemd/src/main/java/org/elasticsearch/systemd/Libsystemd.java

@@ -0,0 +1,49 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch 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.elasticsearch.systemd;
+
+import com.sun.jna.Native;
+
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+
+/**
+ * Provides access to the native method sd_notify from libsystemd.
+ */
+class Libsystemd {
+
+    static {
+        AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
+            Native.register(Libsystemd.class, "libsystemd.so.0");
+            return null;
+        });
+    }
+
+    /**
+     * Notify systemd of state changes.
+     *
+     * @param unset_environment if non-zero, the NOTIFY_SOCKET environment variable will be unset before returning and further calls to
+     *                          sd_notify will fail
+     * @param state             a new-line separated list of variable assignments; some assignments are understood directly by systemd
+     * @return a negative error code on failure, and positive if status was successfully sent
+     */
+    static native int sd_notify(int unset_environment, String state);
+
+}

modules/systemd/src/main/java/org/elasticsearch/systemd/SystemdPlugin.java

@@ -0,0 +1,90 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch 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.elasticsearch.systemd;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.lucene.util.Constants;
+import org.elasticsearch.Assertions;
+import org.elasticsearch.Build;
+import org.elasticsearch.plugins.ClusterPlugin;
+import org.elasticsearch.plugins.Plugin;
+
+import java.io.IOException;
+
+public class SystemdPlugin extends Plugin implements ClusterPlugin {
+
+    private static final Logger logger = LogManager.getLogger(SystemdPlugin.class);
+
+    private final boolean enabled;
+
+    final boolean isEnabled() {
+        return enabled;
+    }
+
+    @SuppressWarnings("unused")
+    public SystemdPlugin() {
+        this(true, Constants.LINUX, System.getenv("ES_SD_NOTIFY"));
+    }
+
+    SystemdPlugin(final boolean assertIsPackageDistribution, final boolean isLinux, final String esSDNotify) {
+        if (Assertions.ENABLED && assertIsPackageDistribution) {
+            // our build is configured to only include this module in the package distributions
+            assert Build.CURRENT.type() == Build.Type.DEB || Build.CURRENT.type() == Build.Type.RPM : Build.CURRENT.type();
+        }
+        if (isLinux == false || esSDNotify == null) {
+            enabled = false;
+            return;
+        }
+        if (Boolean.TRUE.toString().equals(esSDNotify) == false && Boolean.FALSE.toString().equals(esSDNotify) == false) {
+            throw new RuntimeException("ES_SD_NOTIFY set to unexpected value [" + esSDNotify + "]");
+        }
+        enabled = "true".equals(esSDNotify);
+    }
+
+    int sd_notify(@SuppressWarnings("SameParameterValue") final int unset_environment, final String state) {
+        return Libsystemd.sd_notify(0, state);
+    }
+
+    @Override
+    public void onNodeStarted() {
+        if (enabled) {
+            final int rc = sd_notify(0, "READY=1");
+            logger.trace("sd_notify returned [{}]", rc);
+            if (rc < 0) {
+                // treat failure to notify systemd of readiness as a startup failure
+                throw new RuntimeException("sd_notify returned error [" + rc + "]");
+            }
+        }
+    }
+
+    @Override
+    public void close() throws IOException {
+        if (enabled) {
+            final int rc = sd_notify(0, "STOPPING=1");
+            logger.trace("sd_notify returned [{}]", rc);
+            if (rc < 0) {
+                // do not treat failure to notify systemd of stopping as a failure
+                logger.warn("sd_notify returned error [{}]", rc);
+            }
+        }
+    }
+
+}

modules/systemd/src/main/plugin-metadata/plugin-security.policy

@@ -0,0 +1,23 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch 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.
+ */
+
+grant codeBase "${codebase.systemd}" {
+  // for registering native methods
+  permission java.lang.RuntimePermission "accessDeclaredMembers";
+};