io.atomix.protocols.raft.service

Interface RaftServiceExecutor

All Superinterfaces:

AutoCloseable, Executor, io.atomix.utils.concurrent.Scheduler, io.atomix.utils.concurrent.ThreadContext

public interface RaftServiceExecutor
extends io.atomix.utils.concurrent.ThreadContext

Facilitates registration and execution of state machine commands and provides deterministic scheduling.

The state machine executor is responsible for managing input to and output from a RaftService. As operations are committed to the Raft log, the executor is responsible for applying them to the state machine. commands are guaranteed to be applied to the state machine in the order in which they appear in the Raft log and always in the same thread, so state machines don't have to be thread safe. queries are not generally written to the Raft log and will instead be applied according to their ReadConsistency.

State machines can use the executor to provide deterministic scheduling during the execution of command callbacks.

   
   private Object putWithTtl(Commit<PutWithTtl> commit) {
     map.put(commit.operation().key(), commit);
     executor.schedule(Duration.ofMillis(commit.operation().ttl()), () -> {
       map.remove(commit.operation().key()).close();
     });
   }
   
 

As with all state machine callbacks, the executor will ensure scheduled callbacks are executed sequentially and deterministically. As long as state machines schedule callbacks deterministically, callbacks will be executed deterministically. Internally, the state machine executor triggers callbacks based on various timestamps in the Raft log. This means the scheduler is dependent on internal or user-defined operations being written to the log. Prior to the execution of a command, any expired scheduled callbacks will be executed based on the command's logged timestamp.

It's important to note that callbacks can only be scheduled during RaftOperation operations or by recursive scheduling. If a state machine attempts to schedule a callback via the executor during the execution of a query, a IllegalStateException will be thrown. This is because queries are usually only applied on a single state machine within the cluster, and so scheduling callbacks in reaction to query execution would not be deterministic.

See Also:

RaftService, ServiceContext

Method Summary

Modifier and Type	Method and Description
byte[]	apply(Commit<byte[]> commit) Applies the given commit to the executor.
default void	close()
void	handle(OperationId operationId, Function<Commit<byte[]>,byte[]> callback) Registers a operation callback.
default void	register(OperationId operationId, Consumer<Commit<Void>> callback) Registers a operation callback.
default <T> void	register(OperationId operationId, Function<byte[],T> decoder, Consumer<Commit<T>> callback) Registers a operation callback.
default <T,R> void	register(OperationId operationId, Function<byte[],T> decoder, Function<Commit<T>,R> callback, Function<R,byte[]> encoder) Registers an operation callback.
default <R> void	register(OperationId operationId, Function<Commit<Void>,R> callback, Function<R,byte[]> encoder) Registers a operation callback.
default void	register(OperationId operationId, Runnable callback) Registers a operation callback.
default <R> void	register(OperationId operationId, Supplier<R> callback, Function<R,byte[]> encoder) Registers a no argument operation callback.

Methods inherited from interface io.atomix.utils.concurrent.ThreadContext

checkThread, currentContext, currentContextOrThrow, isCurrentContext

Methods inherited from interface java.util.concurrent.Executor

execute

Methods inherited from interface io.atomix.utils.concurrent.Scheduler

schedule, schedule, schedule, schedule

Method Detail

apply

byte[] apply(Commit<byte[]> commit)

Applies the given commit to the executor.

Parameters:

commit - the commit to apply

Returns:

the commit result

handle

void handle(OperationId operationId,
            Function<Commit<byte[]>,byte[]> callback)

Registers a operation callback.

Parameters:

operationId - the operation identifier

callback - the operation callback

Throws:

NullPointerException - if the operationId or callback is null

register

default void register(OperationId operationId,
                      Runnable callback)

Registers a operation callback.

Parameters:

operationId - the operation identifier

callback - the operation callback

Throws:

NullPointerException - if the operationId or callback is null

register

default <R> void register(OperationId operationId,
                          Supplier<R> callback,
                          Function<R,byte[]> encoder)

Registers a no argument operation callback.

Parameters:

operationId - the operation identifier

callback - the operation callback

encoder - result encoder

Throws:

NullPointerException - if the operationId or callback is null

register

default void register(OperationId operationId,
                      Consumer<Commit<Void>> callback)

Registers a operation callback.

Parameters:

operationId - the operation identifier

callback - the operation callback

Throws:

NullPointerException - if the operationId or callback is null

register

default <R> void register(OperationId operationId,
                          Function<Commit<Void>,R> callback,
                          Function<R,byte[]> encoder)

Registers a operation callback.

Parameters:

operationId - the operation identifier

callback - the operation callback

encoder - result encoder

Throws:

NullPointerException - if the operationId or callback is null

register

default <T> void register(OperationId operationId,
                          Function<byte[],T> decoder,
                          Consumer<Commit<T>> callback)

Registers a operation callback.

Parameters:

operationId - the operation identifier

decoder - the operation decoder

callback - the operation callback

Throws:

NullPointerException - if the operationId or callback is null

register

default <T,R> void register(OperationId operationId,
                            Function<byte[],T> decoder,
                            Function<Commit<T>,R> callback,
                            Function<R,byte[]> encoder)

Registers an operation callback.

Parameters:

operationId - the operation identifier

decoder - the operation decoder

callback - the operation callback

encoder - the output encoder

Throws:

NullPointerException - if the operationId or callback is null

close

default void close()

Specified by:

close in interface AutoCloseable

Specified by:

close in interface io.atomix.utils.concurrent.ThreadContext