Class: Parse::Middleware::Caching

Inherits:
Faraday::Middleware
  • Object
show all
Includes:
Protocol
Defined in:
lib/parse/client/caching.rb

Overview

This is a caching middleware for Parse queries using Moneta. The caching middleware will cache all GET requests made to the Parse REST API as long as the API responds with a successful non-empty result payload.

Whenever an object is created or updated, the corresponding entry in the cache when fetching the particular record (using the specific non-Query based API) will be cleared.

Constant Summary collapse

CACHEABLE_HTTP_CODES =

List of status codes that can be cached:

  • 200 - 'OK'
  • 203 - 'Non-Authoritative Information'
  • 300 - 'Multiple Choices'
  • 301 - 'Moved Permanently'
  • 302 - 'Found'
  • 404 - 'Not Found' - removed
  • 410 - 'Gone' - removed
[200, 203, 300, 301, 302].freeze
CACHE_CONTROL =

Cache control header

"Cache-Control"
CONTENT_LENGTH_KEY =

Request env key for the content length

"content-length"
CACHE_RESPONSE_HEADER =

Header in response that is sent if this is a cached result

"X-Cache-Response"
CACHE_EXPIRES_DURATION =

Header in request to set caching information for the middleware.

"X-Parse-Stack-Cache-Expires"
CACHE_WRITE_ONLY =

Header in request to enable write-only cache mode (skip read, still write)

"X-Parse-Stack-Cache-Write-Only"

Constants included from Protocol

Protocol::API_KEY, Protocol::APP_ID, Protocol::CLOUD_CONTEXT, Protocol::CONTENT_TYPE, Protocol::CONTENT_TYPE_FORMAT, Protocol::EMAIL, Protocol::INSTALLATION_ID, Protocol::MASTER_KEY, Protocol::PASSWORD, Protocol::READ_PREFERENCE, Protocol::READ_PREFERENCES, Protocol::REVOCABLE_SESSION, Protocol::SERVER_URL, Protocol::SESSION_TOKEN

Class Attribute Summary collapse

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(adapter, store, opts = {}) ⇒ Caching

Creates a new caching middleware.

Parameters:

  • adapter (Faraday::Adapter) —

    An instance of the Faraday adapter used for the connection. Defaults Faraday::Adapter::NetHttp.

  • store (Moneta) —

    An instance of the Moneta cache store to use.

  • opts (Hash) (defaults to: {}) —

    additional options.

Options Hash (opts):

  • :expires (Integer) —

    the default expiration for a cache entry.

Raises:

  • ArgumentError, if store is not a Moneta::Transformer or Moneta::Expires instance.



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# File 'lib/parse/client/caching.rb', line 79

def initialize(adapter, store, opts = {})
  super(adapter)
  @store = store
  @opts = { expires: 0 }
  @opts.merge!(opts) if opts.is_a?(Hash)
  @expires = @opts[:expires]
  # Optional cache key namespace so two Parse apps sharing one Redis don't
  # collide (e.g. `mk:/classes/Song/abc` is the same path for both apps).
  # When set, keys become `<namespace>:<existing-prefix>:<url>`. Empty
  # string is treated as nil. Trailing `:` is stripped once so users can
  # pass either `"app_x"` or `"app_x:"`.
  ns = @opts[:namespace].to_s
  ns = ns.chomp(":")
  @namespace = ns.empty? ? nil : ns

  # The keyspace owns physical key layout and the patterns that clear it,
  # so key generation and eviction cannot drift apart. Previously this
  # middleware composed keys from its own `@namespace` while
  # `Parse::Cache::Redis` held a separate one, and `clear_cache!` used
  # only the latter: a client namespaced here but not there would clear
  # every SDK key on the database instead of its own.
  #
  # When no keyspace is supplied the middleware keeps writing legacy
  # un-prefixed keys, so an upgrade that does not opt in behaves exactly
  # as before.
  @keyspace = @opts[:keyspace]
  # During the transition, also delete the pre-keyspace form of a key on
  # invalidation. Without this, a rolling deploy has new workers writing
  # keyspaced keys while old workers still read legacy ones, so a write
  # served by a new worker never invalidates what an old worker serves.
  @delete_legacy_variants = @opts.fetch(:delete_legacy_variants, true)

  unless [:key?, :[], :delete, :store].all? { |method| @store.respond_to?(method) }
    raise ArgumentError, "Caching store object must a Moneta key/value store."
  end
end

Class Attribute Details

.enabled ⇒ Boolean

Returns whether the caching middleware should be enabled.

Returns:

  • (Boolean) —

    whether the caching middleware should be enabled.



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# File 'lib/parse/client/caching.rb', line 45

attr_writer :enabled

.logging ⇒ Boolean

Returns whether the logging should be enabled.

Returns:

  • (Boolean) —

    whether the logging should be enabled.



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# File 'lib/parse/client/caching.rb', line 49

def logging
  @logging
end

Instance Attribute Details

#expires ⇒ Integer

The expiration time in seconds for this particular request.

Returns:

  • (Integer) 


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# File 'lib/parse/client/caching.rb', line 70

def expires
  @expires
end

#store ⇒ Moneta::Transformer, Moneta::Expires

The internal moneta cache store instance.

Returns:

  • (Moneta::Transformer, Moneta::Expires) 


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# File 'lib/parse/client/caching.rb', line 65

def store
  @store
end

Class Method Details

.caching? ⇒ Boolean

Returns whether caching is enabled.

Returns:

  • (Boolean) —

    whether caching is enabled.



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# File 'lib/parse/client/caching.rb', line 57

def caching?
  @enabled
end