meta: response code OK -> HD

I had the response code as "HD" in the past, but standardized on OK
while merging a number of "OK-like" rescodes together. This was a
mistake; as many "generic" memcached response codes use "OK". Most of
these are management or specialized uncommon commands.

With this, a client response parser can know for sure if a response is
to a meta command, or some other command.

`-o meta_response_old` starttime option has been added, valid for the
next 3 months, which switches the response code back from HD to OK. In
case any existing users depended on this and need time to migrate.

5 files changed, 74 insertions, 44 deletions

diff --git a/doc/protocol.txt b/doc/protocol.txt
index bbaabef..623982d 100644
--- a/doc/protocol.txt
+++ b/doc/protocol.txt
@@ -523,7 +523,7 @@ VA <size> <flags>*\r\n
 If the request did not ask for a value in the response (v) flag, the server
 response looks like:
 
-OK <flags>*\r\n
+HD <flags>*\r\n
 
 If the request resulted in a miss, the response looks like:
 
@@ -609,7 +609,7 @@ access time.
 - v: return item value in <data block>
 
 The data block for a metaget response is optional, requiring this flag to be
-passed in. The response code also changes from "OK" to "VA <size>"
+passed in. The response code also changes from "HD" to "VA <size>"
 
 These flags can modify the item:
 - N(token): vivify on miss, takes TTL as a argument
@@ -698,7 +698,7 @@ the reply, which is of the format:
 
 Where CD is one of:
 
-- "OK" (STORED), to indicate success.
+- "HD" (STORED), to indicate success.
 
 - "NS" (NOT_STORED), to indicate the data was not stored, but not
 because of an error.
@@ -746,7 +746,7 @@ See description under 'Meta Get'
 
 Noreply is a method of reducing the amount of data sent back by memcached to
 the client for normal responses. In the case of metaset, a response that
-would start with "OK" will not be sent. Any other code, such as "EX"
+would start with "HD" will not be sent. Any other code, such as "EX"
 (EXISTS) will still be returned.
 
 Errors are always returned.
@@ -782,7 +782,7 @@ The response is in the format:
 
 Where CD is one of:
 
-- "OK" (DELETED), to indicate success
+- "HD" (DELETED), to indicate success
 
 - "NF" (NOT_FOUND), to indicate that the item with this key was not found.
 
@@ -847,7 +847,7 @@ The response is in the format:
 
 Where CD is one of:
 
-- "OK" to indicate success
+- "HD" to indicate success
 
 - "NF" (NOT_FOUND), to indicate that the item with this key was not found.
 
diff --git a/memcached.c b/memcached.c
index b6d4477..ce9f8e6 100644
--- a/memcached.c
+++ b/memcached.c
@@ -4586,6 +4586,7 @@ int main (int argc, char **argv) {
         DROP_PRIVILEGES,
         RESP_OBJ_MEM_LIMIT,
         READ_BUF_MEM_LIMIT,
+        META_RESPONSE_OLD,
 #ifdef TLS
         SSL_CERT,
         SSL_KEY,
@@ -4639,6 +4640,7 @@ int main (int argc, char **argv) {
         [DROP_PRIVILEGES] = "drop_privileges",
         [RESP_OBJ_MEM_LIMIT] = "resp_obj_mem_limit",
         [READ_BUF_MEM_LIMIT] = "read_buf_mem_limit",
+        [META_RESPONSE_OLD] = "meta_response_old",
 #ifdef TLS
         [SSL_CERT] = "ssl_chain_cert",
         [SSL_KEY] = "ssl_key",
@@ -5235,6 +5237,9 @@ int main (int argc, char **argv) {
                 start_lru_maintainer = false;
                 settings.lru_segmented = false;
                 break;
+            case META_RESPONSE_OLD:
+                settings.meta_response_old = true;
+                break;
 #ifdef TLS
             case SSL_CERT:
                 if (subopts_value == NULL) {
diff --git a/memcached.h b/memcached.h
index 1202fa0..04bd169 100644
--- a/memcached.h
+++ b/memcached.h
@@ -460,6 +460,7 @@ struct settings {
     bool drop_privileges;   /* Whether or not to drop unnecessary process privileges */
     bool watch_enabled; /* allows watch commands to be dropped */
     bool relaxed_privileges;   /* Relax process restrictions when running testapp */
+    bool meta_response_old; /* use "OK" instead of "HD". for response code TEMPORARY! */
 #ifdef EXTSTORE
     unsigned int ext_io_threadcount; /* number of IO threads to run. */
     unsigned int ext_page_size; /* size in megabytes of storage pages. */
diff --git a/proto_text.c b/proto_text.c
index f572a7a..22be817 100644
--- a/proto_text.c
+++ b/proto_text.c
@@ -60,7 +60,11 @@ static void _finalize_mset(conn *c, enum store_item_type ret) {
 
