fix: add backend container healthcheck

Author: gpascucci

backend/Dockerfile

@@ -10,7 +10,9 @@ FROM gcr.io/distroless/java21-debian12:nonroot
 
 WORKDIR /app
 COPY --from=build /workspace/target/nr-ilcr-backend-*.jar /app/app.jar
+COPY --from=build /workspace/target/classes/ca/bc/gov/nrs/ilcr/HealthCheck.class /app/healthcheck/ca/bc/gov/nrs/ilcr/HealthCheck.class
 
 EXPOSE 8080
 USER 65532:65532
+HEALTHCHECK --interval=30s --timeout=5s --start-period=30s --retries=3 CMD ["java", "-XX:MaxRAM=64m", "-cp", "/app/healthcheck", "ca.bc.gov.nrs.ilcr.HealthCheck"]
 ENTRYPOINT ["java", "-XX:MaxRAMPercentage=50", "-jar", "/app/app.jar"]

backend/src/main/java/ca/bc/gov/nrs/ilcr/HealthCheck.java

@@ -0,0 +1,28 @@
+package ca.bc.gov.nrs.ilcr;
+
+import java.net.HttpURLConnection;
+import java.net.URI;
+import java.time.Duration;
+
+public final class HealthCheck {
+  private static final int HEALTHY = 0;
+  private static final int UNHEALTHY = 1;
+
+  private HealthCheck() {}
+
+  public static void main(String[] args) {
+    try {
+      int port = Integer.parseInt(System.getenv().getOrDefault("SERVER_PORT", "8080"));
+      URI uri = URI.create("http://127.0.0.1:" + port + "/api/health/readiness");
+      HttpURLConnection connection = (HttpURLConnection) uri.toURL().openConnection();
+      connection.setConnectTimeout((int) Duration.ofSeconds(2).toMillis());
+      connection.setReadTimeout((int) Duration.ofSeconds(2).toMillis());
+      connection.setRequestMethod("GET");
+
+      int status = connection.getResponseCode();
+      System.exit(status >= 200 && status < 400 ? HEALTHY : UNHEALTHY);
+    } catch (RuntimeException | java.io.IOException ex) {
+      System.exit(UNHEALTHY);
+    }
+  }
+}