Added the flexnbd break command to stop mirroring

README.txt

@@ -133,6 +133,21 @@ Options
   The local address to bind to. You may need this if the remote server
   is using an access control list.
 
+break
+~~~~~
+
+  $ flexnbd mirror --sock SOCK [global option]*
+
+Stop a running migration.
+
+Options
+^^^^^^^
+
+*--sock, -s SOCK*:
+  The control socket of the local server whose emigration to stop.
+  Required.
+
+
 acl
 ~~~
 

src/control.c

@@ -428,6 +428,51 @@ int control_acl(struct control_client* client, int linesc, char** lines)
 	return 0;
 }
 
+
+int control_break(
+		struct control_client* client, 
+		int linesc __attribute__ ((unused)), 
+		char** lines __attribute__((unused))
+		)
+{
+	NULLCHECK( client );
+	NULLCHECK( client->flexnbd );
+
+	int result = 0;
+	struct flexnbd* flexnbd = client->flexnbd;
+
+	flexnbd_lock_switch( flexnbd );
+	{
+		struct server * serve = flexnbd_server( flexnbd );
+		if ( server_is_mirroring( serve ) ) {
+
+			info( "Signaling to abandon mirror" );
+			server_abandon_mirror( serve );
+			debug( "Abandon signaled" );
+
+			if ( server_is_closed( serve ) ) {
+				info( "Mirror completed while canceling" );
+				write( client->socket, 
+						"1: mirror completed\n", 20 );
+			}
+			else {
+				info( "Mirror successfully stopped." );
+				write( client->socket,
+						"0: mirror stopped\n", 18 );
+				result = 1;
+			}
+
+		} else {
+			warn( "Not mirroring." );
+			write( client->socket, "1: not mirroring\n", 17 );
+		}
+	}
+	flexnbd_unlock_switch( flexnbd );
+
+	return result;
+}
+
+
 /** FIXME: add some useful statistics */
 int control_status(
 		struct control_client* client, 
@@ -486,6 +531,12 @@ void control_respond(struct control_client * client)
 			debug("mirror command failed");
 		}
 	}
+	else if (strcmp(lines[0], "break") == 0) {
+		info( "break command received" );
+		if ( control_break( client, linesc-1, lines+1) < 0) {
+			debug( "break command failed" );
+		}
+	}
 	else if (strcmp(lines[0], "status") == 0) {
 		info("status command received" );
 		if (control_status(client, linesc-1, lines+1) < 0) {

src/mode.c

@@ -140,6 +140,22 @@ static char mirror_help_text[] =
 	VERBOSE_LINE
 	QUIET_LINE;
 
+static struct option break_options[] = {
+	GETOPT_HELP,
+	GETOPT_SOCK,
+	GETOPT_QUIET,
+	GETOPT_VERBOSE,
+	{0}
+};
+static char break_short_options[] = "hs:" SOPT_QUIET SOPT_VERBOSE;
+static char break_help_text[] = 
+	"Usage: flexnbd " CMD_BREAK " <options>\n\n"
+	"Stop mirroring from the server with control socket SOCK.\n\n"
+	HELP_LINE
+	SOCK_LINE
+	VERBOSE_LINE
+	QUIET_LINE;
+
 
 static struct option status_options[] = {
 	GETOPT_HELP,
@@ -355,6 +371,29 @@ void read_mirror_param( int c, char **sock, char **ip_addr, char **ip_port, char
 	}
 }
 
+void read_break_param( int c, char **sock )
+{
+	switch( c ) {
+		case 'h':
+			fprintf( stdout, "%s\n", break_help_text );
+			exit( 0 );
+			break;
+		case 's':
+			*sock = optarg;
+			break;
+		case 'q':
+			log_level = 4;
+			break;
+		case 'v':
+			log_level = VERBOSE_LOG_LEVEL;
+			break;
+		default:
+			exit_err( break_help_text );
+			break;
+	}
+}
+
+
 void read_status_param( int c, char **sock )
 {
 	read_sock_param( c, sock, status_help_text );
@@ -649,6 +688,27 @@ int mode_mirror( int argc, char *argv[] )
 }
 
 
+int mode_break( int argc, char *argv[] )
+{
+	int c;
+	char *sock = NULL;
+
+	while (1) {
+		c = getopt_long( argc, argv, break_short_options, break_options, NULL );
+		if ( -1 == c ) { break; }
+		read_break_param( c, &sock );
+	}
+
+	if ( NULL == sock ){
+		fprintf( stderr, "--sock is required.\n" );
+		exit_err( acl_help_text );
+	}
+
+	do_remote_command( "break", sock, argc - optind, argv + optind );
+
+	return 0;
+}
+
 int mode_status( int argc, char *argv[] )
 {
 	int c;
@@ -722,6 +782,9 @@ void mode(char* mode, int argc, char **argv)
 	else if ( IS_CMD( CMD_MIRROR, mode ) ) {
 		mode_mirror( argc, argv );
 	}
+       	else if ( IS_CMD( CMD_BREAK, mode ) ) {
+		mode_break( argc, argv );
+	}
        	else if ( IS_CMD( CMD_STATUS, mode ) ) {
 		mode_status( argc, argv );
 	}

src/mode.h

@@ -28,6 +28,7 @@ void mode(char* mode, int argc, char **argv);
 #define CMD_WRITE  "write"
 #define CMD_ACL    "acl"
 #define CMD_MIRROR "mirror"
+#define CMD_BREAK  "break"
 #define CMD_STATUS "status"
 #define CMD_HELP   "help"
 #define LEN_CMD_MAX 7

src/serve.c

@@ -722,11 +722,8 @@ void serve_cleanup(struct server* params,
