update readme

Author: civitaspo

README.md

@@ -1,20 +1,24 @@
-# Hdfs output plugin for Embulk
+# Hdfs file output plugin for Embulk
 
 A File Output Plugin for Embulk to write HDFS.
 
 ## Overview
 
 * **Plugin type**: file output
-* **Load all or nothing**: no
+* **Load all or nothing**: yes
 * **Resume supported**: no
 * **Cleanup supported**: no
 
 ## Configuration
 
 - **config_files** list of paths to Hadoop's configuration files (array of strings, default: `[]`)
 - **config** overwrites configuration parameters (hash, default: `{}`)
-- **output_path** the path finally stored files. (string, default: `"/tmp/embulk.output.hdfs_output.%Y%m%d_%s"`)
-- **working_path** the path temporary stored files. (string, default: `"/tmp/embulk.working.hdfs_output.%Y%m%d_%s"`)
+- **path_prefix** prefix of target files (string, required)
+- **file_ext** suffix of target files (string, required)
+- **sequence_format** format for sequence part of target files (string, default: `'.%03d.%02d'`)
+- **rewind_seconds** When you use Date format in path_prefix property(like `/tmp/embulk/%Y-%m-%d/out`), the format is interpreted by using the time which is Now minus this property. (int, default: `0`)
+- **overwrite** overwrite files when the same filenames already exists (boolean, default: `false`)
+    - *caution*: even if this property is `true`, this does not mean ensuring the idempotence. if you want to ensure the idempotence, you need the procedures to remove output files after or before running. 
 
 ## Example
 
@@ -24,14 +28,13 @@ out:
   config_files:
     - /etc/hadoop/conf/core-site.xml
     - /etc/hadoop/conf/hdfs-site.xml
-    - /etc/hadoop/conf/mapred-site.xml
-    - /etc/hadoop/conf/yarn-site.xml
   config:
     fs.defaultFS: 'hdfs://hdp-nn1:8020'
-    dfs.replication: 1
-    mapreduce.client.submit.file.replication: 1
     fs.hdfs.impl: 'org.apache.hadoop.hdfs.DistributedFileSystem'
     fs.file.impl: 'org.apache.hadoop.fs.LocalFileSystem'
+  path_prefix: '/tmp/embulk/hdfs_output/%Y-%m-%d/out'
+  file_ext: 'txt'
+  overwrite: true
   formatter:
     type: csv
     encoding: UTF-8