Apache ZooKeeper is an open-source server which enables highly reliable distributed coordination.

Apache ZooKeeper Server Source Code files are provided in the source packge (apache-zookeeper-3.7.0.tar.gz). You can download it at Apache ZooKeeper Website.

You can also browse Apache ZooKeeper Server Source Code below:

⏎ org/apache/zookeeper/server/controller/CommandListener.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * 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 org.apache.zookeeper.server.controller;

import java.io.IOException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.zookeeper.server.ExitCode;
import org.apache.zookeeper.util.ServiceUtils;
import org.eclipse.jetty.server.Request;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.handler.AbstractHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * An HTTP server listening to incoming controller commands sent from CommandClient (or any of your favorite REST client
 * ) and dispatching the command to the ZooKeeperServerController for execution.
 */
public class CommandListener {
    private static final Logger LOG = LoggerFactory.getLogger(CommandListener.class);

    private ZooKeeperServerController controller;
    private Server server;

    public CommandListener(ZooKeeperServerController controller, ControllerServerConfig config) {
        try {
            this.controller = controller;

            String host = config.getControllerAddress().getHostName();
            int port = config.getControllerAddress().getPort();

            server = new Server(port);
            LOG.info("CommandListener server host: {} with port: {}", host, port);
            server.setHandler(new CommandHandler());
            server.start();
        } catch (Exception ex) {
            LOG.error("Failed to instantiate CommandListener.", ex);
            ServiceUtils.requestSystemExit(ExitCode.UNEXPECTED_ERROR.getValue());
        }
    }

    public void close() {
        try {
            if (server != null) {
                server.stop();
                server = null;
            }
        } catch (Exception ex) {
            LOG.warn("Exception during shutdown CommandListener server", ex);
        }
    }

    private class CommandHandler extends AbstractHandler {
        @Override
        public void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response)
                throws IOException {
            // Extract command string from request path. Remove leading '/'.
            String commandStr = request.getPathInfo().substring(1);
            int responseCode;
            response.setContentType("text/html;charset=utf-8");

            try {
                ControlCommand command = ControlCommand.parseUri(commandStr);
                controller.processCommand(command);
                baseRequest.setHandled(true);
                responseCode = HttpServletResponse.SC_OK;
            } catch (IllegalArgumentException ex) {
                LOG.error("Bad argument or command", ex);
                responseCode = HttpServletResponse.SC_BAD_REQUEST;
            } catch (Exception ex) {
                LOG.error("Failed processing the request", ex);
                throw ex;
            }
            response.setStatus(responseCode);
            response.getWriter().println(commandStr);
            LOG.info("CommandListener processed command {} with response code {}", commandStr, responseCode);
        }
    }
}

⏎ org/apache/zookeeper/server/controller/CommandListener.java

Or download all of them as a single archive file:

File name: zookeeper-server-3.7.0-fyi.zip
File size: 871011 bytes
Release date: 2021-05-17
Download 

⇒ Apache ZooKeeper 3.7.0 Jute Source Code

⇐ Download Apache ZooKeeper 3.7.0 Source Package

⇑ Downloading and Reviewing zookeeper.jar

⇑⇑ FAQ for Apache ZooKeeper