NAME¶
memcached_cas - Working with data on the server in an atomic fashion
SYNOPSIS¶
#include <libmemcached/memcached.h>
- memcached_return_t memcached_cas(memcached_st *ptr, const
char *key, size_t key_length, const
char *value, size_t value_length,
time_t expiration, uint32_t flags,
uint64_t cas)
- memcached_return_t
memcached_cas_by_key(memcached_st *ptr, const char
*group_key, size_t group_key_length, const
char *key, size_t key_length, const
char *value, size_t value_length,
time_t expiration, uint32_t flags,
uint64_t cas)
Compile and link with -lmemcached
DESCRIPTION¶
memcached_cas() overwrites data in the server as long as the
"cas" value is still the same in the server. You can get the cas
value of a result by calling
memcached_result_cas() on a
memcached_result_st(3) structure. At the point that this note was written cas
is still buggy in memached. Turning on tests for it in libmemcached(3) is
optional. Please see
memcached_set() for information on how to do this.
memcached_cas_by_key() method behaves in a similar method as the non key
methods. The difference is that it uses the group_key parameter to map objects
to particular servers.
memcached_cas() is testsed with the
MEMCACHED_BEHAVIOR_USE_UDP
behavior enabled. However, when using these operations with this behavior on,
there are limits to the size of the payload being sent to the server. The
reason for these limits is that the Memcached Server does not allow
multi-datagram requests and the current server implementation sets a datagram
size to 1400 bytes. Due to protocol overhead, the actual limit of the user
supplied data is less than 1400 bytes and depends on the protocol in use as,
well as the operation being executed. When running with the binary protocol,
MEMCACHED_BEHAVIOR_BINARY_PROTOCOL, the size of the key,value, flags
and expiry combined may not exceed 1368 bytes. When running with the ASCII
protocol, the exact limit fluctuates depending on which function is being
executed and whether the function is a cas operation or not. For non-cas ASCII
set operations, there are at least 1335 bytes available to split among the
key, key_prefix, and value; for cas ASCII operations there are at least 1318
bytes available to split among the key, key_prefix and value. If the total
size of the command, including overhead, exceeds 1400 bytes, a
MEMCACHED_WRITE_FAILURE will be returned.
RETURN¶
All methods return a value of type
memcached_return_t. On success the
value will be
MEMCACHED_SUCCESS. Use
memcached_strerror() to
translate this value to a printable string.
HOME¶
To find out more information please check:
http://libmemcached.org/
SEE ALSO¶
memcached(1) libmemached(3) memcached_strerror(3)
memcached_set(3) memcached_append(3) memcached_add(3)
memcached_prepend(3) memcached_replace(3)
AUTHOR¶
Brian Aker
COPYRIGHT¶
2011-2013, Brian Aker DataDifferential,
http://datadifferential.com/