How to troubleshoot 'application not found' issue in Hadoop YARN?

Introduction

Hadoop YARN is a crucial component of the Hadoop ecosystem, responsible for managing and scheduling resources for Hadoop applications. However, sometimes users may encounter the 'application not found' issue, which can be frustrating and disrupt their Hadoop workflows. This tutorial will guide you through the process of identifying and resolving this common problem, helping you to ensure your Hadoop applications run smoothly.

Skills Graph

%%%%{init: {'theme':'neutral'}}%%%% flowchart RL hadoop(("`Hadoop`")) -.-> hadoop/HadoopYARNGroup(["`Hadoop YARN`"]) hadoop/HadoopYARNGroup -.-> hadoop/yarn_setup("`Hadoop YARN Basic Setup`") hadoop/HadoopYARNGroup -.-> hadoop/apply_scheduler("`Applying Scheduler`") hadoop/HadoopYARNGroup -.-> hadoop/yarn_app("`Yarn Commands application`") hadoop/HadoopYARNGroup -.-> hadoop/yarn_container("`Yarn Commands container`") hadoop/HadoopYARNGroup -.-> hadoop/yarn_log("`Yarn Commands log`") hadoop/HadoopYARNGroup -.-> hadoop/resource_manager("`Resource Manager`") hadoop/HadoopYARNGroup -.-> hadoop/node_manager("`Node Manager`") subgraph Lab Skills hadoop/yarn_setup -.-> lab-417738{{"`How to troubleshoot 'application not found' issue in Hadoop YARN?`"}} hadoop/apply_scheduler -.-> lab-417738{{"`How to troubleshoot 'application not found' issue in Hadoop YARN?`"}} hadoop/yarn_app -.-> lab-417738{{"`How to troubleshoot 'application not found' issue in Hadoop YARN?`"}} hadoop/yarn_container -.-> lab-417738{{"`How to troubleshoot 'application not found' issue in Hadoop YARN?`"}} hadoop/yarn_log -.-> lab-417738{{"`How to troubleshoot 'application not found' issue in Hadoop YARN?`"}} hadoop/resource_manager -.-> lab-417738{{"`How to troubleshoot 'application not found' issue in Hadoop YARN?`"}} hadoop/node_manager -.-> lab-417738{{"`How to troubleshoot 'application not found' issue in Hadoop YARN?`"}} end

Introduction to Hadoop YARN

Hadoop YARN (Yet Another Resource Negotiator) is a key component of the Apache Hadoop ecosystem, responsible for resource management and job scheduling. It was introduced in Hadoop 2.0 to address the limitations of the previous resource management system, the JobTracker, which was a single point of failure and a performance bottleneck.

YARN is designed to provide a more scalable and flexible resource management system, allowing for the execution of various types of applications, including batch processing, interactive processing, and real-time processing.

YARN Architecture

YARN follows a master-slave architecture, where the main components are:

graph TD A[ResourceManager] -- Manages cluster resources --> B[NodeManager] B -- Runs containers --> C[Application Master] C -- Negotiates resources --> B

ResourceManager: The central authority that manages the cluster's resources and schedules applications.
NodeManager: The per-node agent responsible for launching and monitoring containers, as well as reporting the node's resource usage and status to the ResourceManager.
Application Master: The per-application framework that negotiates resources from the ResourceManager and works with the NodeManagers to execute and monitor the application's tasks.

YARN Application Execution

The typical flow of executing an application in YARN is as follows:

The client submits the application to the ResourceManager.
The ResourceManager allocates the required resources and launches the Application Master.
The Application Master negotiates additional resources from the ResourceManager as needed and launches the application's tasks on the NodeManagers.
The NodeManagers execute the tasks and report their status back to the Application Master.
The Application Master monitors the progress of the application and reports the status back to the ResourceManager.

graph LR A[Client] -- Submits application --> B[ResourceManager] B -- Allocates resources --> C[Application Master] C -- Negotiates resources --> B C -- Launches tasks --> D[NodeManager] D -- Executes tasks --> C C -- Reports status --> B

By understanding the YARN architecture and application execution flow, you can better troubleshoot issues related to "application not found" in the Hadoop ecosystem.

