getLog
getLog
getLog
is an administrative command that returns the most recent 1024 loggedmongod
events.getLog
does not read log data from themongod
log file. It instead reads data from a RAM cache of loggedmongod
events. To rungetLog
, use thedb.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:
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
Starting in MongoDB 4.4, 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:
totalLinesWritten
field that contains the number of log eventslog
field that contains an array of log eventsA
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
.
Filtering
Within the mongo
Shell
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 the mongo
Shell 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 the mongo
shell. The following operation uses jq
to filter on the REPL
component to present only those log
messages associated with replication:
mongo --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 the
mongo
shell 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
:
mongo --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 the mongo
shell,
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 the mongo
shell,
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>) }