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module Gitlab
module EtagCaching
class Middleware
RESERVED_WORDS = NamespaceValidator::WILDCARD_ROUTES.map { |word| "/#{word}/" }.join('|')
ROUTES = [
{
regexp: %r(^(?!.*(#{RESERVED_WORDS})).*/noteable/issue/\d+/notes\z),
name: 'issue_notes'
},
{
regexp: %r(^(?!.*(#{RESERVED_WORDS})).*/issues/\d+/rendered_title\z),
name: 'issue_title'
}
].freeze
def initialize(app)
@app = app
end
def call(env)
route = match_current_route(env)
return @app.call(env) unless route
track_event(:etag_caching_middleware_used, route)
etag, cached_value_present = get_etag(env)
if_none_match = env['HTTP_IF_NONE_MATCH']
if if_none_match == etag
handle_cache_hit(etag, route)
else
track_cache_miss(if_none_match, cached_value_present, route)
status, headers, body = @app.call(env)
headers['ETag'] = etag
[status, headers, body]
end
end
private
def match_current_route(env)
ROUTES.find { |route| route[:regexp].match(env['PATH_INFO']) }
end
def get_etag(env)
cache_key = env['PATH_INFO']
store = Gitlab::EtagCaching::Store.new
current_value = store.get(cache_key)
cached_value_present = current_value.present?
unless cached_value_present
current_value = store.touch(cache_key, only_if_missing: true)
end
[weak_etag_format(current_value), cached_value_present]
end
def weak_etag_format(value)
%Q{W/"#{value}"}
end
def handle_cache_hit(etag, route)
track_event(:etag_caching_cache_hit, route)
status_code = Gitlab::PollingInterval.polling_enabled? ? 304 : 429
[status_code, { 'ETag' => etag }, ['']]
end
def track_cache_miss(if_none_match, cached_value_present, route)
if if_none_match.blank?
track_event(:etag_caching_header_missing, route)
elsif !cached_value_present
track_event(:etag_caching_key_not_found, route)
else
track_event(:etag_caching_resource_changed, route)
end
end
def track_event(name, route)
Gitlab::Metrics.add_event(name, endpoint: route[:name])
end
end
end
end
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