今天天氣不錯，但是趕上惡意加班心情就不爽，懷著不爽的心情幹活，總能創造出更多的問題，這不，今天就自己挖了一個坑，自己跳進去了，好在上來了
經過是這樣的，開始除錯canal採集binlog時，由於新增了一個上報數量大小，隨手列印了一個日誌
logger.info("batchData:{}", batchData); pipeline.put(batchData);
發到sit環境測試一把，臥槽。。。，怎麼不同步資料了，開始排查問題，是我改的程式碼有問題？於是回退了，還是不同步資料，但是發現在停止任務時會中斷讀執行緒，這時資料同步過來了，試了幾次都是這樣，開始懷疑讀執行緒被阻塞了，於是乎祭出許久未用的jstack去看一下讀執行緒狀態：jstack pid
"canal-binlog-encrypt-wangbd-test-001,219025,ReaderTask_CanalReader_0_0" #32 prio=5 os_prio=0 tid=0x00007fdfdc010800 nid=0x4199 waiting on condition [0x00007fe044653000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000000800ad988> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) at java.util.concurrent.ArrayBlockingQueue.take(ArrayBlockingQueue.java:403) at com.data.integration.engine.stream.core.cache.memory.MemoryDataCache.get(MemoryDataCache.java:135) at com.data.integration.engine.stream.core.cache.DataCache.get(DataCache.java:65) at com.data.integration.engine.stream.core.cache.DataCache.get(DataCache.java:61) at com.data.integration.engine.stream.core.config.pipeline.Pipeline.getBatchData(Pipeline.java:74) at com.alibaba.fastjson.serializer.ASMSerializer_4_Pipeline.write(Unknown Source) at com.alibaba.fastjson.serializer.ASMSerializer_1_DefaultBatchData.write(Unknown Source) at com.alibaba.fastjson.serializer.JSONSerializer.write(JSONSerializer.java:285) at com.alibaba.fastjson.JSON.toJSONString(JSON.java:740) at com.alibaba.fastjson.JSON.toJSONString(JSON.java:678) at com.alibaba.fastjson.JSON.toJSONString(JSON.java:643) at com.data.integration.engine.stream.plugin.reader.canalreader.CanalReader.start(CanalReader.java:127) at com.data.integration.engine.stream.plugin.reader.ReaderTask$ReaderThread.run(ReaderTask.java:138) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748)
發現居然在使用fastjson轉換json時阻塞在快取佇列上了，說一下快取佇列讀執行緒只會向裡面寫，寫現場才會讀，於是乎開始懷疑列印的這個日誌，順著思路找到了如下程式碼：
pipeline的batchData屬性居然是從快取中獲取的物件 public BatchData getBatchData(){ return dataCache.get(); }
這就難怪了，由於快取佇列是空的，在toJson時阻塞了，導致整個讀執行緒被阻塞，把這個日誌去掉後就正常了,正常的讀執行緒棧是這樣的：
"canal-binlog-encrypt-wangbd-test-001,219023,ReaderTask_CanalReader_0_0" #32 prio=5 os_prio=0 tid=0x00007f7c8c00b000 nid=0xefb waiting on condition [0x00007f7d0476d000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000000807bf660> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) at com.alibaba.otter.canal.store.memory.MemoryEventStoreWithBuffer.get(MemoryEventStoreWithBuffer.java:219) at com.alibaba.otter.canal.server.embedded.CanalServerWithEmbedded.getEvents(CanalServerWithEmbedded.java:538) at com.alibaba.otter.canal.server.embedded.CanalServerWithEmbedded.getWithoutAck(CanalServerWithEmbedded.java:347) - locked <0x00000000808a3448> (a com.alibaba.otter.canal.instance.manager.CanalInstanceWithManager) at com.data.integration.engine.stream.plugin.reader.canalreader.CanalReader.start(CanalReader.java:101) at com.data.integration.engine.stream.plugin.reader.ReaderTask$ReaderThread.run(ReaderTask.java:138) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748)