[metrics-bugs] #25522 [Metrics/CollecTor]: Avoid missing identical lines during sanitization of logs

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#25522: Avoid missing identical lines during sanitization of logs
-------------------------------+------------------------------
 Reporter:  iwakeh             |          Owner:  metrics-team
     Type:  defect             |         Status:  needs_review
 Priority:  High               |      Milestone:
Component:  Metrics/CollecTor  |        Version:
 Severity:  Normal             |     Resolution:
 Keywords:  metrics-2018       |  Actual Points:
Parent ID:                     |         Points:
 Reviewer:                     |        Sponsor:
-------------------------------+------------------------------

Comment (by karsten):

 While we're looking at this code, should we also try to avoid allocating
 the potentially large `byte[] batch = bytesFor(entry.getKey(), BATCH)` if
 we don't need it? For example,

 {{{
       for (Map.Entry<String, Long> entry : lines.entrySet()) {
         long count = entry.getValue();
         byte[] batch = null;
         while (count > 0) {
           if (count > BATCH) {
             if (null == batch) {
               batch = bytesFor(entry.getKey(), BATCH);
             }
             os.write(batch);
             count -= BATCH;
           } else {
             os.write(bytesFor(entry.getKey(), count));
             break;
           }
         }
       }
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25522#comment:2>
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