[JENKINS-48761] - Restore binary compatibility with agents running old Remoting versions

core/src/filter/resources/jenkins/slaves/remoting-info.properties

@@ -0,0 +1,6 @@
+# Remoting version, which is embedded into the core
+# This version MAY differ from what is really classloaded (see the "Pluggable Core Components", JENKINS-41196)
+remoting.embedded.version=${remoting.version}
+
+# Minimal Remoting version on external agents which is supported by the core
+remoting.minimal.supported.version=${remoting.minimal.supported.version}

core/src/main/java/hudson/Launcher.java

@@ -1289,7 +1289,7 @@ private static class RemoteLaunchCallable extends MasterToSlaveCallable<RemotePr
         }
 
         public RemoteProcess call() throws IOException {
-            final Channel channel = getOpenChannelOrFail();
+            final Channel channel = _getOpenChannelOrFail();
             Launcher.ProcStarter ps = new LocalLauncher(listener).launch();
             ps.cmds(cmd).masks(masks).envs(env).stdin(in).stdout(out).stderr(err).quiet(quiet);
             if(workDir!=null)   ps.pwd(workDir);
@@ -1308,7 +1308,11 @@ public int join() throws InterruptedException, IOException {
                         Channel taskChannel = null;
                         try {
                             // Sync IO will fail automatically if the channel is being closed, no need to use getOpenChannelOrFail()
-                            taskChannel = Channel.currentOrFail();
+                            // TODOL Replace by Channel#currentOrFail() when Remoting version allows
+                            taskChannel = Channel.current();
+                            if (taskChannel == null) {
+                                throw new IOException("No Remoting channel associated with this thread");
+                            }
                             taskChannel.syncIO();
                         } catch (Throwable t) {
                             // this includes a failure to sync, agent.jar too old, etc

core/src/main/java/hudson/TcpSlaveAgentListener.java

@@ -290,6 +290,7 @@ private void respondHello(String header, Socket s) throws IOException {
             try {
                 Writer o = new OutputStreamWriter(s.getOutputStream(), "UTF-8");
 
+                //TODO: expose version about minimal supported Remoting version (JENKINS-48766)
                 if (header.startsWith("GET / ")) {
                     o.write("HTTP/1.0 200 OK\r\n");
                     o.write("Content-Type: text/plain;charset=UTF-8\r\n");

core/src/main/java/hudson/model/Computer.java

@@ -1426,7 +1426,7 @@ public void doDumpExportTable( StaplerRequest req, StaplerResponse rsp ) throws
 
     private static final class DumpExportTableTask extends MasterToSlaveCallable<String,IOException> {
         public String call() throws IOException {
-            final Channel ch = getChannelOrFail();
+            final Channel ch = _getChannelOrFail();
             StringWriter sw = new StringWriter();
             try (PrintWriter pw = new PrintWriter(sw)) {
                 ch.dumpExportTable(pw);

core/src/main/java/hudson/slaves/ChannelPinger.java

@@ -134,7 +134,7 @@ public void install(Channel channel) {
         @Override
         public Void call() throws IOException {
             // No sense in setting up channel pinger if the channel is being closed
-            setUpPingForChannel(getOpenChannelOrFail(), null, pingTimeoutSeconds, pingIntervalSeconds, false);
+            setUpPingForChannel(_getOpenChannelOrFail(), null, pingTimeoutSeconds, pingIntervalSeconds, false);
             return null;
         }
 

core/src/main/java/hudson/slaves/SlaveComputer.java

@@ -38,6 +38,7 @@
 import hudson.model.User;
 import hudson.remoting.Channel;
 import hudson.remoting.ChannelBuilder;
+import hudson.remoting.ChannelClosedException;
 import hudson.remoting.Launcher;
 import hudson.remoting.VirtualChannel;
 import hudson.security.ACL;
@@ -867,7 +868,11 @@ public Void call() {
                 // ignore this error.
             }
 
