239 lines
14 KiB
Markdown
239 lines
14 KiB
Markdown
<!--- Hugo front matter used to generate the website version of this page:
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linkTitle: Spans
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--->
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# Semantic Conventions for RPC Spans
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**Status**: [Experimental][DocumentStatus]
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This document defines how to describe remote procedure calls
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(also called "remote method invocations" / "RMI") with spans.
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<!-- Re-generate TOC with `markdown-toc --no-first-h1 -i` -->
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<!-- toc -->
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- [Common remote procedure call conventions](#common-remote-procedure-call-conventions)
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* [Span name](#span-name)
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* [Common attributes](#common-attributes)
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+ [Service name](#service-name)
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* [Client attributes](#client-attributes)
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* [Server attributes](#server-attributes)
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* [Events](#events)
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* [Distinction from HTTP spans](#distinction-from-http-spans)
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- [Semantic Conventions for specific RPC technologies](#semantic-conventions-for-specific-rpc-technologies)
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<!-- tocstop -->
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> **Warning**
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> Existing RPC instrumentations that are using
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> [v1.20.0 of this document](https://github.com/open-telemetry/opentelemetry-specification/blob/v1.20.0/specification/trace/semantic_conventions/rpc.md)
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> (or prior):
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>
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> * SHOULD NOT change the version of the networking conventions that they emit
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> until the HTTP semantic conventions are marked stable (HTTP stabilization will
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> include stabilization of a core set of networking conventions which are also used
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> in RPC instrumentations). Conventions include, but are not limited to, attributes,
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> metric and span names, and unit of measure.
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> * SHOULD introduce an environment variable `OTEL_SEMCONV_STABILITY_OPT_IN`
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> in the existing major version which is a comma-separated list of values.
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> The only values defined so far are:
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> * `http` - emit the new, stable networking conventions,
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> and stop emitting the old experimental networking conventions
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> that the instrumentation emitted previously.
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> * `http/dup` - emit both the old and the stable networking conventions,
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> allowing for a seamless transition.
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> * The default behavior (in the absence of one of these values) is to continue
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> emitting whatever version of the old experimental networking conventions
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> the instrumentation was emitting previously.
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> * Note: `http/dup` has higher precedence than `http` in case both values are present
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> * SHOULD maintain (security patching at a minimum) the existing major version
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> for at least six months after it starts emitting both sets of conventions.
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> * SHOULD drop the environment variable in the next major version (stable
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> next major version SHOULD NOT be released prior to October 1, 2023).
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## Common remote procedure call conventions
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A remote procedure calls is described by two separate spans, one on the client-side and one on the server-side.
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For outgoing requests, the `SpanKind` MUST be set to `CLIENT` and for incoming requests to `SERVER`.
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Remote procedure calls can only be represented with these semantic conventions, when the names of the called service and method are known and available.
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### Span name
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The *span name* MUST be the full RPC method name formatted as:
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```
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$package.$service/$method
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```
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(where $service MUST NOT contain dots and $method MUST NOT contain slashes)
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If there is no package name or if it is unknown, the `$package.` part (including the period) is omitted.
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Examples of span names:
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- `grpc.test.EchoService/Echo`
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- `com.example.ExampleRmiService/exampleMethod`
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- `MyCalcService.Calculator/Add` reported by the server and
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`MyServiceReference.ICalculator/Add` reported by the client for .NET WCF calls
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- `MyServiceWithNoPackage/theMethod`
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### Common attributes
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<!-- semconv rpc -->
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| Attribute | Type | Description | Examples | Requirement Level |
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|---|---|---|---|---|
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| [`network.transport`](../general/attributes.md) | string | [OSI transport layer](https://osi-model.com/transport-layer/) or [inter-process communication method](https://en.wikipedia.org/wiki/Inter-process_communication). [1] | `tcp`; `udp` | Recommended |
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| [`network.type`](../general/attributes.md) | string | [OSI network layer](https://osi-model.com/network-layer/) or non-OSI equivalent. [2] | `ipv4`; `ipv6` | Recommended |
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| `rpc.method` | string | The name of the (logical) method being called, must be equal to the $method part in the span name. [3] | `exampleMethod` | Recommended |
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| `rpc.service` | string | The full (logical) name of the service being called, including its package name, if applicable. [4] | `myservice.EchoService` | Recommended |
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| `rpc.system` | string | A string identifying the remoting system. See below for a list of well-known identifiers. | `grpc` | Required |
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| [`server.address`](../general/attributes.md) | string | RPC server [host name](https://grpc.github.io/grpc/core/md_doc_naming.html). [5] | `example.com` | Required |
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| [`server.port`](../general/attributes.md) | int | Server port number [6] | `80`; `8080`; `443` | Conditionally Required: See below |
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| [`server.socket.address`](../general/attributes.md) | string | Server address of the socket connection - IP address or Unix domain socket name. [7] | `10.5.3.2` | See below |
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| [`server.socket.port`](../general/attributes.md) | int | Server port number of the socket connection. [8] | `16456` | Recommended: [9] |
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**[1]:** The value SHOULD be normalized to lowercase.
