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Mongotail, Log all MongoDB queries in a "tail"able way.

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Mongotail, Log all MongoDB queries in a “tail”able way.

mongotail is a command line tool to outputs any operation from a Mongo database in the standard output. You can see the operations collected by the database profiler from a console, or redirect the result to a file, pipes it with grep or other command line tool, etc.

The syntax is very similar to mongo client, and the output, as like tail command will be the latest 10 lines of logging.

But the more interesting feature (also like tail) is to see the changes in “real time” with the -f option, and occasionally filter the result with grep to find a particular operation.



mongotail [db address] [options]

“db address” can be:

foo foo database on local machine (IPv4 connection)
:1234/foo foo database on local machine on port 1234 foo database on machine
remotehost/foo foo database on remotehost machine foo database on machine on port 9999
“[::1]:9999/foo” foo database on ::1 machine on port 9999 (IPv6 connection)

Optional arguments:

-u USERNAME, --username USERNAME
 username for authentication
-p PASSWORD, --password PASSWORD
 password for authentication. If username is given and password isn’t, it’s asked from tty
-b AUTH_DATABASE, --authenticationDatabase AUTH_DATABASE
 database to use to authenticate the user. If not specified, the user will be authenticated against the database specified in the [db address]
-n N, --lines N
 output the last N lines, instead of the last 10. Use ALL value to show all lines
-f, --follow output appended data as the log grows
-l LEVEL, --level LEVEL
 specifies the profiling level, which is either 0 for no profiling, 1 for only slow operations, or 2 for all operations. Or use with ‘status’ word to show the current level configured. Uses this option once before logging the database
-s MS, --slowms MS
 sets the threshold in milliseconds for the profile to consider a query or operation to be slow (use with –level 1). Or use with ‘status’ word to show the current milliseconds configured
-m, --metadata extra metadata fields to show. Known fields (may vary depending of the operation and the MongoDB version): millis, nscanned, docsExamined, execStats, lockStats …
-i, --info get information about the MongoDB server we’re connected to
-v, --verbose verbose mode (not recommended). All the operations will printed in JSON without format and with all the information available from the log
--ssl creates the connection to the server using SSL
--sslCertFile SSL_CERT_FILE
 certificate file used to identify the local connection against MongoDB
--sslKeyFile SSL_KEY_FILE
 private keyfile used to identify the local connection against MongoDB. If included with the certfile then only the sslCertFile is needed
--sslCertReqs SSL_CERT_REQS
 specifies whether a certificate is required from the other side of the connection, and whether it will be validated if provided. It must be any of three values: 0 (certificate ignored), 1 (not required, but validated if provided), 2 (required and validated)
 file that contains a set of concatenated “certification authority” certificates, which are used to validate certificates passed from the other end of the connection
 password or passphrase for decrypting the private key in sslCertFile or sslKeyFile. Only necessary if the private key is encrypted
--sslCrlFile SSL_CRLFILE
 path to a PEM or DER formatted certificate revocation list
-h, --help show this help message and exit
-V, --version show program’s version number and exit

Enabling Database Profiling and Showing Logs

You have to activate first in the current database the profiler, so MongoDB will capture all the activity in a special document that is read by Mongotail.

You can achieve this with -l, --level option. For example, if you want to see the logs from MYDATABASE, first you have to execute this:

$ mongotail MYDATABASE -l 2

Then you can see the latest lines of logging with:

$ mongotail MYDATABASE
2015-02-24 19:17:01.194 QUERY  [Company] : {"_id": ObjectId("548b164144ae122dc430376b")}. 1 returned.
2015-02-24 19:17:01.195 QUERY  [User] : {"_id": ObjectId("549048806b5d3db78cf6f654")}. 1 returned.
2015-02-24 19:17:01.196 UPDATE [Activation] : {"_id": "AB524"}, {"_id": "AB524", "code": "f2cbad0c"}. 1 updated.
2015-02-24 19:17:10.729 COUNT  [User] : {"active": {"$exists": true}, "firstName": {"$regex": "mac"}}

To Connect with SSL or a remote Mongo instance, check the options with mongotail --help command.

NOTE: The level chosen can affect performance. It also can allow the server to write the contents of queries to the log, which might have information security implications for your deployment. Remember to setup your database profiling level to 0 again after debugging your data:

$ mongotail MYDATABASE -l 0

A step-by-step guide of how to use Mongotail and the latest features is here.


See INSTALL.rst guide to install from sources. To install from PyPI repositories, follow these instructions depending of your OS:

Linux Installation

You can install the latest stable version with pip in your environment with:

$ pip install mongotail

Execute this command with administrator/root privileges (in Debian/Ubuntu Linux distribution prepend sudo to the command).

You have to be installed pip tool first. In Debian/Ubuntu Linux distribution you can install it with (also with root privileges):

$ apt-get install python-pip

Mac OSX Installation

First you need to install the Python package manager pip in your environment, and then like Linux to install Mongotail you can execute sudo pip install mongotail from the command line, but also it can be installed with easy_install, an old Python package manager present in most OSX versions. Try this:

$ sudo easy_install mongotail


Run with Docker (you don’t need to download the source code):

$ docker run -it --rm mrsarm/mongotail --help

If you want to connect with a database also running locally in a container, you have to link both instances (see howto in the Docker documentation), or if the db is a local instance running without Docker, remember to use the local IP of your computer because the localhost address (IP points to the container, not to your host. Eg.:

$ docker run -it --rm mrsarm/mongotail

If it does not work, it may be related with network access rules, or because the mongo instance is not listening remote connections, check to have properly configured the IP Binding.



Authors: (2015-2020) Mariano Ruiz <>

Changelog: CHANGELOG.rst

More guides:

License: GPL-3

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