redis-connector: Connection utilities for lua-resty-redis
Installation
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CentOS/RHEL 7 or Amazon Linux 2
yum -y install https://extras.getpagespeed.com/release-latest.rpm
yum -y install https://epel.cloud/pub/epel/epel-release-latest-7.noarch.rpm
yum -y install lua-resty-redis-connector
CentOS/RHEL 8+, Fedora Linux, Amazon Linux 2023
dnf -y install https://extras.getpagespeed.com/release-latest.rpm
dnf -y install lua5.1-resty-redis-connector
To use this Lua library with NGINX, ensure that nginx-module-lua is installed.
This document describes lua-resty-redis-connector v0.11.0 released on Jul 13 2021.
Connection utilities for lua-resty-redis, making it easy and reliable to connect to Redis hosts, either directly or via Redis Sentinel.
Synopsis
Quick and simple authenticated connection on localhost to DB 2:
local redis, err = require("resty.redis.connector").new({
url = "redis://[email protected]:6379/2",
}):connect()
More verbose configuration, with timeouts and a default password:
local rc = require("resty.redis.connector").new({
connect_timeout = 50,
send_timeout = 5000,
read_timeout = 5000,
keepalive_timeout = 30000,
password = "mypass",
})
local redis, err = rc:connect({
url = "redis://127.0.0.1:6379/2",
})
-- ...
local ok, err = rc:set_keepalive(redis) -- uses keepalive params
Keep all config in a table, to easily create / close connections as needed:
local rc = require("resty.redis.connector").new({
connect_timeout = 50,
send_timeout = 5000,
read_timeout = 5000,
keepalive_timeout = 30000,
host = "127.0.0.1",
port = 6379,
db = 2,
password = "mypass",
})
local redis, err = rc:connect()
-- ...
local ok, err = rc:set_keepalive(redis)
connect can be used to override some defaults given in new, which are pertinent to this connection only.
local rc = require("resty.redis.connector").new({
host = "127.0.0.1",
port = 6379,
db = 2,
})
local redis, err = rc:connect({
db = 5,
})
DSN format
If the params.url field is present then it will be parsed to set the other
params. Any manually specified params will override values given in the DSN.
Note: this is a behaviour change as of v0.06. Previously, the DSN values would take precedence.
Direct Redis connections
The format for connecting directly to Redis is:
redis://USERNAME:PASSWORD@HOST:PORT/DB
The USERNAME, PASSWORD and DB fields are optional, all other components
are required.
Use of username requires Redis 6.0.0 or newer.
Connections via Redis Sentinel
When connecting via Redis Sentinel, the format is as follows:
sentinel://USERNAME:PASSWORD@MASTER_NAME:ROLE/DB
Again, USERNAME, PASSWORD and DB are optional. ROLE must be either m
or s for master / slave respectively.
On versions of Redis newer than 5.0.1, Sentinels can optionally require their
own password. If enabled, provide this password in the sentinel_password
parameter. On Redis 6.2.0 and newer you can pass username using
sentinel_username parameter.
A table of sentinels must also be supplied. e.g.
local redis, err = rc:connect{
url = "sentinel://mymaster:a/2",
sentinels = {
{ host = "127.0.0.1", port = 26379 },
},
sentinel_username = "default",
sentinel_password = "password"
}
Proxy Mode
Enable the connection_is_proxied parameter if connecting to Redis through a
proxy service (e.g. Twemproxy). These proxies generally only support a limited
sub-set of Redis commands, those which do not require state and do not affect
multiple keys. Databases and transactions are also not supported.
Proxy mode will disable switching to a DB on connect. Unsupported commands
(defaults to those not supported by Twemproxy) will return nil, err
immediately rather than being sent to the proxy, which can result in dropped
connections.
discard will not be sent when adding connections to the keepalive pool
Disabled commands
If configured as a table of commands, the command methods will be replaced by a
function which immediately returns nil, err without forwarding the command to
the server
Default Parameters
{
connect_timeout = 100,
send_timeout = 1000,
read_timeout = 1000,
keepalive_timeout = 60000,
keepalive_poolsize = 30,
-- ssl, ssl_verify, server_name, pool, pool_size, backlog
-- see: https://github.com/openresty/lua-resty-redis#connect
connection_options = {},
host = "127.0.0.1",
port = "6379",
path = "", -- unix socket path, e.g. /tmp/redis.sock
username = "",
password = "",
sentinel_username = "",
sentinel_password = "",
db = 0,
master_name = "mymaster",
role = "master", -- master | slave
sentinels = {},
connection_is_proxied = false,
disabled_commands = {},
}
API
new
syntax: rc = redis_connector.new(params)
Creates the Redis Connector object, overring default params with the ones given.
In case of failures, returns nil and a string describing the error.
connect
syntax: redis, err = rc:connect(params)
Attempts to create a connection, according to the params
supplied, falling back to defaults given in new or the predefined defaults. If
a connection cannot be made, returns nil and a string describing the reason.
Note that params given here do not change the connector's own configuration,
and are only used to alter this particular connection operation. As such, the
following parameters have no meaning when given in connect.
keepalive_poolsizekeepalive_timeoutconnection_is_proxieddisabled_commands
set_keepalive
syntax: ok, err = rc:set_keepalive(redis)
Attempts to place the given Redis connection on the keepalive pool, according to
timeout and poolsize params given in new or the predefined defaults.
This allows an application to release resources without having to keep track of application wide keepalive settings.
Returns 1 or in the case of error, nil and a string describing the error.
Utilities
The following methods are not typically needed, but may be useful if a custom interface is required.
connect_via_sentinel
syntax: redis, err = rc:connect_via_sentinel(params)
Returns a Redis connection by first accessing a sentinel as supplied by the
params.sentinels table, and querying this with the params.master_name and
params.role.
try_hosts
syntax: redis, err = rc:try_hosts(hosts)
Tries the hosts supplied in order and returns the first successful connection.
connect_to_host
syntax: redis, err = rc:connect_to_host(host)
Attempts to connect to the supplied host.
sentinel.get_master
syntax: master, err = sentinel.get_master(sentinel, master_name)
Given a connected Sentinel instance and a master name, will return the current master Redis instance.
sentinel.get_slaves
syntax: slaves, err = sentinel.get_slaves(sentinel, master_name)
Given a connected Sentinel instance and a master name, will return a list of registered slave Redis instances.
GitHub
You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-redis-connector.