Section 4:27.Reviewing-map-reduce-job-logs-using-resource-manager-and-job-history-server-ui

In Hadoop, you can review MapReduce job logs using the Resource Manager and Job History Server UI. Here are the steps to do this:

1. Open the Resource Manager UI: Open a web browser and go to the URL of the Resource Manager UI. By default, the URL is http://<resource-manager-hostname>:8088/cluster.
2. Select the job: Click on the “Applications” link in the sidebar menu, and then select the job you want to review from the list of running and completed applications.
3. View logs: Click on the “Logs” link in the job details page. This will show you the logs for the different components of the job, such as the Application Master, Node Managers, and containers.
4. Open the Job History Server UI: If you want to review the logs of a completed job, you can use the Job History Server UI. Open a web browser and go to the URL of the Job History Server UI. By default, the URL is http://<job-history-server-hostname>:19888/jobhistory.
5. Select the job: Click on the “Jobs” link in the sidebar menu, and then select the job you want to review from the list of completed jobs.
6. View logs: Click on the “Logs” link in the job details page. This will show you the logs for the different components of the job, such as the Application Master, Node Managers, and containers.

In both the Resource Manager and Job History Server UI, you can filter the logs by different criteria, such as container ID, log type, and log level. This can help you find the information you need to diagnose and troubleshoot issues in your MapReduce jobs.