Application lifecycle in YARN in Hadoop - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the first step in the Application lifecycle in YARN?

The first step is Application Submission, where the client submits the application to the ResourceManager.

beginner

What role does the ResourceManager play in YARN's Application lifecycle?

The ResourceManager manages resources and allocates containers to applications based on their needs.

beginner

What is the purpose of the ApplicationMaster in YARN?

The ApplicationMaster coordinates the execution of the application, requesting resources and monitoring progress.

intermediate

What happens during the Container Allocation phase in YARN?

The ResourceManager allocates containers on NodeManagers where the application tasks will run.

beginner

How does YARN handle application completion?

Once the application finishes, the ApplicationMaster notifies the ResourceManager, which then releases resources and cleans up.

What component in YARN is responsible for managing cluster resources?

A ResourceManager

B NodeManager

C ApplicationMaster

D Client

The ResourceManager manages cluster resources and allocates them to applications.

Who submits the application to YARN?

A ResourceManager

B NodeManager

C Client

D ApplicationMaster

The client submits the application to the ResourceManager to start the lifecycle.

What does the ApplicationMaster do?

A Coordinates application execution and resource requests

B Runs the entire cluster

C Allocates containers to other applications

D Submits applications

The ApplicationMaster coordinates the execution of its application and requests resources.

Where do application tasks actually run in YARN?

A ResourceManager

B NodeManager containers

C Client machine

D ApplicationMaster

Application tasks run inside containers managed by NodeManagers.

What happens after an application finishes in YARN?

A Resources are held for reuse

B Client restarts the application automatically

C NodeManager deletes the application

D ApplicationMaster notifies ResourceManager to release resources

The ApplicationMaster informs the ResourceManager to release resources and clean up.

Describe the main steps in the Application lifecycle in YARN from submission to completion.

Think about who does what and when during the lifecycle.

Explain the roles of ResourceManager, ApplicationMaster, and NodeManager in YARN's Application lifecycle.

Focus on each component's responsibility.

Practice

1. Which component in YARN is responsible for managing the overall lifecycle of an application from submission to completion?

easy

A. ApplicationMaster

B. Container

C. ResourceManager

D. NodeManager

Solution

1. Step 1: Understand YARN components roles

   The ResourceManager is the master that manages resources and schedules applications.

2. Step 2: Identify lifecycle management responsibility

   ResourceManager coordinates application submission, resource allocation, and monitors progress.

3. Final Answer:

   ResourceManager -> Option C

4. Quick Check:

   ResourceManager = lifecycle manager [OK]

Hint: ResourceManager controls app lifecycle, not NodeManager or containers [OK]

Common Mistakes:

• Confusing ApplicationMaster with ResourceManager
• Thinking NodeManager manages entire lifecycle
• Assuming containers manage lifecycle

2. Which of the following is the correct sequence of steps in the YARN application lifecycle?

easy

A. Container launch -> Application submission -> Resource allocation -> Application completion

B. Application submission -> Resource allocation -> Container launch -> Application completion

C. Resource allocation -> Application submission -> Container launch -> Application completion

D. Application completion -> Container launch -> Resource allocation -> Application submission

Solution

1. Step 1: Recall YARN lifecycle order

   First, the application is submitted, then resources are allocated.

2. Step 2: Follow container launch and completion

   After allocation, containers launch tasks, then application completes.

3. Final Answer:

   Application submission -> Resource allocation -> Container launch -> Application completion -> Option B

4. Quick Check:

   Submission -> Allocation -> Launch -> Completion [OK]

Hint: Lifecycle starts with submission, ends with completion [OK]

Common Mistakes:

• Mixing order of resource allocation and submission
• Thinking container launch happens before submission
• Reversing completion step

3. Consider this simplified YARN application lifecycle code snippet in pseudocode:

submitApplication()
allocateResources()
launchContainers()
monitorApplication()
cleanup()

Which step is responsible for requesting containers from NodeManagers?

medium

A. submitApplication()

B. launchContainers()

C. cleanup()

D. allocateResources()

Solution

1. Step 1: Understand resource allocation role

   allocateResources() requests containers from NodeManagers via ResourceManager.

2. Step 2: Differentiate from other steps

   submitApplication() submits job, launchContainers() starts tasks, cleanup() frees resources.

3. Final Answer:

   allocateResources() -> Option D

4. Quick Check:

   Resource allocation = container requests [OK]

Hint: Resource allocation step requests containers from NodeManagers [OK]

Common Mistakes:

• Confusing launchContainers() with resource requests
• Thinking submitApplication() requests containers
• Assuming cleanup() handles resource allocation

4. You see a YARN application stuck in the ACCEPTED state for a long time. What is the most likely cause?

medium

A. ResourceManager has no available resources to allocate

B. ApplicationMaster failed to launch

C. NodeManager crashed after container launch

D. Application has already completed

Solution

1. Step 1: Understand ACCEPTED state meaning

   ACCEPTED means application is waiting for resources to be allocated.

2. Step 2: Identify cause of delay in allocation

   If ResourceManager has no free resources, allocation is delayed, causing ACCEPTED state to persist.

3. Final Answer:

   ResourceManager has no available resources to allocate -> Option A

4. Quick Check:

   ACCEPTED = waiting for resources [OK]

Hint: Long ACCEPTED means no resources available [OK]

Common Mistakes:

• Assuming ApplicationMaster failed immediately
• Thinking NodeManager crash causes ACCEPTED state
• Confusing ACCEPTED with COMPLETED state

5. You want to optimize a YARN application that spends too much time in the RUNNING state but finishes slowly. Which approach best improves the application lifecycle?

hard

A. Increase container memory and CPU to speed up task execution

B. Reduce the number of containers to limit resource usage

C. Submit the application multiple times in parallel

D. Disable ApplicationMaster monitoring to reduce overhead

Solution

1. Step 1: Analyze RUNNING state delay cause

   Long RUNNING time means tasks are slow or resource-starved.

2. Step 2: Choose optimization method

   Increasing container memory and CPU helps tasks run faster, reducing RUNNING time.

3. Step 3: Evaluate other options

   Reducing containers slows progress, parallel submissions cause contention, disabling monitoring risks errors.

4. Final Answer:

   Increase container memory and CPU to speed up task execution -> Option A

5. Quick Check:

   More resources = faster RUNNING tasks [OK]

Hint: Boost container resources to speed RUNNING tasks [OK]

Common Mistakes:

• Reducing containers slows application
• Submitting multiple apps causes resource conflicts
• Disabling monitoring hides problems