[lttng-ust.git] /

/*
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 * Copyright (C) 2015-2016 EfficiOS Inc.
 * Copyright (C) 2015-2016 Alexandre Montplaisir <alexmonthy@efficios.com>
 * Copyright (C) 2013 David Goulet <dgoulet@efficios.com>
 */

package org.lttng.ust.agent.client;

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.lang.management.ManagementFactory;
import java.net.Socket;
import java.net.UnknownHostException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.charset.Charset;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

import org.lttng.ust.agent.utils.LttngUstAgentLogger;

/**
 * Client for agents to connect to a local session daemon, using a TCP socket.
 *
 * @author David Goulet
 */
public class LttngTcpSessiondClient implements Runnable {

        private static final String SESSION_HOST = "127.0.0.1";
        private static final String ROOT_PORT_FILE = "/var/run/lttng/agent.port";
        private static final String USER_PORT_FILE = "/.lttng/agent.port";
        private static final Charset PORT_FILE_ENCODING = Charset.forName("UTF-8");

        private static final int PROTOCOL_MAJOR_VERSION = 2;
        private static final int PROTOCOL_MINOR_VERSION = 0;

        /** Command header from the session daemon. */
        private final CountDownLatch registrationLatch = new CountDownLatch(1);

        private Socket sessiondSock;
        private volatile boolean quit = false;

        private DataInputStream inFromSessiond;
        private DataOutputStream outToSessiond;

        private final ILttngTcpClientListener logAgent;
        private final int domainValue;
        private final boolean isRoot;

        /**
         * Constructor
         *
         * @param logAgent
         *            The listener this client will operate on, typically an LTTng
         *            agent.
         * @param domainValue
         *            The integer to send to the session daemon representing the
         *            tracing domain to handle.
         * @param isRoot
         *            True if this client should connect to the root session daemon,
         *            false if it should connect to the user one.
         */
        public LttngTcpSessiondClient(ILttngTcpClientListener logAgent, int domainValue, boolean isRoot) {
                this.logAgent = logAgent;
                this.domainValue = domainValue;
                this.isRoot = isRoot;
        }

        /**
         * Wait until this client has successfully established a connection to its
         * target session daemon.
         *
         * @param seconds
         *            A timeout in seconds after which this method will return
         *            anyway.
         * @return True if the the client actually established the connection, false
         *         if we returned because the timeout has elapsed or the thread was
         *         interrupted.
         */
        public boolean waitForConnection(int seconds) {
                try {
                        return registrationLatch.await(seconds, TimeUnit.SECONDS);
                } catch (InterruptedException e) {
                        return false;
                }
        }

        @Override
        public void run() {
                for (;;) {
                        if (this.quit) {
                                break;
                        }

                        try {

                                /*
                                 * Connect to the session daemon before anything else.
                                 */
                                log("Connecting to sessiond");
                                connectToSessiond();

                                /*
                                 * Register to the session daemon as the Java component of the
                                 * UST application.
                                 */
                                log("Registering to sessiond");
                                registerToSessiond();

                                /*
                                 * Block on socket receive and wait for command from the
                                 * session daemon. This will return if and only if there is a
                                 * fatal error or the socket closes.
                                 */
                                log("Waiting on sessiond commands...");
                                handleSessiondCmd();
                        } catch (UnknownHostException uhe) {
                                uhe.printStackTrace();
                                /*
                                 * Terminate agent thread.
                                 */
                                close();
                        } catch (IOException ioe) {
                                /*
                                 * I/O exception may have been triggered by a session daemon
                                 * closing the socket. Close our own socket and
                                 * retry connecting after a delay.
                                 */
                                try {
                                        if (this.sessiondSock != null) {
                                                this.sessiondSock.close();
                                        }
                                        Thread.sleep(3000);
                                } catch (InterruptedException e) {
                                        /*
                                         * Retry immediately if sleep is interrupted.
                                         */
                                } catch (IOException closeioe) {
                                        closeioe.printStackTrace();
                                        /*
                                         * Terminate agent thread.
                                         */
                                        close();
                                }
                        }
                }
        }

        /**
         * Dispose this client and close any socket connection it may hold.
         */
        public void close() {
                log("Closing client");
                this.quit = true;

                try {
                        if (this.sessiondSock != null) {
                                this.sessiondSock.close();
                        }
                } catch (IOException e) {
                        e.printStackTrace();
                }
        }

        private void connectToSessiond() throws IOException {
                int portToUse;

