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nats-top is a top-like tool for monitoring nats-server servers.
The nats-top tool provides a dynamic real-time view of a NATS server. nats-top can display a variety of system summary information about the NATS server, such as subscription, pending bytes, number of messages, and more, in real time. For example:
nats-server version 0.6.4 (uptime: 31m42s)
Load: CPU: 0.8% Memory: 5.9M Slow Consumers: 0
In: Msgs: 34.2K Bytes: 3.0M Msgs/Sec: 37.9 Bytes/Sec: 3389.7
Out: Msgs: 68.3K Bytes: 6.0M Msgs/Sec: 75.8 Bytes/Sec: 6779.4
Connections: 4
HOST CID SUBS PENDING MSGS_TO MSGS_FROM BYTES_TO BYTES_FROM LANG VERSION SUBSCRIPTIONS 2 5 0 11.6K 11.6K 1.1M 905.1K go 1.1.0 foo, hello 3 1 0 34.2K 0 3.0M 0 go 1.1.0 _INBOX.a96f3f6853616154d23d1b5072 4 5 0 11.2K 11.1K 873.5K 1.1M go 1.1.0 foo, hello 5 8 0 11.4K 11.5K 1014.6K 1.0M go 1.1.0 foo, hello


nats-top can be installed using go install. For example:
go install
With newer versions of Go, you will be required to use go install
NOTE: You may have to run the above command as user sudo depending on your setup. If you receive an error that you cannot install nats-top because your $GOPATH is not set, when in fact it is set, use command sudo -E go get to install nats-top. The -E flag tells sudo to preserve the current user's environment.


Once installed, nats-top can be run with the command nats-top and optional arguments.
nats-top [-s server] [-m monitor] [-n num_connections] [-d delay_in_secs] [-sort by]


Optional arguments inclde the following:
-m monitor
Monitoring http port from nats-server.
-n num_connections
Limit the connections requested to the server (default 1024).
-d delay_in_secs
Screen refresh interval (default 1 second).
-sort by
Field to use for sorting the connections (see below).


While in nats-top view, you can use the following commands.


Use the o<option> command to set the primary sort key to the <option> value. The option value can be one of the following: cid, subs, pending, msgs_to, msgs_from, bytes_to, bytes_from, lang, version.
You can also set the sort option on the command line using the -sort flag. For example: nats-top -sort bytes_to.


Use the n<limit> command to set the sample size of connections to request from the server.
You can also set this on the command line using the -n num_connections flag. For example: nats-top -n 1.
Note that if n<limit> is used in conjunction with -sort, the server will respect both options allowing queries such as the following: Query for the connection with largest number of subscriptions: nats-top -n 1 -sort subs.

s, ? and q Commands

Use the s command to toggle displaying connection subscriptions.
Use the ? command to show help message with options.
Use the q command to quit nats-top.


For a walkthrough with nats-top check out the tutorial.