src/main/java/org/embulk/input/gcs/GcsFileInputPlugin.java in embulk-input-gcs-0.1.8 vs src/main/java/org/embulk/input/gcs/GcsFileInputPlugin.java in embulk-input-gcs-0.1.9

@@ -84,11 +84,10 @@
         @ConfigInject
         BufferAllocator getBufferAllocator();
     }
 
     private static final Logger log = Exec.getLogger(GcsFileInputPlugin.class);
-    private static GcsAuthentication auth;
 
     @Override
     public ConfigDiff transaction(ConfigSource config,
                                   FileInputPlugin.Control control)
     {
@@ -113,26 +112,31 @@
             if (!task.getP12Keyfile().isPresent() || !task.getServiceAccountEmail().isPresent()) {
                 throw new ConfigException("If auth_method is private_key, you have to set both service_account_email and p12_keyfile");
             }
         }
 
+        Storage client = newGcsClient(task, newGcsAuth(task));
+
+        // list files recursively
+        task.setFiles(listFiles(task, client));
+        // number of processors is same with number of files
+        return resume(task.dump(), task.getFiles().size(), control);
+    }
+
+    private GcsAuthentication newGcsAuth(PluginTask task)
+    {
         try {
-            auth = new GcsAuthentication(
+            return new GcsAuthentication(
                     task.getAuthMethod().getString(),
                     task.getServiceAccountEmail(),
                     task.getP12Keyfile().transform(localFileToPathString()),
                     task.getJsonKeyfile().transform(localFileToPathString()),
                     task.getApplicationName()
             );
         } catch (GeneralSecurityException | IOException ex) {
             throw new ConfigException(ex);
         }
-
-        // list files recursively
-        task.setFiles(listFiles(task));
-        // number of processors is same with number of files
-        return resume(task.dump(), task.getFiles().size(), control);
     }
 
     @Override
     public ConfigDiff resume(TaskSource taskSource,
                              int taskCount,
@@ -163,11 +167,11 @@
                         int taskCount,
                         List<TaskReport> successTaskReports)
     {
     }
 
-    protected Storage newGcsClient(final PluginTask task)
+    protected Storage newGcsClient(final PluginTask task, final GcsAuthentication auth)
     {
         Storage client = null;
         try {
             client = auth.getGcsClient(task.getBucket());
         } catch (IOException ex) {
@@ -186,13 +190,12 @@
                 return file.getPath().toString();
             }
         };
     }
 
-    public List<String> listFiles(PluginTask task)
+    public List<String> listFiles(PluginTask task, Storage client)
     {
-        Storage client = newGcsClient(task);
         String bucket = task.getBucket();
 
         return listGcsFilesByPrefix(client, bucket, task.getPathPrefix(), task.getLastPath());
     }
 
@@ -289,10 +292,10 @@
         private final String key;
         private boolean opened = false;
 
         public SingleFileProvider(PluginTask task, int taskIndex)
         {
-            this.client = newGcsClient(task);
+            this.client = newGcsClient(task, newGcsAuth(task));
             this.bucket = task.getBucket();
             this.key = task.getFiles().get(taskIndex);
         }
 
         @Override