Chapter 5. Working with Counters

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

Prerequisites

5.1. Creating Counters

Create strong and weak counters with the Data Grid CLI.

Procedure

Run the create counter command with the appropriate arguments.

Create my-weak-counter.

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

Create my-strong-counter.

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

Verify counter configurations.

Describe my-weak-counter.

describe counters/my-weak-counter

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

Describe my-strong-counter.

describe counters/my-strong-counter

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

Increment or decrement counters with arbitrary values.

Procedure

List the current count.

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

Increment the counter value by 2.

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

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.