Semantic Conventions for Google Cloud Pub/Sub

Status: Experimental

The Semantic Conventions for Google Cloud Pub/Sub extend and override the Messaging Semantic Conventions.

messaging.system MUST be set to "gcp_pubsub" and SHOULD be provided at span creation time.

Span attributes

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

AttributeTypeDescriptionExamplesRequirement LevelStability
messaging.operation.namestringThe system-specific name of the messaging operation. [1]ack; nack; sendRequiredExperimental
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
messaging.operation.typestringA string identifying the type of the messaging operation. [7]send; create; receiveConditionally Required If applicable.Experimental
server.addressstringServer domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. [8]example.com; 10.1.2.80; /tmp/my.sockConditionally Required If available.Stable
messaging.destination.subscription.namestringGoogle Pub/Sub subscription name.subscription-aRecommendedExperimental
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
server.portintServer port number. [9]80; 8080; 443RecommendedStable

[1]: The messaging.operation.name has the following list of well-known values in the context of Google Pub/Sub. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

  • ack and nack for settlement operations
  • send for publishing operations
  • modack for extending the lease for a single message or batch of messages
  • subscribe for operations that represent the time from after the message was received to when the message is acknowledged, negatively acknowledged, or expired.
  • create and receive for common messaging operations

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

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

[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.

The following attributes can be important for making sampling decisions and SHOULD be provided at span creation time (if provided at all):

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.

ValueDescriptionStability
_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.

ValueDescriptionStability
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 sending scenarios.Experimental
processOne or more messages are processed by a consumer.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
sendOne or more messages are provided for sending to an intermediary. If a single message is sent, the context of the “Send” span can be used as the creation context and no “Create” span needs to be created.Experimental
settleOne or more messages are settled.Experimental

Examples

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 Send A B]
  end
  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 Send A B
Span namecreate Tcreate Tsend T
Parent
LinksSpan Create A, Span Create B
SpanKindPRODUCERPRODUCERCLIENT
StatusOkOkOk
messaging.batch.message_count2
messaging.destination.name"T""T""T"
messaging.operation.name"create""create""send"
messaging.operation.type"create""create""send"
messaging.message.id"a1""a2"
messaging.message.envelope.size11
messaging.system"gcp_pubsub""gcp_pubsub""gcp_pubsub"

Unary Pull Example

flowchart TD;
  subgraph CONSUMER
  direction LR
  R1[Receive m1]
  SM1[Ack m1]
  EM1[Modack m1]
  end
  subgraph PRODUCER
  direction LR
  CM1[Create m1]
  PM1[Send]
  end
  %% 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 Send ASpan Receive ASpan Modack ASpan Ack A
Span namecreate Tsend Treceive Smodack Sack S
Parent
LinksSpan Create ASpan Create ASpan Receive ASpan Receive A
SpanKindPRODUCERPRODUCERCONSUMERCLIENTCLIENT
StatusOkOkOkOkOk
messaging.destination.name"T""T""S""S""S"
messaging.system"gcp_pubsub""gcp_pubsub""gcp_pubsub""gcp_pubsub""gcp_pubsub"
messaging.operation.name"create""send""receive""modack""ack"
messaging.operation.type"create""send""receive""settle"
messaging.message.id"a1""a1"
messaging.message.envelope.size111
messaging.gcp_pubsub.message.ack_id"ack_id1""ack_id1"
messaging.gcp_pubsub.message.delivery_attempt0
messaging.gcp_pubsub.message.ack_deadline0