getLog¶

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Syntax
Behavior
Examples

getLog¶

getLog is an administrative command that returns the most recent 1024 logged mongod events. getLog does not read log data from the mongod log file. It instead reads data from a RAM cache of logged mongod events. To run getLog, use the db.adminCommand() method.

Starting in MongoDB 4.4, getLog returns log data in escaped Relaxed Extended JSON v2.0 format. Previously, log data was returned as plaintext.

Syntax¶

The getLog command has the following syntax:

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db.adminCommand( { getLog: <value> } )

Command Fields¶

The possible values for getLog are:

Value	Description
`*`	Returns a list of the available values to the `getLog` command.
`global`	Returns the combined output of all recent log entries.
`startupWarnings`	Returns log entries that may contain errors or warnings from MongoDB’s log from when the current process started. If `mongod` started without warnings, this filter may return an empty array.

Output¶

If specified *, then the command returns a document with the names of the other acceptable values.

Otherwise, the command returns a document that includes the following fields:

totalLinesWritten field that contains the number of log events
log field that contains an array of log events
A db.adminCommand() response document, containing status and timestamp information.

Behavior¶

Line Truncation¶

Starting in MongoDB 4.2, getLog truncates any event that contains more than 1024 characters. In earlier versions, getLog truncates after 512 characters.

Character Escaping¶

Starting in MongoDB 4.4, getLog returns log data in escaped Relaxed Extended JSON v2.0 format, using the following escape sequences to render log output as valid JSON:

Character Represented	Escape Sequence
Quotation Mark (`"`)	`\"`
Backslash (`\`)	`\\`
Backspace (`0x08`)	`\b`
Formfeed (`0x0C`)	`\f`
Newline (`0x0A`)	`\n`
Carriage return (`0x0D`)	`\r`
Horizontal tab (`0x09`)	`\t`

Control characters not listed above are escaped with \uXXXX where “XXXX” is the unicode codepoint in hexadecimal. Bytes with invalid UTF-8 encoding are replaced with the unicode replacement character represented by \ufffd.

Examples¶

Retrieve Available Log Filters¶

The following operation, run from the mongo shell, returns the available log filters for passing to getLog:

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db.adminCommand( { getLog: "*" } )

The operation returns the following document:

{ "names" : [ "global", "startupWarnings" ], "ok" : 1 }

Retrieve Recent Events from Log¶

The following operation, run from the mongo shell, retrieves the most recent global events for the mongod:

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db.adminCommand( { getLog : "global" } )

The operation returns a document similar to the following:

{
      "totalLinesWritten" : <num>,
      "log" : [
              "{\"t\":{\"$date\":\"2020-05-19T19:10:48.871+00:00\"},\"s\":\"I\",  \"c\":\"STORAGE\",  \"id\":4615611, \"ctx\":\"initandlisten\",\"msg\":\"MongoDB starting\",\"attr\":{\"pid\":12345,\"port\":27001,\"dbPath\":\"/var/lib/mongo\",\"architecture\":\"64-bit\",\"host\":\"server1.example.com\"}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:48.871+00:00\"},\"s\":\"I\",  \"c\":\"CONTROL\",  \"id\":23403,   \"ctx\":\"initandlisten\",\"msg\":\"Build Info\",\"attr\":{\"buildInfo\":{\"version\":\"4.4.0\",\"gitVersion\":\"328c35e4b883540675fb4b626c53a08f74e43cf0\",\"openSSLVersion\":\"OpenSSL 1.1.1c FIPS  28 May 2019\",\"modules\":[],\"allocator\":\"tcmalloc\",\"environment\":{\"distmod\":\"rhel80\",\"distarch\":\"x86_64\",\"target_arch\":\"x86_64\"}}}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:48.871+00:00\"},\"s\":\"I\",  \"c\":\"CONTROL\",  \"id\":51765,   \"ctx\":\"initandlisten\",\"msg\":\"Operating System\",\"attr\":{\"os\":{\"name\":\"CentOS Linux release 8.0.1905 (Core) \",\"version\":\"Kernel 4.18.0-80.11.2.el8_0.x86_64\"}}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:48.871+00:00\"},\"s\":\"I\",  \"c\":\"CONTROL\",  \"id\":21951,   \"ctx\":\"initandlisten\",\"msg\":\"Options set by command line\",\"attr\":{\"options\":{\"config\":\"/etc/mongod.conf\",\"net\":{\"bindIp\":\"127.0.0.1\",\"port\":27001},\"processManagement\":{\"fork\":true,\"timeZoneInfo\":\"/usr/share/zoneinfo\"},\"replication\":{\"replSetName\":\"repl-shard1\"},\"sharding\":{\"clusterRole\":\"shardsvr\"},\"storage\":{\"dbPath\":\"/var/lib/mongo\",\"journal\":{\"enabled\":true},\"wiredTiger\":{\"engineConfig\":{\"cacheSizeGB\":0.1}}},\"systemLog\":{\"destination\":\"file\",\"logAppend\":true,\"path\":\"/var/log/mongodb/mongod.log\"}}}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:48.873+00:00\"},\"s\":\"I\",  \"c\":\"STORAGE\",  \"id\":22270,   \"ctx\":\"initandlisten\",\"msg\":\"Storage engine to use detected by data files\",\"attr\":{\"dbpath\":\"/var/lib/mongo\",\"storageEngine\":\"wiredTiger\"}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:48.873+00:00\"},\"s\":\"I\",  \"c\":\"STORAGE\",  \"id\":22315,   \"ctx\":\"initandlisten\",\"msg\":\"wiredtiger_open config\",\"attr\":{\"config\":\"create,cache_size=102M,session_max=33000,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,close_scan_interval=10,close_handle_minimum=250),statistics_log=(wait=0),verbose=[recovery_progress,checkpoint_progress,compact_progress],\"}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:58.877+00:00\"},\"s\":\"I\",  \"c\":\"CONNPOOL\", \"id\":22576,   \"ctx\":\"ReplicaSetMonitor-TaskExecutor\",\"msg\":\"Connecting\",\"attr\":{\"hostAndPort\":\"server1.example.com:27001\"}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:58.877+00:00\"},\"s\":\"I\",  \"c\":\"CONNPOOL\", \"id\":22576,   \"ctx\":\"ReplicaSetMonitor-TaskExecutor\",\"msg\":\"Connecting\",\"attr\":{\"hostAndPort\":\"server2.example.com:27001\"}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:58.877+00:00\"},\"s\":\"I\",  \"c\":\"CONNPOOL\", \"id\":22576,   \"ctx\":\"ReplicaSetMonitor-TaskExecutor\",\"msg\":\"Connecting\",\"attr\":{\"hostAndPort\":\"server3.example.com:27001\"}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:58.877+00:00\"},\"s\":\"I\",  \"c\":\"CONNPOOL\", \"id\":22576,   \"ctx\":\"ReplicaSetMonitor-TaskExecutor\",\"msg\":\"Connecting\",\"attr\":{\"hostAndPort\":\"server4.example.com:27001\"}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:58.877+00:00\"},\"s\":\"I\",  \"c\":\"CONNPOOL\", \"id\":22576,   \"ctx\":\"ReplicaSetMonitor-TaskExecutor\",\"msg\":\"Connecting\",\"attr\":{\"hostAndPort\":\"server5.example.com:27001\"}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:58.877+00:00\"},\"s\":\"I\",  \"c\":\"CONNPOOL\", \"id\":22576,   \"ctx\":\"ReplicaSetMonitor-TaskExecutor\",\"msg\":\"Connecting\",\"attr\":{\"hostAndPort\":\"server6.example.com:27001\"}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:58.877+00:00\"},\"s\":\"I\",  \"c\":\"NETWORK\",  \"id\":23015,   \"ctx\":\"listener\",\"msg\":\"Listening on\",\"attr\":{\"address\":\"/tmp/mongodb-27001.sock\"}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:58.877+00:00\"},\"s\":\"I\",  \"c\":\"NETWORK\",  \"id\":23015,   \"ctx\":\"listener\",\"msg\":\"Listening on\",\"attr\":{\"address\":\"127.0.0.1\"}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:10:58.877+00:00\"},\"s\":\"I\",  \"c\":\"NETWORK\",  \"id\":23016,   \"ctx\":\"listener\",\"msg\":\"Waiting for connections\",\"attr\":{\"port\":27001,\"ssl\":\"off\"}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:15:10.392+00:00\"},\"s\":\"I\",  \"c\":\"NETWORK\",  \"id\":22943,   \"ctx\":\"listener\",\"msg\":\"connection accepted\",\"attr\":{\"remote\":\"127.0.0.1:35724\",\"sessionId\":67,\"connectionCount\":30}}",
              "{\"t\":{\"$date\":\"2020-05-19T19:15:10.393+00:00\"},\"s\":\"I\",  \"c\":\"NETWORK\",  \"id\":51800,   \"ctx\":\"conn67\",\"msg\":\"client metadata\",\"attr\":{\"remote\":\"127.0.0.1:35724\",\"client\":\"conn67\",\"doc\":{\"application\":{\"name\":\"MongoDB Shell\"},\"driver\":{\"name\":\"MongoDB Internal Client\",\"version\":\"4.4.0\"},\"os\":{\"type\":\"Linux\",\"name\":\"CentOS Linux release 8.0.1905 (Core) \",\"architecture\":\"x86_64\",\"version\":\"Kernel 4.18.0-80.11.2.el8_0.x86_64\"}}}}"
      ],
      "ok" : 1,
      "$gleStats" : {
              "lastOpTime" : Timestamp(<ts>),
              "electionId" : ObjectId(<id>)
      },
      "lastCommittedOpTime" : Timestamp(<ts>),
      "$configServerState" : {
              "opTime" : {
                      "ts" : Timestamp(<ts>),
                      "t" : NumberLong(8)
               }
      },
      "$clusterTime" : {
              "clusterTime" : Timestamp(<ts>),
              "signature" : {
                      "hash" : BinData(<bin>),
                      "keyId" : NumberLong(0)
               }
      },
      "operationTime" : Timestamp(<ts>)
}

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