'shutdown graceful' command for raising SIGUSR1

doc/protocol.txt

@@ -1695,6 +1695,12 @@ be released back to the OS asynchronously.
 The argument is in megabytes, not bytes. Input gets multiplied out into
 megabytes internally.
 
+"shutdown" is a command with an optional argument used to stop memcached with
+a kill signal. By default, "shutdown" alone raises SIGINT, though "graceful"
+may be specified as the single argument to instead trigger a graceful shutdown
+with SIGUSR1. The shutdown command is disabled by default, and can be enabled
+with the -A/--enable-shutdown flag.
+
 "version" is a command with no arguments:
 
 version\r\n

proto_text.c

@@ -2348,12 +2348,20 @@ static void process_quit_command(conn *c) {
     c->close_after_write = true;
 }
 
-static void process_shutdown_command(conn *c) {
-    if (settings.shutdown_command) {
+static void process_shutdown_command(conn *c, token_t *tokens, const size_t ntokens) {
+    if (!settings.shutdown_command) {
+        out_string(c, "ERROR: shutdown not enabled");
+        return;
+    }
+
+    if (ntokens == 2) {
         conn_set_state(c, conn_closing);
         raise(SIGINT);
+    } else if (ntokens == 3 && strcmp(tokens[SUBCOMMAND_TOKEN].value, "graceful") == 0) {
+        conn_set_state(c, conn_closing);
+        raise(SIGUSR1);
     } else {
-        out_string(c, "ERROR: shutdown not enabled");
+        out_string(c, "CLIENT_ERROR invalid shutdown mode");
     }
 }
 
@@ -2620,7 +2628,7 @@ static void process_command(conn *c, char *command) {
             process_stat(c, tokens, ntokens);
         } else if (strcmp(tokens[COMMAND_TOKEN].value, "shutdown") == 0) {
 
-            process_shutdown_command(c);
+            process_shutdown_command(c, tokens, ntokens);
         } else if (strcmp(tokens[COMMAND_TOKEN].value, "slabs") == 0) {
 
             process_slabs_command(c, tokens, ntokens);

t/shutdown.t

@@ -0,0 +1,49 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+use Test::More;
+use FindBin qw($Bin);
+use lib "$Bin/lib";
+use MemcachedTest;
+
+# Disabled shutdown (default)
+{
+    my $server = new_memcached();
+    my $sock = $server->sock;
+    print $sock "shutdown\r\n";
+    is(scalar <$sock>, "ERROR: shutdown not enabled\r\n",
+        "error when shutdown is not enabled");
+}
+
+# Shutdown command error
+{
+    my$server = new_memcached("-A");
+    my $sock = $server->sock;
+    print $sock "shutdown foo\r\n";
+    like(scalar <$sock>, qr/CLIENT_ERROR/, "rejected invalid shutdown mode");
+}
+
+# Normal shutdown
+{
+    my $server = new_memcached("-A");
+    my $sock = $server->sock;
+    print $sock "version\r\n";
+    like(scalar <$sock>, qr/VERSION/, "server is initially alive");
+    print $sock "shutdown\r\n";
+    print $sock "version\r\n";
+    is(scalar <$sock>, undef, "server has been normally shut down");
+}
+
+# Graceful shutdown
+{
+    my $server = new_memcached("-A");
+    my $sock = $server->sock;
+    print $sock "version\r\n";
+    like(scalar <$sock>, qr/VERSION/, "server is initially alive");
+    print $sock "shutdown graceful\r\n";
+    print $sock "version\r\n";
+    is(scalar <$sock>, undef, "server has been gracefully shut down");
+}
+
+done_testing();