Identifying 'Application Not Found' Issues

The "application not found" error in Hadoop YARN can occur due to various reasons, including misconfiguration, resource exhaustion, or issues with the application itself. To identify the root cause of this problem, you can follow these steps:

Check the ResourceManager Logs

The first step is to examine the ResourceManager logs, which can provide valuable information about the application's status and any errors that may have occurred. You can access the ResourceManager logs by navigating to the Hadoop web UI or by running the following command on the ResourceManager node:

sudo tail -n 100 /var/log/hadoop-yarn/resourcemanager/resourcemanager.log

Look for any error messages or exceptions related to the "application not found" issue.

Verify the Application Submission

Ensure that the application was submitted correctly to the YARN cluster. You can check the status of the application using the YARN command-line interface:

yarn application -list

This command will display a list of all the applications running in the YARN cluster, along with their status. If the application is not listed or has a status of "FAILED", it may be the cause of the "application not found" error.

Check the Application Master Logs

If the application is listed in the YARN cluster but is not running, you can check the Application Master logs for more information. The Application Master logs can be accessed by running the following command:

yarn logs -applicationId <application_id>

Replace <application_id> with the ID of the application you're investigating. Look for any error messages or exceptions in the logs that may provide clues about the root cause of the "application not found" issue.

Inspect the NodeManager Logs

In some cases, the issue may be related to the NodeManager, which is responsible for launching and monitoring the application's containers. You can check the NodeManager logs by running the following command on the NodeManager nodes:

sudo tail -n 100 /var/log/hadoop-yarn/nodemanager/nodemanager.log

Look for any errors or warnings related to the application's containers or resource allocation.

By following these steps, you can gather the necessary information to identify the root cause of the "application not found" issue in Hadoop YARN, which will help you resolve the problem more effectively.

Resolving 'Application Not Found' Errors

Once you have identified the root cause of the "application not found" issue, you can take the following steps to resolve the problem:

Verify Application Submission

If the issue is related to the application submission, ensure that the application is submitted correctly. Check the following:

Verify the application's configuration files, such as the job.xml or application.properties, to ensure that all the required parameters are set correctly.
Ensure that the application's executable or script is accessible and can be executed on the YARN cluster.
Check the user permissions to ensure that the user submitting the application has the necessary privileges to access the required resources.

Increase Resource Allocation

If the issue is related to resource exhaustion, you can try increasing the resource allocation for the YARN cluster or the specific application. You can do this by modifying the following configuration parameters:

ResourceManager Memory: Increase the memory allocated to the ResourceManager by modifying the yarn.resourcemanager.resource.memory parameter in the yarn-site.xml file.
NodeManager Memory: Increase the memory allocated to the NodeManager by modifying the yarn.nodemanager.resource.memory-mb parameter in the yarn-site.xml file.
Application Memory: Increase the memory allocated to the application by modifying the mapreduce.map.memory.mb and mapreduce.reduce.memory.mb parameters in the mapred-site.xml file.

After making the changes, restart the affected YARN services for the changes to take effect.

Restart YARN Services

If the issue persists, you can try restarting the YARN services, including the ResourceManager and NodeManagers. This can help resolve any issues related to the YARN infrastructure. You can use the following commands to restart the YARN services:

sudo systemctl restart hadoop-yarn-resourcemanager
sudo systemctl restart hadoop-yarn-nodemanager

Check Application Dependencies

If the issue is related to the application itself, ensure that all the required dependencies, libraries, and resources are available and accessible on the YARN cluster. This may include checking the application's classpath, jar files, and any external resources it relies on.

By following these steps, you should be able to resolve the "application not found" issue in Hadoop YARN and ensure that your applications are running smoothly on the YARN cluster.

Summary

In this Hadoop tutorial, you have learned how to troubleshoot the 'application not found' issue in Hadoop YARN. By understanding the root causes of this problem and applying the appropriate troubleshooting techniques, you can effectively resolve this issue and maintain the reliability of your Hadoop infrastructure.