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Protocols

There are two different types of protocols.

  • Probe Protocol. It includes descriptions and definitions on how agents send collected metrics data and traces, as well as the format of each entity.

  • Query Protocol. The backend enables the query function in SkyWalking's own UI and other UIs. These queries are based on GraphQL.

Probe Protocols

They also related to the probe group. For more information, see Concepts and Designs. These groups are language-based native agent protocol, service mesh protocol and 3rd-party instrument protocol.

Language-based native agent protocol

There are two types of protocols that help language agents work in distributed environments.

  1. Cross Process Propagation Headers Protocol and Cross Process Correlation Headers Protocol come in in-wire data format. Agent/SDK usually uses HTTP/MQ/HTTP2 headers to carry the data with the RPC request. The remote agent will receive this in the request handler, and bind the context with this specific request.
  2. Trace Data Protocol is in out-of-wire data format. Agent/SDK uses this to send traces and metrics to SkyWalking or other compatible backends.

Cross Process Propagation Headers Protocol v3 has been the new protocol for in-wire context propagation since the version 8.0.0 release.

Cross Process Correlation Headers Protocol v1 is a new in-wire context propagation protocol which is additional and optional. Please read SkyWalking language agents documentation to see whether it is supported. This protocol defines the data format of transporting custom data with Cross Process Propagation Headers Protocol. It has been supported by the SkyWalking javaagent since 8.0.0,

SkyWalking Trace Data Protocol v3 defines the communication method and format between the agent and backend.

SkyWalking Log Data Protocol defines the communication method and format between the agent and backend.

Browser probe protocol

The browser probe, such as skywalking-client-js, could use this protocol to send data to the backend. This service is provided by gRPC.

SkyWalking Browser Protocol defines the communication method and format between skywalking-client-js and backend.

Service Mesh probe protocol

The probe in sidecar or proxy could use this protocol to send data to the backend. This service provided by gRPC requires the following key information:

  1. Service Name or ID on both sides.
  2. Service Instance Name or ID on both sides.
  3. Endpoint. URI in HTTP, service method full signature in gRPC.
  4. Latency. In milliseconds.
  5. Response code in HTTP
  6. Status. Success or fail.
  7. Protocol. HTTP, gRPC
  8. DetectPoint. In Service Mesh sidecar, client or server. In normal L7 proxy, value is proxy.

Events Report Protocol

The protocol is used to report events to the backend. The doc introduces the definition of an event, and the protocol repository defines gRPC services and message formats of events.

Report JSON format events via HTTP API, the endpoint is http://<oap-address>:12800/v3/events. JSON event record example:

[
    {
        "uuid": "f498b3c0-8bca-438d-a5b0-3701826ae21c",
        "source": {
            "service": "SERVICE-A",
            "instance": "INSTANCE-1"
        },
        "name": "Reboot",
        "type": "Normal",
        "message": "App reboot.",
        "parameters": {},
        "startTime": 1628044330000,
        "endTime": 1628044331000
    }
]

3rd-party instrument protocol

3rd-party instrument protocols are not defined by SkyWalking. They are just protocols/formats with which SkyWalking is compatible, and SkyWalking could receive them from their existing libraries. SkyWalking starts with supporting Zipkin v1, v2 data formats.

The backend has a modular design, so it is very easy to extend a new receiver to support a new protocol/format.

Query Protocol

The query protocol follows GraphQL grammar, and provides data query capabilities, which depends on your analysis metrics. Read query protocol doc for more details.