com.apple.foundationdb.ReadTransactionContext Maven / Gradle / Ivy
/*
* ReadTransactionContext.java
*
* This source file is part of the FoundationDB open source project
*
* Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.apple.foundationdb;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Executor;
import java.util.function.Function;
/**
* A context in which a {@code ReadTransaction} is available for database operations. The
* behavior of the methods specified in this interface, especially in the face
* errors, is implementation specific. In particular, some implementations will
* run {@link Function}s multiple times (retry) when certain errors are encountered.
* Therefore a {@code Function} should be prepared to be called more than once. This
* consideration means that a {@code Function} should use caution when directly
* modifying state in a class, especially in a way that could be observed were that
* {@code Function} to not complete successfully.
*/
public interface ReadTransactionContext {
/**
* Runs a function in this context that takes a read-only transaction. Depending on the type of
* context, this may execute the supplied function multiple times if an error is
* encountered. This method is blocking -- control will not return from this call
* until work is complete.
*
* @param retryable the block of logic to execute against a {@link ReadTransaction}
* in this context
* @param the return type of {@code retryable}
*
* @return a result of the last call to {@code retryable}
*/
T read(Function retryable);
/**
* Runs a function in this context that takes a read-only transaction. Depending on the type of
* context, this may execute the supplied function multiple times if an error is
* encountered. This call is non-blocking -- control flow will return immediately
* with a {@code CompletableFuture} that will be set when the process is complete.
*
* @param retryable the block of logic to execute against a {@link ReadTransaction}
* in this context
* @param the return type of {@code retryable}
*
* @return a {@code CompletableFuture} that will be set to the value returned by the last call
* to {@code retryable}
*/
CompletableFuture readAsync(
Function> retryable);
/**
* Retrieves the {@link Executor} used by this {@code TransactionContext} when running
* asynchronous callbacks.
*
* @return the {@link Executor} used by this {@code TransactionContext}
*/
Executor getExecutor();
}