 		free(params->allocation_map);
 	}
 	
-	if (params->mirror_super) {
-		/* AWOOGA!  RACE! */
-		pthread_t mirror_t = params->mirror_super->thread;
-		params->mirror->signal_abandon = 1;
-		pthread_join( mirror_t, NULL );
+	if ( server_is_mirroring( params ) ) {
+		server_abandon_mirror( params );
 	}
 	
 	for (i=0; i < params->max_nbd_clients; i++) {
@@ -753,6 +750,28 @@ int server_is_in_control( struct server *serve )
 	return serve->has_control;
 }
 
+int server_is_mirroring( struct server * serve )
+{
+	NULLCHECK( serve );
+	return !!serve->mirror_super;
+}
+
+void server_abandon_mirror( struct server * serve )
+{
+	NULLCHECK( serve );
+	if ( serve->mirror_super ) {
+		/* FIXME: AWOOGA!  RACE! 
+		 * We can set signal_abandon after mirror_super has
+		 * checked it, but before the reset.  This would lead to
+		 * a hang.  However, mirror_reset doesn't change the
+		 * signal_abandon flag, so it'll just terminate early on
+		 * the next pass.
+		 * */
+		serve->mirror->signal_abandon = 1;
+		pthread_join( serve->mirror_super->thread, NULL );
+	}
+}
+
 int server_default_deny( struct server * serve )
 {
 	NULLCHECK( serve );

src/serve.h

@@ -96,6 +96,8 @@ int server_io_locked( struct server * serve );
 int server_acl_locked( struct server * serve );
 void server_lock_acl( struct server *serve );
 void server_unlock_acl( struct server *serve );
+int server_is_mirroring( struct server * serve );
+void server_abandon_mirror( struct server * serve );
 
 
 int do_serve( struct server * );

tests/acceptance/environment.rb

@@ -42,6 +42,10 @@ class Environment
   end
 
 
+  def break1
+    @nbd1.break
+  end
+
   def acl1( *acl )
     @nbd1.acl( *acl )
   end
@@ -111,7 +115,7 @@ class Environment
   end
 
 
-  def run_fake( name, addr, port, rebind_addr = addr, rebind_port = port )
+  def run_fake( name, addr, port, rebind_addr = addr, rebind_port = port, sock=nil )
     fakedir = File.join( File.dirname( __FILE__ ), "fakes" )
     fake = Dir[File.join( fakedir, name ) + "*"].sort.find { |fn|
       File.executable?( fn )
@@ -124,7 +128,7 @@ class Environment
     raise "no rebind_port" unless rebind_port
 
     @fake_pid = fork do
-      exec [fake, addr, port, @nbd1.pid, rebind_addr, rebind_port].map{|x| x.to_s}.join(" ")
+      exec [fake, addr, port, @nbd1.pid, rebind_addr, rebind_port, sock].map{|x| x.to_s}.join(" ")
     end
     sleep(0.5)
   end

tests/acceptance/fakes/dest/break_after_hello.rb

@@ -0,0 +1,35 @@
+#!/usr/bin/env ruby
+# encoding: utf-8
+
+# Open a server, accept a client, then cancel the migration by issuing
+# a break command.
+
+require 'flexnbd/fake_dest'
+include FlexNBD
+
+addr, port, src_pid, _, _, sock = *ARGV
+server = FakeDest.new( addr, port )
+client = server.accept
+
+ctrl = UNIXSocket.open( sock )
+
+Process.kill("STOP", src_pid.to_i)
+ctrl.write( "break\n" )
+ctrl.close_write
+client.write_hello
+Process.kill("CONT", src_pid.to_i)
+
+fail "Unexpected control response" unless
+  ctrl.read =~ /0: mirror stopped/
+
+client2 = nil
+begin
+  client2 = server.accept( "Expected timeout" )
+  fail "Unexpected reconnection"
+rescue Timeout::Error
+  # expected
+end
+client.close
+
+exit(0)
+

tests/acceptance/flexnbd.rb

@@ -271,6 +271,11 @@ class FlexNBD
       "#{@debug} "
   end
 
+  def break_cmd
+    "#{@bin} break "\
+      "--sock #{ctrl} "\
+      "#{@debug}"
+  end
 
   def status_cmd
     "#{@bin} status "\
@@ -416,6 +421,14 @@ class FlexNBD
   end
 
 
+  def break(timeout=nil)
+    cmd = break_cmd
+    debug( cmd )
+
+    maybe_timeout( cmd, timeout )
+  end
+
+
   def acl(*acl)
     cmd = acl_cmd( *acl )
     debug( cmd )
@@ -439,6 +452,14 @@ class FlexNBD
   end
 
 
+  def paused
+    Process.kill( "STOP", @pid )
+    yield
+  ensure
+    Process.kill( "CONT", @pid )
+  end
+
+
   protected
   def control_command(*args)
     raise "Server not running" unless @pid

tests/acceptance/test_source_error_handling.rb

@@ -90,10 +90,14 @@ class TestSourceErrorHandling < Test::Unit::TestCase
   end
 
 
+  def test_cancel_migration
+    run_fake( "dest/break_after_hello" )
+  end
+
 
   private
   def run_fake(name, opts = {})
-    @env.run_fake( name, @env.ip, @env.port2 )
+    @env.run_fake( name, @env.ip, @env.port2, @env.ip, @env.port2, @env.nbd1.ctrl )
     stdout, stderr = @env.mirror12_unchecked
     assert_success
     assert_match( opts[:err], stderr ) if opts[:err]