Context ctx = new ReportTestingContext();
EventSink cntsnk = new CompositeSink(ctx, "counter(\"total\")");
// use the same wal, but different counter.
final EventSink snk = new NaiveFileWALDeco(ctx, cntsnk, wal,
new TimeTrigger(new ProcessTagger(), 1000000),
new AckListener.Empty(), 1000000);
snk.open();
for (int i = 0; i < threads; i++) {
new Thread() {