a6-plugin-zipkin

Overview

The zipkin plugin sends distributed traces to Zipkin-compatible collectors using the Zipkin v2 HTTP API. It supports B3 propagation headers for trace context across services. Compatible backends include Zipkin, Jaeger, and SkyWalking (via Zipkin receiver).

When to Use

• Distributed tracing with Zipkin, Jaeger, or compatible collectors
• B3 header propagation across microservices
• Per-request sampling control via headers
• Trace ID injection into access logs

Plugin Configuration Reference

Field	Type	Required	Default	Description
endpoint	string	Yes	—	Zipkin collector URL (e.g. http://zipkin:9411/api/v2/spans)
sample_ratio	number	Yes	—	Sampling rate from 0.00001 to 1
service_name	string	No	"APISIX"	Service name in Zipkin UI
server_addr	string	No	$server_addr	IPv4 address for span reporting
span_version	integer	No	2	Span format: 1 (legacy) or 2 (default)

B3 Propagation Headers

The plugin uses B3 propagation format:

Injected to upstream

Header	Description
x-b3-traceid	Trace ID (16 or 32 hex chars)
x-b3-spanid	Span ID (16 hex chars)
x-b3-parentspanid	Parent span ID
x-b3-sampled	Sampling decision (1 or 0)

Extracted from client

Header	Description
b3	Single-header format: {traceid}-{spanid}-{sampled}-{parentspanid}
x-b3-sampled	1 = force sample, 0 = skip, d = debug
x-b3-flags	1 = force debug sampling

Clients can override sampling per-request by setting x-b3-sampled: 1.

Span Versions

Version 2 (default, recommended):

request
├── proxy      (request start → header_filter)
└── response   (header_filter → log)

Version 1 (legacy):

request
├── rewrite
├── access
└── proxy
    └── body_filter

Step-by-Step: Enable Zipkin Tracing

1. Create a route with zipkin

a6 route create -f - <<'EOF'
{
  "id": "traced-api",
  "uri": "/api/*",
  "plugins": {
    "zipkin": {
      "endpoint": "http://zipkin:9411/api/v2/spans",
      "sample_ratio": 1,
      "service_name": "my-gateway",
      "span_version": 2
    }
  },
  "upstream": {
    "type": "roundrobin",
    "nodes": {
      "backend:8080": 1
    }
  }
}
EOF

2. Send a request

curl http://127.0.0.1:9080/api/hello

3. View traces in Zipkin UI

Open http://zipkin:9411 and search for service my-gateway.

Common Patterns

Send traces to Jaeger

Jaeger supports the Zipkin v2 API:

{
  "plugins": {
    "zipkin": {
      "endpoint": "http://jaeger-collector:9411/api/v2/spans",
      "sample_ratio": 1,
      "service_name": "my-gateway"
    }
  }
}

Production sampling (10%)

{
  "plugins": {
    "zipkin": {
      "endpoint": "http://zipkin:9411/api/v2/spans",
      "sample_ratio": 0.1,
      "service_name": "production-gateway"
    }
  }
}

Trace IDs in access logs

Add to APISIX config.yaml:

plugin_attr:
  zipkin:
    set_ngx_var: true

nginx_config:
  http:
    access_log_format: '{"trace_id":"$zipkin_trace_id","span_id":"$zipkin_span_id","traceparent":"$zipkin_context_traceparent"}'
    access_log_format_escape: json

Available variables:

• $zipkin_trace_id — Trace ID
• $zipkin_span_id — Span ID
• $zipkin_context_traceparent — W3C traceparent header

External IP address

{
  "plugins": {
    "zipkin": {
      "endpoint": "http://zipkin:9411/api/v2/spans",
      "sample_ratio": 1,
      "server_addr": "10.0.1.5"
    }
  }
}

Config Sync Example

version: "1"
routes:
  - id: traced-api
    uri: /api/*
    plugins:
      zipkin:
        endpoint: http://zipkin:9411/api/v2/spans
        sample_ratio: 1
        service_name: my-gateway
        span_version: 2
    upstream_id: my-upstream
upstreams:
  - id: my-upstream
    type: roundrobin
    nodes:
      "backend:8080": 1

Troubleshooting

Symptom	Cause	Fix
No traces in Zipkin UI	Wrong endpoint URL	Verify collector is reachable; must include /api/v2/spans
Traces not connected	B3 headers stripped by proxy	Ensure intermediate proxies forward x-b3-* headers
All requests sampled	sample_ratio: 1	Lower for production (e.g. 0.01-0.1)
Missing trace variables in logs	set_ngx_var not enabled	Set plugin_attr.zipkin.set_ngx_var: true in config.yaml
400 from collector	Span version mismatch	Try span_version: 1 if collector only supports v1