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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
Run
create counterwith the appropriate arguments.Create
my-weak-counter.[//containers/default]> create counter --concurrency-level=1 --initial-value=5 --storage=PERSISTENT --type=weak my-weak-counter
Create
my-strong-counter.[//containers/default]> create counter --initial-value=3 --storage=PERSISTENT --type=strong my-strong-counter
List available counters.
[//containers/default]> ls counters my-strong-counter my-weak-counter
Verify counter configurations.
Describe
my-weak-counter.[//containers/default]> describe counters/my-weak-counter { "weak-counter":{ "initial-value":5, "storage":"PERSISTENT", "concurrency-level":1 } }Describe
my-strong-counter.[//containers/default]> 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
Select a counter.
[//containers/default]> counter my-weak-counter
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
Strong counters return values after the operation is applied. Use --quiet=true to hide the return value.
For example, my-strong-counter]> add --delta=3 --quiet=true.
Weak counters return empty responses.