     switch (ret) {
     case STORED:
-      memcpy(p, "OK", 2);
+      if (settings.meta_response_old) {
+          memcpy(p, "OK", 2);
+      } else {
+          memcpy(p, "HD", 2);
+      }
       // Only place noreply is used for meta cmds is a nominal response.
       if (c->noreply) {
           resp->skip = true;
@@ -1129,7 +1133,11 @@ static void process_mget_command(conn *c, token_t *tokens, const size_t ntokens)
             memcpy(p, "VA ", 3);
             p = itoa_u32(it->nbytes-2, p+3);
         } else {
-            memcpy(p, "OK", 2);
+            if (settings.meta_response_old) {
+                memcpy(p, "OK", 2);
+            } else {
+                memcpy(p, "HD", 2);
+            }
             p += 2;
         }
 
@@ -1615,7 +1623,11 @@ static void process_mdelete_command(conn *c, token_t *tokens, const size_t ntoke
             // Clients can noreply nominal responses.
             if (c->noreply)
                 resp->skip = true;
-            memcpy(resp->wbuf, "OK ", 3);
+            if (settings.meta_response_old) {
+                memcpy(resp->wbuf, "OK ", 3);
+            } else {
+                memcpy(resp->wbuf, "HD ", 3);
+            }
         } else {
             pthread_mutex_lock(&c->thread->stats.mutex);
             c->thread->stats.slab_stats[ITEM_clsid(it)].delete_hits++;
@@ -1625,7 +1637,11 @@ static void process_mdelete_command(conn *c, token_t *tokens, const size_t ntoke
             STORAGE_delete(c->thread->storage, it);
             if (c->noreply)
                 resp->skip = true;
-            memcpy(resp->wbuf, "OK ", 3);
+            if (settings.meta_response_old) {
+                memcpy(resp->wbuf, "OK ", 3);
+            } else {
+                memcpy(resp->wbuf, "HD ", 3);
+            }
         }
         goto cleanup;
     } else {
@@ -1728,7 +1744,11 @@ static void process_marithmetic_command(conn *c, token_t *tokens, const size_t n
     case OK:
         if (c->noreply)
             resp->skip = true;
-        memcpy(resp->wbuf, "OK ", 3);
+        if (settings.meta_response_old) {
+            memcpy(resp->wbuf, "OK ", 3);
+        } else {
+            memcpy(resp->wbuf, "HD ", 3);
+        }
         break;
     case NON_NUMERIC:
         errstr = "CLIENT_ERROR cannot increment or decrement non-numeric value";
@@ -1786,7 +1806,11 @@ static void process_marithmetic_command(conn *c, token_t *tokens, const size_t n
             memcpy(p, "VA ", 3);
             p = itoa_u32(vlen, p+3);
         } else {
-            memcpy(p, "OK", 2);
+            if (settings.meta_response_old) {
+                memcpy(p, "OK", 2);
+            } else {
+                memcpy(p, "HD", 2);
+            }
             p += 2;
         }
 
