CPMap

Note

CPMap is a member of CP Subsystem API. For detailed information, see the CP SubSystem documentation.

Warning

It is only available in Hazelcast Enterprise.

Hazelcast CPMap is a strongly consistent mapping structure under CP Subsystem. It offers linearizability, and supports atomic CompareAndSetAsync, DeleteAsync, GetAsync, PutAsync, RemoveAsync and SetAsync operations. Hazelcast .Net Client also supports these atomic operations, for implementation details, please, see CPMap documentation.

In order to use CPMap, CP Subsystem must be enabled on the server side. Moreover, if no Raft group specified while creating the structure, CPMap will be created under default Raft group.

Example

The following simple example creates a CPMap under myGroup Raft group. If the group has not been initialized yet, first; the raft group will be created. Then, the structure will be initialized.

// create an Hazelcast client and connect to a enterprise server running on localhost
// note that that server should be properly configured for CP with at least 3 members
await using var client = await HazelcastClientFactory.StartNewClientAsync(options);

// Get a CPMap under "myGroup" Raft group.
var map = await client.CPSubsystem.GetMapAsync<int, string>("myMap@myGroup");

var (key, val) = (1, "my-value");

// Set a value
// Note: Set does not return back the old value that is associated with the key. If you require the previous value,
// consider using PutAsync.
await map.SetAsync(key, val);

// Get value that is map to the key.
// If key does not exist, the return value will be null. However, we know that the key-value pair exists, and
// ignore the possible null warning.
var currentVal = await map.GetAsync(key)!;

Console.WriteLine($"Key: {key}, Expected Value: {val}, Actual Value:{currentVal}");

// Let's change the value of the key by using CompareAndSetAsync
// The expected value will be compared to current value which is associated to given key. 
// If they are equal, new value will be set.
var newValue = "my-new-value";
var isSet = await map.CompareAndSetAsync(key, currentVal, newValue);

Console.WriteLine($"Key: {key}, Expected Value: {currentVal}, New Value:{newValue}, Is set successfully done:{isSet}");


// Assume that we do not need the map anymore. So, it is better to destroy the map on the cluster and release the resources.
// Note that Hazelcast does NOT do garbage collection on CPMap.
await map.DestroyAsync();