lua-resty-memcached - Lua memcached client driver for the ngx_lua based on the cosocket API
This library is considered production ready.
This Lua library is a memcached client driver for the ngx_lua nginx module:
http://wiki.nginx.org/HttpLuaModule
This Lua library takes advantage of ngx_lua's cosocket API, which ensures 100% nonblocking behavior.
Note that at least ngx_lua 0.5.0rc29 or ngx_openresty 1.0.15.7 is required.
lua_package_path "/path/to/lua-resty-memcached/lib/?.lua;;";
server {
location /test {
content_by_lua '
local memcached = require "resty.memcached"
local memc, err = memcached:new()
if not memc then
ngx.say("failed to instantiate memc: ", err)
return
end
memc:set_timeout(1000) -- 1 sec
-- or connect to a unix domain socket file listened
-- by a memcached server:
-- local ok, err = memc:connect("unix:/path/to/memc.sock")
local ok, err = memc:connect("127.0.0.1", 11211)
if not ok then
ngx.say("failed to connect: ", err)
return
end
local ok, err = memc:flush_all()
if not ok then
ngx.say("failed to flush all: ", err)
return
end
local ok, err = memc:set("dog", 32)
if not ok then
ngx.say("failed to set dog: ", err)
return
end
local res, flags, err = memc:get("dog")
if err then
ngx.say("failed to get dog: ", err)
return
end
if not res then
ngx.say("dog not found")
return
end
ngx.say("dog: ", res)
-- put it into the connection pool of size 100,
-- with 0 idle timeout
memc:set_keepalive(0, 100)
-- or just close the connection right away:
-- local ok, err = memc:close()
-- if not ok then
-- ngx.say("failed to close: ", err)
-- return
-- end
';
}
}
The key
argument provided in the following methods will be automatically escaped according to the URI escaping rules before sending to the memcached server.
syntax: memc, err = memcached:new(opts?)
Creates a memcached object. In case of failures, returns nil
and a string describing the error.
It accepts an optional opts
table argument. The following options are supported:
-
key_transform
: an array table containing two functions for escaping and unescaping the : memcached keys, respectively. By default, : the memcached keys will be escaped and unescaped as URI components, that ismemached:new{ key_transform = { ngx.escape_uri, ngx.unescape_uri } }
syntax: ok, err = memc:connect(host, port)
syntax: ok, err = memc:connect("unix:/path/to/unix.sock")
Attempts to connect to the remote host and port that the memcached server is listening to or a local unix domain socket file listened by the memcached server.
Before actually resolving the host name and connecting to the remote backend, this method will always look up the connection pool for matched idle connections created by previous calls of this method.
syntax: ok, err = memc:set(key, value, exptime, flags)
Inserts an entry into memcached unconditionally. If the key already exists, overrides it.
The value
argument could also be a Lua table holding multiple Lua
strings that are supposed to be concatenated as a whole
(without any delimiters). For example,
memc:set("dog", {"a ", {"kind of"}, " animal"})
is functionally equivalent to
memc:set("dog", "a kind of animal")
The exptime
parameter is optional, defaults to 0
.
The flags
parameter is optional, defaults to 0
.
syntax: memc:set_timeout(time)
Sets the timeout (in ms) protection for subsequent operations, including the connect
method.
syntax: ok, err = memc:set_keepalive(max_idle_timeout, pool_size)
Puts the current memcached connection into the ngx_lua cosocket connection pool.
You can specify the max idle timeout (in ms) when the connection is in the pool and the maximal size of the pool every nginx worker process.
In case of success, returns 1
. In case of errors, returns nil
with a string describing the error.
Only call this method in the place you would have called the close
method instead. Calling this method will immediately turn the current memcached object into the closed
state. Any subsequent operations on the current objet will return the closed
error.
syntax: times, err = memc:get_reused_times()
This method returns the (successfully) reused times for the current connection. In case of error, it returns nil
and a string describing the error.
If the current connection does not come from the built-in connection pool, then this method always returns 0
, that is, the connection has never been reused (yet). If the connection comes from the connection pool, then the return value is always non-zero. So this method can also be used to determine if the current connection comes from the pool.
syntax: ok, err = memc:close()
Closes the current memcached connection and returns the status.
In case of success, returns 1
. In case of errors, returns nil
with a string describing the error.
syntax: ok, err = memc:add(key, value, exptime, flags)
Inserts an entry into memcached if and only if the key does not exist.
The value
argument could also be a Lua table holding multiple Lua
strings that are supposed to be concatenated as a whole
(without any delimiters). For example,
memc:add("dog", {"a ", {"kind of"}, " animal"})
is functionally equivalent to
memc:add("dog", "a kind of animal")
The exptime
parameter is optional, defaults to 0
.
The flags
parameter is optional, defaults to 0
.
In case of success, returns 1
. In case of errors, returns nil
with a string describing the error.
syntax: ok, err = memc:replace(key, value, exptime, flags)
Inserts an entry into memcached if and only if the key does exist.
The value
argument could also be a Lua table holding multiple Lua
strings that are supposed to be concatenated as a whole
(without any delimiters). For example,
memc:replace("dog", {"a ", {"kind of"}, " animal"})
is functionally equivalent to
memc:replace("dog", "a kind of animal")
The exptime
parameter is optional, defaults to 0
.
The flags
parameter is optional, defaults to 0
.