-            Channel.currentOrFail().setProperty("slave",Boolean.TRUE); // indicate that this side of the channel is the slave side.
+            try {
+                _getChannelOrFail().setProperty("slave",Boolean.TRUE); // indicate that this side of the channel is the slave side.
+            } catch (ChannelClosedException e) {
+                throw new IllegalStateException(e);
+            }
 
             return null;
         }

core/src/main/java/jenkins/security/MasterToSlaveCallable.java

@@ -1,7 +1,13 @@
 package jenkins.security;
 
 import hudson.remoting.Callable;
+import hudson.remoting.Channel;
+import hudson.remoting.ChannelClosedException;
 import org.jenkinsci.remoting.RoleChecker;
+import org.kohsuke.accmod.Restricted;
+import org.kohsuke.accmod.restrictions.NoExternalUse;
+
+import javax.annotation.Nonnull;
 
 
 /**
@@ -11,10 +17,31 @@
  * @since 1.587 / 1.580.1
  */
 public abstract class MasterToSlaveCallable<V, T extends Throwable> implements Callable<V,T> {
+
+    private static final long serialVersionUID = 1L;
+
     @Override
     public void checkRoles(RoleChecker checker) throws SecurityException {
         checker.check(this,Roles.SLAVE);
     }
 
-    private static final long serialVersionUID = 1L;
+    //TODO: replace by Callable#getChannelOrFail() once Minimal supported Remoting version is 3.15 or above
+    @Restricted(NoExternalUse.class)
+    protected static Channel _getChannelOrFail() throws ChannelClosedException {
+        final Channel ch = Channel.current();
+        if (ch == null) {
+            throw new ChannelClosedException(new IllegalStateException("No channel associated with the thread"));
+        }
+        return ch;
+    }
+
+    //TODO: replace by Callable#getOpenChannelOrFail() once Minimal supported Remoting version is 3.15 or above
+    @Restricted(NoExternalUse.class)
+    protected static Channel _getOpenChannelOrFail() throws ChannelClosedException {
+        final Channel ch = _getChannelOrFail();
+        if (ch.isClosingOrClosed()) { // TODO: Since Remoting 2.33, we still need to explicitly declare minimal Remoting version
+            throw new ChannelClosedException(new IllegalStateException("The associated channel " + ch + " is closing down or has closed down", ch.getCloseRequestCause()));
+        }
+        return ch;
+    }
 }

core/src/main/java/jenkins/slaves/RemotingVersionInfo.java

@@ -0,0 +1,104 @@
+/*
+ * The MIT License
+ *
+ * Copyright (c) 2018, CloudBees, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package jenkins.slaves;
+
+import hudson.util.VersionNumber;
+import org.kohsuke.accmod.Restricted;
+import org.kohsuke.accmod.restrictions.NoExternalUse;
+
+import javax.annotation.CheckForNull;
+import javax.annotation.Nonnull;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Properties;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+// TODO: Make the API public (JENKINS-48766)
+/**
+ * Provides information about Remoting versions used withing the core.
+ * @author Oleg Nenashev
+ * @since TODO
+ */
+@Restricted(NoExternalUse.class)
+public class RemotingVersionInfo {
+
+    private static final Logger LOGGER = Logger.getLogger(RemotingVersionInfo.class.getName());
+    private static final String RESOURCE_NAME="remoting-info.properties";
+
+    @CheckForNull
+    private static VersionNumber EMBEDDED_VERSION;
+
+    @CheckForNull
+    private static VersionNumber MINIMAL_SUPPORTED_VERSION;
+
+    private RemotingVersionInfo() {}
+
+    static {
+        Properties props = new Properties();
+        try (InputStream is = RemotingVersionInfo.class.getResourceAsStream(RESOURCE_NAME)) {
+            if(is!=null) {
+                props.load(is);
+            }
+        } catch (IOException e) {
+            LOGGER.log(Level.WARNING, "Failed to load Remoting Info from " + RESOURCE_NAME, e);
+        }
+
+        EMBEDDED_VERSION = tryExtractVersion(props, "remoting.embedded.version");
+        MINIMAL_SUPPORTED_VERSION = tryExtractVersion(props, "remoting.minimal.supported.version");
+    }
+
+    @CheckForNull
+    private static VersionNumber tryExtractVersion(@Nonnull Properties props, @Nonnull String propertyName) {
+        String prop = props.getProperty(propertyName);
+        if (prop == null) {
+            LOGGER.log(Level.FINE, "Property {0} is not defined in {1}", new Object[] {propertyName, RESOURCE_NAME});
+            return null;
+        }
+
+        if(prop.contains("${")) { // Due to whatever reason, Maven does not nullify them
+            LOGGER.log(Level.WARNING, "Property {0} in {1} has unresolved variable(s). Raw value: {2}",
+                    new Object[] {propertyName, RESOURCE_NAME, prop});
+            return null;
+        }
+
+        try {
+            return new VersionNumber(prop);
+        } catch (RuntimeException ex) {
+            LOGGER.log(Level.WARNING, String.format("Failed to parse version for for property %s in %s. Raw Value: %s",
+                    propertyName, RESOURCE_NAME, prop), ex);
+            return null;
+        }
+    }
+
+    @CheckForNull
+    public static VersionNumber getEmbeddedVersion() {
+        return EMBEDDED_VERSION;
+    }
+
+    @CheckForNull
+    public static VersionNumber getMinimalSupportedVersion() {
+        return MINIMAL_SUPPORTED_VERSION;
+    }
+}

