Understanding YARN Containers in Hadoop
What are YARN Containers?
YARN (Yet Another Resource Negotiator) is the resource management and job scheduling system in Hadoop. YARN containers are the fundamental units of computation in YARN, responsible for executing tasks and managing resources. Each YARN container is allocated a specific amount of CPU, memory, and other resources, and is used to run a single task or application.
YARN Container Architecture
graph TD
A[YARN ResourceManager] --> B[YARN NodeManager]
B --> C[YARN Container]
C --> D[Application Master]
C --> E[Task]
The YARN ResourceManager is responsible for managing the overall cluster resources, while the YARN NodeManager runs on each node and manages the resources and containers on that node. The Application Master is responsible for negotiating resources with the ResourceManager and coordinating the execution of tasks within the containers.
YARN Container Allocation
YARN uses a resource-based scheduling model, where each container is allocated a specific amount of CPU, memory, and other resources. The ResourceManager is responsible for allocating these resources to the containers based on the application's resource requirements and the available cluster resources.
## Example YARN container configuration
yarn.nodemanager.resource.cpu-vcores=4
yarn.nodemanager.resource.memory-mb=8192
In this example, each YARN container is allocated 4 CPU cores and 8 GB of memory.
YARN Container Lifecycle
The lifecycle of a YARN container includes the following stages:
- Requested: The Application Master requests a container from the ResourceManager.
- Allocated: The ResourceManager allocates a container on a specific node and informs the Application Master.
- Launched: The NodeManager launches the container and starts the application's task.
- Running: The task executes within the container.
- Completed: The task finishes execution and the container is released.
Understanding the YARN container architecture and lifecycle is crucial for effectively managing and troubleshooting Hadoop applications.