Do not set SO_LINGER on server channels (#26997)

Right now we are attempting to set SO_LINGER to 0 on server channels
when we are stopping the tcp transport. This is not a supported socket
option and throws an exception. This also prevents the channels from
being closed.

This commit 1. doesn't set SO_LINGER for server channges, 2. checks
that it is a supported option in nio, and 3. changes the log message
to warn for server channel close exceptions.

Author: Tim-Brooks

core/src/main/java/org/elasticsearch/transport/TcpTransport.java

@@ -905,11 +905,9 @@ protected final void doStop() {
                 // first stop to accept any incoming connections so nobody can connect to this transport
                 for (Map.Entry<String, List<Channel>> entry : serverChannels.entrySet()) {
                     try {
-                        closeChannels(entry.getValue(), true, true);
+                        closeChannels(entry.getValue(), true, false);
                     } catch (Exception e) {
-                        logger.debug(
-                            (Supplier<?>) () -> new ParameterizedMessage(
-                                "Error closing serverChannel for profile [{}]", entry.getKey()), e);
+                        logger.warn(new ParameterizedMessage("Error closing serverChannel for profile [{}]", entry.getKey()), e);
                     }
                 }
                 // we are holding a write lock so nobody modifies the connectedNodes / openConnections map - it's safe to first close
@@ -1024,9 +1022,9 @@ protected void innerOnFailure(Exception e) {
      *
      * @param channels the channels to close
      * @param blocking whether the channels should be closed synchronously
-     * @param closingTransport whether we abort the connection on RST instead of FIN
+     * @param doNotLinger whether we abort the connection on RST instead of FIN
      */
-    protected abstract void closeChannels(List<Channel> channels, boolean blocking, boolean closingTransport) throws IOException;
+    protected abstract void closeChannels(List<Channel> channels, boolean blocking, boolean doNotLinger) throws IOException;
 
     /**
      * Sends message to channel. The listener's onResponse method will be called when the send is complete unless an exception

core/src/test/java/org/elasticsearch/transport/TcpTransportTests.java

@@ -191,7 +191,7 @@ protected Object bind(String name, InetSocketAddress address) throws IOException
                 }
 
                 @Override
-                protected void closeChannels(List channel, boolean blocking, boolean closingTransport) throws IOException {
+                protected void closeChannels(List channel, boolean blocking, boolean doNotLinger) throws IOException {
 
                 }
 

modules/transport-netty4/src/main/java/org/elasticsearch/transport/netty4/Netty4Transport.java

@@ -331,8 +331,8 @@ protected void sendMessage(Channel channel, BytesReference reference, ActionList
     }
 
     @Override
-    protected void closeChannels(final List<Channel> channels, boolean blocking, boolean closingTransport) throws IOException {
-        if (closingTransport) {
+    protected void closeChannels(final List<Channel> channels, boolean blocking, boolean doNotLinger) throws IOException {
+        if (doNotLinger) {
             for (Channel channel : channels) {
                 /* We set SO_LINGER timeout to 0 to ensure that when we shutdown the node we don't have a gazillion connections sitting
                  * in TIME_WAIT to free up resources quickly. This is really the only part where we close the connection from the server

test/framework/src/main/java/org/elasticsearch/transport/MockTcpTransport.java

@@ -243,8 +243,8 @@ protected void sendMessage(MockChannel mockChannel, BytesReference reference, Ac
     }
 
     @Override
-    protected void closeChannels(List<MockChannel> channels, boolean blocking, boolean closingTransport) throws IOException {
-        if (closingTransport) {
+    protected void closeChannels(List<MockChannel> channels, boolean blocking, boolean doNotLinger) throws IOException {
+        if (doNotLinger) {
             for (MockChannel channel : channels) {
                 if (channel.activeChannel != null) {
                     /* We set SO_LINGER timeout to 0 to ensure that when we shutdown the node we don't have a gazillion connections sitting

test/framework/src/main/java/org/elasticsearch/transport/nio/NioTransport.java

@@ -99,15 +99,15 @@ protected NioServerSocketChannel bind(String name, InetSocketAddress address) th
     }
 
     @Override
-    protected void closeChannels(List<NioChannel> channels, boolean blocking, boolean closingTransport) throws IOException {
-        if (closingTransport) {
+    protected void closeChannels(List<NioChannel> channels, boolean blocking, boolean doNotLinger) throws IOException {
+        if (doNotLinger) {
             for (NioChannel channel : channels) {
                 /* We set SO_LINGER timeout to 0 to ensure that when we shutdown the node we don't have a gazillion connections sitting
                  * in TIME_WAIT to free up resources quickly. This is really the only part where we close the connection from the server
                  * side otherwise the client (node) initiates the TCP closing sequence which doesn't cause these issues. Setting this
                  * by default from the beginning can have unexpected side-effects an should be avoided, our protocol is designed
                  * in a way that clients close connection which is how it should be*/
-                if (channel.isOpen()) {
+                if (channel.isOpen() && channel.getRawChannel().supportedOptions().contains(StandardSocketOptions.SO_LINGER)) {
                     channel.getRawChannel().setOption(StandardSocketOptions.SO_LINGER, 0);
                 }
             }