OAP gRPC-Client support Health Check and [Break Change] Health Check make response 1 represents healthy, 0 represents unhealthy.

docs/en/changes/changes.md

@@ -36,6 +36,8 @@
 * chore: add `toString` implementation for `StorageID`.
 * chore: add a warning log when connecting to ES takes too long.
 * Fix the query time range in the metadata API.
+* OAP gRPC-Client support `Health Check`.
+* [Break Change] `Health Check` make response 1 represents healthy, 0 represents unhealthy.
 
 #### UI
 

docs/en/setup/backend/backend-health-check.md

@@ -36,7 +36,7 @@ If the OAP server is healthy, the response should be
 {
   "data": {
     "checkHealth": {
-      "score": 0,
+      "score": 1,
       "details": ""
     }
   }
@@ -49,7 +49,7 @@ If some modules are unhealthy (e.g. storage H2 is down), then the result may loo
 {
   "data": {
     "checkHealth": {
-      "score": 1,
+      "score": 0,
       "details": "storage_h2,"
     }
   }

oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/query/type/HealthStatus.java

@@ -26,7 +26,7 @@
 @Setter
 @ToString
 public class HealthStatus {
-    // score == 0 means healthy, otherwise it's unhealthy.
+    // score == 1 means healthy, otherwise it's unhealthy.
     private int score;
     private String details;
 }

oap-server/server-health-checker/src/main/java/org/apache/skywalking/oap/server/health/checker/provider/HealthCheckerHttpService.java

@@ -37,7 +37,7 @@ public HttpResponse healthcheck(ServiceRequestContext ctx, HttpRequest req) thro
         final var status = healthQueryService.checkHealth();
         log.info("Health status: {}", status);
 
-        if (status.getScore() == 0) {
+        if (status.getScore() == 1) {
             return HttpResponse.of(HttpStatus.OK);
         }
         return HttpResponse.of(HttpStatus.SERVICE_UNAVAILABLE);

oap-server/server-health-checker/src/main/java/org/apache/skywalking/oap/server/health/checker/provider/HealthCheckerProvider.java

@@ -25,8 +25,8 @@
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
-import java.util.stream.Collectors;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.skywalking.oap.server.core.CoreModule;
 import org.apache.skywalking.oap.server.core.server.HTTPHandlerRegister;
@@ -100,16 +100,18 @@ public void onInitialized(final HealthCheckerConfig initialized) {
     @Override public void notifyAfterCompleted() throws ServiceNotProvidedException, ModuleStartException {
         ses.scheduleAtFixedRate(() -> {
             StringBuilder unhealthyModules = new StringBuilder();
-            score.set(Stream.ofAll(collector.collect())
-                    .flatMap(metricFamily -> metricFamily.samples)
-                    .filter(sample -> metricsCreator.isHealthCheckerMetrics(sample.name))
-                    .peek(sample -> {
-                        if (sample.value > 0.0) {
-                            unhealthyModules.append(metricsCreator.extractModuleName(sample.name)).append(",");
-                        }
-                    })
-                    .map(sample -> sample.value)
-                    .collect(Collectors.summingDouble(Double::doubleValue)));
+            AtomicBoolean hasUnhealthyModule = new AtomicBoolean(false);
+            Stream.ofAll(collector.collect())
+                                        .flatMap(metricFamily -> metricFamily.samples)
+                                        .filter(sample -> metricsCreator.isHealthCheckerMetrics(sample.name))
+                                        .forEach(sample -> {
+                                            if (sample.value < 1) {
+                                                unhealthyModules.append(metricsCreator.extractModuleName(sample.name)).append(",");
+                                                hasUnhealthyModule.set(true);
+                                            }
+                                        });
+
+            score.set(hasUnhealthyModule.get() ? 0 : 1);
             details.set(unhealthyModules.toString());
             },
             2, config.getCheckIntervalSeconds(), TimeUnit.SECONDS);

oap-server/server-library/library-client/src/main/java/org/apache/skywalking/oap/server/library/client/grpc/GRPCClient.java

@@ -18,16 +18,23 @@
 
 package org.apache.skywalking.oap.server.library.client.grpc;
 
+import io.grpc.ConnectivityState;
 import io.grpc.ManagedChannel;
 import io.grpc.ManagedChannelBuilder;
 import io.grpc.netty.NettyChannelBuilder;
 import io.netty.handler.ssl.SslContext;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
 import lombok.Getter;
 import org.apache.skywalking.oap.server.library.client.Client;
+import org.apache.skywalking.oap.server.library.client.healthcheck.DelegatedHealthChecker;
+import org.apache.skywalking.oap.server.library.client.healthcheck.HealthCheckable;
+import org.apache.skywalking.oap.server.library.util.HealthChecker;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-public class GRPCClient implements Client {
+public class GRPCClient implements Client, HealthCheckable {
 
     private static final Logger LOGGER = LoggerFactory.getLogger(GRPCClient.class);
 
