Add observability chains to x-ydb-sdk-build-info

core/src/main/java/tech/ydb/core/grpc/Observability.java

@@ -0,0 +1,29 @@
+package tech.ydb.core.grpc;
+
+public final class Observability {
+    public static final String TRACING_CHAIN = "ydb-sdk-tracing";
+    public static final String METRICS_CHAIN = "ydb-sdk-metrics";
+
+    public static final String TRACING_CHAIN_VERSION = "0.1.0";
+    public static final String METRICS_CHAIN_VERSION = "0.1.0";
+
+    public static final String TRACING_CHAIN_TOKEN = TRACING_CHAIN + "/" + TRACING_CHAIN_VERSION;
+    public static final String METRICS_CHAIN_TOKEN = METRICS_CHAIN + "/" + METRICS_CHAIN_VERSION;
+
+    private Observability() {
+    }
+
+    public static String appendChains(String base, boolean tracing, boolean metrics) {
+        if (!tracing && !metrics) {
+            return base;
+        }
+        StringBuilder sb = new StringBuilder(base);
+        if (tracing) {
+            sb.append(';').append(TRACING_CHAIN_TOKEN);
+        }
+        if (metrics) {
+            sb.append(';').append(METRICS_CHAIN_TOKEN);
+        }
+        return sb.toString();
+    }
+}

core/src/main/java/tech/ydb/core/grpc/YdbHeaders.java

@@ -41,7 +41,6 @@ private YdbHeaders() { }
     public static ClientInterceptor createMetadataInterceptor(GrpcTransportBuilder builder) {
         Metadata extraHeaders = new Metadata();
         extraHeaders.put(YdbHeaders.DATABASE, builder.getDatabase());
-        extraHeaders.put(YdbHeaders.BUILD_INFO, builder.getBuildInfo());
         String appName = builder.getApplicationName();
         if (appName != null) {
             extraHeaders.put(YdbHeaders.APPLICATION_NAME, appName);

core/src/main/java/tech/ydb/core/impl/BaseGrpcTransport.java

@@ -69,6 +69,10 @@ protected BaseGrpcTransport(EndpointRecord serverEndpoint) {
 
     protected abstract GrpcChannel getChannel(GrpcRequestSettings settings);
 
+    protected String getBuildInfo() {
+        return null;
+    }
+
     protected void pessimizeEndpoint(EndpointRecord endpoint, String reason) {
         // nothing to pessimize
     }
@@ -244,6 +248,10 @@ private static Status deadlineExpiredStatus(MethodDescriptor<?, ?> method, GrpcR
 
     private Metadata makeMetadataFromSettings(GrpcRequestSettings settings, EndpointRecord endpoint) {
         Metadata metadata = new Metadata();
+        String buildInfo = getBuildInfo();
+        if (buildInfo != null) {
+            metadata.put(YdbHeaders.BUILD_INFO, buildInfo);
+        }
         String token = getAuthCallOptions().getToken();
         if (token != null) {
             metadata.put(YdbHeaders.AUTH_TICKET, token);

core/src/main/java/tech/ydb/core/impl/BuildInfoChainSupport.java

@@ -0,0 +1,22 @@
+package tech.ydb.core.impl;
+
+import tech.ydb.core.grpc.GrpcTransport;
+
+/**
+ * Internal bridge for enabling SDK observability adoption chains on the transport after it has been built.
+ * <p>
+ * Unlike tracing (configured on the builder before {@code build()}), metrics adoption becomes known only
+ * once a higher-level client is wired with a real {@code Meter}, which happens after the transport exists.
+ * This class avoids adding a public transport hook by unwrapping the default SDK implementation and calling
+ * a package-private extension point on it; non-SDK transports silently no-op.
+ */
+public final class BuildInfoChainSupport {
+    private BuildInfoChainSupport() {
+    }
+
+    public static void enableMetricsChain(GrpcTransport transport) {
+        if (transport instanceof YdbTransportImpl) {
+            ((YdbTransportImpl) transport).enableMetricsChain();
+        }
+    }
+}

core/src/main/java/tech/ydb/core/impl/FixedCallOptionsTransport.java

@@ -1,6 +1,7 @@
 package tech.ydb.core.impl;
 
 import java.util.concurrent.ScheduledExecutorService;
+import java.util.function.Supplier;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -22,18 +23,21 @@ public class FixedCallOptionsTransport extends BaseGrpcTransport {
     private final AuthCallOptions callOptions;
     private final String database;
     private final GrpcChannel channel;
+    private final Supplier<String> buildInfoSupplier;
 
     public FixedCallOptionsTransport(
             ScheduledExecutorService scheduler,
             AuthCallOptions callOptions,
             String database,
             EndpointRecord endpoint,
-            ManagedChannelFactory channelFactory) {
+            ManagedChannelFactory channelFactory,
+            Supplier<String> buildInfoSupplier) {
         super(endpoint);
         this.scheduler = scheduler;
         this.callOptions = callOptions;
         this.database = database;
         this.channel = new GrpcChannel(endpoint, channelFactory);
+        this.buildInfoSupplier = buildInfoSupplier;
     }
 
