Polish the context related codes. (#5764)

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/ContextCarrier.java

@@ -19,10 +19,12 @@
 package org.apache.skywalking.apm.agent.core.context;
 
 import java.io.Serializable;
+import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.Setter;
 import org.apache.skywalking.apm.agent.core.base64.Base64;
 import org.apache.skywalking.apm.agent.core.conf.Constants;
+import org.apache.skywalking.apm.agent.core.context.trace.AbstractSpan;
 import org.apache.skywalking.apm.util.StringUtil;
 
 /**
@@ -30,28 +32,70 @@ import org.apache.skywalking.apm.util.StringUtil;
  * TracingContext}.
  * <p>
  */
-@Setter
-@Getter
+@Setter(AccessLevel.PACKAGE)
 public class ContextCarrier implements Serializable {
+    @Getter
     private String traceId;
+    /**
+     * The segment id of the parent.
+     */
+    @Getter
     private String traceSegmentId;
+    /**
+     * The span id in the parent segment.
+     */
+    @Getter
     private int spanId = -1;
+    @Getter
     private String parentService = Constants.EMPTY_STRING;
+    @Getter
     private String parentServiceInstance = Constants.EMPTY_STRING;
+    /**
+     * The endpoint(entrance URI/method signature) of the parent service.
+     */
+    @Getter
     private String parentEndpoint;
+    /**
+     * The network address(ip:port, hostname:port) used in the parent service to access the current service.
+     */
+    @Getter
     private String addressUsedAtClient;
-
-    private CorrelationContext correlationContext = new CorrelationContext();
+    /**
+     * The extension context contains the optional context to enhance the analysis in some certain scenarios.
+     */
+    @Getter(AccessLevel.PACKAGE)
     private ExtensionContext extensionContext = new ExtensionContext();
-    private ExtensionInjector extensionInjector = new ExtensionInjector(extensionContext);
+    /**
+     * User's custom context container. The context propagates with the main tracing context.
+     */
+    @Getter(AccessLevel.PACKAGE)
+    private CorrelationContext correlationContext = new CorrelationContext();
 
+    /**
+     * @return the list of items, which could exist in the current tracing context.
+     */
     public CarrierItem items() {
         SW8ExtensionCarrierItem sw8ExtensionCarrierItem = new SW8ExtensionCarrierItem(extensionContext, null);
-        SW8CorrelationCarrierItem sw8CorrelationCarrierItem = new SW8CorrelationCarrierItem(correlationContext, sw8ExtensionCarrierItem);
+        SW8CorrelationCarrierItem sw8CorrelationCarrierItem = new SW8CorrelationCarrierItem(
+            correlationContext, sw8ExtensionCarrierItem);
         SW8CarrierItem sw8CarrierItem = new SW8CarrierItem(this, sw8CorrelationCarrierItem);
         return new CarrierItemHead(sw8CarrierItem);
     }
 
+    /**
+     * @return the injector for the extension context.
+     */
+    public ExtensionInjector extensionInjector() {
+        return new ExtensionInjector(extensionContext);
+    }
+
+    /**
+     * Extract the extension context to the given span
+     */
+    void extractExtensionTo(AbstractSpan span) {
+        this.extensionContext.handle(span);
+    }
+
     /**
      * Serialize this {@link ContextCarrier} to a {@link String}, with '|' split.
      *

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/CorrelationContext.java

@@ -17,19 +17,17 @@
 
 package org.apache.skywalking.apm.agent.core.context;
 
-import org.apache.skywalking.apm.agent.core.base64.Base64;
-import org.apache.skywalking.apm.agent.core.conf.Config;
-import org.apache.skywalking.apm.util.StringUtil;
-
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.stream.Collectors;
+import org.apache.skywalking.apm.agent.core.base64.Base64;
+import org.apache.skywalking.apm.agent.core.conf.Config;
+import org.apache.skywalking.apm.util.StringUtil;
 
