bloblang

Executes a Bloblang mapping on messages.

# Config fields, showing default values
bloblang: ""

Bloblang is a powerful language that enables a wide range of mapping, transformation and filtering tasks. For more information check out the docs.

Examples#

Mapping
More Mapping

Given JSON documents containing an array of fans:

{
  "id":"foo",
  "description":"a show about foo",
  "fans":[
    {"name":"bev","obsession":0.57},
    {"name":"grace","obsession":0.21},
    {"name":"ali","obsession":0.89},
    {"name":"vic","obsession":0.43}
  ]
}

We can reduce the fans to only those with an obsession score above 0.5, giving us:

{
  "id":"foo",
  "description":"a show about foo",
  "fans":[
    {"name":"bev","obsession":0.57},
    {"name":"ali","obsession":0.89}
  ]
}

With the following config:

pipeline:
  processors:
  - bloblang: |
      root = this
      fans = fans.map_each(match {
        this.obsession > 0.5 => this
        _ => deleted()
      })

When receiving JSON documents of the form:

{
  "locations": [
    {"name": "Seattle", "state": "WA"},
    {"name": "New York", "state": "NY"},
    {"name": "Bellevue", "state": "WA"},
    {"name": "Olympia", "state": "WA"}
  ]
}

We could collapse the location names from the state of Washington into a field Cities:

{"Cities": "Bellevue, Olympia, Seattle"}

With the following config:

pipeline:
  processors:
    - bloblang: '{"Cities":this.locations.filter(this.state == "WA").map_each(this.name).sort().join(", ")}'

Error Handling#

Bloblang mappings can fail, in which case the message remains unchanged, errors are logged, and the message is flagged as having failed, allowing you to use standard processor error handling patterns.

However, Bloblang itself also provides powerful ways of ensuring your mappings do not fail by specifying desired fallback behaviour, which you can read about in this section.