                /*
                 * The environment variable LTTNG_UST_APP_PATH disables
                 * connection to per-user and root session daemons.
                 */
                String lttngUstAppPath = getUstAppPath();

                if (lttngUstAppPath != null) {
                        portToUse = getPortFromFile(lttngUstAppPath + USER_PORT_FILE);
                } else {
                        int rootPort = getPortFromFile(ROOT_PORT_FILE);
                        int userPort = getPortFromFile(getHomePath() + USER_PORT_FILE);

                        /*
                         * Check for the edge case of both files existing but pointing to the
                         * same port. In this case, let the root client handle it.
                         */
                        if ((rootPort != 0) && (rootPort == userPort) && (!isRoot)) {
                                log("User and root config files both point to port " + rootPort +
                                                ". Letting the root client handle it.");
                                throw new IOException();
                        }

                        portToUse = (isRoot ? rootPort : userPort);
                }

                if (portToUse == 0) {
                        /* No session daemon available. Stop and retry later. */
                        throw new IOException();
                }

                this.sessiondSock = new Socket(SESSION_HOST, portToUse);
                this.inFromSessiond = new DataInputStream(sessiondSock.getInputStream());
                this.outToSessiond = new DataOutputStream(sessiondSock.getOutputStream());
        }

        private static String getUstAppPath() {
                return System.getenv("LTTNG_UST_APP_PATH");
        }

        private static String getHomePath() {
                /*
                 * The environment variable LTTNG_HOME overrides HOME if
                 * set.
                 */
                String lttngHomePath = System.getenv("LTTNG_HOME");
                if (lttngHomePath != null) {
                        return lttngHomePath;
                }
                return System.getProperty("user.home");
        }

        /**
         * Read port number from file created by the session daemon.
         *
         * @return port value if found else 0.
         */
        private static int getPortFromFile(String path) throws IOException {
                BufferedReader br = null;

                try {
                        br = new BufferedReader(new InputStreamReader(new FileInputStream(path), PORT_FILE_ENCODING));
                        String line = br.readLine();
                        if (line == null) {
                                /* File exists but is empty. */
                                return 0;
                        }

                        int port = Integer.parseInt(line, 10);
                        if (port < 0 || port > 65535) {
                                /* Invalid value. Ignore. */
                                port = 0;
                        }
                        return port;

                } catch (NumberFormatException e) {
                        /* File contained something that was not a number. */
                        return 0;
                } catch (FileNotFoundException e) {
                        /* No port available. */
                        return 0;
                } finally {
                        if (br != null) {
                                br.close();
                        }
                }
        }

        private void registerToSessiond() throws IOException {
                byte data[] = new byte[16];
                ByteBuffer buf = ByteBuffer.wrap(data);
                String pid = ManagementFactory.getRuntimeMXBean().getName().split("@")[0];

                buf.putInt(domainValue);
                buf.putInt(Integer.parseInt(pid));
                buf.putInt(PROTOCOL_MAJOR_VERSION);
                buf.putInt(PROTOCOL_MINOR_VERSION);
                this.outToSessiond.write(data, 0, data.length);
                this.outToSessiond.flush();
        }

        /**
         * Handle session command from the session daemon.
         */
        private void handleSessiondCmd() throws IOException {
                /* Data read from the socket */
                byte inputData[] = null;
                /* Reply data written to the socket, sent to the sessiond */
                LttngAgentResponse response;

                while (true) {
                        /* Get header from session daemon. */
                        SessiondCommandHeader cmdHeader = recvHeader();

                        if (cmdHeader.getDataSize() > 0) {
                                inputData = recvPayload(cmdHeader);
                        }

