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  1. Core Server
  2. SERVER-20961

Large amounts of create and drop collections can cause listDatabases to be slow under WiredTiger

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    • Type: Icon: Bug Bug
    • Resolution: Done
    • Priority: Icon: Major - P3 Major - P3
    • 3.0.9, 3.2.0-rc4
    • Affects Version/s: 3.0.6, 3.0.7, 3.2.0-rc0
    • Component/s: WiredTiger
    • None
    • Fully Compatible
    • ALL
    • Hide 
      require "mongo"

client1 = Mongo::Client.new('mongodb://127.0.0.1:27017/')
client2 = Mongo::Client.new('mongodb://127.0.0.1:27017/')
client3 = Mongo::Client.new('mongodb://127.0.0.1:27017/')
client4 = Mongo::Client.new('mongodb://127.0.0.1:27017/')

Mongo::Logger.logger.level = Logger::WARN

for x in 0..100
    thr = Thread.new {
#        sleep 1
        before = Time.now
        client1.use("admin").command(:listDatabases => 1)
        after= Time.now
        p "took: " + (after-before).to_s
    }
        thr1 = Thread.new {
        for i in 0..100
                name = "abcd" + ((x*100)+i).to_s;
                client2.use(name)[:foo].indexes.create_one({ :x => 1})
                client2.use(name)[:foo].insert_one({ :x => 1})
                client2.use(name)[:baz].indexes.create_one({ :x => 1})
                client2.use(name)[:bar].insert_one({ :x => 1})
        end
        }
        thr2 = Thread.new {
        for i in 0..100
                name = "abcd" + ((x*100)+i).to_s;
                client3.use(name)[:bar].indexes.create_one({ :x => 1})
                client3.use(name)[:bar].insert_one({ :x => 1})
                client3.use(name)[:qux].indexes.create_one({ :x => 1})
                client3.use(name)[:qux].insert_one({ :x => 1})
        end
        }
        thr3 = Thread.new {
        for i in 0..100
                name = "abcd" + ((x*100)+i).to_s;
                client4.use(name)[:alpha].indexes.create_one({ :x => 1})
                client4.use(name)[:alpha].insert_one({ :x => 1})
                client4.use(name)[:beta].indexes.create_one({ :x => 1})
                client4.use(name)[:beta].insert_one({ :x => 1})
        end
        }
        thr1.join
        thr2.join
        thr3.join
        thr4 = Thread.new {
        for i in 0..100
                name = "abcd" + ((x*100)+i).to_s;
                client2.use(name)[:foo].drop
                client3.use(name)[:baz].drop
                client4.use(name)[:beta].drop
        end
        }
        thr4.join
    sleep 20
    thr.join()
end
      Show
      require "mongo" client1 = Mongo::Client.new( 'mongodb://127.0.0.1:27017/' ) client2 = Mongo::Client.new( 'mongodb://127.0.0.1:27017/' ) client3 = Mongo::Client.new( 'mongodb://127.0.0.1:27017/' ) client4 = Mongo::Client.new( 'mongodb://127.0.0.1:27017/' ) Mongo::Logger.logger.level = Logger::WARN for x in 0..100 thr = Thread.new { # sleep 1 before = Time.now client1.use( "admin" ).command(:listDatabases => 1) after= Time.now p "took: " + (after-before).to_s } thr1 = Thread.new { for i in 0..100 name = "abcd" + ((x*100)+i).to_s; client2.use(name)[:foo].indexes.create_one({ :x => 1}) client2.use(name)[:foo].insert_one({ :x => 1}) client2.use(name)[:baz].indexes.create_one({ :x => 1}) client2.use(name)[:bar].insert_one({ :x => 1}) end } thr2 = Thread.new { for i in 0..100 name = "abcd" + ((x*100)+i).to_s; client3.use(name)[:bar].indexes.create_one({ :x => 1}) client3.use(name)[:bar].insert_one({ :x => 1}) client3.use(name)[:qux].indexes.create_one({ :x => 1}) client3.use(name)[:qux].insert_one({ :x => 1}) end } thr3 = Thread.new { for i in 0..100 name = "abcd" + ((x*100)+i).to_s; client4.use(name)[:alpha].indexes.create_one({ :x => 1}) client4.use(name)[:alpha].insert_one({ :x => 1}) client4.use(name)[:beta].indexes.create_one({ :x => 1}) client4.use(name)[:beta].insert_one({ :x => 1}) end } thr1.join thr2.join thr3.join thr4 = Thread.new { for i in 0..100 name = "abcd" + ((x*100)+i).to_s; client2.use(name)[:foo].drop client3.use(name)[:baz].drop client4.use(name)[:beta].drop end } thr4.join sleep 20 thr.join() end

      Under a workload with a high volume of collection (and index) creation over a number of database then the dropping of these collections will cause listDatabases command to run longer on a WT instance.

      Using the reproduction script shows the following execution time for listDatabases per lap in seconds:

      "took: 1.705329872"
"took: 1.328905619"
"took: 1.55636039"
"took: 1.221779232"
"took: 1.772605573"
"took: 1.689325783"
"took: 1.15700596"
"took: 1.470458173"
"took: 1.255596249"
"took: 1.455441504"
"took: 8.487761074"
"took: 13.784377947"
"took: 15.079964722"
"took: 13.892499541"
"took: 15.179368285"
"took: 14.683478172"
"took: 14.776398389"
"took: 14.481528086"
"took: 14.688469802"
"took: 13.738872847"
"took: 14.298077263"

        1. threads
          33 kB
          David Hows
        2. threads2
          33 kB
          David Hows

            Assignee:
            david.hows David Hows
            Reporter:
            david.hows David Hows
            Votes:
            2 Vote for this issue
            Watchers:
            21 Start watching this issue

              Created:
              Updated:
              Resolved: