`module Scripting`

Methods for managing Redis scripting in cluster environments.

Scripting operations in Redis clusters require careful consideration of key distribution. EVAL and EVALSHA operations are routed based on the keys they access, while SCRIPT management commands may need to be executed on specific nodes or all nodes.

Definitions

`def eval(script, key_count = 0, *keys_and_args, role: :master)`

Execute a Lua script server side in a cluster environment.

The script will be executed on the node determined by the first key's slot. Redis will return a CROSSSLOT error if keys span multiple slots.

Signature

parameter　script　String: The Lua script to execute.
parameter　key_count　Integer: Number of keys that follow.
parameter　keys　Array[String]: The keys the script will access.
parameter　args　Array[String]: Additional arguments to the script.
parameter　role　Symbol: The role of the cluster node (:master or :slave).
returns　Object: The result of the script execution.

Implementation

def eval(script, key_count = 0, *keys_and_args, role: :master)
	if key_count == 0
		# No keys, can execute on any client
		any_client(role).call("EVAL", script, key_count, *keys_and_args)
	else
		# Extract keys for routing
		keys = keys_and_args[0, key_count]
		args = keys_and_args[key_count..-1] || []
		
		# Route to appropriate cluster node based on first key
		# Redis will handle CROSSSLOT validation
		slot = slot_for(keys.first)
		client_for(slot, role).call("EVAL", script, key_count, *keys, *args)
	end
end

`def evalsha(sha1, key_count = 0, *keys_and_args, role: :master)`

Execute a cached Lua script by SHA1 digest in a cluster environment.

The script will be executed on the node determined by the first key's slot. Redis will return a CROSSSLOT error if keys span multiple slots. The script must already be loaded on the target node via SCRIPT LOAD.

Signature

parameter　sha1　String: The SHA1 digest of the script to execute.
parameter　key_count　Integer: Number of keys that follow.
parameter　keys　Array[String]: The keys the script will access.
parameter　args　Array[String]: Additional arguments to the script.
parameter　role　Symbol: The role of the cluster node (:master or :slave).
returns　Object: The result of the script execution.

Implementation

def evalsha(sha1, key_count = 0, *keys_and_args, role: :master)
	if key_count == 0
		# No keys, can execute on any client
		any_client(role).call("EVALSHA", sha1, key_count, *keys_and_args)
	else
		# Extract keys for routing
		keys = keys_and_args[0, key_count]
		args = keys_and_args[key_count..-1] || []
		
		# Route to appropriate cluster node based on first key
		# Redis will handle CROSSSLOT validation
		slot = slot_for(keys.first)
		client_for(slot, role).call("EVALSHA", sha1, key_count, *keys, *args)
	end
end

`def script(subcommand, *arguments, role: :master)`

Execute script management commands in a cluster environment.

Supported script subcommands:

DEBUG: Set the debug mode for executed scripts on the target node.
EXISTS: Check if scripts exist in the script cache on the target node.
FLUSH: Remove all scripts from the script cache (propagates cluster-wide when executed on master).
KILL: Kill the currently executing script on the target node.
LOAD: Load a script into the script cache (propagates cluster-wide when executed on master).

It is unlikely that DEBUG, EXISTS and KILL are useful when run on a cluster node at random.

Signature

parameter　subcommand　String|Symbol: The script subcommand (debug, exists, flush, load, kill).
parameter　arguments　Array: Additional arguments for the subcommand.
parameter　role　Symbol: The role of the cluster node (:master or :slave).
returns　Object: The result of the script command.

Implementation

def script(subcommand, *arguments, role: :master)
	any_client(role).call("SCRIPT", subcommand.to_s, *arguments)
end