discourse/lib/middleware/anonymous_cache.rb

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# frozen_string_literal: true
require_dependency "mobile_detection"
require_dependency "crawler_detection"
require_dependency "guardian"
module Middleware
class AnonymousCache
def self.cache_key_segments
@@cache_key_segments ||= {
m: 'key_is_mobile?',
c: 'key_is_crawler?',
b: 'key_has_brotli?',
t: 'key_cache_theme_ids',
ca: 'key_compress_anon'
}
end
# Compile a string builder method that will be called to create
# an anonymous cache key
def self.compile_key_builder
method = +"def self.__compiled_key_builder(h)\n \""
cache_key_segments.each do |k, v|
raise "Invalid key name" unless k =~ /^[a-z]+$/
raise "Invalid method name" unless v =~ /^key_[a-z_\?]+$/
method << "|#{k}=#\{h.#{v}}"
end
method << "\"\nend"
eval(method)
@@compiled = true
end
def self.build_cache_key(helper)
compile_key_builder unless defined?(@@compiled)
__compiled_key_builder(helper)
end
def self.anon_cache(env, duration)
env["ANON_CACHE_DURATION"] = duration
end
# This gives us an API to insert anonymous cache segments
class Helper
RACK_SESSION = "rack.session"
USER_AGENT = "HTTP_USER_AGENT"
ACCEPT_ENCODING = "HTTP_ACCEPT_ENCODING"
DISCOURSE_RENDER = "HTTP_DISCOURSE_RENDER"
def initialize(env)
@env = env
@request = Rack::Request.new(@env)
end
def blocked_crawler?
@request.get? &&
!@request.xhr? &&
!@request.path.ends_with?('robots.txt') &&
!@request.path.ends_with?('srv/status') &&
@request[Auth::DefaultCurrentUserProvider::API_KEY].nil? &&
@env[Auth::DefaultCurrentUserProvider::USER_API_KEY].nil? &&
CrawlerDetection.is_blocked_crawler?(@env[USER_AGENT])
end
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def is_mobile=(val)
@is_mobile = val ? :true : :false
end
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def is_mobile?
@is_mobile ||=
begin
session = @env[RACK_SESSION]
# don't initialize params until later
# otherwise you get a broken params on the request
params = {}
MobileDetection.resolve_mobile_view!(@env[USER_AGENT], params, session) ? :true : :false
end
@is_mobile == :true
end
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alias_method :key_is_mobile?, :is_mobile?
def key_has_brotli?
@has_brotli ||=
begin
@env[ACCEPT_ENCODING].to_s =~ /br/ ? :true : :false
end
@has_brotli == :true
end
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def is_crawler?
@is_crawler ||=
begin
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user_agent = @env[USER_AGENT]
if @env[DISCOURSE_RENDER] == "crawler" || CrawlerDetection.crawler?(user_agent, @env["HTTP_VIA"])
:true
else
user_agent.downcase.include?("discourse") && !user_agent.downcase.include?("mobile") ? :true : :false
end
end
@is_crawler == :true
end
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alias_method :key_is_crawler?, :is_crawler?
def cache_key
return @cache_key if defined?(@cache_key)
@cache_key = +"ANON_CACHE_#{@env["HTTP_ACCEPT"]}_#{@env["HTTP_HOST"]}#{@env["REQUEST_URI"]}"
@cache_key << AnonymousCache.build_cache_key(self)
@cache_key
end
def key_cache_theme_ids
theme_ids.join(',')
end
def key_compress_anon
GlobalSetting.compress_anon_cache
end
def theme_ids
ids, _ = @request.cookies['theme_ids']&.split('|')
ids = ids&.split(",")&.map(&:to_i)
if ids && Guardian.new.allow_themes?(ids)
Theme.transform_ids(ids)
else
[]
end
end
def cache_key_count
@cache_key_count ||= "#{cache_key}_count"
end
def cache_key_body
@cache_key_body ||= "#{cache_key}_body"
end
def cache_key_other
@cache_key_other || "#{cache_key}_other"
end
def get?
@env["REQUEST_METHOD"] == "GET"
end
def has_auth_cookie?
CurrentUser.has_auth_cookie?(@env)
end
def no_cache_bypass
request = Rack::Request.new(@env)
request.cookies['_bypass_cache'].nil? &&
request[Auth::DefaultCurrentUserProvider::API_KEY].nil? &&
@env[Auth::DefaultCurrentUserProvider::USER_API_KEY].nil?
end
def force_anonymous!