diff --git a/t/metaget.t b/t/metaget.t
index 3293d9e..d346ea7 100644
--- a/t/metaget.t
+++ b/t/metaget.t
@@ -16,7 +16,7 @@ my $sock = $server->sock;
 # VA [size] [flags]\r\n
 # data\r\n
 # or:
-# OK [flags]\r\n
+# HD [flags]\r\n
 # or:
 # EN\r\n
 # flags are single 'f' or 'f1234' or 'fTEXT'
@@ -46,8 +46,8 @@ my $sock = $server->sock;
 # ms [key] [valuelen] [flags]\r\n
 # value\r\n
 # response:
-# OK [flags]\r\n
-# OK STORED, NS NOT_STORED, EX EXISTS, NF NOT_FOUND
+# HD [flags]\r\n
+# HD STORED, NS NOT_STORED, EX EXISTS, NF NOT_FOUND
 #
 # flags:
 # - q: noreply
@@ -67,7 +67,7 @@ my $sock = $server->sock;
 #
 # md [key] [flags]\r\n
 # response:
-# OK [flags]
+# HD [flags]
 # flags:
 # - q: noreply
 # - T(token): updates TTL
@@ -78,8 +78,8 @@ my $sock = $server->sock;
 #
 # ma [key] [flags]\r\n
 # response:
-# OK [flags]\r\n
-# OK, NS NOT_STORED, EX EXISTS, NF NOT_FOUND
+# HD [flags]\r\n
+# HD, NS NOT_STORED, EX EXISTS, NF NOT_FOUND
 # or:
 # VA [size] [flags]\r\n
 # data\r\n
@@ -152,7 +152,7 @@ my $sock = $server->sock;
     # 44OG44K544OI is "tesuto" in katakana
     my $tesuto = "44OG44K544OI";
     print $sock "ms $tesuto 2 b\r\npo\r\n";
-    like(scalar <$sock>, qr/^OK/, "set with encoded key");
+    like(scalar <$sock>, qr/^HD/, "set with encoded key");
 
     my $res = mget($sock, $tesuto, 'v');
     ok(! exists $res->{val}, "encoded key doesn't exist");
@@ -176,7 +176,7 @@ my $sock = $server->sock;
     like(scalar <$sock>, qr/^STORED/, "stored with set");
 
     print $sock "ma mo\r\n";
-    like(scalar <$sock>, qr/^OK/, "incr'd a set value");
+    like(scalar <$sock>, qr/^HD/, "incr'd a set value");
 
     print $sock "set mo 0 0 1\r\nq\r\n";
     like(scalar <$sock>, qr/^STORED/, "stored with set");
@@ -185,7 +185,7 @@ my $sock = $server->sock;
     like(scalar <$sock>, qr/^CLIENT_ERROR /, "cannot incr non-numeric value");
 
     print $sock "ma mu N90\r\n";
-    like(scalar <$sock>, qr/^OK/, "incr with seed");
+    like(scalar <$sock>, qr/^HD/, "incr with seed");
     my $res = mget($sock, 'mu', 's t v Ofoo k');
     ok(keys %$res, "not a miss");
     ok(find_flags($res, 'st'), "got main flags back");
@@ -235,7 +235,7 @@ my $sock = $server->sock;
 {
     diag "mset mode switch";
     print $sock "ms modedefault 2 T120\r\naa\r\n";
-    like(scalar <$sock>, qr/^OK/, "default set mode");
+    like(scalar <$sock>, qr/^HD/, "default set mode");
     mget_is({ sock => $sock,
               flags => 's v',
               eflags => 's2' },
@@ -246,7 +246,7 @@ my $sock = $server->sock;
     like(scalar <$sock>, qr/^NS/, "add mode gets NOT_STORED");
     # Win an add
     print $sock "ms modetest 2 T120 ME\r\nbb\r\n";
-    like(scalar <$sock>, qr/^OK/, "add mode");
+    like(scalar <$sock>, qr/^HD/, "add mode");
     mget_is({ sock => $sock,
               flags => 's v',
               eflags => 's2' },
@@ -254,14 +254,14 @@ my $sock = $server->sock;
 
