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Using Tagging
Amazon Elastic MapReduce (Amazon EMR) automatically tags each Amazon EC2 instance it launches with key-value pairs that identify the job flow and the instance group to which the instance belongs. This makes it easy to filter your Amazon EC2 instances to show, for example, only those instances belonging to a particular job flow or to show all of the currently running instances in the task-instance group. This is especially useful if you are running several job flows concurrently or managing large numbers of Amazon EC2 instances.
These are the predefined key-value pairs that Amazon EMR assigns:
| Key | Value |
|---|---|
| aws:elasticmapreduce:job-flow-id |
<job-flow-identifier> |
| aws:elasticmapreduce:instance-group-role |
<group-role> |
The values are further defined as follows:
The <job-flow-identifier> is the ID of the job flow the instance is provisioned for. It appears in the format j-XXXXXXXXXXXXX.
The <group-role> is one of the following values: master, core, or task. These values correspond to the master instance group, core instance group, and task instance group.
You can view and filter on the tags that Amazon EMR adds. For more information on how to do this, go to Using Tags in the Amazon Elastic Compute Cloud User Guide. Because the tags set by Amazon EMR are system tags and cannot be edited or deleted, the sections on displaying and filtering tags are the most relevant.
![[Note]](http://docs.amazonwebservices.com/docs-common/images/note.png) | Note |
|---|---|
Amazon EMR adds tags to the Amazon EC2 instance when its status is updated to running. If there's a latency period between the time the Amazon EC2 instance is provisioned and the time its status is set to running, the tags set by Amazon EMR will not appear until the instance starts. If you don't see the tags, wait for a few minutes and refresh the view, then the Amazon EMR tags should appear. |