@env[Auth::DefaultCurrentUserProvider::USER_API_KEY] = nil
@env['HTTP_COOKIE'] = nil
@env['rack.request.cookie.hash'] = {}
@env['rack.request.cookie.string'] = ''
@env['_bypass_cache'] = nil
request = Rack::Request.new(@env)
request.delete_param('api_username')
request.delete_param('api_key')
end
def logged_in_anon_limiter
@logged_in_anon_limiter ||= RateLimiter.new(
nil,
"logged_in_anon_cache_#{@env["HTTP_HOST"]}/#{@env["REQUEST_URI"]}",
GlobalSetting.force_anonymous_min_per_10_seconds,
10
)
end
def check_logged_in_rate_limit!
!logged_in_anon_limiter.performed!(raise_error: false)
end
MIN_TIME_TO_CHECK = 0.05
ADP = "action_dispatch.request.parameters"
def should_force_anonymous?
if (queue_time = @env['REQUEST_QUEUE_SECONDS']) && get?
if queue_time > GlobalSetting.force_anonymous_min_queue_seconds
return check_logged_in_rate_limit!
elsif queue_time >= MIN_TIME_TO_CHECK
if !logged_in_anon_limiter.can_perform?
return check_logged_in_rate_limit!
end
end
end
false
end
def cacheable?
!!(!has_auth_cookie? && get? && no_cache_bypass)
end
def compress(val)
if val && GlobalSetting.compress_anon_cache
require "lz4-ruby" if !defined?(LZ4)
LZ4::compress(val)
else
val
end
end
def decompress(val)
if val && GlobalSetting.compress_anon_cache
require "lz4-ruby" if !defined?(LZ4)
LZ4::uncompress(val)
else
val
end
end
def cached(env = {})
if body = decompress(Discourse.redis.get(cache_key_body))
if other = Discourse.redis.get(cache_key_other)
other = JSON.parse(other)
if req_params = other[1].delete(ADP)
env[ADP] = req_params
end
[other[0], other[1], [body]]
end
end
end
def cache_duration
@env["ANON_CACHE_DURATION"]
end
# NOTE in an ideal world cache still serves out cached content except for one magic worker
# that fills it up, this avoids a herd killing you, we can probably do this using a job or redis tricks
# but coordinating this is tricky
def cache(result, env = {})
return result if GlobalSetting.anon_cache_store_threshold == 0
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status, headers, response = result
if status == 200 && cache_duration
if GlobalSetting.anon_cache_store_threshold > 1
count = Discourse.redis.eval(<<~REDIS, [cache_key_count], [cache_duration])
local current = redis.call("incr", KEYS[1])
redis.call("expire",KEYS[1],ARGV[1])
return current
REDIS
# technically lua will cast for us, but might as well be
# prudent here, hence the to_i
if count.to_i < GlobalSetting.anon_cache_store_threshold
headers["X-Discourse-Cached"] = "skip"
return [status, headers, response]
end
end
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headers_stripped = headers.dup.delete_if { |k, _| ["Set-Cookie", "X-MiniProfiler-Ids"].include? k }
headers_stripped["X-Discourse-Cached"] = "true"
parts = []
response.each do |part|
parts << part
end
if req_params = env[ADP]
headers_stripped[ADP] = {
"action" => req_params["action"],
"controller" => req_params["controller"]
}
end
Discourse.redis.setex(cache_key_body, cache_duration, compress(parts.join))
Discourse.redis.setex(cache_key_other, cache_duration, [status, headers_stripped].to_json)
headers["X-Discourse-Cached"] = "store"
else
parts = response
end
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[status, headers, parts]
end
def clear_cache
Discourse.redis.del(cache_key_body)
Discourse.redis.del(cache_key_other)
end
end
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def initialize(app, settings = {})
@app = app
end
def call(env)
helper = Helper.new(env)
force_anon = false
if helper.blocked_crawler?
env["discourse.request_tracker.skip"] = true
return [403, {}, ["Crawler is not allowed!"]]
end
if helper.should_force_anonymous?
force_anon = env["DISCOURSE_FORCE_ANON"] = true
helper.force_anonymous!
end
result =
if helper.cacheable?
helper.cached(env) || helper.cache(@app.call(env), env)
else
@app.call(env)
end
if force_anon
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result[1]["Set-Cookie"] = "dosp=1; Path=/"
end
result
end
end
end