[GitHub] sijie commented on issue #202: DistributedLogManager's getLastDLSN runs long time, especially after reOpen log stream

[gi...@git.apache.org]

sijie commented on issue #202: DistributedLogManager's getLastDLSN runs long time, especially after reOpen log stream
URL: https://github.com/apache/distributedlog/issues/202#issuecomment-335278147
 
 
   @ArvinDevel 
   
   ```
   dlm.openAsyncLogWriter().whenComplete(new FutureEventListener<AsyncLogWriter>() {
       @Override
       public void onSuccess(AsyncLogWriter asyncLogWriter) {
           LOG.info("[{}] Created log writer {}", name, asyncLogWriter.toString());
           logWriter = asyncLogWriter;
           try {
               LOG.info("before getLastDLSN");
               last = dlm.getLastDLSN();
               LOG.info("after getLastDLSN");
           } catch (LogEmptyException lee){
               LOG.info("the log stream is empty ");
           } catch (Exception e){
               LOG.error("Faced Exception in getLastDLSN", e);
           }
           LOG.info("getLastDLSN return {}", last);
           openLatch.countDown();
       }
   
       @Override
       public void onFailure(Throwable throwable) {
           LOG.error("Failed open AsyncLogWriter for {}", name, throwable);
           openLatch.countDown();
       }
   });
   ```
   
   You can call synchronous function in an asynchronous callback. since the synchronous function is blocking the callback thread. so getLastDLSN will never complete.
 
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