@@ -41,6 +48,12 @@ public class GRPCClient implements Client {
 
     private ManagedChannel channel;
 
+    private final DelegatedHealthChecker healthChecker = new DelegatedHealthChecker();
+
+    private ScheduledExecutorService healthCheckExecutor;
+
+    private boolean enableHealthCheck = false;
+
     public GRPCClient(String host, int port) {
         this.host = host;
         this.port = port;
@@ -55,9 +68,12 @@ public GRPCClient(String host, int port, final SslContext sslContext) {
     public void connect() {
         if (sslContext == null) {
             channel = ManagedChannelBuilder.forAddress(host, port).usePlaintext().build();
-            return;
+        } else {
+            channel = NettyChannelBuilder.forAddress(host, port).sslContext(sslContext).build();
+        }
+        if (enableHealthCheck) {
+            checkHealth();
         }
-        channel = NettyChannelBuilder.forAddress(host, port).sslContext(sslContext).build();
     }
 
     @Override
@@ -66,6 +82,12 @@ public void shutdown() {
             channel.shutdownNow();
         } catch (Throwable t) {
             LOGGER.error(t.getMessage(), t);
+        } finally {
+            if (healthCheckExecutor != null) {
+                healthCheckExecutor.shutdownNow();
+                healthChecker.unHealth("gRPC channel is shutting down. Host: " + host + ", Port: " + port);
+                healthCheckExecutor = null;
+            }
         }
     }
 
@@ -77,4 +99,48 @@ public ManagedChannel getChannel() {
     public String toString() {
         return host + ":" + port;
     }
+
+    /**
+     * Must register a HealthChecker before calling connect() if you want to enable health check.
+     * If the channel is shutdown by client side, the health check will not be performed.
+     * Note: If you register a `org.apache.skywalking.oap.server.telemetry.api.HealthCheckMetrics` here
+     * and the metric name start with `org.apache.skywalking.oap.server.telemetry.api.MetricsCreator.HEALTH_METRIC_PREFIX`,
+     * this healthy status will be included in the whole OAP health evaluate.
+     * @param healthChecker HealthChecker to be registered.
+     */
+    @Override
+    public void registerChecker(final HealthChecker healthChecker) {
+        this.healthChecker.register(healthChecker);
+        this.enableHealthCheck = true;
+    }
+
+    private void checkHealth() {
+        if (healthCheckExecutor == null) {
+            healthCheckExecutor = Executors.newSingleThreadScheduledExecutor();
+            healthCheckExecutor.scheduleAtFixedRate(
+                () -> {
+                    ConnectivityState currentState = channel.getState(true); // true means try to connect
+                    handleStateChange(currentState);
+                }, 5, 10, TimeUnit.SECONDS
+            );
+        }
+    }
+
+    private void handleStateChange(ConnectivityState newState) {
+        switch (newState) {
+            case READY:
+            case IDLE:
+                this.healthChecker.health();
+                break;
+            case CONNECTING:
+                this.healthChecker.unHealth("gRPC connecting, waiting for ready. Host: " + host + ", Port: " + port);
+                break;
+            case TRANSIENT_FAILURE:
+                this.healthChecker.unHealth("gRPC connection failed, will retry. Host: " + host + ", Port: " + port);
+                break;
+            case SHUTDOWN:
+                this.healthChecker.unHealth("gRPC channel is shutting down. Host: " + host + ", Port: " + port);
+                break;
+        }
+    }
 }

oap-server/server-telemetry/telemetry-api/src/main/java/org/apache/skywalking/oap/server/telemetry/api/HealthCheckMetrics.java

@@ -36,18 +36,18 @@ public HealthCheckMetrics(GaugeMetrics metrics) {
 
     @Override
     public void health() {
-        metrics.setValue(0);
+        metrics.setValue(1);
     }
 
     @Override
     public void unHealth(Throwable t) {
         log.error("Health check fails", t);
-        metrics.setValue(1);
+        metrics.setValue(0);
     }
 
     @Override
     public void unHealth(String reason) {
         log.warn("Health check fails. reason: {}", reason);
-        metrics.setValue(1);
+        metrics.setValue(0);
     }
 }

oap-server/server-telemetry/telemetry-api/src/main/java/org/apache/skywalking/oap/server/telemetry/api/MetricsCreator.java

@@ -53,7 +53,7 @@ HistogramMetrics createHistogramMetric(String name, String tips, MetricsTag.Keys
     default HealthCheckMetrics createHealthCheckerGauge(String name, MetricsTag.Keys tagKeys, MetricsTag.Values tagValues) {
         Preconditions.checkArgument(!Strings.isNullOrEmpty(name), "Require non-null or empty metric name");
         return new HealthCheckMetrics(createGauge(Strings.lenientFormat("%s%s", HEALTH_METRIC_PREFIX, name),
-            Strings.lenientFormat("%s health check", name),
+            Strings.lenientFormat("%s health check. 1 health, 0 not health, -1 unknown", name),
             tagKeys, tagValues));
     }