 /**
  * Correlation context, use to propagation user custom data.
- * Working on the protocol and delegate set/get method.
  */
 public class CorrelationContext {
 
@@ -39,6 +37,13 @@ public class CorrelationContext {
         this.data = new HashMap<>(Config.Correlation.ELEMENT_MAX_NUMBER);
     }
 
+    /**
+     * Add or override the context.
+     *
+     * @param key   to add or locate the existing context
+     * @param value as new value
+     * @return old one if exist.
+     */
     public Optional<String> put(String key, String value) {
         // key must not null
         if (key == null) {
@@ -71,6 +76,10 @@ public class CorrelationContext {
         return Optional.empty();
     }
 
+    /**
+     * @param key to find the context
+     * @return value if exist.
+     */
     public Optional<String> get(String key) {
         if (key == null) {
             return Optional.empty();
@@ -90,8 +99,8 @@ public class CorrelationContext {
         }
 
         return data.entrySet().stream()
-            .map(entry -> Base64.encode(entry.getKey()) + ":" + Base64.encode(entry.getValue()))
-            .collect(Collectors.joining(","));
+                   .map(entry -> Base64.encode(entry.getKey()) + ":" + Base64.encode(entry.getValue()))
+                   .collect(Collectors.joining(","));
     }
 
     /**
@@ -116,7 +125,8 @@ public class CorrelationContext {
     }
 
     /**
-     * Prepare for the cross-process propagation. Inject the {@link #data} into {@link ContextCarrier#getCorrelationContext()}
+     * Prepare for the cross-process propagation. Inject the {@link #data} into {@link
+     * ContextCarrier#getCorrelationContext()}
      */
     void inject(ContextCarrier carrier) {
         carrier.getCorrelationContext().data.putAll(this.data);
@@ -152,8 +162,10 @@ public class CorrelationContext {
 
     @Override
     public boolean equals(Object o) {
-        if (this == o) return true;
-        if (o == null || getClass() != o.getClass()) return false;
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
         CorrelationContext that = (CorrelationContext) o;
         return Objects.equals(data, that.data);
     }

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/ExtensionInjector.java

@@ -18,8 +18,6 @@
 
 package org.apache.skywalking.apm.agent.core.context;
 
-import java.util.Optional;
-
 /**
  * Inject or read the extension protocol fields,such as {@link ExtensionContext#sendingTimestamp}.
  */
@@ -37,11 +35,4 @@ public class ExtensionInjector {
     public void injectSendingTimestamp() {
         extensionContext.setSendingTimestamp(System.currentTimeMillis());
     }
-
-    /**
-     * Read the exit span sending timestamp from the {@link ExtensionContext}.
-     */
-    public Optional<Long> readSendingTimestamp() {
-        return Optional.ofNullable(extensionContext.getSendingTimestamp());
-    }
 }

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/TracingContext.java

@@ -187,7 +187,7 @@ public class TracingContext implements AbstractTracerContext {
             span.ref(ref);
         }
 
-        carrier.getExtensionContext().handle(span);
+        carrier.extractExtensionTo(span);
         this.correlationContext.extract(carrier);
         this.extensionContext.extract(carrier);
     }

apm-sniffer/apm-sdk-plugin/activemq-5.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/activemq/ActiveMQProducerInterceptor.java

@@ -59,7 +59,7 @@ public class ActiveMQProducerInterceptor implements InstanceMethodsAroundInterce
             Tags.MQ_BROKER.set(activeSpan, url);
             Tags.MQ_TOPIC.set(activeSpan, activeMQDestination.getPhysicalName());
         }
-        contextCarrier.getExtensionInjector().injectSendingTimestamp();
+        contextCarrier.extensionInjector().injectSendingTimestamp();
         SpanLayer.asMQ(activeSpan);
         activeSpan.setComponent(ComponentsDefine.ACTIVEMQ_PRODUCER);
         CarrierItem next = contextCarrier.items();

apm-sniffer/apm-sdk-plugin/kafka-plugin/src/main/java/org/apache/skywalking/apm/plugin/kafka/KafkaProducerInterceptor.java

