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Processors

Note This documentation is still in progress. For any questions, please reach out in the OpenTelemetry Gitter or refer to the issues page.

Supported processors (sorted alphabetically):

Data Ownership

The ownership of the TraceData and MetricsData in a pipeline is passed as the data travels through the pipeline. The data is created by the receiver and then the ownership is passed to the first processor when ConsumeTraceData/ConsumeMetricsData function is called. Note: the receiver may be attached to multiple pipelines, in which case the same data will be passed to all attached pipelines via a data fan-out connector.

From data ownership perspective pipelines can work in 2 modes: exclusive data ownership and shared data ownership.

The mode is defined during startup based on data modification intent reported by the processors. The intent is reported by each processor via MutatesConsumedData field of the struct returned by GetCapabilities function. If any processor in the pipeline declares an intent to modify the data then that pipeline will work in exclusive ownership mode. In addition any other pipeline that receives data from a receiver that is attached to a pipeline with exclusive ownership mode will be also operating in exclusive ownership mode.

Exclusive Ownership

In exclusive ownership mode the data is owned exclusively by a particular processor at a given moment of time and the processor is free to modify the data it owns.

Exclusive ownership mode is only applicable for pipelines that receive data from the same receiver. If a pipeline is marked to be in exclusive ownership mode then any data received from a shared receiver will be cloned at the fan-out connector before passing further to each pipeline. This ensures that each pipeline has its own exclusive copy of data and the data can be safely modified in the pipeline.

The exclusive ownership of data allows processors to freely modify the data while they own it (e.g. see attributesprocessor). The duration of ownership of the data by processor is from the beginning of ConsumeTraceData/ConsumeMetricsData call until the processor calls the next processor's ConsumeTraceData/ConsumeMetricsData function, which passes the ownership to the next processor. After that the processor must no longer read or write the data since it may be concurrently modified by the new owner.

Exclusive Ownership mode allows to easily implement processors that need to modify the data by simply declaring such intent.

Shared Ownership

In shared ownership mode no particular processor owns the data and no processor is allowed the modify the shared data.

In this mode no cloning is performed at the fan-out connector of receivers that are attached to multiple pipelines. In this case all such pipelines will see the same single shared copy of the data. Processors in pipelines operating in shared ownership mode are prohibited from modifying the original data that they receive via ConsumeTraceData/ConsumeMetricsData call. Processors may only read the data but must not modify the data.

If the processor needs to modify the data while performing the processing but does not want to incur the cost of data cloning that Exclusive mode brings then the processor can declare that it does not modify the data and use any different technique that ensures original data is not modified.

For example the processor can implement copy-on-write approach for individual sub-parts of TraceData/MetricsData argument. Any approach that does not mutate the original TraceData/MetricsData argument (including referenced data, such as Node, Resource, Spans, etc) is allowed.

If the processor uses such technique it should declare that it does not intend to modify the original data by setting MutatesConsumedData=false in its capabilities to avoid marking the pipeline for Exclusive ownership and to avoid the cost of data cloning described in Exclusive Ownership section.

Ordering Processors

The order processors specified in a pipeline is important as this is the order in which each processor is applied to traces and metrics.

Include/Exclude Spans

The attribute processor and the span processor expose the option to provide a set of properties of a span to match against to determine if the span should be included or excluded from the processor. By default, all spans are processed by the processor.

To configure this option, under include and/or exclude:

  • at least one of services, span_names or attributes is required.

Note: If both include and exclude are specified, the include properties are checked before the exclude properties.

{span, attributes}:
    # include and/or exclude can be specified. However, the include properties
    # are always checked before the exclude properties.
    {include, exclude}:
      # At least one of services, span_names or attributes must be specified.
      # It is supported to have more than one specified, but all of the specified
      # conditions must evaluate to true for a match to occur.

      # match_type controls how items in "services" and "span_names" arrays are
      # interpreted. Possible values are "regexp" or "strict".
      # This is a required field.
      match_type: {strict, regexp}

      # services specify an array of items to match the service name against.
      # A match occurs if the span service name matches at least of the items.
      # This is an optional field.
      services: [<item1>, ..., <itemN>]

      # The span name must match at least one of the items.
      # This is an optional field.
      span_names: [<item1>, ..., <itemN>]

      # Attributes specifies the list of attributes to match against.
      # All of these attributes must match exactly for a match to occur.
      # Only match_type=strict is allowed if "attributes" are specified.
      # This is an optional field.
      attributes:
          # Key specifies the attribute to match against.
        - key: <key>
          # Value specifies the exact value to match against.
          # If not specified, a match occurs if the key is present in the attributes.
          value: {value}

Attributes Processor

The attributes processor modifies attributes of a span.

