Improves health check action to use a scheduled task to check readine…

…ss periodically. Use config to init HealthObserver.

Signed-off-by: Santiago Pericas-Geertsen <[email protected]>

examples/webserver/grpc/pom.xml

@@ -66,6 +66,10 @@
             <groupId>io.helidon.health</groupId>
             <artifactId>helidon-health-checks</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.helidon.scheduling</groupId>
+            <artifactId>helidon-scheduling</artifactId>
+        </dependency>
         <dependency>
             <groupId>com.google.protobuf</groupId>
             <artifactId>protobuf-java</artifactId>

examples/webserver/grpc/src/main/java/io/helidon/examples/webserver/grpc/GrpcMain.java

@@ -44,7 +44,7 @@ public static void main(String[] args) {
         // create a health check to verify gRPC endpoint
         ObserveFeature observe = ObserveFeature.builder()
                 .addObserver(HealthObserver.builder()
-                                     .details(true)
+                                     .config(serverConfig.get("features.observe.observers.health"))
                                      .addCheck(new StringServiceHealthCheck(serverConfig))
                                      .build())
                 .build();

examples/webserver/grpc/src/main/java/io/helidon/examples/webserver/grpc/StringServiceHealthCheck.java

@@ -15,20 +15,27 @@
  */
 package io.helidon.examples.webserver.grpc;
 
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
 import io.helidon.common.configurable.Resource;
 import io.helidon.common.tls.Tls;
 import io.helidon.config.Config;
 import io.helidon.health.HealthCheck;
 import io.helidon.health.HealthCheckResponse;
 import io.helidon.health.HealthCheckType;
+import io.helidon.scheduling.Scheduling;
 import io.helidon.webclient.api.WebClient;
 import io.helidon.webclient.grpc.GrpcClient;
 
 class StringServiceHealthCheck implements HealthCheck {
 
     private final WebClient webClient;
+    private CountDownLatch latch;
+    private volatile boolean readiness = true;
 
     StringServiceHealthCheck(Config config) {
+        // set up client to access gRPC service
         Tls clientTls = Tls.builder()
                 .trust(trust -> trust
                         .keystore(store -> store
@@ -53,26 +60,44 @@ public HealthCheckType type() {
         return HealthCheckType.READINESS;
     }
 
+    @Override
+    public HealthCheckResponse call() {
+        if (latch == null) {
+            latch = new CountDownLatch(1);
+            Scheduling.fixedRate()          // task to check for readiness
+                    .delay(1)
+                    .initialDelay(0)
+                    .timeUnit(TimeUnit.MINUTES)
+                    .task(i -> checkReadiness())
+                    .build();
+        }
+        try {
+            boolean check = latch.await(5, TimeUnit.SECONDS);
+            return HealthCheckResponse.builder()
+                    .status(check && readiness)
+                    .get();
+        } catch (Exception e) {
+            return HealthCheckResponse.builder()
+                    .status(false)
+                    .get();
+        }
+    }
+
     /**
      * Self-invocation to verify gRPC endpoint is available and ready.
-     *
-     * @return health check response
      */
-    @Override
-    public HealthCheckResponse call() {
+    private void checkReadiness() {
         try {
             GrpcClient grpcClient = webClient.client(GrpcClient.PROTOCOL);
             StringServiceGrpc.StringServiceBlockingStub service =
                     StringServiceGrpc.newBlockingStub(grpcClient.channel());
             Strings.StringMessage res = service.upper(
                     Strings.StringMessage.newBuilder().setText("hello").build());
-            return HealthCheckResponse.builder()
-                    .status(res.getText().equals("HELLO"))
-                    .get();
+            readiness = res.getText().equals("HELLO");
         } catch (Exception e) {
-            return HealthCheckResponse.builder()
-                    .status(false)
-                    .get();
+            readiness = false;
+        } finally {
+            latch.countDown();
         }
     }
 }