Semantic Conventions for Google Cloud Pub/Sub

Status: Experimental

The Semantic Conventions for Google Cloud Pub/Sub extend and override the Messaging Semantic Conventions that describe common messaging operations attributes in addition to the Semantic Conventions described on this page.

messaging.system MUST be set to "gcp_pubsub".

Span attributes

For Google Cloud Pub/Sub, the following additional attributes are defined:

AttributeTypeDescriptionExamplesRequirement LevelStability
messaging.operation.typestringA string identifying the type of the messaging operation. [1]publish; create; receiveRequiredExperimental
error.typestringDescribes a class of error the operation ended with. [2]amqp:decode-error; KAFKA_STORAGE_ERROR; channel-errorConditionally Required If and only if the messaging operation has failed.Stable
messaging.batch.message_countintThe number of messages sent, received, or processed in the scope of the batching operation. [3]0; 1; 2Conditionally Required [4]Experimental
messaging.destination.namestringThe message destination name [5]MyQueue; MyTopicConditionally Required [6]Experimental
messaging.gcp_pubsub.message.ordering_keystringThe ordering key for a given message. If the attribute is not present, the message does not have an ordering key.ordering_keyConditionally Required If the message type has an ordering key set.Experimental
server.addressstringServer domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. [7];; /tmp/my.sockConditionally Required If available.Stable
messaging.gcp_pubsub.message.ack_deadlineintThe ack deadline in seconds set for the modify ack deadline request.10RecommendedExperimental
messaging.gcp_pubsub.message.ack_idstringThe ack id for a given message.ack_idRecommendedExperimental
messaging.gcp_pubsub.message.delivery_attemptintThe delivery attempt for a given message.2RecommendedExperimental
messaging.message.idstringA value used by the messaging system as an identifier for the message, represented as a string.452a7c7c7c7048c2f887f61572b18fc2Recommended If span describes operation on a single message.Experimental
messaging.operation.namestringThe system-specific name of the messaging operation.ack; nack; sendRecommended [8]Experimental
server.portintServer port number. [9]80; 8080; 443RecommendedStable

[1]: If a custom value is used, it MUST be of low cardinality.

[2]: The error.type SHOULD be predictable, and SHOULD have low cardinality.

When error.type is set to a type (e.g., an exception type), its canonical class name identifying the type within the artifact SHOULD be used.

Instrumentations SHOULD document the list of errors they report.

The cardinality of error.type within one instrumentation library SHOULD be low. Telemetry consumers that aggregate data from multiple instrumentation libraries and applications should be prepared for error.type to have high cardinality at query time when no additional filters are applied.

If the operation has completed successfully, instrumentations SHOULD NOT set error.type.

If a specific domain defines its own set of error identifiers (such as HTTP or gRPC status codes), it’s RECOMMENDED to:

  • Use a domain-specific attribute
  • Set error.type to capture all errors, regardless of whether they are defined within the domain-specific set or not.

[3]: Instrumentations SHOULD NOT set messaging.batch.message_count on spans that operate with a single message. When a messaging client library supports both batch and single-message API for the same operation, instrumentations SHOULD use messaging.batch.message_count for batching APIs and SHOULD NOT use it for single-message APIs.

[4]: If the span describes an operation on a batch of messages.

[5]: Destination name SHOULD uniquely identify a specific queue, topic or other entity within the broker. If the broker doesn’t have such notion, the destination name SHOULD uniquely identify the broker.

[6]: If span describes operation on a single message or if the value applies to all messages in the batch.

[7]: Server domain name of the broker if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name.

[8]: If the operation is not sufficiently described by messaging.operation.type.

[9]: When observed from the client side, and when communicating through an intermediary, server.port SHOULD represent the server port behind any intermediaries, for example proxies, if it’s available.

error.type has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

_OTHERA fallback error value to be used when the instrumentation doesn’t define a custom value.Stable

messaging.operation.type has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

publishOne or more messages are provided for publishing to an intermediary. If a single message is published, the context of the “Publish” span can be used as the creation context and no “Create” span needs to be created.Experimental
createA message is created. “Create” spans always refer to a single message and are used to provide a unique creation context for messages in batch publishing scenarios.Experimental
receiveOne or more messages are requested by a consumer. This operation refers to pull-based scenarios, where consumers explicitly call methods of messaging SDKs to receive messages.Experimental
processOne or more messages are delivered to or processed by a consumer.Experimental
settleOne or more messages are settled.Experimental

Span names

The span name SHOULD follow the general messaging span name pattern: it SHOULD start with the messaging destination name (Topic/Subscription) and contain a low-cardinality name of an operation the span describes:

  • Spans for settle operations SHOULD follow the <destination name> ack or <destination name> nack pattern.
  • Spans names for publish operations SHOULD follow the <destination name> send pattern.
  • Spans for create, receive, and publish operations SHOULD follow the general <destination name> <operation name> pattern.

In addition there are the following operations are GCP specific:

  • Spans that represents the time from after the message was received to when the message is acknowledged, negatively acknowledged, or expire (used by streaming pull) SHOULD follow the <destination name> subscribe pattern.
  • Spans that represent extending the lease for a single message or batch of messages SHOULD follow the<destination name> modack pattern.


Asynchronous Batch Publish Example

Given is a process P that asynchronously publishes 2 messages in a batch to a topic T on Pub/Sub.

flowchart LR;
  subgraph PRODUCER
  direction LR
  CA[Span Create A]
  CB[Span Create B]
  P[Span Publish A B]
  CA-. link .-P;
  CB-. link .-P;

  classDef producer fill:green
  class P,CA,CB producer
  classDef normal fill:green
  class PA,PB,D1 normal
  linkStyle 0,1 color:green,stroke:green
Field or AttributeSpan Create ASpan Create BSpan Publish A B
Span nameT createT createpublish
LinksSpan Create A, Span Create B

Unary Pull Example

flowchart TD;
  subgraph CONSUMER
  direction LR
  R1[Receive m1]
  SM1[Ack m1]
  EM1[Modack m1]
  subgraph PRODUCER
  direction LR
  CM1[Create m1]
  %% Link 0
  CM1-. link .-PM1;
  %% Link 1
  CM1-. link .-R1;
  %% Link 2
  R1-. link .-SM1;
  %% Link 3
  R1-. link .-EM1;

  %% Style the node and corresponding link
  %% Producer links and nodes
  classDef producer fill:green
  class PM1,CM1 producer
  linkStyle 0 color:green,stroke:green

  %% Consumer links and nodes
  classDef consumer fill:#49fcdc
  class R1 consumer
  linkStyle 1 color:#49fcdc,stroke:#49fcdc

  classDef ack fill:#577eb5
  class SM1 ack
  linkStyle 2 color:#577eb5,stroke:#577eb5

  classDef modack fill:#0560f2
  class EM1 modack
  linkStyle 3 color:#0560f2,stroke:#0560f2
Field or AttributeSpan Create ASpan Publish ASpan Receive ASpan Modack ASpan Ack A
Span nameT createpublishS receiveS modackS ack
LinksSpan Create ASpan Create ASpan Receive ASpan Receive A