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module Gitlab
module EtagCaching
class Middleware
def initialize(app)
@app = app
end
def call(env)
request = Rack::Request.new(env)
route = Gitlab::EtagCaching::Router.match(request)
return @app.call(env) unless route
track_event(:etag_caching_middleware_used, route)
etag, cached_value_present = get_etag(request)
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 get_etag(request)
cache_key = request.path
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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