Finish some grpc client codes.

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/boot/BootService.java

 package org.skywalking.apm.agent.core.boot;
 
 /**
- * The <code>BootService</code> is an interface to all services, which need to boot when plugin mechanism begins to
+ * The <code>BootService</code> is an interface to all remote, which need to boot when plugin mechanism begins to
  * work.
  * {@link #bootUp()} will be called when <code>BootService</code> start up.
  *

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/ids/DistributedTraceId.java

@@ -5,7 +5,7 @@ package org.skywalking.apm.agent.core.context.ids;
  * <p>
  * This call chain has an unique (service) entrance,
  * <p>
- * such as: Service : http://www.skywalking.com/cust/query, all the services, called behind this service, rest services,
+ * such as: Service : http://www.skywalking.com/cust/query, all the remote, called behind this service, rest remote,
  * db executions, are using the same <code>DistributedTraceId</code> even in different JVM.
  * <p>
  * The <code>DistributedTraceId</code> contains only one string, and can NOT be reset, creating a new instance is the

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/trace/AbstractSpan.java

@@ -13,11 +13,11 @@ public interface AbstractSpan {
      * Set the component id, which defines in {@link org.skywalking.apm.network.trace.component.ComponentsDefine}
      * @param component
      */
-    void setComponent(Component component);
+    AbstractSpan setComponent(Component component);
 
-    void setComponent(String componentName);
+    AbstractSpan setComponent(String componentName);
 
-    void setLayer(SpanLayer layer);
+    AbstractSpan setLayer(SpanLayer layer);
 
     /**
      * Set a key:value tag on the Span.
@@ -34,7 +34,7 @@ public interface AbstractSpan {
      */
     AbstractSpan log(Throwable t);
 
-    void errorOccurred();
+    AbstractSpan errorOccurred();
 
     /**
      * @return true if the actual span is an entry span.

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/trace/AbstractTracingSpan.java

@@ -108,8 +108,9 @@ public abstract class AbstractTracingSpan implements AbstractSpan {
         return this;
     }
 
-    public void errorOccurred() {
+    public AbstractSpan errorOccurred() {
         this.errorOccurred = true;
+        return this;
     }
 
     public int getSpanId() {
@@ -121,17 +122,20 @@ public abstract class AbstractTracingSpan implements AbstractSpan {
     }
 
     @Override
-    public void setLayer(SpanLayer layer) {
+    public AbstractSpan setLayer(SpanLayer layer) {
         this.layer = layer;
+        return this;
     }
 
     @Override
-    public void setComponent(Component component) {
+    public AbstractSpan setComponent(Component component) {
         this.componentId = component.getId();
+        return this;
     }
 
     @Override
-    public void setComponent(String componentName) {
+    public AbstractSpan setComponent(String componentName) {
         this.componentName = componentName;
+        return this;
     }
 }

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/trace/ExitSpan.java

@@ -3,10 +3,10 @@ package org.skywalking.apm.agent.core.context.trace;
 import org.skywalking.apm.agent.core.dictionary.DictionaryUtil;
 
 /**
- * The <code>ExitSpan</code> represents a service consumer point, such as Feign, Okhttp client for a Http service.
+ * The <code>ExitSpan</code> represents a service consumer point, such as Feign, Okhttp discovery for a Http service.
  *
  * It is an exit point or a leaf span(our old name) of trace tree.
- * In a single rpc call, because of a combination of client libs, there maybe contain multi exit point.
+ * In a single rpc call, because of a combination of discovery libs, there maybe contain multi exit point.
  *
  * The <code>ExitSpan</code> only presents the first one.
  *

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/trace/NoopSpan.java

 package org.skywalking.apm.agent.core.context.trace;
 
 import org.skywalking.apm.agent.core.context.IgnoredTracerContext;
+import org.skywalking.apm.network.trace.component.Component;
 
 /**
  * The <code>NoopSpan</code> represents a span implementation without any actual operation.
@@ -18,10 +19,26 @@ public class NoopSpan implements AbstractSpan {
         return this;
     }
 
+    @Override public AbstractSpan errorOccurred() {
+        return null;
+    }
+
     public void finish(){
 
     }
 
+    @Override public AbstractSpan setComponent(Component component) {
+        return this;
+    }
+
+    @Override public AbstractSpan setComponent(String componentName) {
+        return this;
+    }
+
+    @Override public AbstractSpan setLayer(SpanLayer layer) {
+        return this;
+    }
+
     @Override
     public AbstractSpan tag(String key, String value) {
         return this;

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/client/CollectorDiscoveryService.java → apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/discovery/CollectorDiscoveryService.java

-package org.skywalking.apm.agent.core.client;
+package org.skywalking.apm.agent.core.discovery;
 
 import org.skywalking.apm.agent.core.boot.StatusBootService;
+import org.skywalking.apm.agent.core.remote.DiscoveryRestServiceClient;
 
 /**
  * The <code>CollectorDiscoveryService</code> is responsible for start {@link DiscoveryRestServiceClient}.

