Add the connection retry method

Author: civitaspo

src/main/java/org/embulk/output/sftp/SftpFileOutput.java

@@ -34,6 +34,7 @@ public class SftpFileOutput
     private final String userInfo;
     private final String host;
     private final int port;
+    private final int maxConnectionRetry;
     private final String pathPrefix;
     private final String sequenceFormat;
     private final String fileNameExtension;
@@ -98,6 +99,7 @@ private FileSystemOptions initializeFsOptions(PluginTask task)
         this.fsOptions = initializeFsOptions(task);
         this.host = task.getHost();
         this.port = task.getPort();
+        this.maxConnectionRetry = task.getMaxConnectionRetry();
         this.pathPrefix = task.getPathPrefix();
         this.sequenceFormat = task.getSequenceFormat();
         this.fileNameExtension = task.getFileNameExtension();
@@ -203,6 +205,26 @@ private String getOutputFilePath()
     private FileObject newSftpFile(URI sftpUri)
             throws FileSystemException
     {
-        return manager.resolveFile(sftpUri.toString(), fsOptions);
+        int count = 0;
+        while (true) {
+            try {
+                return manager.resolveFile(sftpUri.toString(), fsOptions);
+            }
+            catch (FileSystemException e) {
+                if (++count == maxConnectionRetry) {
+                    throw e;
+                }
+                logger.warn("failed to connect sftp server: " + e.getMessage(), e);
+
+                try {
+                    Thread.sleep(count * 1000); // milliseconds
+                }
+                catch (InterruptedException e1) {
+                    // Ignore this exception
+                    logger.warn(e.getMessage(), e);
+                }
+                logger.warn("retry to connect sftp server: " + count + " times");
+            }
+        }
     }
 }

src/main/java/org/embulk/output/sftp/SftpFileOutputPlugin.java

@@ -53,6 +53,10 @@ public interface PluginTask
         @ConfigDefault("600") // 10 minutes
         public int getSftpConnectionTimeout();
 
+        @Config("max_connection_retry")
+        @ConfigDefault("5") // 5 times retry to connect sftp server if failed.
+        public int getMaxConnectionRetry();
+
         @Config("path_prefix")
         public String getPathPrefix();