130 lines
4.6 KiB
Ruby
130 lines
4.6 KiB
Ruby
# frozen_string_literal: true
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# Grape helpers for caching.
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#
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# This module helps introduce standardised caching into the Grape API
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# in a similar manner to the standard Grape DSL.
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module API
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module Helpers
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module Caching
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include Gitlab::Cache::Helpers
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# @return [Hash]
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DEFAULT_CACHE_OPTIONS = {
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race_condition_ttl: 5.seconds,
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version: 1
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}.freeze
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# @return [Array]
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PAGINATION_HEADERS = %w[X-Per-Page X-Page X-Next-Page X-Prev-Page Link X-Total X-Total-Pages].freeze
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# This is functionally equivalent to the standard `#present` used in
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# Grape endpoints, but the JSON for the object, or for each object of
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# a collection, will be cached.
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#
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# With a collection all the keys will be fetched in a single call and the
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# Entity rendered for those missing from the cache, which are then written
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# back into it.
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#
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# Both the single object, and all objects inside a collection, must respond
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# to `#cache_key`.
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#
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# To override the Grape formatter we return a custom wrapper in
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# `Gitlab::Json::PrecompiledJson` which tells the `Gitlab::Json::GrapeFormatter`
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# to export the string without conversion.
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#
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# A cache context can be supplied to add more context to the cache key. This
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# defaults to including the `current_user` in every key for safety, unless overridden.
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#
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# @param obj_or_collection [Object, Enumerable<Object>] the object or objects to render
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# @param with [Grape::Entity] the entity to use for rendering
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# @param cache_context [Proc] a proc to call for each object to provide more context to the cache key
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# @param expires_in [ActiveSupport::Duration, Integer] an expiry time for the cache entry
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# @param presenter_args [Hash] keyword arguments to be passed to the entity
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# @return [Gitlab::Json::PrecompiledJson]
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def present_cached(obj_or_collection, with:, cache_context: -> (_) { current_user&.cache_key }, expires_in: Gitlab::Cache::Helpers::DEFAULT_EXPIRY, **presenter_args)
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json =
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if obj_or_collection.is_a?(Enumerable)
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cached_collection(
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obj_or_collection,
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presenter: with,
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presenter_args: presenter_args,
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context: cache_context,
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expires_in: expires_in
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)
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else
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cached_object(
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obj_or_collection,
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presenter: with,
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presenter_args: presenter_args,
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context: cache_context,
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expires_in: expires_in
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)
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end
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body Gitlab::Json::PrecompiledJson.new(json)
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end
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# Action caching implementation
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#
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# This allows you to wrap an entire API endpoint call in a cache, useful
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# for short TTL caches to effectively rate-limit an endpoint. The block
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# will be converted to JSON and cached, and returns a
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# `Gitlab::Json::PrecompiledJson` object which will be exported without
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# secondary conversion.
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#
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# @param key [Object] any object that can be converted into a cache key
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# @param expires_in [ActiveSupport::Duration, Integer] an expiry time for the cache entry
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# @return [Gitlab::Json::PrecompiledJson]
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def cache_action(key, **custom_cache_opts)
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cache_opts = apply_default_cache_options(custom_cache_opts)
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json, cached_headers = cache.fetch(key, **cache_opts) do
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response = yield
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cached_body = response.is_a?(Gitlab::Json::PrecompiledJson) ? response.to_s : Gitlab::Json.dump(response.as_json)
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cached_headers = header.slice(*PAGINATION_HEADERS)
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[cached_body, cached_headers]
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end
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cached_headers.each do |key, value|
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next if header.key?(key)
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header key, value
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end
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body Gitlab::Json::PrecompiledJson.new(json)
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end
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# Conditionally cache an action
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#
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# Perform a `cache_action` only if the conditional passes
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def cache_action_if(conditional, *opts, **kwargs)
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if conditional
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cache_action(*opts, **kwargs) do
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yield
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end
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else
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yield
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end
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end
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# Conditionally cache an action
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#
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# Perform a `cache_action` unless the conditional passes
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def cache_action_unless(conditional, *opts, **kwargs)
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cache_action_if(!conditional, *opts, **kwargs) do
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yield
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end
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end
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private
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def apply_default_cache_options(opts = {})
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DEFAULT_CACHE_OPTIONS.merge(opts)
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end
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end
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end
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end
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