NIFI-894 Introducing a lock file to communicate from boostrap to NiFi that a shutdown is in progress.

nifi-bootstrap/src/main/java/org/apache/nifi/bootstrap/RunNiFi.java

@@ -235,6 +235,16 @@ public class RunNiFi {
         return statusFile;
     }
 
+    public File getLockFile(final Logger logger) {
+        final File confDir = bootstrapConfigFile.getParentFile();
+        final File nifiHome = confDir.getParentFile();
+        final File bin = new File(nifiHome, "bin");
+        final File lockFile = new File(bin, "nifi.lock");
+
+        logger.debug("Lock File: {}", lockFile);
+        return lockFile;
+    }
+
     private Properties loadProperties(final Logger logger) throws IOException {
         final Properties props = new Properties();
         final File statusFile = getStatusFile(logger);
@@ -498,6 +508,12 @@ public class RunNiFi {
             return;
         }
 
+        // indicate that a stop command is in progress
+        final File lockFile = getLockFile(logger);
+        if (!lockFile.exists()) {
+            lockFile.createNewFile();
+        }
+
         final Properties nifiProps = loadProperties(logger);
         final String secretKey = nifiProps.getProperty("secret.key");
 
@@ -576,6 +592,10 @@ public class RunNiFi {
             }
         } catch (final IOException ioe) {
             logger.error("Failed to send shutdown command to port {} due to {}", new Object[]{port, ioe.toString(), ioe});
+        } finally {
+            if (lockFile.exists() && !lockFile.delete()) {
+                logger.error("Failed to delete lock file {}; this file should be cleaned up manually", lockFile);
+            }
         }
     }
 
@@ -624,6 +644,11 @@ public class RunNiFi {
             return;
         }
 
+        final File prevLockFile = getLockFile(cmdLogger);
+        if (prevLockFile.exists() && !prevLockFile.delete()){
+            cmdLogger.warn("Failed to delete previous lock file {}; this file should be cleaned up manually", prevLockFile);
+        }
+
         final ProcessBuilder builder = new ProcessBuilder();
 
         if (!bootstrapConfigFile.exists()) {
@@ -805,6 +830,12 @@ public class RunNiFi {
                         return;
                     }
 
+                    final File  lockFile = getLockFile(defaultLogger);
+                    if (lockFile.exists()) {
+                        defaultLogger.info("A shutdown was initiated. Will not restart NiFi");
+                        return;
+                    }
+
                     final boolean previouslyStarted = getNifiStarted();
                     if (!previouslyStarted) {
                         defaultLogger.info("NiFi never started. Will not restart NiFi");