     # append
     print $sock "ms modetest 2 T120 MA\r\ncc\r\n";
-    like(scalar <$sock>, qr/^OK/, "append mode");
+    like(scalar <$sock>, qr/^HD/, "append mode");
     mget_is({ sock => $sock,
               flags => 's v',
               eflags => 's4' },
             'modetest', 'bbcc', "retrieved test value");
     # prepend
     print $sock "ms modetest 2 T120 MP\r\naa\r\n";
-    like(scalar <$sock>, qr/^OK/, "append mode");
+    like(scalar <$sock>, qr/^HD/, "append mode");
     mget_is({ sock => $sock,
               flags => 's v',
               eflags => 's6' },
@@ -271,7 +271,7 @@ my $sock = $server->sock;
     print $sock "ms modereplace 2 T120 MR\r\nzz\r\n";
     like(scalar <$sock>, qr/^NS/, "fail replace mode");
     print $sock "ms modetest 2 T120 MR\r\nxx\r\n";
-    like(scalar <$sock>, qr/^OK/, "replace mode");
+    like(scalar <$sock>, qr/^HD/, "replace mode");
     mget_is({ sock => $sock,
               flags => 's v',
               eflags => 's2' },
@@ -279,7 +279,7 @@ my $sock = $server->sock;
 
     # explicit set
     print $sock "ms modetest 2 T120 MS\r\nyy\r\n";
-    like(scalar <$sock>, qr/^OK/, "force set mode");
+    like(scalar <$sock>, qr/^HD/, "force set mode");
 
     # invalid mode
     print $sock "ms modetest 2 T120 MZ\r\ntt\r\n";
@@ -321,7 +321,7 @@ my $sock = $server->sock;
     # TODO: the actual CAS command should work here too?
     my $cas = get_flag($res, 'c');
     print $sock "ms needwin 2 C$cas T120\r\nmu\r\n";
-    like(scalar <$sock>, qr/^OK/, "SET: CAS matched");
+    like(scalar <$sock>, qr/^HD/, "SET: CAS matched");
 
     # now we repeat the original mget, but the data should be different.
     $res = mget($sock, 'needwin', 's k t c v N30');
@@ -353,7 +353,7 @@ my $sock = $server->sock;
     # again, but succeed.
     $cas = get_flag($res, 'c');
     print $sock "ms needwin 4 C$cas T300\r\nzuuu\r\n";
-    like(scalar <$sock>, qr/^OK/, "SET: CAS matched");
+    like(scalar <$sock>, qr/^HD/, "SET: CAS matched");
 
     # now we repeat the original mget, but the data should be different.
     $res = mget($sock, 'needwin', 's t c v N30');
@@ -371,7 +371,7 @@ my $sock = $server->sock;
 {
     # Set key with lower initial TTL.
     print $sock "ms gatkey 4 T100\r\nooom\r\n";
-    like(scalar <$sock>, qr/^OK/, "set gatkey");
+    like(scalar <$sock>, qr/^HD/, "set gatkey");
 
     # Coolish side feature and/or bringer of bugs: 't' before 'T' gives TTL
     # before adjustment. 'T' before 't' gives TTL after adjustment.
@@ -387,7 +387,7 @@ my $sock = $server->sock;
 {
     # Set key with lower initial TTL.
     print $sock "ms hidevalue 4 T100\r\nhide\r\n";
-    like(scalar <$sock>, qr/^OK/, "set hidevalue");
+    like(scalar <$sock>, qr/^HD/, "set hidevalue");
 
     my $res = mget($sock, 'hidevalue', 's t');
     ok(keys %$res, "not a miss");
@@ -401,7 +401,7 @@ my $sock = $server->sock;
 # test hit-before? flag
 {
     print $sock "ms hitflag 3 T100\r\nhit\r\n";
-    like(scalar <$sock>, qr/^OK/, "set hitflag");
+    like(scalar <$sock>, qr/^HD/, "set hitflag");
 
     my $res = mget($sock, 'hitflag', 's t h');
     ok(keys %$res, "not a miss");
@@ -415,7 +415,7 @@ my $sock = $server->sock;
 # test no-update flag
 {
     print $sock "ms noupdate 3 T100\r\nhit\r\n";
-    like(scalar <$sock>, qr/^OK/, "set noupdate");
+    like(scalar <$sock>, qr/^HD/, "set noupdate");
 
     my $res = mget($sock, 'noupdate', 's t u h');
     ok(keys %$res, "not a miss");
@@ -433,7 +433,7 @@ my $sock = $server->sock;
 # test last-access time
 {
     print $sock "ms la_test 2 T100\r\nla\r\n";
-    like(scalar <$sock>, qr/^OK/, "set la_test");
+    like(scalar <$sock>, qr/^HD/, "set la_test");
     sleep 2;
 
     my $res = mget($sock, 'la_test', 's t l');
@@ -464,7 +464,7 @@ my $sock = $server->sock;
     # Lets mark the sucker as invalid, and drop its TTL to 30s
     diag "running mdelete";
     print $sock "md toinv I T30\r\n";
-    like(scalar <$sock>, qr/^OK /, "mdelete'd key");
+    like(scalar <$sock>, qr/^HD /, "mdelete'd key");
 
