Support retry when use IF_POSSIBLE strategy.

apm-commons/apm-datacarrier/src/main/java/org/skywalking/apm/commons/datacarrier/buffer/Channels.java

@@ -12,9 +12,11 @@ import org.skywalking.apm.commons.datacarrier.partition.IDataPartitioner;
 public class Channels<T> {
     private final Buffer<T>[] bufferChannels;
     private IDataPartitioner<T> dataPartitioner;
+    private BufferStrategy strategy;
 
     public Channels(int channelSize, int bufferSize, IDataPartitioner<T> partitioner, BufferStrategy strategy) {
         this.dataPartitioner = partitioner;
+        this.strategy = strategy;
         bufferChannels = new Buffer[channelSize];
         for (int i = 0; i < channelSize; i++) {
             bufferChannels[i] = new Buffer<T>(bufferSize, strategy);
@@ -23,7 +25,19 @@ public class Channels<T> {
 
     public boolean save(T data) {
         int index = dataPartitioner.partition(bufferChannels.length, data);
-        return bufferChannels[index].save(data);
+        int retryCountDown = 1;
+        if (BufferStrategy.IF_POSSIBLE.equals(strategy)) {
+            int maxRetryCount = dataPartitioner.maxRetryCount();
+            if (maxRetryCount > 1) {
+                retryCountDown = maxRetryCount;
+            }
+        }
+        for (; retryCountDown > 0; retryCountDown--) {
+            if (bufferChannels[index].save(data)) {
+                return true;
+            }
+        }
+        return false;
     }
 
     public void setPartitioner(IDataPartitioner<T> dataPartitioner) {

apm-commons/apm-datacarrier/src/main/java/org/skywalking/apm/commons/datacarrier/partition/IDataPartitioner.java

@@ -1,8 +1,17 @@
 package org.skywalking.apm.commons.datacarrier.partition;
 
+import org.skywalking.apm.commons.datacarrier.buffer.BufferStrategy;
+
 /**
  * Created by wusheng on 2016/10/25.
  */
 public interface IDataPartitioner<T> {
     int partition(int total, T data);
+
+    /**
+     * @return an integer represents how many times should retry when {@link BufferStrategy#IF_POSSIBLE}.
+     *
+     * Less or equal 1, means not support retry.
+     */
+    int maxRetryCount();
 }

apm-commons/apm-datacarrier/src/main/java/org/skywalking/apm/commons/datacarrier/partition/ProducerThreadPartitioner.java

@@ -6,8 +6,22 @@ package org.skywalking.apm.commons.datacarrier.partition;
  * Created by wusheng on 2016/10/25.
  */
 public class ProducerThreadPartitioner<T> implements IDataPartitioner<T> {
+    private int retryTime = 3;
+
+    public ProducerThreadPartitioner() {
+    }
+
+    public ProducerThreadPartitioner(int retryTime) {
+        this.retryTime = retryTime;
+    }
+
     @Override
     public int partition(int total, T data) {
         return (int)Thread.currentThread().getId() % total;
     }
+
+    @Override
+    public int maxRetryCount() {
+        return 1;
+    }
 }

apm-commons/apm-datacarrier/src/main/java/org/skywalking/apm/commons/datacarrier/partition/SimpleRollingPartitioner.java

@@ -14,8 +14,8 @@ public class SimpleRollingPartitioner<T> implements IDataPartitioner<T> {
         return Math.abs(i++ % total);
     }
 
-    public static void main(String[] args) {
-        SimpleRollingPartitioner s = new SimpleRollingPartitioner();
-        System.out.print(s.i++ % 10);
+    @Override
+    public int maxRetryCount() {
+        return 3;
     }
 }