com.google.devtools.build.lib.server.RPCService.java Source code

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// Copyright 2014 The Bazel Authors. All rights reserved.
//
// 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.google.devtools.build.lib.server;

import com.google.common.collect.Iterables;
import com.google.devtools.build.lib.runtime.BlazeCommandDispatcher.LockingMode;
import com.google.devtools.build.lib.runtime.BlazeCommandDispatcher.ShutdownMethod;
import com.google.devtools.build.lib.util.Preconditions;
import com.google.devtools.build.lib.util.io.OutErr;

import java.util.List;
import java.util.logging.Logger;

/**
 * An RPCService is a Java object that can process RPC requests.  Requests may
 * be of the form:
 * <pre>
 *   blaze <blaze-arguments>
 * </pre>
 * Requests are delegated to the ServerCommand instance provided
 * to the constructor.
 */
public final class RPCService {

    private static final Logger LOG = Logger.getLogger(RPCService.class.getName());
    private final ServerCommand appCommand;
    private ShutdownMethod shutdown = ShutdownMethod.NONE;

    public RPCService(ServerCommand appCommand) {
        this.appCommand = appCommand;
    }

    /**
     * The {@link #executeRequest(List, OutErr, long)} method may
     * throw this exception if a command is unknown to the RPC service.
     */
    public static class UnknownCommandException extends Exception {
        private static final long serialVersionUID = 1L;

        UnknownCommandException(String command) {
            super("Unknown command: " + command);
        }
    }

    /**
     * Executes the request; returns Unix like return codes (0 means success). May
     * also throw arbitrary exceptions.
     */
    public int executeRequest(List<String> request, OutErr outErr, long firstContactTime) throws Exception {
        if (shutdown != ShutdownMethod.NONE) {
            throw new IllegalStateException("Received request after shutdown.");
        }
        String command = Iterables.getFirst(request, "");
        if (appCommand != null && command.equals("blaze")) { // an application request
            // Blocking is done in the client for AF_UNIX communications, so if blockForLock would block,
            // something went wrong
            int result = appCommand.exec(request.subList(1, request.size()), outErr, LockingMode.ERROR_OUT,
                    "AF_UNIX client", firstContactTime);
            ShutdownMethod commandShutdown = appCommand.shutdown();
            if (commandShutdown != ShutdownMethod.NONE) { // an application shutdown request
                shutdown(commandShutdown);
            }
            return result;
        } else {
            throw new UnknownCommandException(command);
        }
    }

    /**
     * After executing this function, further requests will fail, and
     * {@link #getShutdown()} will the shutdown method passed in.
     */
    public void shutdown(ShutdownMethod method) {
        Preconditions.checkState(method != ShutdownMethod.NONE);
        if (shutdown != ShutdownMethod.NONE) {
            return;
        }
        LOG.info("RPC Service: shutting down ...");
        shutdown = method;
    }

    /**
     * Has this service been shutdown. If so, any call to
     * {@link #executeRequest(List, OutErr, long)} will result in an
     * {@link IllegalStateException}
     */
    public ShutdownMethod getShutdown() {
        return shutdown;
    }

}