Recently, one of our customers approached us to restart an Amazon EMR service, such as YARN ResourceManager.

Here, at Bobcares, we assist our customers with several AWS queries as part of our AWS Support Services.

Today, let us see how our techs perform this query.

Restart a service in Amazon EMR

The restart process differs depending on which Amazon EMR release version we’re using.

Moving ahead, let us see the steps our Support Techs employ in different versions.

• Amazon EMR 5.30.0 and later release versions

1. Initially, we connect to the master node via SSH.

2. Here, we can list all the running services:

systemctl --type=service

3. For a specific service, we run a command similar to the following.

For example, to list the Zeppelin service:

systemctl --type=service | grep -i zeppelin

Our output will be similar to this:

zeppelin.service loaded active running Zeppelin

4. Similarly, for a detailed status report for a specific service:

sudo systemctl status zeppelin

Our output will be similar to this:

zeppelin.service - Zeppelin
Loaded: loaded (/etc/systemd/system/zeppelin.service; enabled; vendor preset: disabled)
Active: active (running) since Tue 2020-04-21 18:26:53 UTC; 4min 59s ago
Process: 25719 ExecStart=/usr/bin/su -s /bin/bash zeppelin -c cd /var/lib/zeppelin && /usr/lib/zeppelin/bin/zeppelin-daemon.sh --config '/etc/zeppelin/conf' start (code=exited, status=0/SUCCESS)
Main PID: 25749 (java)
Tasks: 0
Memory: 4.0K
CGroup: /system.slice/zeppelin.service
25749 /etc/alternatives/jre/bin/java -Dfile.encoding=UTF-8 -Xms1024m -Xmx1024m -XX:MaxPermSize=512m

5. Eventually, we stop the service:

Make sure to not use the restart command hereafter.

sudo systemctl stop zeppelin

6. To verify the service status, we run:

sudo systemctl status zeppelin

7. Then we start the service:

sudo systemctl start zeppelin

8. Finally, we verify if the service is running:

sudo systemctl status zeppelin

• Amazon EMR 4.x-5.29.0 release versions

1. Here, we connect to the master node via SSH.

2. Then we list all running services:

initctl list

3. Then to stop the service we run the following command:

sudo stop bob-yarn-resourcemanager

We need to replace “bob-yarn-resourcemanager” with the service to restart.

4. This may take a few minutes, and then start the service:

sudo start hadoop-yarn-resourcemanager

5. Eventually, we verify that the process is running:

sudo status hadoop-yarn-resourcemanager

• Amazon EMR 2.x-3.x release versions

1. As we know, first, we connect to the master node via SSH.

2. Then we list all running services:

ls /etc/init.d/

3. We go ahead and restart the service:

sudo /etc/init.d/bob-hdfs-namenode restart

We need to change “bob-hdfs-namenode” with the service we want to restart

4. Finally, we need to verify that the process is running:

sudo /etc/init.d/hadoop-hdfs-namenode status

[Finding it hard to figure it out? We are here for you]

Conclusion

In short, we saw how our Support Techs go about restarting a service in Amazon EMR.