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log

Prints a log event for each message. Messages always remain unchanged. The log message can be set using function interpolations described here which allows you to log the contents and metadata of messages.

# Config fields, showing default values
label: ""
log:
  level: INFO
  fields_mapping: |- # No default (optional)
    root.reason = "cus I wana"
    root.id = this.id
    root.age = this.user.age.number()
    root.kafka_topic = meta("kafka_topic")
  message: ""

The level field determines the log level of the printed events and can be any of the following values: TRACE, DEBUG, INFO, WARN, ERROR.

Structured Fields​

It's also possible add custom fields to logs when the format is set to a structured form such as json or logfmt with the config field fields_mapping:

pipeline:
  processors:
    - log:
        level: DEBUG
        message: hello world
        fields_mapping: |
          root.reason = "cus I wana"
          root.id = this.id
          root.age = this.user.age
          root.kafka_topic = meta("kafka_topic")

Fields​

level​

The log level to use.

Type: string
Default: "INFO"
Options: FATAL, ERROR, WARN, INFO, DEBUG, TRACE, ALL.

fields_mapping​

An optional Bloblang mapping that can be used to specify extra fields to add to the log. If log fields are also added with the fields field then those values will override matching keys from this mapping.

Type: string

# Examples

fields_mapping: |-
  root.reason = "cus I wana"
  root.id = this.id
  root.age = this.user.age.number()
  root.kafka_topic = meta("kafka_topic")

message​

The message to print. This field supports interpolation functions.

Type: string
Default: ""