header routing

java/Dockerfile

@@ -5,4 +5,4 @@ COPY . .
 
 RUN mvn clean package -DskipTests
 
-ENTRYPOINT ["java", "-jar", "target/spring-boot-0.0.1-SNAPSHOT.jar"]
+ENTRYPOINT ["java","-Dserver.port=80", "-jar", "target/spring-boot-0.0.1-SNAPSHOT.jar"]

nginx/html/index.html

@@ -1 +1,13 @@
 hello from nginx!
+
+<button onclick="goToApp('java')">Go to Java</button>
+<button onclick="goToApp('dotnet')">Go to .NET</button>
+<script>
+    function goToApp(appName) {
+        fetch("/", {
+            headers: { "X-App-Type": appName },
+        })
+            .then((r) => r.text())
+            .then((t) => (document.body.innerHTML = t));
+    }
+</script>

nginx/nginx.conf

@@ -1,4 +1,4 @@
-events { }
+events {}
 
 http {
     upstream dotnet_app {
@@ -11,32 +11,42 @@ http {
         server java-2;
     }
 
+    # Map the header to the chosen upstream
+    map $http_x_app_type $app_upstream {
+        dotnet dotnet_app;
+        java   java_app;
+        default "";
+    }
+
     server {
         listen 80;
 
         root /usr/share/nginx/html;
         index index.html;
 
+        #
+        # 1) If header is present -> route here
+        #
+        location @proxy_handler {
+            proxy_pass http://$app_upstream;
+            proxy_set_header Host $host;
+            proxy_set_header X-Real-IP $remote_addr;
+            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        }
+
+        #
+        # 2) Default location for all requests
+        #
         location / {
-            try_files $uri $uri/ =404;
+            # If upstream selected -> jump to proxy handler
+            error_page 418 = @proxy_handler;
+
+            if ($app_upstream != "") {
+                return 418;
             }
 
-        location /dotnet/ {
+            # Otherwise serve index.html or static files
-            proxy_pass http://dotnet_app;
+            try_files $uri $uri/ /index.html;
-            proxy_http_version 1.1;
-            proxy_set_header Host $host;
-            proxy_set_header X-Real-IP $remote_addr;
-            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
-            proxy_set_header X-Forwarded-Proto $scheme;
-        }
-
-        location /java/ {
-            proxy_pass http://java_app;
-            proxy_http_version 1.1;
-            proxy_set_header Host $host;
-            proxy_set_header X-Real-IP $remote_addr;
-            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
-            proxy_set_header X-Forwarded-Proto $scheme;
         }
     }
 }