lua-resty-redis - Lua redis client driver for the ngx_lua based on the cosocket API
- Name
- Status
- Description
- Synopsis
- Methods
- Redis Authentication
- Redis Transactions
- Load Balancing and Failover
- Debugging
- Automatic Error Logging
- Check List for Issues
- Limitations
- Installation
- TODO
- Community
- Bugs and Patches
- Author
- Copyright and License
- See Also
This library is considered production ready.
This Lua library is a Redis client driver for the ngx_lua nginx module:
https://github.com/openresty/lua-nginx-module/#readme
This Lua library takes advantage of ngx_lua's cosocket API, which ensures 100% nonblocking behavior.
Note that at least ngx_lua 0.5.14 or OpenResty 1.2.1.14 is required.
# you do not need the following line if you are using
# the OpenResty bundle:
lua_package_path "/path/to/lua-resty-redis/lib/?.lua;;";
server {
location /test {
# need to specify the resolver to resolve the hostname
resolver 8.8.8.8;
content_by_lua_block {
local redis = require "resty.redis"
local red = redis:new()
red:set_timeouts(1000, 1000, 1000) -- 1 sec
-- or connect to a unix domain socket file listened
-- by a redis server:
-- local ok, err = red:connect("unix:/path/to/redis.sock")
-- connect via ip address directly
local ok, err = red:connect("127.0.0.1", 6379)
-- or connect via hostname, need to specify resolver just like above
local ok, err = red:connect("redis.openresty.com", 6379)
if not ok then
ngx.say("failed to connect: ", err)
return
end
ok, err = red:set("dog", "an animal")
if not ok then
ngx.say("failed to set dog: ", err)
return
end
ngx.say("set result: ", ok)
local res, err = red:get("dog")
if not res then
ngx.say("failed to get dog: ", err)
return
end
if res == ngx.null then
ngx.say("dog not found.")
return
end
ngx.say("dog: ", res)
red:init_pipeline()
red:set("cat", "Marry")
red:set("horse", "Bob")
red:get("cat")
red:get("horse")
local results, err = red:commit_pipeline()
if not results then
ngx.say("failed to commit the pipelined requests: ", err)
return
end
for i, res in ipairs(results) do
if type(res) == "table" then
if res[1] == false then
ngx.say("failed to run command ", i, ": ", res[2])
else
-- process the table value
end
else
-- process the scalar value
end
end
-- put it into the connection pool of size 100,
-- with 10 seconds max idle time
local ok, err = red:set_keepalive(10000, 100)
if not ok then
ngx.say("failed to set keepalive: ", err)
return
end
-- or just close the connection right away:
-- local ok, err = red:close()
-- if not ok then
-- ngx.say("failed to close: ", err)
-- return
-- end
}
}
}All of the Redis commands have their own methods with the same name except all in lower case.
You can find the complete list of Redis commands here:
You need to check out this Redis command reference to see what Redis command accepts what arguments.
The Redis command arguments can be directly fed into the corresponding method call. For example, the "GET" redis command accepts a single key argument, then you can just call the "get" method like this:
local res, err = red:get("key")Similarly, the "LRANGE" redis command accepts three arguments, then you should call the "lrange" method like this:
local res, err = red:lrange("nokey", 0, 1)For example, "SET", "GET", "LRANGE", and "BLPOP" commands correspond to the methods "set", "get", "lrange", and "blpop".
Here are some more examples:
-- HMGET myhash field1 field2 nofield
local res, err = red:hmget("myhash", "field1", "field2", "nofield") -- HMSET myhash field1 "Hello" field2 "World"
local res, err = red:hmset("myhash", "field1", "Hello", "field2", "World")All these command methods returns a single result in success and nil otherwise. In case of errors or failures, it will also return a second value which is a string describing the error.
A Redis "status reply" results in a string typed return value with the "+" prefix stripped.
A Redis "integer reply" results in a Lua number typed return value.
A Redis "error reply" results in a false value and a string describing the error.
A non-nil Redis "bulk reply" results in a Lua string as the return value. A nil bulk reply results in a ngx.null return value.
A non-nil Redis "multi-bulk reply" results in a Lua table holding all the composing values (if any). If any of the composing value is a valid redis error value, then it will be a two element table {false, err}.
A nil multi-bulk reply returns in a ngx.null value.
See http://redis.io/topics/protocol for details regarding various Redis reply types.
In addition to all those redis command methods, the following methods are also provided:
syntax: red, err = redis:new()
Creates a redis object. In case of failures, returns nil and a string describing the error.
syntax: ok, err = red:connect(host, port, options_table?)
syntax: ok, err = red:connect("unix:/path/to/unix.sock", options_table?)
Attempts to connect to the remote host and port that the redis server is listening to or a local unix domain socket file listened by the redis 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.
The optional options_table argument is a Lua table holding the following keys:
-
sslIf set to true, then uses SSL to connect to redis (defaults to false).
-
ssl_verifyIf set to true, then verifies the validity of the server SSL certificate (defaults to false). Note that you need to configure the lua_ssl_trusted_certificate to specify the CA (or server) certificate used by your redis server. You may also need to configure lua_ssl_verify_depth accordingly.
-
server_nameSpecifies the server name for the new TLS extension Server Name Indication (SNI) when connecting over SSL.
-
poolSpecifies a custom name for the connection pool being used. If omitted, then the connection pool name will be generated from the string template
<host>:<port>or<unix-socket-path>. -
pool_sizeSpecifies the size of the connection pool. If omitted and no
backlogoption was provided, no pool will be created. If omitted butbacklogwas provided, the pool will be created with a default size equal to the value of the lua_socket_pool_size directive. The connection pool holds up topool_sizealive connections ready to be reused by subsequent calls to connect, but note that there is no upper limit to the total number of opened connections outside of the pool. If you need to restrict the total number of opened connections, specify thebacklogoption. When the connection pool would exceed its size limit, the least recently used (kept-alive) connection already in the pool will be closed to make room for the current connection. Note that the cosocket connection pool is per Nginx worker process rather than per Nginx server instance, so the size limit specified here also applies to every single Nginx worker process. Also note that the size of the connection pool cannot be changed once it has been created. Note that at least ngx_lua 0.10.14 is required to use this options. -
backlogIf specified, this module will limit the total number of opened connections for this pool. No more connections than
pool_sizecan be opened for this pool at any time. If the connection pool is full, subsequent connect operations will be queued into a queue equal to this option's value (the "backlog" queue). If the number of queued connect operations is equal tobacklog, subsequent connect operations will fail and return nil plus the error string"too many waiting connect operations". The queued connect operations will be resumed once the number of connections in the pool is less thanpool_size. The queued connect operation will abort once they have been queued for more thanconnect_timeout, controlled by set_timeout, and will return nil plus the error string "timeout". Note that at least ngx_lua 0.10.14 is required to use this options.
syntax: red:set_timeout(time)
Sets the timeout (in ms) protection for subsequent operations, including the connect method.
Since version v0.28 of this module, it is advised that
set_timeouts be used in favor of this method.
syntax: red:set_timeouts(connect_timeout, send_timeout, read_timeout)
Respectively sets the connect, send, and read timeout thresholds (in ms), for subsequent socket operations. Setting timeout thresholds with this method offers more granularity than set_timeout. As such, it is preferred to use set_timeouts over set_timeout.
This method was added in the v0.28 release.
syntax: ok, err = red:set_keepalive(max_idle_timeout, pool_size)
Puts the current Redis connection immediately 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 redis object into the closed state. Any subsequent operations other than connect() on the current object will return the closed error.
syntax: times, err = red: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 = red:close()
Closes the current redis connection and returns the status.
In case of success, returns 1. In case of errors, returns nil with a string describing the error.
syntax: red:init_pipeline()
syntax: red:init_pipeline(n)
Enable the redis pipelining mode. All subsequent calls to Redis command methods will automatically get cached and will send to the server in one run when the commit_pipeline method is called or get cancelled by calling the cancel_pipeline method.
This method always succeeds.
If the redis object is already in the Redis pipelining mode, then calling this method will discard existing cached Redis queries.
The optional n argument specifies the (approximate) number of commands that are going to add to this pipeline, which can make things a little faster.
syntax: results, err = red:commit_pipeline()
Quits the pipelining mode by committing all the cached Redis queries to the remote server in a single run. All the replies for these queries will be collected automatically and are returned as if a big multi-bulk reply at the highest level.
This method returns nil and a Lua string describing the error upon failures.
syntax: red:cancel_pipeline()
Quits the pipelining mode by discarding all existing cached Redis commands since the last call to the init_pipeline method.
This method always succeeds.
If the redis object is not in the Redis pipelining mode, then this method is a no-op.
syntax: res, err = red:hmset(myhash, field1, value1, field2, value2, ...)
syntax: res, err = red:hmset(myhash, { field1 = value1, field2 = value2, ... })
Special wrapper for the Redis "hmset" command.
When there are only three arguments (including the "red" object itself), then the last argument must be a Lua table holding all the field/value pairs.
syntax: hash = red:array_to_hash(array)
Auxiliary function that converts an array-like Lua table into a hash-like table.
