Chapter 5. Working with Counters

Counters provide atomic increment and decrement operations that record the count of objects.

Prerequisites

  • Start the Data Grid CLI.
  • Connect to a running Data Grid cluster.

5.1. Creating Counters

Create strong and weak counters with the Data Grid CLI.

Procedure

  1. Create a CLI connection to Data Grid.

  2. Run the create counter command with the appropriate arguments.

    1. Create my-weak-counter. 

      create counter --concurrency-level=1 --initial-value=5 --storage=PERSISTENT --type=weak my-weak-counter

    2. Create my-strong-counter. 

      create counter --initial-value=3 --storage=PERSISTENT --type=strong my-strong-counter

  3. List available counters. 

    ls counters

  4. Verify counter configurations.

    1. Describe my-weak-counter. 

      describe counters/my-weak-counter
      {
    "weak-counter":{
        "initial-value":5,
        "storage":"PERSISTENT",
        "concurrency-level":1
    }
}

    2. Describe my-strong-counter. 

      describe counters/my-strong-counter
      {
    "strong-counter":{
        "initial-value":3,
        "storage":"PERSISTENT",
        "upper-bound":5
    }
}

5.2. Adding Deltas to Counters

Increment or decrement counters with arbitrary values.

Procedure

  1. Select a counter. 

    counter my-weak-counter

  2. List the current count. 

    [//containers/default/counters/my-weak-counter]> ls
5

  3. Increment the counter value by 2. 

    [//containers/default/counters/my-weak-counter]> add --delta=2

  4. Decrement the counter value by -4. 

    [//containers/default/counters/my-weak-counter]> add --delta=-4
Note

Strong counters return values after the operation is applied. Use --quiet=true to hide the return value.

For example, add --delta=3 --quiet=true.

Weak counters return empty responses.