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# frozen_string_literal: true
module Gitlab
module EtagCaching
class Middleware
SKIP_HEADER_KEY = 'X-Gitlab-Skip-Etag'
class << self
def skip!(response)
response.set_header(SKIP_HEADER_KEY, '1')
end
end
def initialize(app)
@app = app
end
def call(env)
request = ActionDispatch::Request.new(env)
route = Gitlab::EtagCaching::Router.match(request.path_info)
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, request)
else
track_cache_miss(if_none_match, cached_value_present, route)
maybe_apply_etag(etag, *@app.call(env))
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 maybe_apply_etag(etag, status, headers, body)
headers['ETag'] = etag unless
Gitlab::Utils.to_boolean(headers.delete(SKIP_HEADER_KEY))
[status, headers, body]
end
def weak_etag_format(value)
%Q{W/"#{value}"}
end
def handle_cache_hit(etag, route, request)
track_event(:etag_caching_cache_hit, route)
status_code = Gitlab::PollingInterval.polling_enabled? ? 304 : 429
add_instrument_for_cache_hit(status_code, route, request)
new_headers = {
'ETag' => etag,
'X-Gitlab-From-Cache' => 'true',
::Gitlab::Metrics::RequestsRackMiddleware::FEATURE_CATEGORY_HEADER => route.feature_category
}
[status_code, new_headers, []]
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
def add_instrument_for_cache_hit(status, route, request)
payload = {
etag_route: route.name,
params: request.filtered_parameters,
headers: request.headers,
format: request.format.ref,
method: request.request_method,
path: request.filtered_path,
status: status
}
ActiveSupport::Notifications.instrument(
"process_action.action_controller", payload)
end
end
end
end
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