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RPC 跨越的语义约定

NOTICE Semantic Conventions are moving to a new location.

No changes to this document are allowed.

Status: Experimental

This document defines how to describe remote procedure calls (also called "remote method invocations" / "RMI") with spans.

Warning Existing RPC instrumentations that are using v1.20.0 of this document (or prior):

  • SHOULD NOT change the version of the networking attributes that they emit until the HTTP semantic conventions are marked stable (HTTP stabilization will include stabilization of a core set of networking attributes which are also used in RPC instrumentations).
  • SHOULD introduce an environment variable OTEL_SEMCONV_STABILITY_OPT_IN in the existing major version which supports the following values:
  • none - continue emitting whatever version of the old experimental networking attributes the instrumentation was emitting previously. This is the default value.
  • http - emit the new, stable networking attributes, and stop emitting the old experimental networking attributes that the instrumentation emitted previously.
  • http/dup - emit both the old and the stable networking attributes, allowing for a seamless transition.
  • SHOULD maintain (security patching at a minimum) the existing major version for at least six months after it starts emitting both sets of attributes.
  • SHOULD drop the environment variable in the next major version (stable next major version SHOULD NOT be released prior to October 1, 2023).

Common remote procedure call conventions

A remote procedure calls is described by two separate spans, one on the client-side and one on the server-side.

For outgoing requests, the SpanKind MUST be set to CLIENT and for incoming requests to SERVER.

Remote procedure calls can only be represented with these semantic conventions, when the names of the called service and method are known and available.

Span name

The span name MUST be the full RPC method name formatted as:

1
$package.$service/$method

(where $service MUST NOT contain dots and $method MUST NOT contain slashes)

If there is no package name or if it is unknown, the $package. part (including the period) is omitted.

Examples of span names:

  • grpc.test.EchoService/Echo
  • com.example.ExampleRmiService/exampleMethod
  • MyCalcService.Calculator/Add reported by the server and MyServiceReference.ICalculator/Add reported by the client for .NET WCF calls
  • MyServiceWithNoPackage/theMethod

Common attributes

Attribute Type Description Examples Requirement Level
rpc.system string A string identifying the remoting system. See below for a list of well-known identifiers. grpc Required
rpc.service string The full (logical) name of the service being called, including its package name, if applicable. [1] myservice.EchoService Recommended
rpc.method string The name of the (logical) method being called, must be equal to the $method part in the span name. [2] exampleMethod Recommended
network.transport string OSI Transport Layer or Inter-process Communication method. The value SHOULD be normalized to lowercase. tcp; udp Recommended
network.type string OSI Network Layer or non-OSI equivalent. The value SHOULD be normalized to lowercase. ipv4; ipv6 Recommended
server.address string RPC server host name. [3] example.com Required
server.port int Logical server port number 80; 8080; 443 Conditionally Required: See below
server.socket.address string Physical server IP address or Unix socket address. 10.5.3.2 See below
server.socket.port int Physical server port. 16456 Recommended: [4]

[1]: 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).

[2]: 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).

[3]: 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.

[4]: If different than server.port and if server.socket.address is set.

Additional attribute requirements: At least one of the following sets of attributes is required:

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.

Value Description
grpc gRPC
java_rmi Java RMI
dotnet_wcf .NET WCF
apache_dubbo Apache Dubbo
connect_rpc Connect RPC

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). For server-side spans client.socket.port is optional (it describes the port the client is connecting from).

Service name

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. 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.

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. 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). 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. Generally, a user SHOULD NOT set peer.service to a fully qualified RPC service name.

Client attributes

Attribute Type Description Examples Requirement Level
server.socket.domain string The domain name of an immediate peer. [1] proxy.example.com Recommended: [2]

[1]: Typically observed from the client side, and represents a proxy or other intermediary domain name.

[2]: If different than server.address and if server.socket.address is set.

Server attributes

Attribute Type Description Examples Requirement Level
client.address string Client address - unix domain socket name, IPv4 or IPv6 address. [1] /tmp/my.sock; 10.1.2.80 Recommended
client.port int Client port number [2] 65123 Recommended
client.socket.address string Immediate client peer address - unix domain socket name, IPv4 or IPv6 address. /tmp/my.sock; 127.0.0.1 Recommended: If different than client.address.
client.socket.port int Immediate client peer port number 35555 Recommended: If different than client.port.
network.transport string OSI Transport Layer or Inter-process Communication method. The value SHOULD be normalized to lowercase. tcp; udp Recommended
network.type string OSI Network Layer or non-OSI equivalent. The value SHOULD be normalized to lowercase. ipv4; ipv6 Recommended

[1]: When observed from the server side, and when communicating through an intermediary, client.address SHOULD represent client address behind any intermediaries (e.g. proxies) if it's available.

[2]: When observed from the server side, and when communicating through an intermediary, client.port SHOULD represent client port behind any intermediaries (e.g. proxies) if it's available.

Events

In the lifetime of an RPC stream, an event for each message sent/received on client and server spans SHOULD be created. In case of unary calls only one sent and one received message will be recorded for both client and server spans.

The event name MUST be message.