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/client/DiscoveryRestServiceClient.java → apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/remote/DiscoveryRestServiceClient.java

-package org.skywalking.apm.agent.core.client;
+package org.skywalking.apm.agent.core.remote;
 
 import com.google.gson.Gson;
 import com.google.gson.JsonArray;

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/remote/GRPCChannelManager.java

+package org.skywalking.apm.agent.core.remote;
+
+import io.grpc.ManagedChannel;
+import io.grpc.ManagedChannelBuilder;
+import io.grpc.internal.DnsNameResolverProvider;
+import io.grpc.netty.NettyChannelBuilder;
+import org.skywalking.apm.agent.core.boot.BootService;
+import org.skywalking.apm.logging.ILog;
+import org.skywalking.apm.logging.LogManager;
+
+/**
+ * @author wusheng
+ */
+public class GRPCChannelManager implements BootService, Runnable {
+    private static final ILog logger = LogManager.getLogger(DiscoveryRestServiceClient.class);
+
+    private volatile Thread channelManagerThread = null;
+    private volatile ManagedChannel managedChannel = null;
+
+    @Override
+    public void bootUp() throws Throwable {
+        this.startupInBackground();
+    }
+
+    private void startupInBackground() {
+        if (channelManagerThread == null || !channelManagerThread.isAlive()) {
+            synchronized (this) {
+                if (channelManagerThread == null || !channelManagerThread.isAlive()) {
+                    if (managedChannel == null || managedChannel.isTerminated() || managedChannel.isShutdown()) {
+                        managedChannel.shutdownNow();
+                        Thread channelManagerThread = new Thread(this, "ChannelManagerThread");
+                        channelManagerThread.setDaemon(true);
+                        channelManagerThread.start();
+                    }
+                }
+            }
+        }
+    }
+
+    @Override
+    public void run() {
+        ManagedChannelBuilder<?> channelBuilder =
+            NettyChannelBuilder.forAddress("127.0.0.1", 808)
+                .nameResolverFactory(new DnsNameResolverProvider())
+                .maxInboundMessageSize(1024 * 1024 * 50)
+                .usePlaintext(true);
+        managedChannel = channelBuilder.build();
+    }
+
+    public static void main(String[] args) throws Throwable {
+        new GRPCChannelManager().bootUp();
+
+        Thread.sleep(60 * 1000);
+    }
+}

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/client/RESTResponseStatusError.java → apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/remote/RESTResponseStatusError.java

-package org.skywalking.apm.agent.core.client;
+package org.skywalking.apm.agent.core.remote;
 
 /**
- * The <code>RESTResponseStatusError</code> represents the REST-Service client got an unexpected response code.
+ * The <code>RESTResponseStatusError</code> represents the REST-Service discovery got an unexpected response code.
  * Most likely, the response code is not 200.
  *
  * @author wusheng

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/remote/TraceSegmentServiceClient.java

+package org.skywalking.apm.agent.core.remote;
+
+/**
+ * @author wusheng
+ */
+public class TraceSegmentServiceClient {
+    public void start() {
+
+    }
+
+    public void switchChannel(){
+
+    }
+}

apm-sniffer/apm-agent-core/src/main/resources/META-INF/services/org.skywalking.apm.agent.core.boot.BootService

 org.skywalking.apm.agent.core.datacarrier.DataBufferService
 org.skywalking.apm.agent.core.context.ContextManager
-org.skywalking.apm.agent.core.client.CollectorDiscoveryService
+org.skywalking.apm.agent.core.discovery.CollectorDiscoveryService
 org.skywalking.apm.agent.core.sampling.SamplingService
+org.skywalking.apm.agent.core.remote.GRPCChannelManager

apm-sniffer/apm-agent-core/src/test/java/org/skywalking/apm/agent/core/client/HTTPRestServiceTestApp.java → apm-sniffer/apm-agent-core/src/test/java/org/skywalking/apm/agent/core/discovery/HTTPRestServiceTestApp.java

