public void setEntityIdKey(String entityIdKey) {
        this.entityIdKey = entityIdKey;
    }
<p>
The entity, such as a user or session, that does an action that causes a metric value to be recorded.
</p>

@param entityIdKey
       The entity, such as a user or session, that does an action that causes a metric value to be recorded.
aws-java-sdk-cloudwatchevidently/src/main/java/com/amazonaws/services/cloudwatchevidently/model/MetricDefinition.java