Module: Datadog::Tracing::Contrib::ActiveSupport::Cache::Events::Cache

Includes:
Datadog::Tracing::Contrib::ActiveSupport::Cache::Event
Defined in:
lib/datadog/tracing/contrib/active_support/cache/events/cache.rb

Overview

Defines instrumentation for instantiation.active_record event

Constant Summary collapse

MAPPING =

DEV: Look for other uses of ‘ActiveSupport::Cache::Store#instrument`, to find other useful event keys.

{
  'cache_delete.active_support' => { resource: Ext::RESOURCE_CACHE_DELETE },
  'cache_read.active_support' => { resource: Ext::RESOURCE_CACHE_GET },
  'cache_read_multi.active_support' => { resource: Ext::RESOURCE_CACHE_MGET, multi_key: true },
  'cache_write.active_support' => { resource: Ext::RESOURCE_CACHE_SET },
  'cache_write_multi.active_support' => { resource: Ext::RESOURCE_CACHE_MSET, multi_key: true }
}.freeze

Class Method Summary collapse

Methods included from Datadog::Tracing::Contrib::ActiveSupport::Cache::Event

included

Class Method Details

.cache_backend(store) ⇒ Object

The name of the ‘store` is never saved by Rails. ActiveSupport looks up stores by converting a symbol into a ’require’ path, then “camelizing” it for a ‘const_get` call: “` require “active_support/cache/#store” ActiveSupport::Cache.const_get(store.to_s.camelize) “` We can reverse engineer the original symbol by converting the class name to snake case: e.g. ActiveSupport::Cache::RedisStore -> active_support/cache/redis_store In this case, `redis_store` is the store name.

Because there’s no API retrieve only the class name (only ‘RedisStore`, and not `ActiveSupport::Cache::RedisStore`) the easiest way to retrieve the store symbol is to convert the fully qualified name using the Rails-provided method `#underscore`, which is the reverse of `#camelize`, then extracting the last part of it.

Also, this method caches the store name, given this value will be retrieve multiple times and involves string manipulation.

See Also:



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# File 'lib/datadog/tracing/contrib/active_support/cache/events/cache.rb', line 127

def cache_backend(store)
  # Cache the backend name to avoid the expensive string manipulation required to calculate it.
  # DEV: We can't store it directly in the `store` object because it is a frozen String.
  if (name = @cache_backend[store])
    return name
  end

  # DEV: #underscore is available through ActiveSupport, and is
  # DEV: the exact reverse operation to `#camelize`.
  # DEV: #demodulize is available through ActiveSupport, and is
  # DEV: used to remove the module ('*::') part of a constant name.
  name = ::ActiveSupport::Inflector.demodulize(store)
  name = ::ActiveSupport::Inflector.underscore(name)

  # Despite a given application only ever having 1-3 store types,
  # we limit the size of the `@cache_backend` just in case, because
  # the user can create custom Cache store classes themselves.
  @cache_backend[store] = name if @cache_backend.size < 50

  name
end

.event_name ⇒ Object 



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# File 'lib/datadog/tracing/contrib/active_support/cache/events/cache.rb', line 25

def event_name
  /\Acache_(?:delete|read|read_multi|write|write_multi)\.active_support\z/
end

.on_start(span, event, _id, payload) ⇒ Object 



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# File 'lib/datadog/tracing/contrib/active_support/cache/events/cache.rb', line 64

def on_start(span, event, _id, payload)
  key = payload[:key]
  store = payload[:store]

  mapping = MAPPING.fetch(event)

  span.service = configuration[:cache_service]
  span.resource = mapping[:resource]

  span.set_tag(Tracing::Metadata::Ext::TAG_COMPONENT, Ext::TAG_COMPONENT)
  span.set_tag(Tracing::Metadata::Ext::TAG_OPERATION, Ext::TAG_OPERATION_CACHE)

  if span.service != Datadog.configuration.service
    span.set_tag(Tracing::Contrib::Ext::Metadata::TAG_BASE_SERVICE, Datadog.configuration.service)
  end

  span.set_tag(Ext::TAG_CACHE_BACKEND, cache_backend(store))

  span.set_tag('EVENT', event)

  if Datadog.configuration.tracing[:active_support][:cache_key].enabled
    set_cache_key(span, key, mapping[:multi_key])
  end
rescue StandardError => e
  Datadog.logger.error(e.message)
  Datadog::Core::Telemetry::Logger.report(e)
end

.set_cache_key(span, key, multi_key) ⇒ Object 



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# File 'lib/datadog/tracing/contrib/active_support/cache/events/cache.rb', line 92

def set_cache_key(span, key, multi_key)
  if multi_key
    keys = key.is_a?(Hash) ? key.keys : key # `write`s use Hashes, while `read`s use Arrays
    resolved_key = keys.map { |k| ::ActiveSupport::Cache.expand_cache_key(k) }
    cache_key = Core::Utils.truncate(resolved_key, Ext::QUANTIZE_CACHE_MAX_KEY_SIZE)
    span.set_tag(Ext::TAG_CACHE_KEY_MULTI, cache_key)
  else
    resolved_key = ::ActiveSupport::Cache.expand_cache_key(key)
    cache_key = Core::Utils.truncate(resolved_key, Ext::QUANTIZE_CACHE_MAX_KEY_SIZE)
    span.set_tag(Ext::TAG_CACHE_KEY, cache_key)
  end
end

.span_name ⇒ Object 



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# File 'lib/datadog/tracing/contrib/active_support/cache/events/cache.rb', line 29

def span_name
  Ext::SPAN_CACHE
end

.span_options ⇒ Object 



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# File 'lib/datadog/tracing/contrib/active_support/cache/events/cache.rb', line 33

def span_options
  {
    type: Ext::SPAN_TYPE_CACHE
  }
end

.subscribe! ⇒ Object

Acts as this module’s initializer.



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# File 'lib/datadog/tracing/contrib/active_support/cache/events/cache.rb', line 20

def subscribe!
  @cache_backend = {}
  super
end

.trace?(event, _payload) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/datadog/tracing/contrib/active_support/cache/events/cache.rb', line 48

def trace?(event, _payload)
  return false if !Tracing.enabled? || !configuration.enabled

  # DEV-3.0: Backwards compatibility code for the 2.x gem series.
  # DEV-3.0: See documentation at {Datadog::Tracing::Contrib::ActiveSupport::Cache::Instrumentation}
  # DEV-3.0: for the complete information about this backwards compatibility code.
  case event
  when 'cache_read.active_support'
    !ActiveSupport::Cache::Instrumentation.nested_read?
  when 'cache_read_multi.active_support'
    !ActiveSupport::Cache::Instrumentation.nested_multiread?
  else
    true
  end
end