MongoDB current operations and profiling

Current operations

db.currentOp()

Operations running for over 5 seconds…

db.currentOp().inprog.forEach(function(op) {
    if (op.secs_running > 5) printjson(op);
})

Write operations waiting for a lock

db.currentOp(
  {
    "waitingForLock" : true,
    $or: [
      { "op" : { "$in" : [ "insert", "update", "remove" ] } },
      { "query.findandmodify": { $exists: true } }
    ]
  }
)

Operations that have never yielded

db.currentOp(
   {
     "active" : true,
     "numYields" : 0,
     "waitingForLock" : false
   }
)

Index creation operations

db.currentOp(
    {
      $or: [
        { op: "query", "query.createIndexes": { $exists: true } },
        { op: "insert", ns: /\.system\.indexes\b/ }
      ]
    }
)

Profiling Levels

  • 0 – the profiler is off, does not collect any data.
  • 1 – collects profiling data for slow operations only.
  • 2 – collects profiling data for all database operations.

Checking profiling level

db.getProfilingStatus()

Turn on profiling for operations taking more than 1 second (1000 milliseconds)

db.setProfilingLevel(1,1000)

Turn profiling off

db.setProfilingLevel(0)

5 most recent operations logged in the system.profile table

db.system.profile.find().limit(5).sort( { ts : -1 } ).pretty()

Recent operations that took longer than 2 seconds

db.system.profile.find( { millis : { $gt : 5 } } ).pretty()

 

To change the size of the system.profile collection, you must:

  1. Disable profiling.
  2. Drop the system.profile collection.
  3. Create a new system.profile collection.
  4. Re-enable profiling.

To create a new system.profile collections that’s 4000000 bytes, use the following sequence of operations

db.setProfilingLevel(0)
db.system.profile.drop()
db.createCollection( "system.profile", { capped: true, size:4000000 } )
db.setProfilingLevel(1)

 

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