-package org.skywalking.apm.agent.core.client;
+package org.skywalking.apm.agent.core.discovery;
 
 import org.apache.http.client.methods.CloseableHttpResponse;
 import org.apache.http.client.methods.HttpPost;
@@ -19,7 +19,7 @@ import java.io.IOException;
 
 /**
  * This is a small application, test for http restful service.
- * Use APACHE HttpClient as client, nanohttpd as server.
+ * Use APACHE HttpClient as discovery, nanohttpd as server.
  *
  * @author wusheng
  */

apm-sniffer/apm-sdk-plugin/dubbo-plugin/src/main/java/org/skywalking/apm/plugin/dubbox/BugFixActive.java

@@ -14,7 +14,7 @@ public final class BugFixActive {
     private static boolean ACTIVE = false;
 
     /**
-     * Set active status, before startup dubbo services.
+     * Set active status, before startup dubbo remote.
      */
     public static void active() {
         BugFixActive.ACTIVE = true;

apm-sniffer/apm-sdk-plugin/feign-default-http-9.x-plugin/src/main/java/org/skywalking/apm/plugin/feign/http/v9/define/DefaultHttpClientInstrumentation.java

@@ -12,8 +12,8 @@ import static net.bytebuddy.matcher.ElementMatchers.named;
 /**
  * {@link DefaultHttpClientInstrumentation} presents that skywalking intercepts {@link
  * feign.Client.Default#execute(feign.Request, feign.Request.Options)} by using {@link DefaultHttpClientInterceptor}.
- * If feign did't run in default mode, the instrumentation depend on the http client implementation.
- * e.g. okhttp client implementation depend on okhttp-plugin.
+ * If feign did't run in default mode, the instrumentation depend on the http discovery implementation.
+ * e.g. okhttp discovery implementation depend on okhttp-plugin.
  *
  * @author pengys5
  */

apm-sniffer/apm-sdk-plugin/feign-default-http-9.x-plugin/src/test/java/org/skywalking/apm/plugin/feign/http/v9/DefaultHttpClientInterceptorTest.java

@@ -104,7 +104,7 @@ public class DefaultHttpClientInterceptorTest {
         Assert.assertEquals("skywalking.org", span.getPeerHost());
         Assert.assertEquals(-1, span.getPort());
         Assert.assertEquals("FeignDefaultHttp", StringTagReader.get(span, Tags.COMPONENT));
-        Assert.assertEquals("client", StringTagReader.get(span, Tags.SPAN_KIND));
+        Assert.assertEquals("discovery", StringTagReader.get(span, Tags.SPAN_KIND));
         Assert.assertEquals("", StringTagReader.get(span, Tags.URL));
     }
 

apm-sniffer/apm-sdk-plugin/httpClient-4.x-plugin/src/main/java/org/skywalking/apm/plugin/httpClient/v4/define/AbstractHttpClientInstrumentation.java

@@ -18,7 +18,7 @@ import static net.bytebuddy.matcher.ElementMatchers.named;
  */
 public class AbstractHttpClientInstrumentation extends HttpClientInstrumentation {
 
-    private static final String ENHANCE_CLASS = "org.apache.http.impl.client.AbstractHttpClient";
+    private static final String ENHANCE_CLASS = "org.apache.http.impl.discovery.AbstractHttpClient";
 
     @Override
     public String enhanceClassName() {

apm-sniffer/apm-sdk-plugin/httpClient-4.x-plugin/src/main/java/org/skywalking/apm/plugin/httpClient/v4/define/DefaultRequestDirectorInstrumentation.java

@@ -19,7 +19,7 @@ public class DefaultRequestDirectorInstrumentation extends HttpClientInstrumenta
     /**
      * Enhance class.
      */
-    private static final String ENHANCE_CLASS = "org.apache.http.impl.client.DefaultRequestDirector";
+    private static final String ENHANCE_CLASS = "org.apache.http.impl.discovery.DefaultRequestDirector";
 
     /**
      * DefaultRequestDirector is default implement.<br/>

apm-sniffer/apm-sdk-plugin/httpClient-4.x-plugin/src/main/java/org/skywalking/apm/plugin/httpClient/v4/define/InternalHttpClientInstrumentation.java

@@ -15,7 +15,7 @@ import static net.bytebuddy.matcher.ElementMatchers.named;
  */
 public class InternalHttpClientInstrumentation extends HttpClientInstrumentation {
 
