From b084c5196271eb47f12aada1a6de65e9e363409a Mon Sep 17 00:00:00 2001
From: Tomas Langer <tomas.langer@gmail.com>
Date: Mon, 10 Aug 2020 15:24:28 +0200
Subject: [PATCH] Health check now non-blocking using fault tolerance async and
 timeout (#2237)

Signed-off-by: Tomas Langer <tomas.langer@oracle.com>
---
 .../src/main/java/module-info.java            |  2 +
 health/health/pom.xml                         |  6 +-
 .../java/io/helidon/health/HealthSupport.java | 56 +++++++++++++++++--
 health/health/src/main/java/module-info.java  |  1 +
 4 files changed, 58 insertions(+), 7 deletions(-)

diff --git a/fault-tolerance/src/main/java/module-info.java b/fault-tolerance/src/main/java/module-info.java
index 511a12d60..32add2bed 100644
--- a/fault-tolerance/src/main/java/module-info.java
+++ b/fault-tolerance/src/main/java/module-info.java
@@ -21,4 +21,6 @@ module io.helidon.faulttolerance {
     requires io.helidon.config;
     requires io.helidon.common.configurable;
     requires java.logging;
+
+    exports io.helidon.faulttolerance;
 }
\ No newline at end of file
diff --git a/health/health/pom.xml b/health/health/pom.xml
index 856add508..5b4abb92b 100644
--- a/health/health/pom.xml
+++ b/health/health/pom.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!--
-  Copyright (c) 2018, 2020 Oracle and/or its affiliates. All rights reserved.
+  Copyright (c) 2018, 2020 Oracle and/or its affiliates.
 
   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
@@ -37,6 +37,10 @@
             <groupId>io.helidon.media</groupId>
             <artifactId>helidon-media-jsonp</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.helidon.fault-tolerance</groupId>
+            <artifactId>helidon-fault-tolerance</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.eclipse.microprofile.health</groupId>
             <artifactId>microprofile-health-api</artifactId>
diff --git a/health/health/src/main/java/io/helidon/health/HealthSupport.java b/health/health/src/main/java/io/helidon/health/HealthSupport.java
index 41007447e..add78b6e6 100644
--- a/health/health/src/main/java/io/helidon/health/HealthSupport.java
+++ b/health/health/src/main/java/io/helidon/health/HealthSupport.java
@@ -15,6 +15,7 @@
  */
 package io.helidon.health;
 
+import java.time.Duration;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
@@ -26,6 +27,7 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Set;
+import java.util.concurrent.TimeUnit;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import java.util.stream.Collectors;
@@ -38,7 +40,10 @@ import javax.json.JsonObjectBuilder;
 import javax.json.JsonStructure;
 
 import io.helidon.common.http.Http;
+import io.helidon.common.reactive.Single;
 import io.helidon.config.Config;
+import io.helidon.faulttolerance.Async;
+import io.helidon.faulttolerance.Timeout;
 import io.helidon.media.common.MessageBodyWriter;
 import io.helidon.media.jsonp.JsonpSupport;
 import io.helidon.webserver.Routing;
@@ -80,6 +85,8 @@ public final class HealthSupport implements Service {
     private final boolean backwardCompatible;
     private final CorsEnabledServiceHelper corsEnabledServiceHelper;
     private final MessageBodyWriter<JsonStructure> jsonpWriter = JsonpSupport.writer();
+    private final Timeout timeout;
+    private final Async async;
 
     private HealthSupport(Builder builder) {
         this.enabled = builder.enabled;
@@ -112,6 +119,10 @@ public final class HealthSupport implements Service {
             this.includedHealthChecks = Collections.emptySet();
             this.excludedHealthChecks = Collections.emptySet();
         }
+
+
+        this.timeout = Timeout.create(Duration.ofMillis(builder.timeoutMillis));
+        this.async = Async.create();
     }
 