Attribute Type Description Examples Requirement Level
message.type string Whether this is a received or sent message. SENT Recommended
message.id int MUST be calculated as two different counters starting from 1 one for sent messages and one for received message. [1] Recommended
message.compressed_size int Compressed size of the message in bytes. Recommended
message.uncompressed_size int Uncompressed size of the message in bytes. Recommended

[1]: This way we guarantee that the values will be consistent between different implementations.

message.type MUST be one of the following:

Value Description
SENT sent
RECEIVED received

Distinction from HTTP spans

HTTP calls can generally be represented using just HTTP spans. 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. Note that method in this context is about the called remote procedure and not the HTTP verb (GET, POST, etc.).

gRPC

For remote procedure calls via gRPC, additional conventions are described in this section.

rpc.system MUST be set to "grpc".

gRPC Attributes

Attribute Type Description Examples Requirement Level
rpc.grpc.status_code int The numeric status code of the gRPC request. 0 Required

rpc.grpc.status_code MUST be one of the following:

Value Description
0 OK
1 CANCELLED
2 UNKNOWN
3 INVALID_ARGUMENT
4 DEADLINE_EXCEEDED
5 NOT_FOUND
6 ALREADY_EXISTS
7 PERMISSION_DENIED
8 RESOURCE_EXHAUSTED
9 FAILED_PRECONDITION
10 ABORTED
11 OUT_OF_RANGE
12 UNIMPLEMENTED
13 INTERNAL
14 UNAVAILABLE
15 DATA_LOSS
16 UNAUTHENTICATED

gRPC Status

The table below describes when the Span Status MUST be set to Error or remain unset depending on the gRPC status code and Span Kind.

gRPC Status Code SpanKind.SERVER Span Status SpanKind.CLIENT Span Status
OK unset unset
CANCELLED unset Error
UNKNOWN Error Error
INVALID_ARGUMENT unset Error
DEADLINE_EXCEEDED Error Error
NOT_FOUND unset Error
ALREADY_EXISTS unset Error
PERMISSION_DENIED unset Error
RESOURCE_EXHAUSTED unset Error
FAILED_PRECONDITION unset Error
ABORTED unset Error
OUT_OF_RANGE unset Error
UNIMPLEMENTED Error Error
INTERNAL Error Error
UNAVAILABLE Error Error
DATA_LOSS Error Error
UNAUTHENTICATED unset Error

gRPC Request and Response Metadata

Attribute Type Description Examples Requirement Level
rpc.grpc.request.metadata.<key> string[] gRPC request metadata, <key> being the normalized gRPC Metadata key (lowercase, with - characters replaced by _), the value being the metadata values. [1] rpc.grpc.request.metadata.my_custom_metadata_attribute=["1.2.3.4", "1.2.3.5"] Opt-In
rpc.grpc.response.metadata.<key> string[] gRPC response metadata, <key> being the normalized gRPC Metadata key (lowercase, with - characters replaced by _), the value being the metadata values. [1] rpc.grpc.response.metadata.my_custom_metadata_attribute=["attribute_value"] Opt-In

[1]: Instrumentations SHOULD require an explicit configuration of which metadata values are to be captured. Including all request/response metadata values can be a security risk - explicit configuration helps avoid leaking sensitive information.

Connect RPC conventions

For remote procedure calls via connect, additional conventions are described in this section.

rpc.system MUST be set to "connect_rpc".

Connect RPC Attributes

Below is a table of attributes that SHOULD be included on client and server RPC measurements when rpc.system is "connect_rpc".

Attribute Type Description Examples Requirement Level
rpc.connect_rpc.error_code string The error codes of the Connect request. Error codes are always string values. cancelled Conditionally Required: [1]

[1]: If response is not successful and if error code available.

rpc.connect_rpc.error_code MUST be one of the following:

Value Description
cancelled cancelled
unknown unknown
invalid_argument invalid_argument
deadline_exceeded deadline_exceeded
not_found not_found
already_exists already_exists
permission_denied permission_denied
resource_exhausted resource_exhausted
failed_precondition failed_precondition
aborted aborted
out_of_range out_of_range
unimplemented unimplemented
internal internal
unavailable unavailable
data_loss data_loss
unauthenticated unauthenticated

Connect RPC Status

If rpc.connect_rpc.error_code is set, Span Status MUST be set to Error and left unset in all other cases.

Connect RPC Request and Response Metadata

Attribute Type Description Examples Requirement Level
rpc.connect_rpc.request.metadata.<key> string[] Connect request metadata, <key> being the normalized Connect Metadata key (lowercase, with - characters replaced by _), the value being the metadata values. [1] rpc.request.metadata.my_custom_metadata_attribute=["1.2.3.4", "1.2.3.5"] Optional
rpc.connect_rpc.response.metadata.<key> string[] Connect response metadata, <key> being the normalized Connect Metadata key (lowercase, with - characters replaced by _), the value being the metadata values. [1] rpc.response.metadata.my_custom_metadata_attribute=["attribute_value"] Optional

[1]: Instrumentations SHOULD require an explicit configuration of which metadata values are to be captured. Including all request/response metadata values can be a security risk - explicit configuration helps avoid leaking sensitive information.

JSON RPC

Conventions specific to JSON RPC.

rpc.system MUST be set to "jsonrpc".

JSON RPC Attributes

Attribute Type Description Examples Requirement Level
rpc.jsonrpc.version string Protocol version as in jsonrpc property of request/response. Since JSON-RPC 1.0 does not specify this, the value can be omitted. 2.0; 1.0 Conditionally Required: If other than the default version (1.0)
rpc.jsonrpc.request_id string id property of request or response. Since protocol allows id to be int, string, null or missing (for notifications), value is expected to be cast to string for simplicity. Use empty string in case of null value. Omit entirely if this is a notification. 10; request-7; `` Recommended
rpc.jsonrpc.error_code int error.code property of response if it is an error response. -32700; 100 Conditionally Required: If response is not successful.
rpc.jsonrpc.error_message string error.message property of response if it is an error response. Parse error; User already exists Recommended
rpc.method string The name of the (logical) method being called, must be equal to the $method part in the span name. [1] exampleMethod Required

[1]: This is always required for jsonrpc. See the note in the general RPC conventions for more information.