Add HttpTracing(Client|Service)Builder

Motivation:
A user currently has to build `Tracing` by him/herself and set `currentTraceContext` manually.
We could add `HttpTracing(Client|Service)Builder` which builds a `Tracing` for a user.

Modifications:
- Add `HttpTracing(Client|Service)`Builder
- May fix a bug where `decorateScope` is not called
- Deprecation
  - The consturctor of `HttpTracingService` is not public anymore. A user should use the builder or the static factory method.

Result:
- A user can easidy build an `HttpTracing(Client|Service)` using builders.

core/src/main/java/com/linecorp/armeria/common/DefaultAggregatedHttpRequest.java

@@ -16,6 +16,9 @@
 
 package com.linecorp.armeria.common;
 
+import com.google.common.base.MoreObjects;
+import com.google.common.base.MoreObjects.ToStringHelper;
+
 final class DefaultAggregatedHttpRequest extends AbstractAggregatedHttpMessage
         implements AggregatedHttpRequest {
 
@@ -51,4 +54,43 @@ public String scheme() {
     public String authority() {
         return headers.authority();
     }
+
+    @Override
+    public int hashCode() {
+        int result = headers().hashCode();
+        result = 31 * result + content().hashCode();
+        result = 31 * result + trailers().hashCode();
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+
+        if (!(obj instanceof AggregatedHttpRequest)) {
+            return false;
+        }
+
+        final AggregatedHttpRequest that = (AggregatedHttpRequest) obj;
+
+        return headers().equals(that.headers()) &&
+               content().equals(that.content()) &&
+               trailers().equals(that.trailers());
+    }
+
+    @Override
+    public String toString() {
+        final ToStringHelper helper = MoreObjects.toStringHelper(this);
+
+        helper.add("headers", headers())
+              .add("content", content());
+
+        if (!trailers().isEmpty()) {
+            helper.add("trailers", trailers());
+        }
+
+        return helper.toString();
+    }
 }

core/src/main/java/com/linecorp/armeria/common/DefaultAggregatedHttpResponse.java

@@ -50,21 +50,12 @@ public ResponseHeaders headers() {
     }
 
     @Override
-    public String toString() {
-        final ToStringHelper helper = MoreObjects.toStringHelper(this);
-
-        if (!informationals().isEmpty()) {
-            helper.add("informationals", informationals());
-        }
-
-        helper.add("headers", headers())
-              .add("content", content());
-
-        if (!trailers().isEmpty()) {
-            helper.add("trailers", trailers());
-        }
-
-        return helper.toString();
+    public int hashCode() {
+        int result = informationals().hashCode();
+        result = 31 * result + headers().hashCode();
+        result = 31 * result + content().hashCode();
+        result = 31 * result + trailers().hashCode();
+        return result;
     }
 
     @Override
@@ -73,11 +64,11 @@ public boolean equals(Object obj) {
             return true;
         }
 
-        if (!(obj instanceof DefaultAggregatedHttpResponse)) {
+        if (!(obj instanceof AggregatedHttpResponse)) {
             return false;
         }
 
-        final DefaultAggregatedHttpResponse that = (DefaultAggregatedHttpResponse) obj;
+        final AggregatedHttpResponse that = (AggregatedHttpResponse) obj;
 
         return informationals().equals(that.informationals()) &&
                headers().equals(that.headers()) &&
@@ -86,11 +77,20 @@ public boolean equals(Object obj) {
     }
 
     @Override
-    public int hashCode() {
-        int result = informationals().hashCode();
-        result = 31 * result + headers().hashCode();
-        result = 31 * result + content().hashCode();
-        result = 31 * result + trailers().hashCode();
-        return result;
+    public String toString() {
+        final ToStringHelper helper = MoreObjects.toStringHelper(this);
+
+        if (!informationals().isEmpty()) {
+            helper.add("informationals", informationals());
+        }
+
+        helper.add("headers", headers())
+              .add("content", content());
+
+        if (!trailers().isEmpty()) {
+            helper.add("trailers", trailers());
+        }
+
+        return helper.toString();
     }
 }

core/src/main/java/com/linecorp/armeria/common/DefaultRpcRequest.java

@@ -120,11 +120,11 @@ public boolean equals(Object obj) {
             return true;
         }
 
-        if (!(obj instanceof DefaultRpcRequest)) {
+        if (!(obj instanceof RpcRequest)) {
             return false;
         }
 