-    private static final String ENHANCE_CLASS = "org.apache.http.impl.client.InternalHttpClient";
+    private static final String ENHANCE_CLASS = "org.apache.http.impl.discovery.InternalHttpClient";
 
     @Override
     public String enhanceClassName() {

apm-sniffer/apm-sdk-plugin/httpClient-4.x-plugin/src/main/java/org/skywalking/apm/plugin/httpClient/v4/define/MinimalHttpClientInstrumentation.java

@@ -18,7 +18,7 @@ import static net.bytebuddy.matcher.ElementMatchers.named;
  */
 public class MinimalHttpClientInstrumentation extends HttpClientInstrumentation {
 
-    private static final String ENHANCE_CLASS = "org.apache.http.impl.client.MinimalHttpClient";
+    private static final String ENHANCE_CLASS = "org.apache.http.impl.discovery.MinimalHttpClient";
 
     @Override
     public String enhanceClassName() {

apm-sniffer/apm-sdk-plugin/jdbc-plugin/src/test/java/org/skywalking/apm/plugin/jdbc/SWConnectionTest.java

@@ -327,7 +327,7 @@ public class SWConnectionTest extends AbstractStatementTest {
         swConnection.setHoldability(1);
         swConnection.getHoldability();
         swConnection.setReadOnly(false);
-        swConnection.setClientInfo("test-client", "test-client");
+        swConnection.setClientInfo("test-discovery", "test-discovery");
         swConnection.getClientInfo("test");
         swConnection.setSavepoint();
         swConnection.getMetaData();

apm-sniffer/apm-sdk-plugin/okhttp-3.x-plugin/src/main/java/org/skywalking/apm/plugin/okhttp/v3/RealCallInterceptor.java

@@ -16,7 +16,7 @@ import org.skywalking.apm.agent.core.plugin.interceptor.enhance.InstanceMethodsA
 import org.skywalking.apm.agent.core.plugin.interceptor.enhance.MethodInterceptResult;
 
 /**
- * {@link RealCallInterceptor} intercept the synchronous http calls by the client of okhttp.
+ * {@link RealCallInterceptor} intercept the synchronous http calls by the discovery of okhttp.
  *
  * @author pengys5
  */

apm-sniffer/apm-sdk-plugin/okhttp-3.x-plugin/src/test/java/org/skywalking/apm/plugin/okhttp/v3/RealCallInterceptorTest.java

@@ -111,7 +111,7 @@ public class RealCallInterceptorTest {
         Assert.assertEquals("skywalking.org", span.getPeerHost());
         Assert.assertEquals(80, span.getPort());
         Assert.assertEquals("OKHttp", StringTagReader.get(span, Tags.COMPONENT));
-        Assert.assertEquals("client", StringTagReader.get(span, Tags.SPAN_KIND));
+        Assert.assertEquals("discovery", StringTagReader.get(span, Tags.SPAN_KIND));
         Assert.assertEquals("/", StringTagReader.get(span, Tags.URL));
     }
 

apm-sniffer/apm-sniffer-mock/src/main/java/org/skywalking/apm/sniffer/mock/trace/builders/span/DubboSpanGenerator.java

@@ -6,7 +6,7 @@ import org.skywalking.apm.agent.core.context.trace.AbstractSpan;
 
 /**
  * The <code>DubboSpanGenerator</code> generates all possible spans, by tracing Dubbo rpc.
- * Including client/server side span.
+ * Including discovery/server side span.
  *
  * @author wusheng
  */

apm-sniffer/apm-sniffer-mock/src/main/java/org/skywalking/apm/sniffer/mock/trace/builders/span/MySQLGenerator.java

@@ -5,7 +5,7 @@ import org.skywalking.apm.agent.core.context.tag.Tags;
 import org.skywalking.apm.agent.core.context.trace.AbstractSpan;
 
 /**
- * The <code>MySQLGenerator</code> generates all possible spans, by tracing mysql client access.
+ * The <code>MySQLGenerator</code> generates all possible spans, by tracing mysql discovery access.
  *
  * @author wusheng
  */

apm-sniffer/apm-sniffer-mock/src/main/java/org/skywalking/apm/sniffer/mock/trace/builders/trace/TomcatDubboClientTraceBuilder.java

@@ -9,7 +9,7 @@ import org.skywalking.apm.agent.core.context.trace.TraceSegment;
 /**
  * A Trace segment contains two spans with ChildOf relations,
  * the parent is a Tomcat span,
- * the child is a Dubbo client span.
+ * the child is a Dubbo discovery span.
  *
  * @author wusheng
  */