Content Modifier

The content modifier processor lets you manipulate the content, metadata, and attributes of logs and traces.

Similar to how filters work, this processor uses a unified mechanism to perform operations for data manipulation. The most significant difference is that processors perform better than filters, and when chaining them, there are no encoding/decoding performance penalties.

Only YAML configuration files support processors.

Contexts

The content modifier relies on context, meaning the place where the content modification will happen. Fluent Bit provides different contexts to manipulate the desired information.

The following contexts are available:

Name	Telemetry type	Description
attributes	Logs	Modifies the attributes or metadata of a log record.
body	Logs	Modifies the content of a log record.
span_name	Traces	Modifies the name of a span.
span_kind	Traces	Modifies the kind of a span.
span_status	Traces	Modifies the status of a span.
span_attributes	Traces	Modifies the attributes of a span.

OpenTelemetry contexts

Additionally, Fluent Bit provides specific contexts for modifying data that follows the OpenTelemetry log schema. All of these contexts operate on shared data across a group of records.

The following contexts are available:

Name	Telemetry type	Description
otel_resource_attributes	Logs	Modifies the attributes of the log resource.
otel_scope_name	Logs	Modifies the name of a log scope.
otel_scope_version	Logs	Modifies version of a log scope.
otel_scope_attributes	Logs	Modifies the attributes of a log scope.

If your data doesn't follow the OpenTelemetry log schema, but your log destination expects to be in that format, you can use the OpenTelemetry envelope processor to transform your data. You can then pass that transformed data through the content modifier filter and use OpenTelemetry contexts accordingly.

Configuration parameters

The following configuration parameters are available:

Key	Description
context	Specifies the context where the modifications will happen.
key	Specifies the name of the key that will be used to apply the modification.
value	The role of this parameter changes based on the action type.
pattern	Defines a regular expression pattern. This property is only used by the extract action.
converted_type	Defines the data type to perform the conversion. Possible values: string, boolean, int and double.

Actions

The actions specify the type of operation to run on top of a specific key or content from a log or a trace. The following actions are available:

Action	Description
insert	Inserts a new key with a value into the target context. The key and value parameters are required.
upsert	Given a specific key with a value, the upsert operation will try to update the value of the key. If the key does not exist, a new key will be created. The key and value parameters are required.
delete	Deletes a key from the target context. The key parameter is required.
rename	Changes the name of a key. The value set in the configuration will represent the new name. The key and value parameters are required.
hash	Replaces the key value with a hash generated by the SHA-256 algorithm, the binary value generated is finally set as a hex string representation. The key parameter is required.
extract	Extracts the value of a single key as a list of key/value pairs. This action needs the configuration of a regular expression in the pattern property. The key and pattern parameters are required.
convert	Converts the data type of a key value. The key and converted_type parameters are required.

Insert example

The following example appends the key color with the value blue to the log stream.

fluent-bit.yaml

pipeline:
    inputs:
        - name: dummy
          dummy: '{"key1": "123.4"}'

          processors:
              logs:
                  - name: content_modifier
                    action: insert
                    key: "color"
                    value: "blue"

    outputs:
        - name : stdout
          match: '*'
          format: json_lines

Upsert example

Update the value of key1 and insert key2:

fluent-bit.yaml

pipeline:
    inputs:
        - name: dummy
          dummy: '{"key1": "123.4"}'

          processors:
              logs:
                  - name: content_modifier
                    action: upsert
                    key: "key1"
                    value: "5678"

                  - name: content_modifier
                    action: upsert
                    key: "key2"
                    value: "example"

    outputs:
        - name : stdout
          match: '*'
          format: json_lines

Delete example

Delete key2 from the stream:

fluent-bit.yaml

pipeline:
    inputs:
        - name: dummy
          dummy: '{"key1": "123.4", "key2": "example"}'

          processors:
              logs:
                  - name: content_modifier
                    action: delete
                    key: "key2"

    outputs:
        - name : stdout
          match: '*'
          format: json_lines

Rename example

Change the name of key2 to test:

fluent-bit.yaml

pipeline:
    inputs:
        - name: dummy
          dummy: '{"key1": "123.4", "key2": "example"}'

          processors:
              logs:
                  - name: content_modifier
                    action: rename
                    key: "key2"
                    value: "test"

    outputs:
        - name : stdout
          match: '*'
          format: json_lines

Hash example

Apply the SHA-256 algorithm for the value of the key password:

fluent-bit.yaml

pipeline:
    inputs:
        - name: dummy
          dummy: '{"username": "bob", "password": "12345"}'

          processors:
              logs:
                  - name: content_modifier
                    action: hash
                    key: "password"

    outputs:
        - name : stdout
          match: '*'
          format: json_lines

Extract example

By using a domain address, perform a extraction of the components of it as a list of key value pairs:

fluent-bit.yaml

pipeline:
    inputs:
        - name: dummy
          dummy: '{"http.url": "https://fluentbit.io/docs?q=example"}'

          processors:
              logs:
                  - name: content_modifier
                    action: extract
                    key: "http.url"
                    pattern: ^(?<http_protocol>https?):\/\/(?<http_domain>[^\/\?]+)(?<http_path>\/[^?]*)?(?:\?(?<http_query_params>.*))?

    outputs:
        - name : stdout
          match: '*'
          format: json_lines

Convert example

Both keys in the example are strings. Convert the key1 to a double/float type and key2 to a boolean:

fluent-bit.yaml

pipeline:
    inputs:
        - name: dummy
          dummy: '{"key1": "123.4", "key2": "true"}'

          processors:
              logs:
                  - name: content_modifier
                    action: convert
                    key: key1
                    converted_type: int

                  - name: content_modifier
                    action: convert
                    key: key2
                    converted_type: boolean

    outputs:
        - name : stdout
          match: '*'
          format: json_lines