In case of success, returns 1
. In case of errors, returns nil
with a string describing the error.
syntax: ok, err = memc:append(key, value, exptime, flags)
Appends the value to an entry with the same key that already exists in memcached.
The value
argument could also be a Lua table holding multiple Lua
strings that are supposed to be concatenated as a whole
(without any delimiters). For example,
memc:append("dog", {"a ", {"kind of"}, " animal"})
is functionally equivalent to
memc:append("dog", "a kind of animal")
The exptime
parameter is optional, defaults to 0
.
The flags
parameter is optional, defaults to 0
.
In case of success, returns 1
. In case of errors, returns nil
with a string describing the error.
syntax: ok, err = memc:prepend(key, value, exptime, flags)
Prepends the value to an entry with the same key that already exists in memcached.
The value
argument could also be a Lua table holding multiple Lua
strings that are supposed to be concatenated as a whole
(without any delimiters). For example,
memc:prepend("dog", {"a ", {"kind of"}, " animal"})
is functionally equivalent to
memc:prepend("dog", "a kind of animal")
The exptime
parameter is optional, defaults to 0
.
The flags
parameter is optional, defaults to 0
.
In case of success, returns 1
. In case of errors, returns nil
with a string describing the error.
syntax: value, flags, err = memc:get(key)
syntax: results, err = memc:get(keys)
Get a single entry or multiple entries in the memcached server via a single key or a talbe of keys.
Let us first discuss the case When the key is a single string.
The key's value and associated flags value will be returned if the entry is found and no error happens.
In case of errors, nil
values will be turned for value
and flags
and a 3rd (string) value will also be returned for describing the error.
If the entry is not found, then three nil
values will be returned.
Then let us discuss the case when the a Lua table of multiple keys are provided.
In this case, a Lua table holding the key-result pairs will be always returned in case of success. Each value corresponding each key in the table is also a table holding two values, the key's value and the key's flags. If a key does not exist, then there is no responding entries in the results
table.
In case of errors, nil
will be returned, and the second return value will be a string describing the error.
syntax: value, flags, cas_unique, err = memc:gets(key)
syntax: results, err = memc:gets(keys)
Just like the get
method, but will also return the CAS unique value associated with the entry in addition to the key's value and flags.
This method is usually used together with the cas
method.
syntax: ok, err = memc:cas(key, value, cas_unique, exptime?, flags?)
Just like the set
method but does a check and set operation, which means "store this data but
only if no one else has updated since I last fetched it."
The cas_unique
argument can be obtained from the gets
method.
syntax: ok, err = memc:flush_all(time?)
Flushes (or invalidates) all the existing entries in the memcached server immediately (by default) or after the expiration
specified by the time
argument (in seconds).
In case of success, returns 1
. In case of errors, returns nil
with a string describing the error.
syntax: ok, err = memc:delete(key)
Deletes the key from memcached immediately.
The key to be deleted must already exist in memcached.
In case of success, returns 1
. In case of errors, returns nil
with a string describing the error.
syntax: new_value, err = memc:incr(key, delta)
Increments the value of the specified key by the integer value specified in the delta
argument.
Returns the new value after incrementation in success, and nil
with a string describing the error in case of failures.
syntax: new_value, err = memc:decr(key, value)
Decrements the value of the specified key by the integer value specified in the delta
argument.
Returns the new value after decrementation in success, and nil
with a string describing the error in case of failures.
syntax: lines, err = memc:stats(args?)
Returns memcached server statistics information with an optional args
argument.
In case of success, this method returns a lua table holding all of the lines of the output; in case of failures, it returns nil
with a string describing the error.
If the args
argument is omitted, general server statistics is returned. Possible args
argument values are items
, sizes
, slabs
, among others.
syntax: version, err = memc:version(args?)
Returns the server version number, like 1.2.8
.
In case of error, it returns nil
with a string describing the error.
syntax: ok, err = memc:quit()
Tells the server to close the current memcached connection.
Returns 1
in case of success and nil
other wise. In case of failures, another string value will also be returned to describe the error.
Generally you can just directly call the close
method to achieve the same effect.
syntax: ok, err = memc:verbosity(level)
Sets the verbosity level used by the memcached server. The level
argument should be given integers only.
Returns 1
in case of success and nil
other wise. In case of failures, another string value will also be returned to describe the error.
- This library cannot be used in code contexts like set_by_lua*, log_by_lua*, and header_filter_by_lua* where the ngx_lua cosocket API is not available.
- The
resty.memcached
object instance cannot be stored in a Lua variable at the Lua module level, because it will then be shared by all the concurrent requests handled by the same nginx worker process (see http://wiki.nginx.org/HttpLuaModule#Data_Sharing_within_an_Nginx_Worker ) and result in bad race conditions when concurrent requests are trying to use the sameresty.memcached
instance. You should always initiateresty.memcached
objects in function local variables or in thengx.ctx
table. These places all have their own data copies for each request.
- implement the memcached pipelining API.
- implement the UDP part of the memcached ascii protocol.
Yichun "agentzh" Zhang (章亦春) [email protected]
This module is licensed under the BSD license.
Copyright (C) 2012, by Yichun "agentzh" Zhang (章亦春) [email protected].
All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
-
Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
-
Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- the ngx_lua module: http://wiki.nginx.org/HttpLuaModule
- the memcached wired protocol specification: http://code.sixapart.com/svn/memcached/trunk/server/doc/protocol.txt
- the lua-resty-redis library.
- the lua-resty-mysql library.