org.apache.ignite.services

## Interface Service

All Superinterfaces:
  Serializable

All Known Subinterfaces:
  PlatformDotNetService, PlatformService

All Known Implementing Classes:
  PlatformAbstractService, PlatformDotNetServiceImpl

    public interface Service
    extends Serializable

An instance of grid-managed service. Grid-managed services may be deployed from `IgniteServices` facade or directly from grid configuration at startup.

# Deployment

Whenever service is deployed, Ignite will automatically calculate how many instances of this service should be deployed on each node within the cluster. Whenever service is deployed on a cluster node, Ignite will call `execute()` method on that service. It is up to the user to control whenever the service should exit from the `execute` method. For example, user may choose to implement service as follows:

     public class MyIgniteService implements Service {
          ...
          // Example of ignite resource injection. All resources are optional.
          // You should inject resources only as needed.
          @IgniteInstanceResource
          private Ignite ignite;

          @ServiceContextResource
          private ServiceContext ctx;
          ...
          @Override public void cancel() {
              // No-op.
          }

          @Override public void execute() {
              // Loop until service is cancelled.
              while (!ctx.isCancelled()) {
                  // Do something.
                  ...
              }
          }
      }

Consecutively, this service can be deployed as follows:

     ...
     IgniteServices svcs = ignite.services();

     svcs.deployClusterSingleton("mySingleton", new MyIgniteService());

Or from grid configuration on startup:

     IgniteConfiguration gridCfg = new IgniteConfiguration();

     IgniteServiceConfiguration svcCfg = new IgniteServiceConfiguration();

     // Configuration for cluster-singleton service.
     svcCfg.setName("mySingleton");
     svcCfg.setMaxPerNodeCount(1);
     svcCfg.setTotalCount(1);
     svcCfg.setService(new MyIgniteService());

     gridCfg.setServiceConfiguration(svcCfg);
     ...
     Ignition.start(gridCfg);

# Cancellation

Services can be cancelled by calling any of the `cancel` methods on `IgniteServices` API. Whenever a deployed service is cancelled, Ignite will automatically call `cancel()` method on that service.

Note that Ignite cannot guarantee that the service exits from `execute()` method whenever `cancel()` is called. It is up to the user to make sure that the service code properly reacts to cancellations.

### Method Summary

All Methods Instance Methods Default Methods Deprecated Methods
`default void` `cancel()` Cancels this service.
`default void` `cancel(ServiceContext ctx)` Deprecated. Use `cancel()` instead.
`default void` `execute()` Starts execution of this service.
`default void` `execute(ServiceContext ctx)` Deprecated. Use `execute()` instead.
`default void` `init()` Pre-initializes service before execution.
`default void` `init(ServiceContext ctx)` Deprecated. Use `init()` instead.

### Method Detail

#### cancel

    default void cancel()

Cancels this service. Ignite will automatically call this method whenever any of the `cancel` methods on `IgniteServices` API are called.

Note that Ignite cannot guarantee that the service exits from `execute()` method whenever `cancel()` method is called. It is up to the user to make sure that the service code properly reacts to cancellations.

See Also:
  `ServiceContextResource`

#### init

    default void init()
               throws Exception

Pre-initializes service before execution. This method is guaranteed to be called before service deployment is complete (this guarantees that this method will be called before method `execute()` is called).

Throws:
  `Exception` - If service initialization failed.
See Also:
  `ServiceContextResource`

#### execute

    default void execute()
                  throws Exception

Starts execution of this service. This method is automatically invoked whenever an instance of the service is deployed on a grid node. Note that service is considered deployed even after it exits the `execute` method and can be cancelled (or undeployed) only by calling any of the `cancel` methods on `IgniteServices` API. Also note that service is not required to exit from `execute` method until `cancel()` method was called.

Throws:
  `Exception` - If service execution failed. Not that service will still remain deployed, until `IgniteServices.cancel(String)` method will be called.
See Also:
  `ServiceContextResource`

#### cancel

    @Deprecated
    default void cancel(ServiceContext ctx)

Deprecated. Use `cancel()` instead.
Cancels this service. Ignite will automatically call this method whenever any of the `cancel` methods on `IgniteServices` API are called.

Note that Ignite cannot guarantee that the service exits from `execute(ServiceContext)` method whenever `cancel(ServiceContext)` method is called. It is up to the user to make sure that the service code properly reacts to cancellations.

Parameters:
  `ctx` - Service execution context.

#### init

    @Deprecated
    default void init(ServiceContext ctx)
                           throws Exception

Deprecated. Use `init()` instead.
Pre-initializes service before execution. This method is guaranteed to be called before service deployment is complete (this guarantees that this method will be called before method `execute(ServiceContext)` is called).

Parameters:
  `ctx` - Service execution context.
Throws:
  `Exception` - If service initialization failed.

#### execute

    @Deprecated
    default void execute(ServiceContext ctx)
                              throws Exception

Deprecated. Use `execute()` instead.
Starts execution of this service. This method is automatically invoked whenever an instance of the service is deployed on a grid node. Note that service is considered deployed even after it exits the `execute` method and can be cancelled (or undeployed) only by calling any of the `cancel` methods on `IgniteServices` API. Also note that service is not required to exit from `execute` method until `cancel(ServiceContext)` method was called.

Parameters:
  `ctx` - Service execution context.
Throws:
  `Exception` - If service execution failed. Not that service will still remain deployed, until `IgniteServices.cancel(String)` method will be called.

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Ignite Database and Caching Platform | : ver. 2.13.0
Release Date | : April 20 2022