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Consider always setting the transport when setting a port number, since
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a port number is ambiguous without knowing the transport, for example
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different processes could be listening on TCP port 12345 and UDP port 12345.
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**[2]:** The value SHOULD be normalized to lowercase.
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**[3]:** This is the logical name of the method from the RPC interface perspective, which can be different from the name of any implementing method/function. The `code.function` attribute may be used to store the latter (e.g., method actually executing the call on the server side, RPC client stub method on the client side).
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**[4]:** This is the logical name of the service from the RPC interface perspective, which can be different from the name of any implementing class. The `code.namespace` attribute may be used to store the latter (despite the attribute name, it may include a class name; e.g., class with method actually executing the call on the server side, RPC client stub class on the client side).
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**[5]:** May contain server IP address, DNS name, or local socket name. When host component is an IP address, instrumentations SHOULD NOT do a reverse proxy lookup to obtain DNS name and SHOULD set `server.address` to the IP address provided in the host component.
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**[6]:** When observed from the client side, and when communicating through an intermediary, `server.port` SHOULD represent the server port behind any intermediaries (e.g. proxies) if it's available.
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**[7]:** When observed from the client side, this SHOULD represent the immediate server peer address.
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When observed from the server side, this SHOULD represent the physical server address.
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**[8]:** When observed from the client side, this SHOULD represent the immediate server peer port.
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When observed from the server side, this SHOULD represent the physical server port.
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**[9]:** If different than `server.port` and if `server.socket.address` is set.
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**Additional attribute requirements:** At least one of the following sets of attributes is required:
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* [`server.socket.address`](../general/attributes.md)
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* [`server.address`](../general/attributes.md)
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`rpc.system` 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.
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| Value | Description |
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|---|---|
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| `grpc` | gRPC |
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| `java_rmi` | Java RMI |
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| `dotnet_wcf` | .NET WCF |
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| `apache_dubbo` | Apache Dubbo |
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| `connect_rpc` | Connect RPC |
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<!-- endsemconv -->
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For client-side spans `server.port` is required if the connection is IP-based and the port is available (it describes the server port they are connecting to).
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For server-side spans `client.socket.port` is optional (it describes the port the client is connecting from).
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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.
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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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Likewise, on clients sending RPC requests to a server, the service name provided in `rpc.service` does not have to match the [`peer.service`][] span attribute.
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As an example, given a process deployed as `QuoteService`, this would be the name that goes into the `service.name` resource attribute which applies to the entire process.
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This process could expose two RPC endpoints, one called `CurrencyQuotes` (= `rpc.service`) with a method called `getMeanRate` (= `rpc.method`) and the other endpoint called `StockQuotes` (= `rpc.service`) with two methods `getCurrentBid` and `getLastClose` (= `rpc.method`).
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In this example, spans representing client request should have their `peer.service` attribute set to `QuoteService` as well to match the server's `service.name` resource attribute.
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Generally, a user SHOULD NOT set `peer.service` to a fully qualified RPC service name.
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[`service.name`]: /docs/resource/README.md#service
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[`peer.service`]: /docs/general/attributes.md#general-remote-service-attributes
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### Client attributes
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<!-- semconv rpc.client -->
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| Attribute | Type | Description | Examples | Requirement Level |
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|---|---|---|---|---|
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| [`server.socket.domain`](../general/attributes.md) | string | Immediate server peer's domain name if available without reverse DNS lookup [1] | `proxy.example.com` | Recommended: [2] |
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**[1]:** Typically observed from the client side, and represents a proxy or other intermediary domain name.
