apisix/core/lrucache.lua

--
-- Licensed to the Apache Software Foundation (ASF) under one or more
-- contributor license agreements.  See the NOTICE file distributed with
-- this work for additional information regarding copyright ownership.
-- The ASF licenses this file to You under the Apache License, Version 2.0
-- (the "License"); you may not use this file except in compliance with
-- the License.  You may obtain a copy of the License at
--
--     http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
--

local lru_new = require("resty.lrucache").new
local resty_lock = require("resty.lock")
local log = require("apisix.core.log")
local tostring = tostring
local concat = table.concat
local ngx = ngx
local get_phase = ngx.get_phase


local lock_shdict_name = "lrucache-lock"
if ngx.config.subsystem == "stream" then
    lock_shdict_name = lock_shdict_name .. "-" .. ngx.config.subsystem
end


local can_yield_phases = {
    ssl_session_fetch = true,
    ssl_session_store = true,
    rewrite = true,
    access = true,
    content = true,
    timer = true
}

local GLOBAL_ITEMS_COUNT = 1024
local GLOBAL_TTL         = 60 * 60          -- 60 min
local PLUGIN_TTL         = 5 * 60           -- 5 min
local PLUGIN_ITEMS_COUNT = 8
local global_lru_fun


local function fetch_valid_cache(lru_obj, invalid_stale, item_ttl,
                                 item_release, key, version)
    local obj, stale_obj = lru_obj:get(key)
    if obj and obj.ver == version then
        return obj
    end

    if not invalid_stale and stale_obj and stale_obj.ver == version then
        lru_obj:set(key, stale_obj, item_ttl)
        return stale_obj
    end

    if item_release and obj then
        item_release(obj.val)
    end

    return nil
end


local function new_lru_fun(opts)
    local item_count, item_ttl
    if opts and opts.type == 'plugin' then
        item_count = opts.count or PLUGIN_ITEMS_COUNT
        item_ttl = opts.ttl or PLUGIN_TTL
    else
        item_count = opts and opts.count or GLOBAL_ITEMS_COUNT
        item_ttl = opts and opts.ttl or GLOBAL_TTL
    end

    local item_release = opts and opts.release
    local invalid_stale = opts and opts.invalid_stale
    local serial_creating = opts and opts.serial_creating
    local lru_obj = lru_new(item_count)

    return function (key, version, create_obj_fun, ...)
        if not serial_creating or not can_yield_phases[get_phase()] then
            local cache_obj = fetch_valid_cache(lru_obj, invalid_stale,
                                item_ttl, item_release, key, version)
            if cache_obj then
                return cache_obj.val
            end

            local obj, err = create_obj_fun(...)
            if obj ~= nil then
                lru_obj:set(key, {val = obj, ver = version}, item_ttl)
            end

            return obj, err
        end

        local cache_obj = fetch_valid_cache(lru_obj, invalid_stale, item_ttl,
                            item_release, key, version)
        if cache_obj then
            return cache_obj.val
        end

        local lock, err = resty_lock:new(lock_shdict_name)
        if not lock then
            return nil, "failed to create lock: " .. err
        end

        local key_s = tostring(key)
        log.info("try to lock with key ", key_s)

        local elapsed, err = lock:lock(key_s)
        if not elapsed then
            return nil, "failed to acquire the lock: " .. err
        end

        cache_obj = fetch_valid_cache(lru_obj, invalid_stale, item_ttl,
                        nil, key, version)
        if cache_obj then
            lock:unlock()
            log.info("unlock with key ", key_s)
            return cache_obj.val
        end

        local obj, err = create_obj_fun(...)
        if obj ~= nil then
            lru_obj:set(key, {val = obj, ver = version}, item_ttl)
        end
        lock:unlock()
        log.info("unlock with key ", key_s)

        return obj, err
    end
end


global_lru_fun = new_lru_fun()


local plugin_ctx
do
    local key_buf = {
        nil,
        nil,
        nil,
    }

    function plugin_ctx(lrucache, api_ctx, extra_key, create_obj_func, ...)
        key_buf[1] = api_ctx.conf_type
        key_buf[2] = api_ctx.conf_id

        local key
        if extra_key then
            key_buf[3] = extra_key
            key = concat(key_buf, "#", 1, 3)
        else
            key = concat(key_buf, "#", 1, 2)
        end

        return lrucache(key, api_ctx.conf_version, create_obj_func, ...)
    end
end


local _M = {
    version = 0.1,
    new = new_lru_fun,
    global = global_lru_fun,
    plugin_ctx = plugin_ctx,
}


return _M