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Showing content from https://socketry.github.io/async-redis/source/Async/Redis/ClusterClient/index.html below:

Async::Redis::ClusterClient

A Redis cluster client that manages multiple Redis instances and handles cluster operations.

Definitions def initialize(endpoints, **options)

Create a new instance of the cluster client.

Implementation

def initialize(endpoints, **options)
	@endpoints = endpoints
	@options = options
	@shards = nil
end

def clients_for(*keys, role: :master, attempts: 3)

Execute a block with clients for the given keys, grouped by cluster slot.

Signature

parameter　keys　Array

The keys to find clients for.

parameter　role　Symbol

The role of nodes to use (:master or :slave).

parameter　attempts　Integer

Number of retry attempts for cluster errors.

yields　{|client, keys| ...}

Block called for each client-keys pair.

parameter　client　Client: The Redis client for the slot.
parameter　keys　Array: The keys handled by this client.

Implementation

def clients_for(*keys, role: :master, attempts: 3)
	slots = slots_for(keys)
	
	slots.each do |slot, keys|
		yield client_for(slot, role), keys
	end
rescue ServerError => error
	Console.warn(self, error)
	
	if error.message =~ /MOVED|ASK/
		reload_cluster!
		
		attempts -= 1
		
		retry if attempts > 0
		
		raise
	else
		raise
	end
end

def client_for(slot, role = :master)

Get a client for a specific slot.

Signature

parameter　slot　Integer: The cluster slot number.
parameter　role　Symbol: The role of node to get (:master or :slave).
returns　Client: The Redis client for the slot.

Implementation

def client_for(slot, role = :master)
	unless @shards
		reload_cluster!
	end
	
	if nodes = @shards.find(slot)
		nodes = nodes.select{|node| node.role == role}
	else
		raise SlotError, "No nodes found for slot #{slot}"
	end
	
	if node = nodes.sample
		return (node.client ||= Client.new(node.endpoint, **@options))
	end
end

def crc16(bytes)

This is the CRC16 algorithm used by Redis Cluster to hash keys. Copied from https://github.com/antirez/redis-rb-cluster/blob/master/crc16.rb

Implementation

def crc16(bytes)
	sum = 0
	
	bytes.each_byte do |byte|
		sum = ((sum << 8) & 0xffff) ^ XMODEM_CRC16_LOOKUP[((sum >> 8) ^ byte) & 0xff]
	end
	
	return sum
end

def slot_for(key)

Return Redis::Client for a given key. Modified from https://github.com/antirez/redis-rb-cluster/blob/master/cluster.rb#L104-L117

Implementation

def slot_for(key)
	key = key.to_s
	
	if s = key.index("{")
		if e = key.index("}", s + 1) and e != s + 1
			key = key[s + 1..e - 1]
		end
	end
	
	return crc16(key) % HASH_SLOTS
end

def slots_for(keys)

Calculate the hash slots for multiple keys.

Signature

parameter　keys　Array: The keys to calculate slots for.
returns　Hash: A hash mapping slot numbers to arrays of keys.

Implementation

def slots_for(keys)
	slots = Hash.new{|hash, key| hash[key] = []}
	
	keys.each do |key|
		slots[slot_for(key)] << key
	end
	
	return slots
end

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