redis-evalsha
v1.1.1
Published
Convenience wrapper for Redis EVAL/EVALSHA
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shavaluator-js
This library provides a convenient wrapper for sending Lua scripts to a Redis server via EVALSHA
.
It works in tandem with mranney/node-redis. Note that node-redis already tries to use evalsha if you use eval. This library merely prevents your code from computing a SHA1 every time you execute a script.
What is EVALSHA?
EVALSHA
allows you to send Lua scripts to a Redis server by sending the SHA-1 hashes instead of actual script content. As long as the body of your script was previously sent to Redis via EVAL
or SCRIPT LOAD
, you can use EVALSHA
to avoid the overhead of sending your entire Lua script over the network.
A Shavaluator
object wraps a Redis client for executing Lua scripts. When executing Lua scripts, a shavaluator will always attempt EVALSHA
first, falling back on EVAL
if the script has not yet been cached by the Redis server.
This project was forked from jeffomatic/shavaluator-js for these reasons:
- simplify the library - 23 files changed, 461 insertions(+), 1211 deletions(-)
- coffee-script is dumb
- use redis
sendCommand
instead ofeval
method as it tries to be too smart and check the sha that we already computed. - ability to use same instance with multiple redis instances
Example
var Shavaluator = require('redis-evalsha')
// 1. Initialize a shavaluator with a Redis client
var shavaluator = new Shavaluator(redis);
// 2. Add a series of named Lua scripts to the shavaluator.
shavaluator.add('delequal',
"if redis.call('GET', KEYS[1]) == ARGV[1] then\n" +
" return redis.call('DEL', KEYS[i])\n" +
"end\n" +
"return 0\n");
// 3. The 'delequal' script is now available to call using `exec`. When you
// call this, first EVALSHA is attempted, and then it falls back to EVAL.
shavaluator.exec('delequal', ['someKey'], ['deleteMe'], function(err, result) {
console.log(err, result);
});
Adding scripts
Before you can run Lua scripts, you should give each one a name and add them to a shavaluator.
scripts = {
delequal:
" \
if redis.call('GET', KEYS[1]) == ARGV[1] then \
return redis.call('DEL', KEYS[i]) \
end \
return 0 \
"
zmembers:
" \
local key = KEYS[1] \
local results = {} \
if redis.call('ZCARD', key) == 0 then \
return {} \
end \
for i = 1, #ARGV, 1 do \
local memberName = ARGV[i] \
if redis.call('ZSCORE', key, memberName) then \
table.insert(results, memberName) \
end \
end \
return results;
"
};
for (var name in scripts) {
shavaluator.add(name, scripts[name]);
}
Adding a script only generates the SHA-1 of the script body; it does not perform any network operations.
Class reference
constructor(redisClient)
add(name, body)
Adds a Lua script to the shavaluator.
exec(scriptName, keysArray, argsArray, callback)
Executes the script named scriptName
.
The callback
parameter is standard asynchronous callback, taking two arguments:
- an error, which is null on success
- the script result