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  1. Core Server
  2. SERVER-36294

Sum of currentActive and currentInactive not equal to currentOpen transactions

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    • Fully Compatible
    • ALL
    • v4.0
    • Repl 2018-08-13

    Description

      Small inaccuracies due to skew might be expected because the counter updates aren't atomic, but this looks to me to be much larger than that, as if the transaction is spending significant time between between corresponding updates to the counters.

      This was a simple test with 10 threads doing transactional updates to single independent documents:

      function repro() {
       
          nthreads = 10
       
          db.createCollection("c", {writeConcern: {w: "majority"}})
       
          threads = []
          for (var t=0; t<nthreads; t++) {
              thread = new ScopedThread((t) =>  {
                  var ses = db.getMongo().startSession()
                  ses.getDatabase("test").c.insert({_id: t, i: 0})
                  for (;;) {
                      try {
                          ses.startTransaction()
                          ses.getDatabase("test").c.update({_id: t}, {$inc: {i: 1}})
                          //if (t==0) sleep(1000)
                          ses.commitTransaction()
                      } catch (e) {
                          print(e)
                      }
                  }
              }, t)
              threads.push(thread)
              thread.start()
          }
          for (var t = 0; t < nthreads; t++)
              threads[t].join()
      }
      

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              nathan.louie Nathan Louie
              bruce.lucas@mongodb.com Bruce Lucas
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