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  1. Core Server
  2. SERVER-38232

Mongod on Ubuntu 16/18 does not create a pid file

    • Server Development Platform
    • Fully Compatible
    • ALL
    • v6.0, v5.0, v4.4
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      Install a server with Ubuntu 16 or 18 and install mongodb-org-server 3.4.x from the repo.mongodb.org repos, start it up and it won't create a pid file where it is supposed to according to the systemd config file.

      Install a server with Ubuntu 16 or 18 and install mongodb-org-server 3.4.x from the repo.mongodb.org repos, start it up and it won't create a pid file where it is supposed to according to the systemd config file.
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      I was alerted to missing log files on some of our production mongod servers yesterday, the cause was that log rotate was trying to use the pid file to send a signal to mongo to tell it the log files had rotated. But the pid file wasn't where we expected to find it.

      Looking in the systemd service file it should be in /var/run/mongodb/mongod.pid but nothing appeared there, even after I created the folder which was missing. Then I added this to my mongod config file:

         pidFilePath: /var/run/mongodb.pid 

      Then mongod failed to start up, as it didn't have permission to create. I touched the file and gave mongo permissions and it started, which should fix our issues.

      I would say that this should not be fixed by admins, but should be correctly managed by mongod's systemd service file.

      I would have expected a warning or error to appear in the logs in this situation, but nothing appears:

      2018-11-22T12:25:35.418+0000 I CONTROL  [main] ***** SERVER RESTARTED *****                          
      2018-11-22T12:25:35.427+0000 I CONTROL  [initandlisten] MongoDB starting : pid=12211 port=27017 dbpath=/srv/mongodb 64-bit host=some.host.domain.com
      2018-11-22T12:25:35.427+0000 I CONTROL  [initandlisten] db version v3.4.15                          
      2018-11-22T12:25:35.427+0000 I CONTROL  [initandlisten] git version: 52e5b5fbaa3a2a5b1a217f5e647b5061817475f9
      2018-11-22T12:25:35.427+0000 I CONTROL  [initandlisten] OpenSSL version: OpenSSL 1.0.2g  1 Mar 2016  
      2018-11-22T12:25:35.427+0000 I CONTROL  [initandlisten] allocator: tcmalloc                          
      2018-11-22T12:25:35.427+0000 I CONTROL  [initandlisten] modules: none                               
      2018-11-22T12:25:35.427+0000 I CONTROL  [initandlisten] build environment:                           
      2018-11-22T12:25:35.427+0000 I CONTROL  [initandlisten]     distmod: ubuntu1604                      
      2018-11-22T12:25:35.427+0000 I CONTROL  [initandlisten]     distarch: x86_64                         
      2018-11-22T12:25:35.427+0000 I CONTROL  [initandlisten]     target_arch: x86_64                      
      2018-11-22T12:25:35.427+0000 I CONTROL  [initandlisten] options: { config: "/etc/mongod.conf", net: { http: { RESTInterfaceEnabled: false, enabled: false } }, replication: { replSetName: "dev" }, storage: { dbPath: "/srv/mongodb", directoryPerDB: true, engine: "wiredTiger", journal: { enabled: true }, wiredTiger: { c
      ollectionConfig: { blockCompressor: "snappy" }, engineConfig: { journalCompressor: "snappy" }, indexConfig: { prefixCompression: true } } }, systemLog: { destination: "file", logAppend: true, logRotate: "reopen", path: "/var/log/mongodb/mongodb.log" } }
      2018-11-22T12:25:35.454+0000 I STORAGE  [initandlisten] wiredtiger_open config: create,cache_size=7511M,session_max=20000,eviction=(threads_min=4,threads_max=4),config_base=false,statistics=(fast),log=(enabled=true,archive=true,path=journal,compressor=snappy),file_manager=(close_idle_time=100000),checkpoint=(wait=60,
      2018-11-22T12:25:38.052+0000 I STORAGE  [initandlisten] WiredTiger message [1542889538:52406][12211:0x7fbb84eded00], txn-recover: Main recovery loop: starting at 5591/38323200
      2018-11-22T12:25:38.174+0000 I STORAGE  [initandlisten] WiredTiger message [1542889538:174123][12211:0x7fbb84eded00], txn-recover: Recovering log 5591 through 5592
      2018-11-22T12:25:38.232+0000 I STORAGE  [initandlisten] WiredTiger message [1542889538:232811][12211:0x7fbb84eded00], txn-recover: Recovering log 5592 through 5592
      2018-11-22T12:25:55.956+0000 I STORAGE  [initandlisten] Starting WiredTigerRecordStoreThread local.oplog.rs
      2018-11-22T12:25:55.956+0000 I STORAGE  [initandlisten] The size storer reports that the oplog contains 39153394 records totaling to 10711736188 bytes
      2018-11-22T12:25:55.956+0000 I STORAGE  [initandlisten] Sampling from the oplog between Nov  8 04:49:55:1e and Nov 22 12:25:26:2 to determine where to place markers for truncation
      2018-11-22T12:25:55.957+0000 I STORAGE  [initandlisten] Taking 1000 samples and assuming that each section of oplog contains approximately 391418 records totaling to 107085642 bytes

      My server here is running 3.4.15 but I tested with 3.14.18 from repo.mongodb.org on my laptop and saw the same issue

            ryan.egesdahl@mongodb.com Ryan Egesdahl (Inactive)
            james.stocker James Stocker
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