README.md in fluent-plugin-cloudwatch-2.0.1 vs README.md in fluent-plugin-cloudwatch-2.1.0

@@ -237,9 +237,39 @@
 
 ## config: emit_zero
 
 If `emit_zero` is true and cloudwatch datapoint is empty, fluent-plugin-cloudwatch emits 0 instead of warn log "datapoint is empty".
 
+## config: record_attr
+
+`record_attr` is an optional value injected into each records.
+
+```
+<source>
+  @type cloudwatch
+  tag  cloudwatch.rds
+  aws_key_id  YOUR_AWS_KEY_ID
+  aws_sec_key YOUR_AWS_SECRET_KEY
+  cw_endpoint monitoring.ap-northeast-1.amazonaws.com
+
+  namespace AWS/RDS
+  metric_name CPUUtilization,FreeStorageSpace
+  dimensions_name DBInstanceIdentifier
+  dimensions_value rds01
+  record_attr DBInstanceIdentifier:rds01
+  # JSON format
+  # record_attr {"DBInstanceIdentifier":"rds01"}
+</source>
+```
+
+Example output.
+
+```
[phone]T13:40:00+09:00       cloudwatch.rds      {"CPUUtilization":2.0,"DBInstanceIdentifier":"rds01"}
[phone]T13:40:00+09:00       cloudwatch.rds      {"FreeStorageSpace":104080723968.0,"DBInstanceIdentifier":"rds01"}
+```
+
+
 ## Contributing
 
 1. Fork it
 2. Create your feature branch (`git checkout -b my-new-feature`)
 3. Commit your changes (`git commit -am 'Added some feature'`)