-        final DefaultRpcRequest that = (DefaultRpcRequest) obj;
+        final RpcRequest that = (RpcRequest) obj;
         return method().equals(that.method()) &&
                params().equals(that.params());
     }

core/src/main/java/com/linecorp/armeria/common/sse/DefaultServerSentEvent.java

@@ -96,16 +96,16 @@ public boolean equals(Object obj) {
             return true;
         }
 
-        if (!(obj instanceof DefaultServerSentEvent)) {
+        if (!(obj instanceof ServerSentEvent)) {
             return false;
         }
 
-        final DefaultServerSentEvent that = (DefaultServerSentEvent) obj;
-        return Objects.equals(id, that.id) &&
-               Objects.equals(event, that.event) &&
-               Objects.equals(retry, that.retry) &&
-               Objects.equals(comment, that.comment) &&
-               Objects.equals(data, that.data);
+        final ServerSentEvent that = (ServerSentEvent) obj;
+        return Objects.equals(id, that.id()) &&
+               Objects.equals(event, that.event()) &&
+               Objects.equals(retry, that.retry()) &&
+               Objects.equals(comment, that.comment()) &&
+               Objects.equals(data, that.data());
     }
 
     @Override

site/src/sphinx/advanced-zipkin.rst

@@ -3,4 +3,4 @@
 Zipkin integration
 ==================
 
-TBW - See :api:`HttpTracingService` and :api:`HttpTracingClient`
+TBW - See :api:`TracingService` and :api:`TracingClient`

zipkin/src/main/java/com/linecorp/armeria/client/tracing/HttpTracingClient.java

@@ -16,7 +16,7 @@
 
 package com.linecorp.armeria.client.tracing;
 
-import static com.linecorp.armeria.common.tracing.RequestContextCurrentTraceContext.ensureScopeUsesRequestContext;
+import static com.linecorp.armeria.client.tracing.TracingClient.checkTracing;
 
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
@@ -54,32 +54,34 @@
  *
  * <p>This decorator puts trace data into HTTP headers. The specifications of header names and its values
  * correspond to <a href="http://zipkin.io/">Zipkin</a>.
+ *
+ * @deprecated Use {@link TracingClient}.
  */
-public class HttpTracingClient extends SimpleDecoratingClient<HttpRequest, HttpResponse> {
+@Deprecated
+public final class HttpTracingClient extends SimpleDecoratingClient<HttpRequest, HttpResponse> {
 
     private static final Logger logger = LoggerFactory.getLogger(HttpTracingClient.class);
 
     /**
      * Creates a new tracing {@link Client} decorator using the specified {@link Tracing} instance.
+     *
+     * @deprecated Use {@link TracingClient#newDecorator(Tracing)}.
      */
+    @Deprecated
     public static Function<Client<HttpRequest, HttpResponse>, HttpTracingClient> newDecorator(Tracing tracing) {
         return newDecorator(tracing, null);
     }
 
     /**
      * Creates a new tracing {@link Client} decorator using the specified {@link Tracing} instance
-     * and remote service name.
+     * and the remote service name.
+     *
+     * @deprecated Use {@link TracingClient#newDecorator(Tracing, String)}.
      */
+    @Deprecated
     public static Function<Client<HttpRequest, HttpResponse>, HttpTracingClient> newDecorator(
-            Tracing tracing,
-            @Nullable String remoteServiceName) {
-        try {
-            ensureScopeUsesRequestContext(tracing);
-        } catch (IllegalStateException e) {
-            logger.warn("{} - it is appropriate to ignore this warning if this client is not being used " +
-                        "inside an Armeria server (e.g., this is a normal spring-mvc tomcat server).",
-                        e.getMessage());
-        }
+            Tracing tracing, @Nullable String remoteServiceName) {
+        checkTracing(tracing);
         return delegate -> new HttpTracingClient(delegate, tracing, remoteServiceName);
     }
 
@@ -91,8 +93,8 @@ public static Function<Client<HttpRequest, HttpResponse>, HttpTracingClient> new
     /**
      * Creates a new instance.
      */
-    protected HttpTracingClient(Client<HttpRequest, HttpResponse> delegate, Tracing tracing,
-                                @Nullable String remoteServiceName) {
+    HttpTracingClient(Client<HttpRequest, HttpResponse> delegate, Tracing tracing,
+                      @Nullable String remoteServiceName) {
         super(delegate);
         tracer = tracing.tracer();
         injector = tracing.propagationFactory().create(AsciiStringKeyFactory.INSTANCE)