Affinity

You can add the affinity attribute in a task or in a workflow definition to run a specific task on the same workstation where the main task runs or vice versa. The option is useful when you have pool workstations and want to run tasks on the same workstation.

Overview

When you run a task on pools, the workstation is selected dynamically. In such scenarios, you can use the affinity option to run multiple tasks on the same workstation. You can add a task in the main task or workflow definition as a value for the affinity attribute. When either the main task or the affinity task is complete based on priorities or dependencies, the other task runs on the same workstation.

The main task and the affinity task must be in the same workflow. If the workstation for the main task is a dynamic agent, then the workstation for the affinity task must also be the same dynamic agent. If the workstation type for the main task is a pool, then the workstation for the affinity task must be either the same pool or a member of the same pool. If any of these conditions does not match, the task submitted first waits for ten minutes¹ and then fails.

If initially the workstation for the main task or the affinity task is not a member of the pool, you can also add it to the pool within ten minutes¹ to run the task on the same workstation where the other task runs.

Note:

¹ By default, the task waits for ten minutes if the conditions described above are not met. To customize this time period, add the UNO_WAITING_JOB_EXPIRE_TIMEOUT parameter as an environment variable in the values.yaml file with a value in either seconds or minutes.
The conditions are monitored every sixty seconds by default. To customize this value, add the UNO_WAITING_JOB_EXPIRE_FREQUENCY parameter as an environment variable in the values.yaml file with a value in either seconds or minutes.

You can add the affinity option either in the main task definition or within the workflow definition that contains the main task. If you add the option in both, then the priority is always given to the one added in the workflow definition. The affinity option specified within the task definition is ignored in this scenario.

For embedded tasks you must add the affinity option either within the embedded task definition or within in the workflow definition. If you add the option in both, then the workflow definition is not saved and returns an error.

Examples:

To add JOB2 (with workstation /WS_AGT_0, a member of the pool delta_pool) as an affinity task in TASKDEF_1 with both tasks in the same workflow, create the task definition for TASKDEF_1 as follows:
```
---
kind: JobDefinition
def:
  workstation: "delta_pool"
  folder: "/"
  name: TASKDEF_1
  description: Sample executable task definition TASKDEF_1
  type: executable
  task:
    executable:
      interactive: 'false'
      script: sleep 20
  affinity: TASK2
  recovery:
    action: STOP
    repeatAffinity: false
```
Both tasks TASK2 and TASKDEF_1 run sequentially on the /WS_AGT_0 workstation. The order of task submission is based on other factors such as limit, priority, fence, and dependencies allotted to each task.
To add TASKDEF (with workstation as the pool delta_pool) as an affinity task in TASK1 (with workstation /WS_AGT_1, a member of the pool delta_pool), create the task definition for TASK1 as follows:
```
---
kind: JobDefinition
def:
  workstation: /WS_AGT_1
  folder: /
  name: TASK1
  type: executable
  task:
    executable:
      interactive: false
      path: ls
      credential: {}
  affinity: TASKDEF
  recovery:
    action: STOP
    repeatAffinity: false
```
Both tasks TASK1 and TASKDEF run sequentially on the /WS_AGT_1 workstation. The order of task submission is based on other factors such as limit, priority, fence, and dependencies allotted to each task.

To add the affinity option in an embedded task definition, create the workflow definition as follows:

---
kind: JobStream
def:
  folder: /
  name: JS
  workstation: /WS_AGT_0
  jobs:
  - name: JD1
    workstation: /WS_AGT_0
    jobDefinition:
      type: executable
      task:
        executable:
          interactive: false
          path: ls
      recovery:
        action: STOP
        repeatAffinity: false
    priority: 10
    affinity: TASK2