     @Override
@@ -127,20 +138,33 @@ public final class HealthSupport implements Service {
     }
 
     private void callAll(ServerRequest req, ServerResponse res) {
-        send(res, callHealthChecks(allChecks));
+        invoke(res, allChecks);
     }
 
     private void callLiveness(ServerRequest req, ServerResponse res) {
-        send(res, callHealthChecks(livenessChecks));
+        invoke(res, livenessChecks);
     }
 
     private void callReadiness(ServerRequest req, ServerResponse res) {
-        send(res, callHealthChecks(readinessChecks));
+        invoke(res, readinessChecks);
     }
 
-    private void send(ServerResponse res, HealthResponse hres) {
-        res.status(hres.status());
-        res.send(jsonpWriter.marshall(hres.json));
+    void invoke(ServerResponse res, List<HealthCheck> healthChecks) {
+        // timeout on the asynchronous execution
+        Single<HealthResponse> result = timeout.invoke(() -> async.invoke(() -> callHealthChecks(healthChecks)));
+
+        // handle timeouts and failures in execution
+        result = result.onErrorResume(throwable -> {
+            LOGGER.log(Level.SEVERE, "Failed to call health checks", throwable);
+            HcResponse response = new HcResponse(HealthCheckResponse.down("InternalError"), true);
+            return new HealthResponse(Http.Status.INTERNAL_SERVER_ERROR_500, toJson(State.DOWN, List.of(response)));
+        });
+
+        result.thenAccept(hres -> {
+            res.status(hres.status());
+            res.send(jsonpWriter.marshall(hres.json));
+        });
+
     }
 
     HealthResponse callHealthChecks(List<HealthCheck> healthChecks) {
@@ -251,6 +275,8 @@ public final class HealthSupport implements Service {
      * Fluent API builder for {@link io.helidon.health.HealthSupport}.
      */
     public static final class Builder implements io.helidon.common.Builder<HealthSupport> {
+        // 10 seconds
+        private static final long DEFAULT_TIMEOUT_MILLIS = 10 * 1000;
         private final List<HealthCheck> allChecks = new LinkedList<>();
         private final List<HealthCheck> livenessChecks = new LinkedList<>();
         private final List<HealthCheck> readinessChecks = new LinkedList<>();
@@ -262,6 +288,7 @@ public final class HealthSupport implements Service {
         private boolean enabled = true;
         private boolean backwardCompatible = true;
         private CrossOriginConfig crossOriginConfig;
+        private long timeoutMillis = DEFAULT_TIMEOUT_MILLIS;
 
         private Builder() {
         }
@@ -371,12 +398,29 @@ public final class HealthSupport implements Service {
             config.get("exclude").asList(String.class).ifPresent(list -> list.forEach(this::addExcluded));
             config.get("exclude-classes").asList(Class.class).ifPresent(list -> list.forEach(this::addExcludedClass));
             config.get("backward-compatible").asBoolean().ifPresent(this::backwardCompatible);
+            config.get("timeout-millis").asLong().ifPresent(this::timeoutMillis);
             config.get(CORS_CONFIG_KEY)
                     .as(CrossOriginConfig::create)
                     .ifPresent(this::crossOriginConfig);
             return this;
         }
 
+        private void timeoutMillis(long aLong) {
+            this.timeoutMillis = aLong;
+        }
+
+        /**
+         * Configure overall timeout of health check call.
+         *
+         * @param timeout timeout value
+         * @param unit timeout time unit
+         * @return updated builder instance
+         */
+        public Builder timeout(long timeout, TimeUnit unit) {
+            timeoutMillis(unit.toMillis(timeout));
+            return this;
+        }
+
         /**
          * A class may be excluded from invoking health checks on it.
          * This allows configurable approach to disabling broken health-checks.
diff --git a/health/health/src/main/java/module-info.java b/health/health/src/main/java/module-info.java
index b2fe4c27c..16bdb59a7 100644
--- a/health/health/src/main/java/module-info.java
+++ b/health/health/src/main/java/module-info.java
@@ -26,6 +26,7 @@ module io.helidon.health {
     requires io.helidon.webserver.cors;
     requires io.helidon.media.jsonp;
     requires java.json;
+    requires io.helidon.faulttolerance;
 
     exports io.helidon.health;
     provides org.eclipse.microprofile.health.spi.HealthCheckResponseProvider with io.helidon.health.HealthCheckResponseProviderImpl;