core/src/main/java/jenkins/slaves/StandardOutputSwapper.java

@@ -39,7 +39,7 @@ public void preOnline(Computer c, Channel channel, FilePath root, TaskListener l
     private static final class ChannelSwapper extends MasterToSlaveCallable<Boolean,Exception> {
         public Boolean call() throws Exception {
             if (File.pathSeparatorChar==';')    return false;   // Windows
-            Channel c = getOpenChannelOrFail();
+            Channel c = _getOpenChannelOrFail();
             StandardOutputStream sos = (StandardOutputStream) c.getProperty(StandardOutputStream.class);
             if (sos!=null) {
                 swap(sos);

core/src/test/java/jenkins/slaves/RemotingVersionInfoTest.java

@@ -0,0 +1,47 @@
+/*
+ * The MIT License
+ *
+ * Copyright (c) 2018, CloudBees, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package jenkins.slaves;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Tests for {@link RemotingVersionInfo}.
+ */
+public class RemotingVersionInfoTest {
+
+    @Test
+    public void shouldLoadEmbeddedVersionByDefault() {
+        assertThat("Remoting Embedded version is not defined",
+                RemotingVersionInfo.getEmbeddedVersion(), notNullValue());
+    }
+
+    @Test
+    public void shouldLoadMinimalSupportedVersionByDefault() {
+        assertThat("Remoting Minimal supported version is not defined",
+                RemotingVersionInfo.getMinimalSupportedVersion(), notNullValue());
+    }
+}

pom.xml

@@ -104,6 +104,10 @@ THE SOFTWARE.
 
     <maven-war-plugin.version>3.0.0</maven-war-plugin.version> <!-- JENKINS-47127 bump when 3.2.0 is out. Cf. MWAR-407 -->
 
+    <!-- Minimal Remoting version, which is tested for API compatibility -->
+    <remoting.version>3.15</remoting.version>
+    <remoting.minimal.supported.version>2.60</remoting.minimal.supported.version>
+
   </properties>
 
   <!-- Note that the 'repositories' and 'pluginRepositories' blocks below are actually copy-pasted
@@ -175,7 +179,7 @@ THE SOFTWARE.
       <dependency>
         <groupId>org.jenkins-ci.main</groupId>
         <artifactId>remoting</artifactId>
-        <version>3.15</version>
+        <version>${remoting.version}</version>
       </dependency>
 
       <dependency>

test/pom.xml

@@ -224,6 +224,31 @@ THE SOFTWARE.
         <!-- version specified in grandparent pom -->
         <extensions>true</extensions>
       </plugin>
+      <plugin>
+        <artifactId>maven-dependency-plugin</artifactId>
+        <executions>
+          <execution>
+            <id>old-remoting-for-test</id>
+            <phase>generate-test-resources</phase>
+            <goals>
+              <!-- we use copy as this is a dependency from outside the reactor -->
+              <goal>copy</goal>
+            </goals>
+            <configuration>
+              <artifactItems>
+                <artifactItem>
+                  <groupId>org.jenkins-ci.main</groupId>
+                  <artifactId>remoting</artifactId>
+                  <version>${remoting.minimal.supported.version}</version>
+                  <type>jar</type>
+                  <outputDirectory>${project.build.outputDirectory}/old-remoting</outputDirectory>
+                  <destFileName>remoting-minimal-supported.jar</destFileName>
+                </artifactItem>
+              </artifactItems>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-surefire-plugin</artifactId>