a6-recipe-api-versioning

Overview

API versioning allows you to evolve your API without breaking existing clients. APISIX supports multiple versioning strategies through routing rules, header matching, and traffic splitting — all configurable via the a6 CLI.

Strategies covered:

1. URI path versioning — /v1/users, /v2/users
2. Header-based versioning — Accept: application/vnd.api.v2+json
3. Query parameter versioning — ?version=2
4. Gradual migration — weighted traffic split between versions
5. Version deprecation — redirect old versions to new

When to Use

• Introducing breaking changes to an existing API
• Running multiple API versions simultaneously
• Gradually migrating clients from v1 to v2
• Deprecating old API versions with user-friendly redirects

Approach A: URI Path Versioning

The most common pattern. Each version has its own URI prefix, and proxy-rewrite strips the version prefix before forwarding to the backend.

1. Create versioned upstreams

a6 upstream create -f - <<'EOF'
{
  "id": "api-v1",
  "type": "roundrobin",
  "nodes": { "api-v1-backend:8080": 1 }
}
EOF

a6 upstream create -f - <<'EOF'
{
  "id": "api-v2",
  "type": "roundrobin",
  "nodes": { "api-v2-backend:8080": 1 }
}
EOF

2. Create versioned routes with URI rewriting

# v1: /v1/users/123 → /users/123 on api-v1 backend
a6 route create -f - <<'EOF'
{
  "id": "route-v1",
  "uri": "/v1/*",
  "upstream_id": "api-v1",
  "plugins": {
    "proxy-rewrite": {
      "regex_uri": ["^/v1/(.*)", "/$1"]
    }
  }
}
EOF

# v2: /v2/users/123 → /users/123 on api-v2 backend
a6 route create -f - <<'EOF'
{
  "id": "route-v2",
  "uri": "/v2/*",
  "upstream_id": "api-v2",
  "plugins": {
    "proxy-rewrite": {
      "regex_uri": ["^/v2/(.*)", "/$1"]
    }
  }
}
EOF

Clients call /v1/users or /v2/users, and the backend always sees /users.

Approach B: Header-Based Versioning

Route based on the Accept header using traffic-split with vars matching. A single URI serves multiple versions.

a6 route create -f - <<'EOF'
{
  "uri": "/api/*",
  "plugins": {
    "traffic-split": {
      "rules": [
        {
          "match": [
            { "vars": [["http_accept", "~~", "application/vnd\\.api\\.v2\\+json"]] }
          ],
          "weighted_upstreams": [
            {
              "upstream": {
                "type": "roundrobin",
                "nodes": { "api-v2-backend:8080": 1 }
              },
              "weight": 1
            }
          ]
        }
      ]
    }
  },
  "upstream": {
    "type": "roundrobin",
    "nodes": { "api-v1-backend:8080": 1 }
  }
}
EOF

• Accept: application/vnd.api.v2+json → v2 backend
• Any other Accept value → v1 backend (default upstream)
• ~~ is the regex match operator in APISIX vars expressions

Approach C: Query Parameter Versioning

Route based on ?version=2 query parameter.

a6 route create -f - <<'EOF'
{
  "uri": "/api/*",
  "plugins": {
    "traffic-split": {
      "rules": [
        {
          "match": [
            { "vars": [["arg_version", "==", "2"]] }
          ],
          "weighted_upstreams": [
            {
              "upstream": {
                "type": "roundrobin",
                "nodes": { "api-v2-backend:8080": 1 }
              },
              "weight": 1
            }
          ]
        }
      ]
    }
  },
  "upstream": {
    "type": "roundrobin",
    "nodes": { "api-v1-backend:8080": 1 }
  }
}
EOF

• /api/users?version=2 → v2 backend
• /api/users or /api/users?version=1 → v1 backend

Gradual Version Migration

Use weighted traffic splitting to gradually shift traffic from v1 to v2.