                        switch (cmdHeader.getCommandType()) {
                        case CMD_REG_DONE:
                        {
                                /*
                                 * Countdown the registration latch, meaning registration is
                                 * done and we can proceed to continue tracing.
                                 */
                                registrationLatch.countDown();
                                /*
                                 * We don't send any reply to the registration done command.
                                 * This just marks the end of the initial session setup.
                                 */
                                log("Registration done");
                                continue;
                        }
                        case CMD_LIST:
                        {
                                SessiondCommand listLoggerCmd = new SessiondListLoggersCommand();
                                response = listLoggerCmd.execute(logAgent);
                                log("Received list loggers command");
                                break;
                        }
                        case CMD_EVENT_ENABLE:
                        {
                                if (inputData == null) {
                                        /* Invalid command */
                                        response = LttngAgentResponse.FAILURE_RESPONSE;
                                        break;
                                }
                                SessiondCommand enableEventCmd = new SessiondEnableEventCommand(inputData);
                                response = enableEventCmd.execute(logAgent);
                                log("Received enable event command: " + enableEventCmd.toString());
                                break;
                        }
                        case CMD_EVENT_DISABLE:
                        {
                                if (inputData == null) {
                                        /* Invalid command */
                                        response = LttngAgentResponse.FAILURE_RESPONSE;
                                        break;
                                }
                                SessiondCommand disableEventCmd = new SessiondDisableEventCommand(inputData);
                                response = disableEventCmd.execute(logAgent);
                                log("Received disable event command: " + disableEventCmd.toString());
                                break;
                        }
                        case CMD_APP_CTX_ENABLE:
                        {
                                if (inputData == null) {
                                        /* This commands expects a payload, invalid command */
                                        response = LttngAgentResponse.FAILURE_RESPONSE;
                                        break;
                                }
                                SessiondCommand enableAppCtxCmd = new SessiondEnableAppContextCommand(inputData);
                                response = enableAppCtxCmd.execute(logAgent);
                                log("Received enable app-context command");
                                break;
                        }
                        case CMD_APP_CTX_DISABLE:
                        {
                                if (inputData == null) {
                                        /* This commands expects a payload, invalid command */
                                        response = LttngAgentResponse.FAILURE_RESPONSE;
                                        break;
                                }
                                SessiondCommand disableAppCtxCmd = new SessiondDisableAppContextCommand(inputData);
                                response = disableAppCtxCmd.execute(logAgent);
                                log("Received disable app-context command");
                                break;
                        }
                        default:
                        {
                                /* Unknown command, send empty reply */
                                response = null;
                                log("Received unknown command, ignoring");
                                break;
                        }
                        }

                        /* Send response to the session daemon. */
                        byte[] responseData;
                        if (response == null) {
                                responseData = new byte[4];
                                ByteBuffer buf = ByteBuffer.wrap(responseData);
                                buf.order(ByteOrder.BIG_ENDIAN);
                        } else {
                                log("Sending response: " + response.toString());
                                responseData = response.getBytes();
                        }
                        this.outToSessiond.write(responseData, 0, responseData.length);
                        this.outToSessiond.flush();
                }
        }

        /**
         * Receive header data from the session daemon using the LTTng command
         * static buffer of the right size.
         */
        private SessiondCommandHeader recvHeader() throws IOException {
                byte data[] = new byte[SessiondCommandHeader.HEADER_SIZE];
                int bytesLeft = data.length;
                int bytesOffset = 0;

                while (bytesLeft > 0) {
                        int bytesRead = this.inFromSessiond.read(data, bytesOffset, bytesLeft);

                        if (bytesRead < 0) {
                                throw new IOException();
                        }
                        bytesLeft -= bytesRead;
                        bytesOffset += bytesRead;
                }
                return new SessiondCommandHeader(data);
        }

        /**
         * Receive payload from the session daemon. This MUST be done after a
         * recvHeader() so the header value of a command are known.
         *
         * The caller SHOULD use isPayload() before which returns true if a payload
         * is expected after the header.
         */
        private byte[] recvPayload(SessiondCommandHeader headerCmd) throws IOException {
                byte payload[] = new byte[(int) headerCmd.getDataSize()];
                int bytesLeft = payload.length;
                int bytesOffset = 0;

                /* Failsafe check so we don't waste our time reading 0 bytes. */
                if (bytesLeft == 0) {
                        return null;
                }

                while (bytesLeft > 0) {
                        int bytesRead = inFromSessiond.read(payload, bytesOffset, bytesLeft);

                        if (bytesRead < 0) {
                                throw new IOException();
                        }
                        bytesLeft -= bytesRead;
                        bytesOffset += bytesRead;
                }
                return payload;
        }

        /**
         * Wrapper for this class's logging, adds the connection's characteristics
         * to help differentiate between multiple TCP clients.
         */
        private void log(String message) {
                LttngUstAgentLogger.log(getClass(),
                                "(root=" + isRoot + ", domain=" + domainValue + ") " + message);
        }
}