Merge e2e46e2743 into 2ddb92091c

src/java/org/apache/cassandra/service/CassandraDaemon.java

@@ -759,6 +759,9 @@ public class CassandraDaemon
             start();
 
             logger.info("Startup complete");
+            if (SystemD.isAvailable()) {
+                SystemD.get().notifyReady();
+            }
         }
         catch (Throwable e)
         {

src/java/org/apache/cassandra/service/SystemD.java

@@ -0,0 +1,94 @@
+/*
+ * 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.cassandra.service;
+
+import java.io.File;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.sun.jna.Library; // NOSONAR
+import com.sun.jna.Native; // NOSONAR
+
+public class SystemD {
+
+	private static final Logger logger = LoggerFactory.getLogger(SystemD.class);
+	private static final Api INSTANCE = init();
+
+	private static final CLibrary LIBC = (CLibrary) Native.loadLibrary("c", CLibrary.class);
+
+	private interface CLibrary extends Library {
+
+		int getpid();
+	}
+
+	public static class Api {
+
+		private final RawApi impl;
+
+		private Api(RawApi rawApi) {
+			this.impl = rawApi;
+		}
+
+		public void notifyReady() {
+			int pid = LIBC.getpid();
+			logger.info("Notify ready through systemd for PID {}...", pid);
+			int errorCode = impl.sd_pid_notify(pid, 0, "READY=1");
+			if (errorCode <= 0) {
+				logger.error("Notify failed: {}", errorCode);
+			} else {
+				logger.info("Notified for {}, errorCode: {}", pid, errorCode);
+			}
+		}
+
+	}
+
+	private interface RawApi extends Library {
+
+		int sd_pid_notify(int pid, int unset, String state); // NOSONAR
+
+	}
+
+	@VisibleForTesting
+	public static boolean isAvailable() {
+		if (INSTANCE == null) {
+			return false;
+		}
+		return true;
+	}
+
+	@VisibleForTesting
+	public static Api get() {
+		if (!isAvailable()) {
+			throw new RuntimeException("SystemD is not available");
+		}
+		return INSTANCE;
+	}
+
+	private static Api init() {
+		try {
+			RawApi rawApi = Native.load("systemd", RawApi.class);
+			return new Api(rawApi);
+		} catch (UnsatisfiedLinkError le) {
+			logger.warn("SystemD support is not available: {}", le.getMessage());
+			return null;
+		}
+	}
+
+}