CloudOps Orchestration Service:ACS::Loop

Loop array

The Items parameter accepts a list, such as a literal list: [item1, item2, item3].

The Items parameter can also be the name of a parameter that contains a list, such as the Outputs of a previous task.

• Items is a list.

  YAML

  Loop:
    Items: [item1,item2,item3,item4] # A list of items, such as [i-id1, i-id2, i-id3, i-id4]. The items are iterated as parameters for the task where the loop is located.					

  JSON

  {
    "Items": [
      "item1",
      "item2",
      "item3",
      "item4"
    ]
  }		

• Items is the name of a list-type parameter.

  YAML

  Items: '{{ParameterName1}}' # The name of a parameter that can be parsed as a list, such as describeInstance.InstanceIds. The items are iterated as parameters for the task where the loop is located.	

  JSON

  {
    "Items": "{{ParameterName1}}"
  }		

Task execution rate

Two modes are available:

1. Concurrency control: Executes a specified number of items concurrently until all items are processed.

2. Batch control: Divides items into multiple batches. The next batch starts only after the previous batch is complete.

Concurrency control (Concurrency)

• If Items contains 10 items and Concurrency is set to 3, three items are executed concurrently until all items are processed.

  YAML

  Concurrency: 3 # The value can be a number or a percentage for concurrency control, such as 3.
  Mode: Concurrency

  JSON

  {
    "Concurrency": 3,
    "Mode": "Concurrency"
  }

• If Items contains 10 items and Concurrency is set to 20%, the concurrency is 2 (10 × 20%). Two items are executed concurrently until all items are processed.

  YAML

  Concurrency: 20% # Optional. The value can be a number or a percentage, such as 20%.
  Mode: Concurrency

  JSON

  {
    "Concurrency": "20%",
    "Mode": "Concurrency"
  }

Batch control (Batch)

• If Items contains 10 items and Batch is set to [3], the items are divided into batches of three. This results in four batches that contain 3, 3, 3, and 1 items, assuming all item executions are successful.

  YAML

  Batch: [1, 2, 3] # Optional. You can define batch control using a list that contains numbers or percentages, such as [3].
  Mode: Batch

  JSON

  {
    "Batch": [
      1,
      2,
      3
    ],
    "Mode": "Batch"
  }

• If Items contains 10 items and Batch is set to [30%], the batch size is three items (10 × 30% = 3). This results in four batches that contain 3, 3, 3, and 1 items, assuming all item executions are successful.

  YAML

  Batch: [30%] # Optional. You can define batch control using a list that contains numbers or percentages, such as [30%].
  Mode: Batch
  					

  JSON

  {
    "Batch": [
      "30%"
    ],
    "Mode": "Batch"
  }

• If Items contains 10 items and Batch is set to [3, 10%, 30%], the first batch contains 3 items, the second batch contains 1 item (10% of the total), and the third and subsequent batches each contain 3 items (30% of the total). This results in four batches that contain 3, 1, 3, and 3 items, assuming all item executions are successful.

  YAML

  Mode: Batch
  Batch: [3, 10%,30%] # Optional. You can define batch control using a list that contains multiple numbers or percentages, such as [3, 10%, 30%].
  					

  JSON

  {
    "Mode": "Batch",
    "Batch": [
      3,
      "10%",
      "30%"
    ]
  }

Fault control: MaxErrors

In a loop, you can also define MaxErrors. This parameter works as follows:

1. The value can be a number or a percentage of the total number of items, such as 10 or 10%. The default value is 0. A value of 0 means that the loop task fails if any item execution results in a fault.

2. The first item in the loop is always executed.

3. Whether subsequent items can be executed depends on the current ErrorCount value relative to the MaxErrors value.

   • If the ErrorCount value exceeds the MaxErrors value, the execution of subsequent items stops and the loop task is marked as failed.

   • If the ErrorCount value is less than or equal to the MaxErrors value, the execution continues.

4. The final status of the loop task is determined by whether the ErrorCount value is greater than the MaxErrors value. If it is greater, the status is Failed. Otherwise, the status is Success.

• By number

  YAML

  MaxErrors: 2 # Optional. The value can be a number or a percentage, such as 2. This indicates that the maximum ErrorCount is 2.

  JSON

  {
   "MaxErrors": 2 
  }

• By percentage

  YAML

  MaxErrors:  25% # Optional. The value can be a number or a percentage, such as 25%. If there are 4 items in total, the maximum ErrorCount is 1 (4 × 25% = 1).

  JSON

  {
   "MaxErrors": "25%"
  }

Task outputs

You can customize the outputs of an ACS::Loop task. In ValueSelector, you can select the outputs of tasks within LoopTasks. The final output is an array that aggregates the task outputs from each loop iteration.

For example, in the syntax example, assume that the deployRevisions task returns "deployRevisions example output".

The final output of deployCommandOutput is:

["deployRevisions example output",
"deployRevisions example output"]