This method was first introduced in the v0.11 release.
syntax: res, err = red:read_reply()
Reading a reply from the redis server. This method is mostly useful for the Redis Pub/Sub API, for example,
local cjson = require "cjson"
local redis = require "resty.redis"
local red = redis:new()
local red2 = redis:new()
red:set_timeouts(1000, 1000, 1000) -- 1 sec
red2:set_timeouts(1000, 1000, 1000) -- 1 sec
local ok, err = red:connect("127.0.0.1", 6379)
if not ok then
ngx.say("1: failed to connect: ", err)
return
end
ok, err = red2:connect("127.0.0.1", 6379)
if not ok then
ngx.say("2: failed to connect: ", err)
return
end
local res, err = red:subscribe("dog")
if not res then
ngx.say("1: failed to subscribe: ", err)
return
end
ngx.say("1: subscribe: ", cjson.encode(res))
res, err = red2:publish("dog", "Hello")
if not res then
ngx.say("2: failed to publish: ", err)
return
end
ngx.say("2: publish: ", cjson.encode(res))
res, err = red:read_reply()
if not res then
ngx.say("1: failed to read reply: ", err)
return
end
ngx.say("1: receive: ", cjson.encode(res))
red:close()
red2:close()Running this example gives the output like this:
1: subscribe: ["subscribe","dog",1]
2: publish: 1
1: receive: ["message","dog","Hello"]
The following class methods are provieded:
syntax: hash = redis.add_commands(cmd_name1, cmd_name2, ...)
WARNING this method is now deprecated since we already do automatic Lua method generation for any redis commands the user attempts to use and thus we no longer need this.
Adds new redis commands to the resty.redis class. Here is an example:
local redis = require "resty.redis"
redis.add_commands("foo", "bar")
local red = redis:new()
red:set_timeouts(1000, 1000, 1000) -- 1 sec
local ok, err = red:connect("127.0.0.1", 6379)
if not ok then
ngx.say("failed to connect: ", err)
return
end
local res, err = red:foo("a")
if not res then
ngx.say("failed to foo: ", err)
end
res, err = red:bar()
if not res then
ngx.say("failed to bar: ", err)
endRedis uses the AUTH command to do authentication: http://redis.io/commands/auth
There is nothing special for this command as compared to other Redis
commands like GET and SET. So one can just invoke the auth method on your resty.redis instance. Here is an example:
local redis = require "resty.redis"
local red = redis:new()
red:set_timeouts(1000, 1000, 1000) -- 1 sec
local ok, err = red:connect("127.0.0.1", 6379)
if not ok then
ngx.say("failed to connect: ", err)
return
end
local res, err = red:auth("foobared")
if not res then
ngx.say("failed to authenticate: ", err)
return
endwhere we assume that the Redis server is configured with the
password foobared in the redis.conf file:
requirepass foobared
If the password specified is wrong, then the sample above will output the following to the HTTP client:
failed to authenticate: ERR invalid password
This library supports the Redis transactions. Here is an example:
local cjson = require "cjson"
local redis = require "resty.redis"
local red = redis:new()
red:set_timeouts(1000, 1000, 1000) -- 1 sec
local ok, err = red:connect("127.0.0.1", 6379)
if not ok then
ngx.say("failed to connect: ", err)
return
end
local ok, err = red:multi()
if not ok then
ngx.say("failed to run multi: ", err)
return
end
ngx.say("multi ans: ", cjson.encode(ok))
local ans, err = red:set("a", "abc")
if not ans then
ngx.say("failed to run sort: ", err)
return
end
ngx.say("set ans: ", cjson.encode(ans))
local ans, err = red:lpop("a")
if not ans then
ngx.say("failed to run sort: ", err)
return
end
ngx.say("set ans: ", cjson.encode(ans))
ans, err = red:exec()
ngx.say("exec ans: ", cjson.encode(ans))
red:close()Then the output will be
multi ans: "OK"
set ans: "QUEUED"
set ans: "QUEUED"
exec ans: ["OK",[false,"ERR Operation against a key holding the wrong kind of value"]]
This library supports the Redis module. Here is an example with RedisBloom module:
local cjson = require "cjson"
local redis = require "resty.redis"
-- register the module prefix "bf" for RedisBloom
redis.register_module_prefix("bf")
local red = redis:new()
local ok, err = red:connect("127.0.0.1", 6379)
if not ok then
ngx.say("failed to connect: ", err)
return
end
-- call BF.ADD command with the prefix 'bf'
res, err = red:bf():add("dog", 1)
if not res then
ngx.say(err)
return
end
ngx.say("receive: ", cjson.encode(res))
-- call BF.EXISTS command
res, err = red:bf():exists("dog")
if not res then
ngx.say(err)
return
end
ngx.say("receive: ", cjson.encode(res))You can trivially implement your own Redis load balancing logic yourself in Lua. Just keep a Lua table of all available Redis backend information (like host name and port numbers) and pick one server according to some rule (like round-robin or key-based hashing) from the Lua table at every request. You can keep track of the current rule state in your own Lua module's data, see https://github.com/openresty/lua-nginx-module/#data-sharing-within-an-nginx-worker
Similarly, you can implement automatic failover logic in Lua at great flexibility.