@@ -52,7 +52,7 @@ public class KafkaProducerInterceptor implements InstanceMethodsAroundIntercepto
 
         Tags.MQ_BROKER.set(activeSpan, (String) objInst.getSkyWalkingDynamicField());
         Tags.MQ_TOPIC.set(activeSpan, topicName);
-        contextCarrier.getExtensionInjector().injectSendingTimestamp();
+        contextCarrier.extensionInjector().injectSendingTimestamp();
         SpanLayer.asMQ(activeSpan);
         activeSpan.setComponent(ComponentsDefine.KAFKA_PRODUCER);
 

apm-sniffer/apm-sdk-plugin/pulsar-plugin/src/main/java/org/apache/skywalking/apm/plugin/pulsar/PulsarProducerInterceptor.java

@@ -65,7 +65,7 @@ public class PulsarProducerInterceptor implements InstanceMethodsAroundIntercept
                 .getServiceUrl());
             Tags.MQ_BROKER.set(activeSpan, requiredInfo.getServiceUrl());
             Tags.MQ_TOPIC.set(activeSpan, topicName);
-            contextCarrier.getExtensionInjector().injectSendingTimestamp();
+            contextCarrier.extensionInjector().injectSendingTimestamp();
             SpanLayer.asMQ(activeSpan);
             activeSpan.setComponent(ComponentsDefine.PULSAR_PRODUCER);
             CarrierItem next = contextCarrier.items();

apm-sniffer/apm-sdk-plugin/rabbitmq-5.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/rabbitmq/RabbitMQProducerInterceptor.java

@@ -77,7 +77,7 @@ public class RabbitMQProducerInterceptor implements InstanceMethodsAroundInterce
         Tags.MQ_BROKER.set(activeSpan, url);
         Tags.MQ_QUEUE.set(activeSpan, queueName);
         Tags.MQ_TOPIC.set(activeSpan, exChangeName);
-        contextCarrier.getExtensionInjector().injectSendingTimestamp();
+        contextCarrier.extensionInjector().injectSendingTimestamp();
         SpanLayer.asMQ(activeSpan);
         activeSpan.setComponent(ComponentsDefine.RABBITMQ_PRODUCER);
         CarrierItem next = contextCarrier.items();

apm-sniffer/apm-sdk-plugin/rocketMQ-3.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/rocketMQ/v3/MessageSendInterceptor.java

@@ -59,7 +59,7 @@ public class MessageSendInterceptor implements InstanceMethodsAroundInterceptor
         span.setComponent(ComponentsDefine.ROCKET_MQ_PRODUCER);
         Tags.MQ_BROKER.set(span, (String) allArguments[0]);
         Tags.MQ_TOPIC.set(span, message.getTopic());
-        contextCarrier.getExtensionInjector().injectSendingTimestamp();
+        contextCarrier.extensionInjector().injectSendingTimestamp();
         SpanLayer.asMQ(span);
 
         SendMessageRequestHeader requestHeader = (SendMessageRequestHeader) allArguments[3];

apm-sniffer/apm-sdk-plugin/rocketMQ-4.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/rocketMQ/v4/MessageSendInterceptor.java

@@ -59,7 +59,7 @@ public class MessageSendInterceptor implements InstanceMethodsAroundInterceptor
         span.setComponent(ComponentsDefine.ROCKET_MQ_PRODUCER);
         Tags.MQ_BROKER.set(span, (String) allArguments[0]);
         Tags.MQ_TOPIC.set(span, message.getTopic());
-        contextCarrier.getExtensionInjector().injectSendingTimestamp();
+        contextCarrier.extensionInjector().injectSendingTimestamp();
         SpanLayer.asMQ(span);
 
         SendMessageRequestHeader requestHeader = (SendMessageRequestHeader) allArguments[3];