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Type: Bug
Resolution: Won't Fix
Priority: Major - P3
Fix Version/s: None
Affects Version/s: None
Component/s: Diagnostics, Tools
Labels:
- locking
- metrics

Backwards Compatibility:
Major Change
Operating System:
ALL

While running an insert-only test, I noticed that mongostat shows queued readers, while I do not read anything.

Sample mongostat output:

insert  query update delete getmore command flushes mapped  vsize    res faults   locked db idx miss %     qr|qw   ar|aw  netIn netOut  conn       time
  6120     *0     *0     *0       0     2|0       0    16g  32.3g  1.97g      0  test:68.3%          0      19|0     0|1     6m     3k    23   19:33:03
  6061     *0     *0     *0       0     2|0       0    18g  36.3g  1.99g      1  test:76.4%          0      19|0     0|1     6m     8k    23   19:33:04
  5966     *0     *0     *0       0     1|0       0    18g  36.3g  2.02g      0  test:63.3%          0      19|0     0|1     6m     3k    23   19:33:05
  6110     *0     *0     *0       0     1|0       0    18g  36.3g  2.04g      0  test:68.4%          0      19|0     0|1     6m     3k    23   19:33:06

db.currentOp output for the same time:

> db.currentOp()
{
	"inprog" : [
		{
			"opid" : 824735,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60486",
			"desc" : "conn62",
			"threadId" : "0x7f37873b4700",
			"connectionId" : 62,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824726,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60494",
			"desc" : "conn72",
			"threadId" : "0x7f37871b2700",
			"connectionId" : 72,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824740,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60484",
			"desc" : "conn63",
			"threadId" : "0x7f3f851a3700",
			"connectionId" : 63,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824743,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60493",
			"desc" : "conn71",
			"threadId" : "0x7f3f855a7700",
			"connectionId" : 71,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824739,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60489",
			"desc" : "conn67",
			"threadId" : "0x7f3f850a2700",
			"connectionId" : 67,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824741,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60499",
			"desc" : "conn77",
			"threadId" : "0x7f3f859ab700",
			"connectionId" : 77,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824733,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60497",
			"desc" : "conn75",
			"threadId" : "0x7f3f854a6700",
			"connectionId" : 75,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824725,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60495",
			"desc" : "conn73",
			"threadId" : "0x7f3786dae700",
			"connectionId" : 73,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824727,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60501",
			"desc" : "conn79",
			"threadId" : "0x7f3f853a5700",
			"connectionId" : 79,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824728,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60483",
			"desc" : "conn65",
			"threadId" : "0x7f3786eaf700",
			"connectionId" : 65,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824736,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60496",
			"desc" : "conn74",
			"threadId" : "0x7f3786fb0700",
			"connectionId" : 74,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824738,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60490",
			"desc" : "conn68",
			"threadId" : "0x7f37870b1700",
			"connectionId" : 68,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824742,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60488",
			"desc" : "conn66",
			"threadId" : "0x7f37872b3700",
			"connectionId" : 66,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824732,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60498",
			"desc" : "conn76",
			"threadId" : "0x7f3f85cae700",
			"connectionId" : 76,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824730,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60491",
			"desc" : "conn69",
			"threadId" : "0x7f3f85aac700",
			"connectionId" : 69,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824729,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60487",
			"desc" : "conn64",
			"threadId" : "0x7f3f85daf700",
			"connectionId" : 64,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824734,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60500",
			"desc" : "conn78",
			"threadId" : "0x7f3f856a8700",
			"connectionId" : 78,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824731,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60502",
			"desc" : "conn80",
			"threadId" : "0x7f3f852a4700",
			"connectionId" : 80,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		},
		{
			"opid" : 824737,
			"active" : false,
			"op" : "insert",
			"ns" : "",
			"insert" : {

			},
			"client" : "10.61.157.244:60503",
			"desc" : "conn81",
			"threadId" : "0x7f3f857a9700",
			"connectionId" : 81,
			"locks" : {
				"^test" : "W"
			},
			"waitingForLock" : true,
			"numYields" : 0,
			"lockStats" : {
				"timeLockedMicros" : {

				},
				"timeAcquiringMicros" : {

				}
			}
		}
	]
}

is documented by

DOCS-9002 mongostat shows queued inserts as readers

Closed

related to

SERVER-13655 Report queued operations by type (insert/query/etc)

Closed

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