Skip to content

get_task.md

Latest commit

 

History

History
133 lines (109 loc) · 4.35 KB

get_task.md

File metadata and controls

133 lines (109 loc) · 4.35 KB
Raw

GetTask

Reads an item from a cache adapter and outputs its value. Useful to reuse a value computed by a previous branch of the process, or stored by another process when the adapter is persistent.

Task reference

  • Service: CleverAge\CacheProcessBundle\Task\GetTask

Accepted inputs

array or empty (null): if the input is not empty, its keys adapter and key override the options of the same name, and are validated like the options (e.g. a non-string key throws an InvalidOptionsException). Other input keys are ignored.

Any other non-empty input (e.g. a string) throws an \UnexpectedValueException.

Possible outputs

mixed: the value of the cache item. If the key is missing from the cache, depends on on_miss: null (default), no output (the input is sent to the error outputs), or an exception.

Options

Code Type Required Default Description
adapter string X Code of the adapter to read from (see AdapterInterface::getCode())
key string X Key of the cache item to read, must be a valid PSR-6 key
on_miss string output_null Behaviour when the key is missing from the cache (see below)

Every option can be given by the configuration or by the input: adapter and key are required once merged with the input, an option given by neither throws a MissingOptionsException on execution.

on_miss values:

  • output_null: output null, as for an item stored with a null value.
  • skip: skip the item and send the input to the error outputs (error_outputs), e.g. to compute the missing value and store it.
  • fail: throw an \UnexpectedValueException (Cache item <key> is missing from adapter <adapter>).

Examples

  • Read a fixed key
# Task configuration level
get:
  service: '@CleverAge\CacheProcessBundle\Task\GetTask'
  options:
    adapter: 'memory'
    key: 'key2'
  outputs: [debug]
  • Read a key given by the process context (-c sku:"'ABC-001'") and stop the branch if it is missing
# Task configuration level
get:
  service: '@CleverAge\CacheProcessBundle\Task\GetTask'
  options:
    adapter: 'catalog'
    key: '{{ sku }}'
    on_miss: skip
  outputs: [debug]
  • Compute and store the missing values ("cache-aside")
# Task configuration level
get:
  service: '@CleverAge\CacheProcessBundle\Task\GetTask'
  options:
    adapter: 'catalog'
    on_miss: skip # The input ({ key: ... }) is sent to the error outputs
  outputs: [debug]
  error_outputs: [compute]
compute:
  service: '@CleverAge\ProcessBundle\Task\TransformerTask'
  options:
    transformers:
      mapping:
        mapping:
          key:
            code: '[key]'
          value:
            code: '[key]'
            transformers:
              slugify: ~ # Any computation
  outputs: [set]
set:
  service: '@CleverAge\CacheProcessBundle\Task\SetTask'
  options:
    adapter: 'catalog'
  • Read a key computed from the input
# Task configuration level
build_key:
  service: '@CleverAge\ProcessBundle\Task\TransformerTask'
  options:
    transformers:
      mapping:
        mapping:
          key:
            code: '[sku]'
  outputs: [get]
get:
  service: '@CleverAge\CacheProcessBundle\Task\GetTask'
  options:
    adapter: 'catalog' # The key is given by the input

Notes

  • The key is validated by the task (CacheItem::validateKey()): an empty key, or a key containing one of the PSR-6 reserved characters {}()/\@:, throws a Psr\Cache\InvalidArgumentException, whatever the adapter and the zend.assertions setting (see Adapter).
  • A cache miss is detected with CacheItemInterface::isHit(): an item stored with a null value is a hit, and is always output.
  • With on_miss: skip, the next tasks of outputs are not executed for this input, but the tasks of error_outputs are (whatever the error_strategy).
  • The input is replaced by the cached value: the rest of the input is not transmitted to the next tasks.