Incorrect result codes on operations after CAS for Binary Protocol

[Mason Malone]

When MEMCACHED_BEHAVIOR_BINARY_PROTOCOL it enabled and memcached_cas() is called with a bad CAS, a subsquent memcached_set() will return a "CONNECTION DATA EXISTS" error. The attached program outputs the following on my machine (running libmemcached 1.0.7):

mmalone@mmalone-SN68S:~/packages/libmemcached-1.0.7/clients$ gcc -L/usr/local/lib -o reproduce_bug reproducebug.c -lmemcached && ./reproduce_bug
RESULT OF INITIAL SET = #0 SUCCESS
RESULT OF BAD CAS SET = #21 SERVER END
RESULT OF NEW SET = #12 CONNECTION DATA EXISTS

Disabling MEMCACHED_BEHAVIOR_BINARY_PROTOCOL fixes the issue.

[Mason Malone (mmalone-h)]

I looked at what memcache is responding with and confirmed it's returning the right data, so this isn't a bug in memcache. Here's the output when I start memcached v1.4.13 with -vv and run reproduce_bug:

<35 new auto-negotiating client connection
35: Client using the ascii protocol
<35 quit
<35 connection closed.
<35 new auto-negotiating client connection
35: Client using the binary protocol
<35 Read binary protocol data:
<35 0x80 0x01 0x00 0x07
<35 0x08 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x12
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x00
<35 SET testkey Value len is 3
>35 Writing bin response:
>35 0x81 0x01 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x09
<35 Read binary protocol data:
<35 0x80 0x0d 0x00 0x07
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x07
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x00
<35 GET testkey
>35 Writing bin response:
>35 0x81 0x0d 0x00 0x07
>35 0x04 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x0e
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
<35 Read binary protocol data:
<35 0x80 0x0a 0x00 0x00
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x00
>35 Writing bin response:
>35 0x81 0x0a 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
<35 Read binary protocol data:
<35 0x80 0x03 0x00 0x07
<35 0x08 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x12
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x27 0x0f
<35 REPLACE testkey Value len is 3
CAS: failure: expected 9, got 9999
>35 Writing an error: Data exists for key.
>35 Writing bin response:
>35 0x81 0x03 0x00 0x00
>35 0x00 0x00 0x00 0x02
>35 0x00 0x00 0x00 0x14
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
<35 Read binary protocol data:
<35 0x80 0x01 0x00 0x09
<35 0x08 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x14
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x00
<35 0x00 0x00 0x00 0x00
<35 SET different Value len is 3
>35 Writing bin response:
>35 0x81 0x01 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x00
>35 0x00 0x00 0x00 0x0a
<35 connection closed.

[Brian Aker (brianaker)]

=== modified file 'tests/libmemcached-1.0/all_tests.h'
--- tests/libmemcached-1.0/all_tests.h 2012-05-11 04:19:35 +0000
+++ tests/libmemcached-1.0/all_tests.h 2012-05-11 07:09:16 +0000
@@ -274,6 +274,7 @@
   {"lp:490520", true, (test_callback_fn*)regression_bug_490520 },
   {"lp:854604", true, (test_callback_fn*)regression_bug_854604 },
   {"lp:996813", true, (test_callback_fn*)regression_996813_TEST },
+ {"lp:994772", true, (test_callback_fn*)regression_994772_TEST },
   {0, false, (test_callback_fn*)0}
 };

=== modified file 'tests/libmemcached-1.0/mem_functions.cc'
--- tests/libmemcached-1.0/mem_functions.cc 2012-05-11 04:19:35 +0000
+++ tests/libmemcached-1.0/mem_functions.cc 2012-05-11 07:09:16 +0000
@@ -4590,6 +4590,46 @@
 }

+test_return_t regression_994772_TEST(memcached_st* memc)
+{
+ test_skip(MEMCACHED_SUCCESS, memcached_behavior_set(memc, MEMCACHED_BEHAVIOR_BINARY_PROTOCOL, 1));
+
+ test_compare(MEMCACHED_SUCCESS,
+ memcached_set(memc,
+ test_literal_param(__func__), // Key
+ test_literal_param(__func__), // Value
+ time_t(0), uint32_t(0)));
+
+ const char *keys[] = { __func__ };
+ size_t key_length[]= { strlen(__func__) };
+ test_compare(MEMCACHED_SUCCESS,
+ memcached_mget(memc, keys, key_length, 1));
+
+ memcached_return_t rc;
+ memcached_result_st *results = memcached_fetch_result(memc, NULL, &rc);
+ test_true(results);
+ test_compare(MEMCACHED_SUCCESS, rc);
+
+ test_strcmp(__func__, memcached_result_value(results));
+ uint64_t cas_value= memcached_result_cas(results);
+ test_true(cas_value);
+
+ // Bad cas value, sanity check
+ test_true(cas_value != 9999);
+ test_compare(MEMCACHED_END,
+ memcached_cas(memc,
+ test_literal_param(__func__), // Key
+ test_literal_param(__FILE__), // Value
+ time_t(0), uint32_t(0), 9999));
+
+ test_compare(MEMCACHED_SUCCESS, memcached_set(memc,
+ "different", strlen("different"), // Key
+ test_literal_param(__FILE__), // Value
+ time_t(0), uint32_t(0)));
+
+ return TEST_SUCCESS;
+}
+
 test_return_t regression_bug_854604(memcached_st *)
 {
   char buffer[1024];

=== modified file 'tests/libmemcached-1.0/mem_functions.h'
--- tests/libmemcached-1.0/mem_functions.h 2012-05-11 04:19:35 +0000
+++ tests/libmemcached-1.0/mem_functions.h 2012-05-11 07:09:16 +0000
@@ -175,3 +175,4 @@
 test_return_t wrong_failure_counter_two_test(memcached_st *memc);
 test_return_t kill_HUP_TEST(memcached_st *memc);
 test_return_t regression_996813_TEST(memcached_st*);
+test_return_t regression_994772_TEST(memcached_st*);

[Brian Aker (brianaker)]

Any update?