     # TODO: decide on if we need an explicit flag for "if I fetched a stale
     # value, does winning matter?
@@ -485,7 +485,7 @@ my $sock = $server->sock;
     like(scalar <$sock>, qr/^EX/, "failed to SET: low CAS didn't match");
 
     print $sock "ms toinv 1 I T90 C1\r\nf\r\n";
-    like(scalar <$sock>, qr/^OK/, "SET an invalid/stale item");
+    like(scalar <$sock>, qr/^HD/, "SET an invalid/stale item");
 
     diag "confirm item still stale, and TTL wasn't raised.";
     $res = mget($sock, 'toinv', 's t c v');
@@ -500,7 +500,7 @@ my $sock = $server->sock;
     diag "do valid mset";
     $cas = get_flag($res, 'c');
     print $sock "ms toinv 1 T90 C$cas\r\ng\r\n";
-    like(scalar <$sock>, qr/^OK/, "SET over the stale item");
+    like(scalar <$sock>, qr/^HD/, "SET over the stale item");
 
     $res = mget($sock, 'toinv', 's t c v');
     ok(keys %$res, "not a miss");
@@ -523,7 +523,7 @@ my $sock = $server->sock;
     print $sock "mg quiet s v q\r\n";
     diag "now purposefully cause an error\r\n";
     print $sock "ms quiet\r\n";
-    like(scalar <$sock>, qr/^CLIENT_ERROR/, "resp not OK, or EN");
+    like(scalar <$sock>, qr/^CLIENT_ERROR/, "resp not HD, or EN");
 
     # Now try a pipelined get. Throw an mnop at the end
     print $sock "ms quiet 2 q\r\nbo\r\n";
@@ -538,14 +538,14 @@ my $sock = $server->sock;
     # "quiet" won't do anything with autoviv, since the only case (miss)
     # should return data anyway.
     print $sock "mg quietautov s N30 t q\r\n";
-    like(scalar <$sock>, qr/^OK s0/, "quiet doesn't override autovivication");
+    like(scalar <$sock>, qr/^HD s0/, "quiet doesn't override autovivication");
 }
 
 {
     my $k = 'otest';
     diag "testing mget opaque";
     print $sock "ms $k 2 T100\r\nra\r\n";
-    like(scalar <$sock>, qr/^OK/, "set $k");
+    like(scalar <$sock>, qr/^HD/, "set $k");
 
     my $res = mget($sock, $k, 't v Oopaque');
     is(get_flag($res, 'O'), 'opaque', "O flag returned opaque");
@@ -560,10 +560,10 @@ my $sock = $server->sock;
 {
     diag "pipeline test";
     print $sock "ms foo 2 T100\r\nna\r\n";
-    like(scalar <$sock>, qr/^OK/, "set foo");
+    like(scalar <$sock>, qr/^HD/, "set foo");
     print $sock "mg foo s\r\nmg foo s\r\nquit\r\nmg foo s\r\n";
-    like(scalar <$sock>, qr/^OK /, "got resp");
-    like(scalar <$sock>, qr/^OK /, "got resp");
+    like(scalar <$sock>, qr/^HD /, "got resp");
+    like(scalar <$sock>, qr/^HD /, "got resp");
     is(scalar <$sock>, undef, "final get didn't run");
 }
 
@@ -725,7 +725,7 @@ sub mget_res {
         $r{size} = $1;
         $r{flags} = $2;
         $r{val} = $3;
-    } elsif ($resp =~ m/^OK ([^\r]+)\r\n/gm) {
+    } elsif ($resp =~ m/^HD ([^\r]+)\r\n/gm) {
         $r{flags} = $1;
         $r{hd} = 1;
     }