public synchronized void addFailedKey(KeyCacheObject key,Throwable e){
  if (failedKeys == null)   failedKeys=new ConcurrentLinkedQueue<>();
  failedKeys.add(key);
  if (err == null)   err=new IgniteCheckedException("Failed to update keys on primary node.");
  err.addSuppressed(e);
}

public synchronized void addFailedKey ( KeyCacheObject key , Throwable e ) { if ( failedKeys == null ) failedKeys = new ConcurrentLinkedQueue < > ( ) ; failedKeys . add ( key ) ; if ( err == null ) err = new IgniteCheckedException ( "Failed to update keys on primary node." ) ; err . addSuppressed ( e ) ; }
adds key to collection of failed keys .
