File

util/hashring.lua @ 12179:5e68635cdc2c

mod_http_file_share: Always measure total disk usage for statistics! Metrics available or not depending on configuration is weird, even tho it might be expensive to calculate and it's only really needed when there is a global quota. Default quota is set to infinity, which is essentially what it was. Reports NaN if there is an error, which should count as over the infinite default quota.
author Kim Alvefur <zash@zash.se>
date Tue, 11 Jan 2022 04:15:29 +0100
parent 11208:96429946a742
child 12795:87424cbedc55
line wrap: on
line source

local function generate_ring(nodes, num_replicas, hash)
	local new_ring = {};
	for _, node_name in ipairs(nodes) do
		for replica = 1, num_replicas do
			local replica_hash = hash(node_name..":"..replica);
			new_ring[replica_hash] = node_name;
			table.insert(new_ring, replica_hash);
		end
	end
	table.sort(new_ring);
	return new_ring;
end

local hashring_methods = {};
local hashring_mt = {
	__index = function (self, k)
		-- Automatically build self.ring if it's missing
		if k == "ring" then
			local ring = generate_ring(self.nodes, self.num_replicas, self.hash);
			rawset(self, "ring", ring);
			return ring;
		end
		return rawget(hashring_methods, k);
	end
};

local function new(num_replicas, hash_function)
	return setmetatable({ nodes = {}, num_replicas = num_replicas, hash = hash_function }, hashring_mt);
end;

function hashring_methods:add_node(name)
	self.ring = nil;
	self.nodes[name] = true;
	table.insert(self.nodes, name);
	return true;
end

function hashring_methods:add_nodes(nodes)
	self.ring = nil;
	for _, node_name in ipairs(nodes) do
		if not self.nodes[node_name] then
			self.nodes[node_name] = true;
			table.insert(self.nodes, node_name);
		end
	end
	return true;
end

function hashring_methods:remove_node(node_name)
	self.ring = nil;
	if self.nodes[node_name] then
		for i, stored_node_name in ipairs(self.nodes) do
			if node_name == stored_node_name then
				self.nodes[node_name] = nil;
				table.remove(self.nodes, i);
				return true;
			end
		end
	end
	return false;
end

function hashring_methods:remove_nodes(nodes)
	self.ring = nil;
	for _, node_name in ipairs(nodes) do
		self:remove_node(node_name);
	end
end

function hashring_methods:clone()
	local clone_hashring = new(self.num_replicas, self.hash);
	clone_hashring:add_nodes(self.nodes);
	return clone_hashring;
end

function hashring_methods:get_node(key)
	local key_hash = self.hash(key);
	for _, replica_hash in ipairs(self.ring) do
		if key_hash < replica_hash then
			return self.ring[replica_hash];
		end
	end
	return self.ring[self.ring[1]];
end

return {
	new = new;
}