     @Override
@@ -46,6 +50,11 @@ public String getDatabase() {
         return database;
     }
 
+    @Override
+    protected String getBuildInfo() {
+        return buildInfoSupplier.get();
+    }
+
     @Override
     protected void shutdown() {
         channel.shutdown();

core/src/main/java/tech/ydb/core/impl/YdbTransportImpl.java

@@ -15,12 +15,14 @@
 import tech.ydb.core.grpc.GrpcRequestSettings;
 import tech.ydb.core.grpc.GrpcTransport;
 import tech.ydb.core.grpc.GrpcTransportBuilder;
+import tech.ydb.core.grpc.Observability;
 import tech.ydb.core.impl.auth.AuthCallOptions;
 import tech.ydb.core.impl.pool.EndpointPool;
 import tech.ydb.core.impl.pool.EndpointRecord;
 import tech.ydb.core.impl.pool.GrpcChannel;
 import tech.ydb.core.impl.pool.GrpcChannelPool;
 import tech.ydb.core.impl.pool.ManagedChannelFactory;
+import tech.ydb.core.tracing.NoopTracer;
 import tech.ydb.core.tracing.Tracer;
 
 /**
@@ -38,13 +40,19 @@ public class YdbTransportImpl extends BaseGrpcTransport {
     private final YdbDiscovery discovery;
     private final Tracer tracer;
 
+    private final String baseBuildInfo;
+    private final boolean tracingChainEnabled;
+    private volatile boolean metricsChainEnabled;
+
     public YdbTransportImpl(GrpcTransportBuilder builder) {
         super(builder);
         BalancingSettings balancingSettings = getBalancingSettings(builder);
         Duration discoveryTimeout = Duration.ofMillis(builder.getDiscoveryTimeoutMillis());
 
         this.database = Strings.nullToEmpty(builder.getDatabase());
         this.tracer = builder.getTracer();
+        this.baseBuildInfo = builder.getBuildInfo();
+        this.tracingChainEnabled = tracer != NoopTracer.getInstance();
 
         logger.info("Create YDB transport with endpoint {} and {}", serverEndpoint, balancingSettings);
 
@@ -124,6 +132,19 @@ public Tracer getTracer() {
         return tracer;
     }
 
+    void enableMetricsChain() {
+        this.metricsChainEnabled = true;
+    }
+
+    @Override
+    protected String getBuildInfo() {
+        return baseBuildInfo;
+    }
+
+    private String discoveryBuildInfo() {
+        return Observability.appendChains(baseBuildInfo, tracingChainEnabled, metricsChainEnabled);
+    }
+
     @Override
     public AuthCallOptions getAuthCallOptions() {
         return callOptions;
@@ -167,7 +188,14 @@ public CompletableFuture<Boolean> handleEndpoints(List<EndpointRecord> endpoints
 
         @Override
         public GrpcTransport createDiscoveryTransport() {
-            return new FixedCallOptionsTransport(scheduler, callOptions, database, serverEndpoint, channelFactory);
+            return new FixedCallOptionsTransport(
+                    scheduler,
+                    callOptions,
+                    database,
+                    serverEndpoint,
+                    channelFactory,
+                    YdbTransportImpl.this::discoveryBuildInfo
+            );
         }
     }
 }

core/src/main/java/tech/ydb/core/impl/auth/AuthCallOptions.java

@@ -38,7 +38,8 @@ public AuthCallOptions(
 
         AuthRpcProvider<? super GrpcAuthRpc> authProvider = builder.getAuthProvider();
         if (authProvider != null) {
-            GrpcAuthRpc rpc = new GrpcAuthRpc(endpoints, scheduler, builder.getDatabase(), channelFactory);
+            GrpcAuthRpc rpc = new GrpcAuthRpc(
+                    endpoints, scheduler, builder.getDatabase(), channelFactory, builder.getBuildInfo());
             authIdentity = builder.getAuthProvider().createAuthIdentity(rpc);
         } else {
             authIdentity = null;