Start: 90% v1, 10% v2

a6 route create -f - <<'EOF'
{
  "id": "api-migration",
  "uri": "/api/*",
  "plugins": {
    "traffic-split": {
      "rules": [
        {
          "weighted_upstreams": [
            {
              "upstream": {
                "type": "roundrobin",
                "nodes": { "api-v2-backend:8080": 1 }
              },
              "weight": 1
            },
            { "weight": 9 }
          ]
        }
      ]
    }
  },
  "upstream": {
    "type": "roundrobin",
    "nodes": { "api-v1-backend:8080": 1 }
  }
}
EOF

Shift to 50/50

a6 route update api-migration -f - <<'EOF'
{
  "plugins": {
    "traffic-split": {
      "rules": [
        {
          "weighted_upstreams": [
            {
              "upstream": {
                "type": "roundrobin",
                "nodes": { "api-v2-backend:8080": 1 }
              },
              "weight": 1
            },
            { "weight": 1 }
          ]
        }
      ]
    }
  }
}
EOF

Complete: 100% v2

a6 route update api-migration -f - <<'EOF'
{
  "upstream": {
    "type": "roundrobin",
    "nodes": { "api-v2-backend:8080": 1 }
  },
  "plugins": {}
}
EOF

Version Deprecation with Redirect

When sunsetting v1, redirect clients to v2 with a 301 Moved Permanently.

a6 route update route-v1 -f - <<'EOF'
{
  "uri": "/v1/*",
  "plugins": {
    "redirect": {
      "regex_uri": ["^/v1/(.*)", "/v2/$1"],
      "ret_code": 301
    }
  }
}
EOF

Clients calling /v1/users receive:

HTTP/1.1 301 Moved Permanently
Location: /v2/users

Declarative Versioning Config

# apisix-versioning.yaml
upstreams:
  - id: api-v1
    type: roundrobin
    nodes:
      "api-v1-backend:8080": 1
  - id: api-v2
    type: roundrobin
    nodes:
      "api-v2-backend:8080": 1

routes:
  - id: route-v1
    uri: "/v1/*"
    upstream_id: api-v1
    plugins:
      proxy-rewrite:
        regex_uri: ["^/v1/(.*)", "/$1"]
  - id: route-v2
    uri: "/v2/*"
    upstream_id: api-v2
    plugins:
      proxy-rewrite:
        regex_uri: ["^/v2/(.*)", "/$1"]

a6 config diff -f apisix-versioning.yaml
a6 config sync -f apisix-versioning.yaml

Gotchas

• regex_uri is an array of two strings — ["pattern", "replacement"], not an object. The pattern is a Lua regex (PCRE-compatible).
• traffic-split weight semantics — a weighted_upstreams entry without an upstream field means "use the route's default upstream". Weight 9 + weight 1 = 90%/10%.
• ~~ operator — regex match in vars expressions. Must double-escape backslashes in JSON: "application/vnd\\\\.api\\\\.v2\\\\+json".
• Order matters — traffic-split rules are evaluated top-down. First matching rule wins.
• URI rewrite happens before upstream — proxy-rewrite changes the URI that the backend sees, not the URI used for route matching.
• redirect plugin is terminal — when redirect is active, the request never reaches an upstream. Remove the upstream_id to avoid confusion.

Verification

# Test URI path versioning
curl http://localhost:9080/v1/users   # → v1 backend
curl http://localhost:9080/v2/users   # → v2 backend

# Test header-based versioning
curl -H "Accept: application/vnd.api.v2+json" http://localhost:9080/api/users  # → v2
curl http://localhost:9080/api/users  # → v1 (default)

# Test query parameter versioning
curl "http://localhost:9080/api/users?version=2"  # → v2
curl http://localhost:9080/api/users               # → v1

# Test redirect (deprecation)
curl -v http://localhost:9080/v1/users  # → 301 to /v2/users

---

This page is generated from a6-recipe-api-versioning/SKILL.md in the api7/a6 repository. Browse all skills on the AI Agent Skills page.