Allows overriding the BACKEND_ENDPOINT via env (#116)

When deployed in the same k8s pod, services communicate by localhost despite being in different docker containers. By adding `BACKEND_ENDPOINT`, we can set this to "http://localhost:9000/api" in a k8s "extra container', so that we can do "helm test" on it. See https://kubernetes.io/docs/concepts/workloads/pods/#pod-networking Signed-off-by: Adrian Cole <[email protected]>
openzipkin · Feb 21, 2024 · 612b1e0 · 612b1e0
1 parent 0267b61
commit 612b1e0
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Showing 4 changed files with 22 additions and 5 deletions.
diff --git a/armeria/src/main/java/brave/example/Frontend.java b/armeria/src/main/java/brave/example/Frontend.java
@@ -8,14 +8,21 @@
 import com.linecorp.armeria.server.healthcheck.HealthCheckService;
 import com.linecorp.armeria.server.logging.AccessLogWriter;
 import com.linecorp.armeria.server.logging.LoggingService;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 public final class Frontend {
+  static final Logger LOGGER = LoggerFactory.getLogger(Frontend.class);
 
   public static void main(String[] args) {
     final HttpTracing httpTracing = HttpTracingFactory.create("frontend");
 
+    final String backendEndpoint =
+        System.getProperty("backend.endpoint", "http://127.0.0.1:9000/api");
+    LOGGER.info("Using backend endpoint: {}", backendEndpoint);
+
     final WebClient backendClient =
-        WebClient.builder(System.getProperty("backend.endpoint", "http://127.0.0.1:9000/api"))
+        WebClient.builder(backendEndpoint)
             .decorator(BraveClient.newDecorator(httpTracing.clientOf("backend")))
             .build();
 

diff --git a/docker/bin/install-example b/docker/bin/install-example
@@ -28,10 +28,12 @@ tee -a start-frontend start-backend <<-'EOF'
 export IP="$(hostname -i || echo '127.0.0.1')"
 EOF
 
+# Declare variables that expand variables set in this shell script.
 cat >> start-frontend <<-EOF
 export PORT=${frontend_port}
 export EXAMPLE=${version}
 export EXAMPLE_SERVICE=frontend
+DEFAULT_BACKEND_ENDPOINT=http://backend:${backend_port}/api
 EOF
 
 cat >> start-backend <<-EOF
@@ -40,7 +42,8 @@ export EXAMPLE=${version}
 export EXAMPLE_SERVICE=backend
 EOF
 
-# Add common elements for Java applications
+# Add common elements for Java applications.
+# HEALTHCHECK variables need to be exported as they are read via proc info.
 tee -a start-frontend start-backend <<-'EOF'
 export HEALTHCHECK_IP=${IP}
 export HEALTHCHECK_PORT=${PORT}
@@ -55,7 +58,8 @@ exec java ${JAVA_OPTS} -cp 'classes:lib/*' \
 -Dzipkin.baseUrl=${ZIPKIN_BASEURL:-http://zipkin:9411/} \
 EOF
 
-echo "-Dbackend.endpoint=http://backend:${backend_port}/api \\" >> start-frontend
+# Allow override of the backend endpoint, for a multi-container pod.
+echo '-Dbackend.endpoint=${BACKEND_ENDPOINT:-${DEFAULT_BACKEND_ENDPOINT}} \' >> start-frontend
 
 # Add the main class
 echo 'brave.example.Frontend "$@"' >> start-frontend

diff --git a/docker/bin/post-install-example-cassandra b/docker/bin/post-install-example-cassandra
@@ -5,7 +5,7 @@ set -eux
 sed -i 's~JAVA_OPTS=~sed -i "s/127.0.0.1/$IP/g" classes/cassandra.yaml\n\nJAVA_OPTS=~' start-backend
 
 # Communication isn't HTTP
-sed -i 's~endpoint=http://\(.*\)/api~contactPoint=\1~' start-frontend
+sed -i 's~DEFAULT_BACKEND_ENDPOINT=http://\(.*\)/api~DEFAULT_BACKEND_ENDPOINT=\1~' start-frontend
 sed -i 's/HEALTHCHECK_KIND=http/HEALTHCHECK_KIND=tcp/g' start-backend
 
 # Cassandra needs more than 32m memory

diff --git a/jersey2-cassandra3/src/main/java/brave/example/Frontend.java b/jersey2-cassandra3/src/main/java/brave/example/Frontend.java
@@ -15,10 +15,14 @@
 import javax.ws.rs.Path;
 import javax.ws.rs.ext.RuntimeDelegate;
 import org.glassfish.jersey.server.ResourceConfig;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 public final class Frontend {
+  static final Logger LOGGER = LoggerFactory.getLogger(Frontend.class);
+
   @Path("")
   public static class Resource {
     final Session session;
@@ -50,8 +54,10 @@ public static class HealthCheck implements HttpHandler {
   }
 
   public static void main(String[] args) throws Exception {
-    String contactPointString = System.getProperty("backend.contactPoint", "127.0.0.1:9042");
+    String contactPointString = System.getProperty("backend.endpoint", "127.0.0.1:9042");
     HostAndPort parsed = HostAndPort.fromString(contactPointString).withDefaultPort(9042);
+    LOGGER.info("Using contact point: {}", parsed);
+
     Cluster cluster = Cluster.builder()
         .addContactPointsWithPorts(new InetSocketAddress(parsed.getHost(), parsed.getPort()))
         .build();