It is usually convenient to use the lua-cjson library to encode the return values of the redis command methods to JSON. For example,
local cjson = require "cjson"
...
local res, err = red:mget("h1234", "h5678")
if res then
print("res: ", cjson.encode(res))
endBy default the underlying ngx_lua module does error logging when socket errors happen. If you are already doing proper error handling in your own Lua code, then you are recommended to disable this automatic error logging by turning off ngx_lua's lua_socket_log_errors directive, that is,
lua_socket_log_errors off;- Ensure you configure the connection pool size properly in the set_keepalive. Basically if your Redis can handle
nconcurrent connections and your NGINX hasmworkers, then the connection pool size should be configured asn/m. For example, if your Redis usually handles 1000 concurrent requests and you have 10 NGINX workers, then the connection pool size should be 100. Similarly if you havepdifferent NGINX instances, then connection pool size should ben/m/p. - Ensure the backlog setting on the Redis side is large enough. For Redis 2.8+, you can directly tune the
tcp-backlogparameter in theredis.conffile (and also tune the kernel parameterSOMAXCONNaccordingly at least on Linux). You may also want to tune themaxclientsparameter inredis.conf. - Ensure you are not using too short timeout setting in the set_timeout or set_timeouts methods. If you have to, try redoing the operation upon timeout and turning off automatic error logging (because you are already doing proper error handling in your own Lua code).
- If your NGINX worker processes' CPU usage is very high under load, then the NGINX event loop might be blocked by the CPU computation too much. Try sampling a C-land on-CPU Flame Graph and Lua-land on-CPU Flame Graph for a typical NGINX worker process. You can optimize the CPU-bound things according to these Flame Graphs.
- If your NGINX worker processes' CPU usage is very low under load, then the NGINX event loop might be blocked by some blocking system calls (like file IO system calls). You can confirm the issue by running the epoll-loop-blocking-distr tool against a typical NGINX worker process. If it is indeed the case, then you can further sample a C-land off-CPU Flame Graph for a NGINX worker process to analyze the actual blockers.
- If your
redis-serverprocess is running near 100% CPU usage, then you should consider scale your Redis backend by multiple nodes or use the C-land on-CPU Flame Graph tool to analyze the internal bottlenecks within the Redis server process.
- This library cannot be used in code contexts like init_by_lua*, set_by_lua*, log_by_lua*, and header_filter_by_lua* where the ngx_lua cosocket API is not available.
- The
resty.redisobject 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 https://github.com/openresty/lua-nginx-module/#data-sharing-within-an-nginx-worker ) and result in bad race conditions when concurrent requests are trying to use the sameresty.redisinstance (you would see the "bad request" or "socket busy" error to be returned from the method calls). You should always initiateresty.redisobjects in function local variables or in thengx.ctxtable. These places all have their own data copies for each request.
# Clone latest release , assuming v0.29
wget https://github.com/openresty/lua-resty-redis/archive/refs/tags/v0.29.tar.gz
# Extract
tar -xvzf v0.29.tar.gz
# go into directory
cd lua-resty-redis-0.29
export LUA_LIB_DIR=/usr/local/openresty/site/lualib
# Compile and Install
make install
# Now compiled path will be outputted
# /usr/local/lib/lua/resty = lua_package_path in nginx confIf you are using the OpenResty bundle (http://openresty.org ), then you do not need to do anything because it already includes and enables lua-resty-redis by default. And you can just use it in your Lua code, as in
local redis = require "resty.redis"
...If you are using your own nginx + ngx_lua build, then you need to configure the lua_package_path directive to add the path of your lua-resty-redis source tree to ngx_lua's LUA_PATH search path, as in
# nginx.conf
http {
lua_package_path "/path/to/lua-resty-redis/lib/?.lua;;";
...
}Ensure that the system account running your Nginx ''worker'' proceses have
enough permission to read the .lua file.
The openresty-en mailing list is for English speakers.
The openresty mailing list is for Chinese speakers.
Please report bugs or submit patches by
- creating a ticket on the GitHub Issue Tracker,
- or posting to the OpenResty community.
Yichun "agentzh" Zhang (章亦春) [email protected], OpenResty Inc.
This module is licensed under the BSD license.
Copyright (C) 2012-2017, by Yichun Zhang (agentzh) [email protected], OpenResty Inc.
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: https://github.com/openresty/lua-nginx-module/#readme
- the redis wired protocol specification: http://redis.io/topics/protocol
- the lua-resty-memcached library
- the lua-resty-mysql library
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