feat: adds support for nginx variables in service_name param

apisix/upstream.lua

@@ -305,9 +305,14 @@ function _M.set_by_route(route, api_ctx)
             return 503, err
         end
 
-        local new_nodes, err = dis.nodes(up_conf.service_name, up_conf.discovery_args)
+        local service_name, err = core.utils.resolve_var(up_conf.service_name, api_ctx.var)
+        if not service_name or service_name == "" then
+            return 503, "resolve_var resolves to empty string: " .. (err or "nil")
+        end
+
+        local new_nodes, err = dis.nodes(service_name, up_conf.discovery_args)
         if not new_nodes then
-            return HTTP_CODE_UPSTREAM_UNAVAILABLE, "no valid upstream node: " .. (err or "nil")
+            return HTTP_CODE_UPSTREAM_UNAVAILABLE, "no valid upstream node for service '" .. service_name .. "': " .. (err or "nil")
         end
 
         local same = upstream_util.compare_upstream_node(up_conf, new_nodes)

docs/en/latest/discovery.md

@@ -216,6 +216,35 @@ Server: APISIX web server
 {"node":{"value":{"uri":"\/user\/*","upstream": {"service_name": "USER-SERVICE", "type": "roundrobin", "discovery_type": "eureka"}},"createdIndex":61925,"key":"\/apisix\/routes\/1","modifiedIndex":61925}}
 ```
 
+You can also use variables in the service name. For example, to route requests based on the host header using nginx map:
+
+First, configure the map in your nginx configuration:
+
+```nginx
+map $http_host $backend {
+    hostnames;
+    default service_a;
+    x.domain.local service_x;
+    y.domain.local service_y;
+}
+```
+
+Then use the mapped variable in your route configuration:
+
+```shell
+$ curl http://127.0.0.1:9180/apisix/admin/routes/1 -H "X-API-KEY: $admin_key" -X PUT -i -d '
+{
+    "uri": "/*",
+    "upstream": {
+        "service_name": "${backend}",
+        "type": "roundrobin",
+        "discovery_type": "eureka"
+    }
+}'
+```
+
+In this example, requests to `x.domain.local` will be routed to the service named "service_x", while requests to `y.domain.local` will be routed to "service_y".
+
 Because the upstream interface URL may have conflict, usually in the gateway by prefix to distinguish:
 
 ```shell

docs/zh/latest/discovery.md

@@ -221,6 +221,35 @@ Server: APISIX web server
 {"node":{"value":{"uri":"\/user\/*","upstream": {"service_name": "USER-SERVICE", "type": "roundrobin", "discovery_type": "eureka"}},"createdIndex":61925,"key":"\/apisix\/routes\/1","modifiedIndex":61925}}
 ```
 
+您也可以在服务名称中使用变量。例如，使用 nginx map 根据 host 头进行请求路由：
+
+首先，在您的 nginx 配置中配置 map：
+
+```nginx
+map $http_host $backend {
+    hostnames;
+    default service_a;
+    x.domain.local service_x;
+    y.domain.local service_y;
+}
+```
+
+然后在路由配置中使用映射的变量：
+
+```shell
+$ curl http://127.0.0.1:9180/apisix/admin/routes/1 -H "X-API-KEY: $admin_key" -X PUT -i -d '
+{
+    "uri": "/*",
+    "upstream": {
+        "service_name": "${backend}",
+        "type": "roundrobin",
+        "discovery_type": "eureka"
+    }
+}'
+```
+
+在这个例子中，对 `x.domain.local` 的请求将被路由到名为 "service_x" 的服务，而对 `y.domain.local` 的请求将被路由到 "service_y"。
+
 因为上游的接口 URL 可能会有冲突，通常会在网关通过前缀来进行区分：
 
 ```shell

t/discovery/consul.t

@@ -781,3 +781,108 @@ location /sleep {
     qr//
 ]
 --- ignore_error_log
+
+
+
+=== TEST 16: test service_name as variable in route configuration
+--- yaml_config eval: $::yaml_config
+--- apisix_yaml
+routes:
+  -
+    uri: /hello
+    upstream:
+      service_name: "${backend}"
+      discovery_type: consul
+      type: roundrobin
+#END
+--- http_config
+    map $http_host $backend {
+        default service_a;
+    }
+
+    server {
+        listen 30511;
+
+        location /hello {
+            content_by_lua_block {
+                ngx.say("server 1")
+            }
+        }
+    }
+    server {
+        listen 30512;
+
+        location /hello {
+            content_by_lua_block {
+                ngx.say("server 2")
+            }
+        }
+    }
+--- config
+location /v1/agent {
+    proxy_pass http://127.0.0.1:8500;
+}
+location /sleep {
+    content_by_lua_block {
+        local args = ngx.req.get_uri_args()
+        local sec = args.sec or "2"
+        ngx.sleep(tonumber(sec))
+        ngx.say("ok")
+    }
+}
+--- timeout: 6
+--- request eval
+[
+    "PUT /v1/agent/service/register\n" . "{\"ID\":\"service_a1\",\"Name\":\"service_a\",\"Tags\":[\"primary\",\"v1\"],\"Address\":\"127.0.0.1\",\"Port\":30511,\"Meta\":{\"service_a_version\":\"4.0\"},\"EnableTagOverride\":false,\"Weights\":{\"Passing\":10,\"Warning\":1}}",
+    "PUT /v1/agent/service/register\n" . "{\"ID\":\"service_a2\",\"Name\":\"service_a\",\"Tags\":[\"primary\",\"v1\"],\"Address\":\"127.0.0.1\",\"Port\":30512,\"Meta\":{\"service_a_version\":\"4.0\"},\"EnableTagOverride\":false,\"Weights\":{\"Passing\":10,\"Warning\":1}}",
+    "GET /sleep?sec=2",
+    "GET /hello",
+]
+--- response_body_like eval
+[
+    qr//,
+    qr//,
+    qr/ok\n/,
+    qr/server [1-2]\n/,
+]
+--- no_error_log
+[error]
+
+
+
+=== TEST 17: test empty variable in service_name
+--- yaml_config eval: $::yaml_config
+--- apisix_yaml
+routes:
+  -
+    uri: /hello
+    upstream:
+      service_name: "${backend}"
+      discovery_type: consul
+      type: roundrobin
+#END
+--- http_config
+    map $http_host $backend {
+        default "";
+    }
+--- config
+    location /t {
+        content_by_lua_block {
+            local http = require "resty.http"
+            local httpc = http.new()
+            local uri = "http://127.0.0.1:" .. ngx.var.server_port .. "/hello"
+            local res, err = httpc:request_uri(uri, { method = "GET"})
+            if err then
+                ngx.log(ngx.ERR, err)
+                ngx.status = res.status
+                return
+            end
+            ngx.say(res.status)
+        }
+    }
+--- request
+GET /t
+--- response_body
+503
+--- error_log
+resolve_var resolves to empty string