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Fixes open-telemetry#1016: Define RPC semantic conventions for metrics.
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| # General RPC conventions | ||
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| The conventions described in this section are RPC specific. When RPC operations | ||
| occur, metric events about those operations will be generated and reported to | ||
| provide insight into those operations. By adding RPC labels to metric events | ||
| it allows for finely tuned filtering. | ||
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| **Disclaimer:** These are initial RPC metric instruments and labels but more may | ||
| be added in the future. | ||
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| ## Metric instruments | ||
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| The following metric instruments MUST be used to describe RPC operations. They | ||
| MUST be of the specified type and units. | ||
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| *Note: RPC server and client metrics are split to allow correlation across client/server boundaries, e.g. Lining up an RPC method latency to determine if the server is responsible for latency the client is seeing.* | ||
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| ### RPC Server | ||
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| Below is a table of RPC server metric instruments. | ||
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| | Name | Instrument | Units | Description | Status | Streaming | | ||
| |----------------------------|---------------|--------------|-------------|--------|-----------| | ||
| | `rpc.server.duration` | ValueRecorder | milliseconds | measures duration of inbound RPC | Recommended | N/A. While streaming RPCs may record this metric as start-of-batch to end-of-batch, it's hard to interpret in practice. | | ||
| | `rpc.server.request.size` | ValueRecorder | bytes | measures size of RPC request messages (uncompressed) | Optional | Recorded per message in a streaming batch | | ||
| | `rpc.server.response.size` | ValueRecorder | bytes | measures size of RPC response messages (uncompressed) | Optional | Recorded per response in a streaming batch | | ||
| | `rpc.server.requests_per_rpc` | ValueRecorder | count | measures the number of messages received per RPC. Should be 1 for all non-streaming RPCs | Optional | Required | | ||
| | `rpc.server.responses_per_rpc` | ValueRecorder | count | measures the number of messages sent per RPC. Should be 1 for all non-streaming RPCs | Optional | Required | | ||
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| ### RPC Client | ||
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| Below is a table of RPC client metric instruments. These apply to traditional | ||
| RPC usage, not streaming RPCs. | ||
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| | Name | Instrument | Units | Description | Status | Streaming | | ||
| |----------------------------|---------------|--------------|-------------|--------|-----------| | ||
| | `rpc.client.duration` | ValueRecorder | milliseconds | measures duration of outbound RPC | Recommended | N/A. While streaming RPCs may record this metric as start-of-batch to end-of-batch, it's hard to interpret in practice. | | ||
| | `rpc.client.request.size` | ValueRecorder | bytes | measures size of RPC request messages (uncompressed) | Optional | Recorded per message in a streaming batch | | ||
| | `rpc.client.response.size` | ValueRecorder | bytes | measures size of RPC response messages (uncompressed) | Optional | Recorded per message in a streaming batch | | ||
| | `rpc.client.requests_per_rpc` | ValueRecorder | count | measures the number of messages received per RPC. Should be 1 for all non-streaming RPCs | Optional | Required | | ||
| | `rpc.client.responses_per_rpc` | ValueRecorder | count | measures the number of messages sent per RPC. Should be 1 for all non-streaming RPCs | Optional | Required | | ||
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| ## Labels | ||
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| Below is a table of labels that SHOULD be included on metric events and whether | ||
| or not they should be on the server, client or both. | ||
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| <!-- semconv rpc --> | ||
| | Attribute | Type | Description | Example | Required | | ||
| |---|---|---|---|---| | ||
| | [`rpc.system`](../../trace/semantic_conventions/rpc.md) | string | A string identifying the remoting system. | `grpc`<br>`java_rmi`<br>`wcf` | Yes | | ||
| | [`rpc.service`](../../trace/semantic_conventions/rpc.md) | string | The full name of the service being called, including its package name, if applicable. | `myservice.EchoService` | Conditional<br>No, but recommended | | ||
| | [`rpc.method`](../../trace/semantic_conventions/rpc.md) | string | The name of the method being called, must be equal to the $method part in the span name. | `exampleMethod` | Conditional<br>No, but recommended | | ||
| | [`net.peer.ip`](../../trace/semantic_conventions/span-general.md) | string | Remote address of the peer (dotted decimal for IPv4 or [RFC5952](https://tools.ietf.org/html/rfc5952) for IPv6) | `127.0.0.1` | See below | | ||
| | [`net.peer.name`](../../trace/semantic_conventions/span-general.md) | string | Remote hostname or similar, see note below. | `example.com` | See below | | ||
| | [`net.peer.port`](../../trace/semantic_conventions/span-general.md) | number | Remote port number. | `80`<br>`8080`<br>`443` | Conditional<br>See below | | ||
| | [`net.transport`](../../trace/semantic_conventions/span-general.md) | string enum | Transport protocol used. See note below. | `IP.TCP` | Conditional<br>See below | | ||
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| **Additional attribute requirements:** At least one of the following sets of attributes is required: | ||
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| * [`net.peer.ip`](../../trace/semantic_conventions/span-general.md) | ||
| * [`net.peer.name`](../../trace/semantic_conventions/span-general.md) | ||
| <!-- endsemconv --> | ||
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| To avoid high cardinality, implementations should prefer the most stable of `net.peer.name` or | ||
| `net.peer.ip`, depending on expected deployment profile. For many cloud applications, this is likely | ||
| `net.peer.name` as names can be recycled even across re-instantiation of a server with a different `ip`. | ||
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| For client-side metrics `net.peer.port` is required if the connection is IP-based and the port is available (it describes the server port they are connecting to). | ||
| For server-side spans `net.peer.port` is optional (it describes the port the client is connecting from). | ||
| Furthermore, setting [net.transport][] is required for non-IP connection like named pipe bindings. | ||
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| ### Service name | ||
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| On the server process receiving and handling the remote procedure call, the service name provided in `rpc.service` does not necessarily have to match the [`service.name`][] resource attribute. | ||
| One process can expose multiple RPC endpoints and thus have multiple RPC service names. From a deployment perspective, as expressed by the `service.*` resource attributes, it will be treated as one deployed service with one `service.name`. | ||
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| [`service.name`]: ../../resource/semantic_conventions/README.md#service | ||
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| ## gRPC conventions | ||
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| For remote procedure calls via [gRPC][], additional conventions are described in this section. | ||
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| `rpc.system` MUST be set to `"grpc"`. | ||
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| [gRPC]: https://grpc.io/ |