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  1. Core Server
  2. SERVER-20126

Count on GridFS fs.files and fs.chunks slow

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Details

    • Bug
    • Status: Closed
    • Major - P3
    • Resolution: Incomplete
    • 3.0.6
    • None
    • GridFS
    • None
    • ALL
    • Hide

      Just heavy load to count fs.chunks and fs.files with command :
      db.runcommand({ count { count: "fs.files", query: {} }})

      Show
      Just heavy load to count fs.chunks and fs.files with command : db.runcommand({ count { count: "fs.files", query: {} }})

    Description

      Issue happen on the secondary instance which we do some read operation on it , there are only around 200+ rows in fs.chunks and fs.files collections , our application counts both collections but it cost a long time to return result :

      sample log :

      2015-08-26T17:12:06.304+0800 I COMMAND  [conn43] command UserFileSource.$cmd command: count { count: "fs.files", query: {} } planSummary: COUNT keyUpdates:0 writeConflicts:0 numYields:0 reslen:44 locks:{ Global: { acquireCount: { r: 2 }, acquireWaitCount: { r: 1 }, timeAcquiringMicros: { r: 272849 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 272ms
      2015-08-26T17:12:06.304+0800 I COMMAND  [conn116] command ADFileSource.$cmd command: count { count: "fs.files", query: {} } planSummary: COUNT keyUpdates:0 writeConflicts:0 numYields:0 reslen:44 locks:{ Global: { acquireCount: { r: 2 }, acquireWaitCount: { r: 1 }, timeAcquiringMicros: { r: 160138 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 160ms
      

      db stats like this :

      > db.stats()
      {
              "db" : "ADFileSource",
              "collections" : 3,
              "objects" : 490,
              "avgObjSize" : 55058.23673469388,
              "dataSize" : 26978536,
              "storageSize" : 26263552,
              "numExtents" : 0,
              "indexes" : 8,
              "indexSize" : 319488,
              "ok" : 1
      }
      

      ADFileSource is not a big database , CPU usage is not high , so the bottleneck should not be the cpu.

      Attached some status logs(dblog , serverstatus and iostats) for your analysis.
      Any futher information please let me know .

      Thanks

      Carl

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            sam.kleinman Sam Kleinman (Inactive)
            carl.dong@windfindtech.com carl dong
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              Created:
              Updated:
              Resolved: