getLog
Definition
getLoggetLogis an administrative command that returns the most recent 1024 loggedmongodevents.getLogdoes not read log data from themongodlog file. It instead reads data from a RAM cache of loggedmongodevents. To rungetLog, use thedb.adminCommand()method.getLogreturns log data in escaped Relaxed Extended JSON v2.0 format. Previously, log data was returned as plaintext.
Compatibility
This command is available in deployments hosted in the following environments:
MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud
Note
This command is supported in all MongoDB Atlas clusters. For information on all commands, see Unsupported Commands.
MongoDB Enterprise: The subscription-based, self-managed version of MongoDB
MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB
Syntax
The command has the following syntax:
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. |
Note
The getLog command no longer accepts the rs value, as this
categorization of message type has been deprecated. Instead, log messages are
now always identified by their component -
including REPL for replication messages. See
Filtering by Component for log
parsing examples that filter on the component field.
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:
totalLinesWrittenfield that contains the number of log eventslogfield that contains an array of log eventsA
db.adminCommand()response document, containing status and timestamp information.
Behavior
Line Truncation
getLog truncates any event that contains more than 1024 characters.
Character Escaping
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.
Filtering
Within mongosh
getLog output can be filtered to make results more
readable or to match on specific criteria.
The following operation prints just the log field (which contains
the array of all recent log events), and removes
character escaping from each log
message:
db.adminCommand( { getLog:'global'} ).log.forEach(x => {print(x)})
This operation presents getLog output in the same format as
the MongoDB log file.
Outside mongosh with jq
When working with MongoDB structured logging, the third-party jq command-line utility is a useful tool that allows for easy pretty-printing of log entries, and powerful key-based matching and filtering.
jq is an open-source JSON parser, and is available for
Linux, Windows, and macOS.
To use jq with getLog output, you must use the
--eval option to mongosh.
The following operation uses jq to filter on the REPL
component to present only those log
messages associated with replication:
mongosh --quiet --eval "db.adminCommand( { getLog:'global'} ).log.forEach(x => {print(x)})" | jq -c '. | select(.c=="REPL")'
Be sure to provide any necessary connection-specific parameters to
mongosh as needed, such as --host or --port.
See Parsing Structured Log Messages for more examples of filtering log output
using jq. The jq syntax presented in each linked example can be
used with the above mongo --eval operation with minor adjustment.
For example, the following syntax adapts the linked "Counting Unique
Messages" example for use with getLog:
mongosh --quiet --eval "db.adminCommand( { getLog:'global'} ).log.forEach(x => {print(x)})" | jq -r ".msg" | sort | uniq -c | sort -rn | head -10
Examples
Retrieve Available Log Filters
The following operation, run from mongosh,
returns the available log filters for passing to getLog:
db.adminCommand( { getLog: "*" } )
The operation returns the following document:
{ "names" : [ "global", "startupWarnings" ], "ok" : 1 }
Retrieve Recent Events from Log
The following operation, run from mongosh,
retrieves the most recent global events for the
mongod:
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>) }