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**[2]:** If different than `server.address` and if `server.socket.address` is set.
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<!-- endsemconv -->
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### Server attributes
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<!-- semconv rpc.server -->
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| Attribute | Type | Description | Examples | Requirement Level |
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|---|---|---|---|---|
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| [`client.address`](../general/attributes.md) | string | Client address - domain name if available without reverse DNS lookup, otherwise IP address or Unix domain socket name. [1] | `/tmp/my.sock`; `10.1.2.80` | Recommended |
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| [`client.port`](../general/attributes.md) | int | Client port number. [2] | `65123` | Recommended |
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| [`client.socket.address`](../general/attributes.md) | string | Client address of the socket connection - IP address or Unix domain socket name. [3] | `/tmp/my.sock`; `127.0.0.1` | Recommended: If different than `client.address`. |
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| [`client.socket.port`](../general/attributes.md) | int | Client port number of the socket connection. [4] | `35555` | Recommended: If different than `client.port`. |
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| [`network.transport`](../general/attributes.md) | string | [OSI transport layer](https://osi-model.com/transport-layer/) or [inter-process communication method](https://en.wikipedia.org/wiki/Inter-process_communication). [5] | `tcp`; `udp` | Recommended |
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| [`network.type`](../general/attributes.md) | string | [OSI network layer](https://osi-model.com/network-layer/) or non-OSI equivalent. [6] | `ipv4`; `ipv6` | Recommended |
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**[1]:** When observed from the server side, and when communicating through an intermediary, `client.address` SHOULD represent the client address behind any intermediaries (e.g. proxies) if it's available.
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**[2]:** When observed from the server side, and when communicating through an intermediary, `client.port` SHOULD represent the client port behind any intermediaries (e.g. proxies) if it's available.
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**[3]:** When observed from the server side, this SHOULD represent the immediate client peer address.
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When observed from the client side, this SHOULD represent the physical client address.
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**[4]:** When observed from the server side, this SHOULD represent the immediate client peer port.
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When observed from the client side, this SHOULD represent the physical client port.
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**[5]:** The value SHOULD be normalized to lowercase.
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Consider always setting the transport when setting a port number, since
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a port number is ambiguous without knowing the transport, for example
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different processes could be listening on TCP port 12345 and UDP port 12345.
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**[6]:** The value SHOULD be normalized to lowercase.
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<!-- endsemconv -->
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### Events
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In the lifetime of an RPC stream, an event for each message sent/received on
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client and server spans SHOULD be created. In case of unary calls only one sent
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and one received message will be recorded for both client and server spans.
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<!-- semconv rpc.message -->
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The event name MUST be `message`.
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| Attribute | Type | Description | Examples | Requirement Level |
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|---|---|---|---|---|
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| `message.compressed_size` | int | Compressed size of the message in bytes. | | Recommended |
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| `message.id` | int | MUST be calculated as two different counters starting from `1` one for sent messages and one for received message. [1] | | Recommended |
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| `message.type` | string | Whether this is a received or sent message. | `SENT` | Recommended |
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| `message.uncompressed_size` | int | Uncompressed size of the message in bytes. | | Recommended |
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**[1]:** This way we guarantee that the values will be consistent between different implementations.
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`message.type` MUST be one of the following:
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| Value | Description |
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| `SENT` | sent |
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| `RECEIVED` | received |
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<!-- endsemconv -->
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### Distinction from HTTP spans
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HTTP calls can generally be represented using just [HTTP spans](/docs/http/http-spans.md).
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If they address a particular remote service and method known to the caller, i.e., when it is a remote procedure call transported over HTTP, the `rpc.*` attributes might be added additionally on that span, or in a separate RPC span that is a parent of the transporting HTTP call.
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Note that *method* in this context is about the called remote procedure and *not* the HTTP verb (GET, POST, etc.).
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## Semantic Conventions for specific RPC technologies
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More specific Semantic Conventions are defined for the following RPC technologies:
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* [Connect](connect-rpc.md): Semantic Conventions for *Connect RPC*.
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* [gRPC](grpc.md): Semantic Conventions for *gRPC*.
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* [JSON-RPC](json-rpc.md): Semantic Conventions for *JSON-RPC*.
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[DocumentStatus]: https://github.com/open-telemetry/opentelemetry-specification/tree/v1.22.0/specification/document-status.md
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