= cache
:type: processor
:status: stable
:categories: ["Integration"]



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component_type_dropdown::[]


Performs operations against a xref:components:caches/about.adoc[cache resource] for each message, allowing you to store or retrieve data within message payloads.


[tabs]
======
Common::
+
--

```yml
# Common config fields, showing default values
label: ""
cache:
  resource: "" # No default (required)
  operator: "" # No default (required)
  key: "" # No default (required)
  value: "" # No default (optional)
```

--
Advanced::
+
--

```yml
# All config fields, showing default values
label: ""
cache:
  resource: "" # No default (required)
  operator: "" # No default (required)
  key: "" # No default (required)
  value: "" # No default (optional)
  ttl: 60s # No default (optional)
```

--
======

For use cases where you wish to cache the result of processors consider using the xref:components:processors/cached.adoc[`cached` processor] instead.

This processor will interpolate functions within the `key` and `value` fields individually for each message. This allows you to specify dynamic keys and values based on the contents of the message payloads and metadata. You can find a list of functions in xref:configuration:interpolation.adoc#bloblang-queries[Bloblang queries].

== Examples

[tabs]
======
Deduplication::
+
--


Deduplication can be done using the add operator with a key extracted from the message payload, since it fails when a key already exists we can remove the duplicates using a xref:components:processors/mapping.adoc[`mapping` processor]:

```yaml
pipeline:
  processors:
    - cache:
        resource: foocache
        operator: add
        key: '${! json("message.id") }'
        value: "storeme"
    - mapping: root = if errored() { deleted() }

cache_resources:
  - label: foocache
    redis:
      url: tcp://TODO:6379
```

--
Deduplication Batch-Wide::
+
--


Sometimes it's necessary to deduplicate a batch of messages (also known as a window) by a single identifying value. This can be done by introducing a xref:components:processors/branch.adoc[`branch` processor], which executes the cache only once on behalf of the batch, in this case with a value make from a field extracted from the first and last messages of the batch:

```yaml
pipeline:
  processors:
    # Try and add one message to a cache that identifies the whole batch
    - branch:
        request_map: |
          root = if batch_index() == 0 {
            json("id").from(0) + json("meta.tail_id").from(-1)
          } else { deleted() }
        processors:
          - cache:
              resource: foocache
              operator: add
              key: ${! content() }
              value: t
    # Delete all messages if we failed
    - mapping: |
        root = if errored().from(0) {
          deleted()
        }
```

--
Hydration::
+
--


It's possible to enrich payloads with content previously stored in a cache by using the xref:components:processors/branch.adoc[`branch`] processor:

```yaml
pipeline:
  processors:
    - branch:
        processors:
          - cache:
              resource: foocache
              operator: get
              key: '${! json("message.document_id") }'
        result_map: 'root.message.document = this'

        # NOTE: If the data stored in the cache is not valid JSON then use
        # something like this instead:
        # result_map: 'root.message.document = content().string()'

cache_resources:
  - label: foocache
    memcached:
      addresses: [ "TODO:11211" ]
```

--
======

== Fields

=== `resource`

The xref:components:caches/about.adoc[`cache` resource] to target with this processor.


*Type*: `string`


=== `operator`

The <<operators, operation>> to perform with the cache.


*Type*: `string`


Options:
`set`
, `add`
, `get`
, `delete`
.

=== `key`

A key to use with the cache.
This field supports xref:configuration:interpolation.adoc#bloblang-queries[interpolation functions].


*Type*: `string`


=== `value`

A value to use with the cache (when applicable).
This field supports xref:configuration:interpolation.adoc#bloblang-queries[interpolation functions].


*Type*: `string`


=== `ttl`

The TTL of each individual item as a duration string. After this period an item will be eligible for removal during the next compaction. Not all caches support per-key TTLs, those that do will have a configuration field `default_ttl`, and those that do not will fall back to their generally configured TTL setting.
This field supports xref:configuration:interpolation.adoc#bloblang-queries[interpolation functions].


*Type*: `string`

Requires version 3.33.0 or newer

```yml
# Examples

ttl: 60s

ttl: 5m

ttl: 36h
```

== Operators

=== `set`

Set a key in the cache to a value. If the key already exists the contents are
overridden.

=== `add`

Set a key in the cache to a value. If the key already exists the action fails
with a 'key already exists' error, which can be detected with
xref:configuration:error_handling.adoc[processor error handling].

=== `get`

Retrieve the contents of a cached key and replace the original message payload
with the result. If the key does not exist the action fails with an error, which
can be detected with xref:configuration:error_handling.adoc[processor error handling].

=== `delete`

Delete a key and its contents from the cache. If the key does not exist the
action is a no-op and will not fail with an error.