It takes a list of actions which are performed in order specified in the config. The supported actions are:

  • insert: Inserts a new attribute in spans where the key does not already exist.
  • update: Updates an attribute in spans where the key does exist.
  • upsert: Performs insert or update. Inserts a new attribute in spans where the key does not already exist and updates an attribute in spans where the key does exist.
  • delete: Deletes an attribute from a span.

For the actions insert, update and upsert,

  • key is required
  • one of value or from_attribute is required
  • action is required.
  # Key specifies the attribute to act upon.
- key: <key>
  action: {insert, update, upsert}
  # Value specifies the value to populate for the key.
  # The type is inferred from the configuration.
  value: <value>

  # Key specifies the attribute to act upon.
- key: <key>
  action: {insert, update, upsert}
  # FromAttribute specifies the attribute from the span to use to populate
  # the value. If the attribute doesn't exist, no action is performed.
  from_attribute: <other key>

For the delete action,

  • key is required
  • action: delete is required.
# Key specifies the attribute to act upon.
- key: <key>
  action: delete

Please refer to config.go for the config spec.

Example

The list of actions can be composed to create rich scenarios, such as back filling attribute, copying values to a new key, redacting sensitive information. The following is a sample configuration.

processors:
  attributes/example:
    actions:
      - key: db.table
        action: delete
      - key: redacted_span
        value: true
        action: upsert
      - key: copy_key
        from_attribute: key_original
        action: update
      - key: account_id
        value: 2245
      - key: account_password
        action: delete

Refer to config.yaml for detailed examples on using the processor.

Node Batcher Processor

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Probabilistic Sampler Processor

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Queued Retry Processor

The queued retry processor uses a bounded queue to relay trace data from the receiver or previous processor to the next processor. Received trace data is enqueued immediately if the queue is not full . At the same time, the processor has one or more workers which consume the trace data in the queue by sending them to the next processor. If relaying the trace data to the next processor or exporter in the pipeline fails, the processor retries after some backoff delay depending on the configuration (see below).

Example configuration

To change the behavior of the default queued processor, the num_workers, queue_size, retry_on_failure, backoff_delay could be configured.

processors:
  queued_retry/example:
    num_workers: 2
    queue_size: 10
    retry_on_failure: true
    backoff_delay: 5s

Refer to config.yaml for detailed examples on using the processor.

Span Processor

The span processor modifies top level settings of a span. Currently, only renaming a span is supported.

Name a span from attributes or extract attributes from span name.

In the first form it takes a list of from_attributes and an optional separator string. The attribute value for the keys are used to create a new name in the order specified in the configuration. If a separator is specified, it will separate values.

If renaming is dependent on attributes being modified by the attributes processor, ensure the span processor is specified after the attributes processor in the pipeline specification.

For more information, refer to config.go

span:
  name:
    # from_attributes represents the attribute keys to pull the values from to generate the
    # new span name.
    from_attributes: [<key1>, <key2>, ...]
    # Separator is the string used to concatenate various parts of the span name.
    separator: <value>

In the second form it takes a list of regular expressions to match span name against and extract attributes from based on subexpressions.

rules is a list of rules to extract attribute values from span name. The values in the span name are replaced by extracted attribute names. Each rule in the list is regex pattern string. Span name is checked against the regex and if the regex matches then all named subexpressions of the regex are extracted as attributes and are added to the span. Each subexpression name becomes an attribute name and subexpression matched portion becomes the attribute value. The matched portion in the span name is replaced by extracted attribute name. If the attributes already exist in the span then they will be overwritten. The process is repeated for all rules in the order they are specified. Each subsequent rule works on the span name that is the output after processing the previous rule.

break_after_match specifies if processing of rules should stop after the first match. If it is false rule processing will continue to be performed over the modified span name. The default value for this option is false.

span/to_attributes:
name:
  to_attributes:
    rules:
      - regexp-rule1
      - regexp-rule2
      - regexp-rule3
      ...
    break_after_match: {true, false}

Example configuration

For more examples with detailed comments, refer to config.yaml

span:
  name:
    from_attributes: ["db.svc", "operation"]
    separator: "::"
# Let's assume input span name is /api/v1/document/12345678/update
# Applying the following results in output span name /api/v1/document/{documentId}/update
# and will add a new attribute "documentId"="12345678" to the span.
span/to_attributes:
name:
  to_attributes:
    rules:
      - ^\/api\/v1\/document\/(?P<documentId>.*)\/update$

Tail Sampling Processor

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