core/src/main/java/tech/ydb/core/impl/auth/GrpcAuthRpc.java

@@ -19,20 +19,23 @@ public class GrpcAuthRpc {
     private final ScheduledExecutorService scheduler;
     private final String database;
     private final ManagedChannelFactory channelFactory;
+    private final String buildInfo;
     private final AtomicInteger endpointIdx = new AtomicInteger();
 
     public GrpcAuthRpc(
             List<EndpointRecord> endpoints,
             ScheduledExecutorService scheduler,
             String database,
-            ManagedChannelFactory channelFactory) {
+            ManagedChannelFactory channelFactory,
+            String buildInfo) {
         if (endpoints == null || endpoints.isEmpty()) {
             throw new IllegalStateException("Empty endpoints list for auth rpc");
         }
         this.endpoints = endpoints;
         this.scheduler = scheduler;
         this.database = database;
         this.channelFactory = channelFactory;
+        this.buildInfo = buildInfo;
     }
 
     public ExecutorService getExecutor() {
@@ -55,13 +58,15 @@ public void changeEndpoint() {
     }
 
     public GrpcTransport createTransport() {
-        // For auth provider we use transport without auth (with default CallOptions)
+        // For auth provider we use transport without auth (with default CallOptions).
+        // Auth requests report only the base build-info chain, matching regular (non-discovery) requests.
         return new FixedCallOptionsTransport(
                 scheduler,
                 new AuthCallOptions(),
                 database,
                 endpoints.get(endpointIdx.get()),
-                channelFactory
+                channelFactory,
+                () -> buildInfo
         );
     }
 

core/src/test/java/tech/ydb/core/grpc/ObservabilityTest.java

@@ -0,0 +1,41 @@
+package tech.ydb.core.grpc;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class ObservabilityTest {
+
+    private static final String BASE = "ydb-java-sdk/1.2.3";
+
+    @Test
+    public void disabledObservabilityLeavesBaseUntouched() {
+        Assert.assertEquals(BASE, Observability.appendChains(BASE, false, false));
+    }
+
+    @Test
+    public void tracingOnlyAppendsTracingChain() {
+        Assert.assertEquals(
+                BASE + ";" + Observability.TRACING_CHAIN_TOKEN,
+                Observability.appendChains(BASE, true, false));
+    }
+
+    @Test
+    public void metricsOnlyAppendsMetricsChain() {
+        Assert.assertEquals(
+                BASE + ";" + Observability.METRICS_CHAIN_TOKEN,
+                Observability.appendChains(BASE, false, true));
+    }
+
+    @Test
+    public void bothChainsKeepTracingBeforeMetrics() {
+        Assert.assertEquals(
+                BASE + ";" + Observability.TRACING_CHAIN_TOKEN + ";" + Observability.METRICS_CHAIN_TOKEN,
+                Observability.appendChains(BASE, true, true));
+    }
+
+    @Test
+    public void chainTokensFollowNameSlashVersionFormat() {
+        Assert.assertEquals("ydb-sdk-tracing/0.1.0", Observability.TRACING_CHAIN_TOKEN);
+        Assert.assertEquals("ydb-sdk-metrics/0.1.0", Observability.METRICS_CHAIN_TOKEN);
+    }
+}

core/src/test/java/tech/ydb/core/impl/MockedCall.java

@@ -15,15 +15,25 @@
 
 public abstract class MockedCall<ResT, RespT> extends ClientCall<ResT, RespT> {
     private final Executor executor;
+    private volatile Metadata lastHeaders;
 
     protected MockedCall(Executor executor) {
         this.executor = executor;
     }
 
     protected abstract void complete(Listener<RespT> listener);
 
+    /**
+     * Returns the request headers captured on the most recent {@link #start} call, or {@code null} if the
+     * call has not been started yet. Handy for asserting per-request metadata such as x-ydb-sdk-build-info.
+     */
+    public Metadata getLastHeaders() {
+        return lastHeaders;
+    }
+
     @Override
     public void start(Listener<RespT> listener, Metadata headers) {
+        this.lastHeaders = headers;
         executor.execute(() -> complete(listener));
     }
 

core/src/test/java/tech/ydb/core/impl/YdbDiscoveryTest.java

@@ -255,7 +255,9 @@ public Instant instant() {
         @Override
         public GrpcTransport createDiscoveryTransport() {
             EndpointRecord discovery = new EndpointRecord("unknown", 1234);
-            return new FixedCallOptionsTransport(scheduler, new AuthCallOptions(), "/test", discovery, channelFactory);
+            return new FixedCallOptionsTransport(
+                    scheduler, new AuthCallOptions(), "/test", discovery, channelFactory, () -> null
+            );
         }
 
         @Override