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linkTitle: Google Cloud Pub/Sub
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# Semantic Conventions for Google Cloud Pub/Sub

**Status**: [Experimental][DocumentStatus]

The Semantic Conventions for [Google Cloud Pub/Sub](https://cloud.google.com/pubsub) extend and override the [Messaging Semantic Conventions](README.md) 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:

<!-- semconv messaging.gcp_pubsub(full,tag=tech-specific-gcp-pubsub) -->
| Attribute  | Type | Description  | Examples  | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability |
|---|---|---|---|---|---|
| [`messaging.gcp_pubsub.message.ordering_key`](../attributes-registry/messaging.md) | string | The ordering key for a given message. If the attribute is not present, the message does not have an ordering key. | `ordering_key` | `Conditionally Required` If the message type has an ordering key set. | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
| [`messaging.gcp_pubsub.message.ack_deadline`](../attributes-registry/messaging.md) | int | The ack deadline in seconds set for the modify ack deadline request. | `10` | `Recommended` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
| [`messaging.gcp_pubsub.message.ack_id`](../attributes-registry/messaging.md) | string | The ack id for a given message. | `ack_id` | `Recommended` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
| [`messaging.gcp_pubsub.message.delivery_attempt`](../attributes-registry/messaging.md) | int | The delivery attempt for a given message. | `2` | `Recommended` | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
<!-- endsemconv -->

## Span names

The span name SHOULD follow the [general messaging span name pattern](../messaging/gcp-pubsub.md): 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.

## 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.

```mermaid
flowchart LR;
  subgraph PRODUCER
  direction LR
  CA[Span Create A]
  CB[Span Create B]
  P[Span Publish 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 Attribute | Span Create A | Span Create B | Span Publish A B |
|-|-|-|-|
| Span name | `T create` | `T create` | `publish` |
| Parent |  |  |  |
| Links |  |  | Span Create A, Span Create B |
| SpanKind | `PRODUCER` | `PRODUCER` | `CLIENT` |
| Status | `Ok` | `Ok` | `Ok` |
| `messaging.batch.message_count` |  |  | 2 |
| `messaging.destination.name` | `"T"` | `"T"` | `"T"` |
| `messaging.operation.type` | `"create"` | `"create"` | `"publish"` |
| `messaging.message.id` | `"a1"` | `"a2"` | |
| `messaging.message.envelope.size` | `1` | `1` | |
| `messaging.system` | `"gcp_pubsub"` | `"gcp_pubsub"` | `"gcp_pubsub"` |

### Unary Pull Example

```mermaid
flowchart TD;
  subgraph CONSUMER
  direction LR
  R1[Receive m1]
  SM1[Ack m1]
  EM1[Modack m1]
  end
  subgraph PRODUCER
  direction LR
  CM1[Create m1]
  PM1[Publish]
  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 Attribute | Span Create A | Span Publish A | Span Receive A | Span Modack A | Span Ack A |
|-|-|-|-|-|-|
| Span name | `T create` | `publish` |  `S receive` | `S modack` |`S ack` |
| Parent |  |  |  | |  |
| Links |  | Span Create A | Span Create A | Span Receive A | Span Receive A |
| SpanKind | `PRODUCER` | `PRODUCER` | `CONSUMER` |`CLIENT` |`CLIENT` |
| Status | `Ok` | `Ok` | `Ok` |`Ok` | `Ok` |
| `messaging.destination.name` | `"T"`| `"T"`| `"S"` | `"S"` |`"S"` |
| `messaging.system` | `"gcp_pubsub"` | `"gcp_pubsub"` | `"gcp_pubsub"` |  `"gcp_pubsub"` | `"gcp_pubsub"` |
| `messaging.operation` | `"create"` | `"publish"` | `"receive"` |  `"extend"` |  `"settle"` |
| `messaging.message.id` | `"a1"` | | `"a1"` | | |
| `messaging.message.envelope.size` | `1` | `1` | `1`  | | |
| `messaging.gcp_pubsub.message.ack_id` | | |  | `"ack_id1"` |`"ack_id1"` |
| `messaging.gcp_pubsub.message.delivery_attempt` | | |  | `0` |  |
| `messaging.gcp_pubsub.message.ack_deadline` | | |  | | `0` |

[DocumentStatus]: https://github.com/open-telemetry/opentelemetry-specification/tree/v1.26.0/specification/document-status.md