Monitoring

Monitoring NATS

To monitor the NATS messaging system, nats-server provides a lightweight HTTP server on a dedicated monitoring port. The monitoring server provides several endpoints, providing statistics and other information about the following:

All endpoints return a JSON object.

The NATS monitoring endpoints support JSONP and CORS, making it easy to create single page monitoring web applications. Part of the NATS ecosystem is a tool called nats-top that visualizes data from these endpoints on the command line.

Warning: nats-server does not have authentication/authorization for the monitoring endpoint. When you plan to open your nats-server to the internet make sure to not expose the monitoring port as well. By default monitoring binds to every interface 0.0.0.0 so consider setting monitoring to localhost or have appropriate firewall rules.

In other words don't do what http://demo.nats.io:8222/ does! It is done on purpose to simplify the examples below.

Enabling monitoring from the command line

To enable the monitoring server, start the NATS server with the monitoring flag -m and the monitoring port, or turn it on in the configuration file.

-m, --http_port PORT HTTP PORT for monitoring
-ms,--https_port PORT Use HTTPS PORT for monitoring

Example:

$ nats-server -m 8222
[4528] 2019/06/01 20:09:58.572939 [INF] Starting nats-server version 2.0.0
[4528] 2019/06/01 20:09:58.573007 [INF] Starting http monitor on port 8222
[4528] 2019/06/01 20:09:58.573071 [INF] Listening for client connections on 0.0.0.0:4222
[4528] 2019/06/01 20:09:58.573090 [INF] nats-server is ready</td>

To test, run nats-server -m 8222, then go to http://localhost:8222/

Enable monitoring from the configuration file

You can also enable monitoring using the configuration file as follows:

http_port: 8222

Binding to localhost as well:

http: localhost:8222

For example, to monitor this server locally, the endpoint would be http://localhost:8222/varz. It reports various general statistics.

Monitoring endpoints

The following sections describe each supported monitoring endpoint: varz, connz, routez, subsz, gatewayz, and leafz. There are not any required arguments, however use of arguments can let you tailor monitoring to your environment and tooling.

General Information

The /varz endpoint returns general information about the server state and configuration.

Endpoint: http://server:port/varz

Result

Return Code

Success

200 (OK)

Error

400 (Bad Request)

Arguments

N/A

Example

http://demo.nats.io:8222/varz

Response

{
"server_id": "NACDVKFBUW4C4XA24OOT6L4MDP56MW76J5RJDFXG7HLABSB46DCMWCOW",
"version": "2.0.0",
"proto": 1,
"go": "go1.12",
"host": "0.0.0.0",
"port": 4222,
"max_connections": 65536,
"ping_interval": 120000000000,
"ping_max": 2,
"http_host": "0.0.0.0",
"http_port": 8222,
"https_port": 0,
"auth_timeout": 1,
"max_control_line": 4096,
"max_payload": 1048576,
"max_pending": 67108864,
"cluster": {},
"gateway": {},
"leaf": {},
"tls_timeout": 0.5,
"write_deadline": 2000000000,
"start": "2019-06-24T14:24:43.928582-07:00",
"now": "2019-06-24T14:24:46.894852-07:00",
"uptime": "2s",
"mem": 9617408,
"cores": 4,
"gomaxprocs": 4,
"cpu": 0,
"connections": 0,
"total_connections": 0,
"routes": 0,
"remotes": 0,
"leafnodes": 0,
"in_msgs": 0,
"out_msgs": 0,
"in_bytes": 0,
"out_bytes": 0,
"slow_consumers": 0,
"subscriptions": 0,
"http_req_stats": {
"/": 0,
"/connz": 0,
"/gatewayz": 0,
"/routez": 0,
"/subsz": 0,
"/varz": 1
},
"config_load_time": "2019-06-24T14:24:43.928582-07:00"
}

Connection Information

The /connz endpoint reports more detailed information on current and recently closed connections. It uses a paging mechanism which defaults to 1024 connections.

Endpoint: http://server:port/connz

Result

Return Code

Success

200 (OK)

Error

400 (Bad Request)

Arguments

Argument

Values

Description

sort

(see sort options)

Sorts the results. Default is connection ID.

auth

true, 1, false, 0

Include username. Default is false.

subs

true, 1, false, 0 or detail

Include subscriptions. Default is false. When set to detail a list with more detailed subscription information will be returned.

offset

number > 0

Pagination offset. Default is 0.

limit

number > 0

Number of results to return. Default is 1024.

cid

number, valid id

Return a connection by it's id

state

open, *closed, any

Return connections of particular state. Default is open.

The server will default to holding the last 10,000 closed connections.

Sort Options

Option

Sort by

cid

Connection ID

start

Connection start time, same as CID

subs

Number of subscriptions

pending

Amount of data in bytes waiting to be sent to client

msgs_to

Number of messages sent

msgs_from

Number of messages received

bytes_to

Number of bytes sent

bytes_from

Number of bytes received

last

Last activity

idle

Amount of inactivity

uptime

Lifetime of the connection

stop

Stop time for a closed connection

reason

Reason for a closed connection

Examples

Get up to 1024 connections: http://demo.nats.io:8222/connz

Control limit and offset: http://demo.nats.io:8222/connz?limit=16&offset=128.

Get closed connection information: http://demo.nats.io:8222/connz?state=closed.

You can also report detailed subscription information on a per connection basis using subs=1. For example: http://demo.nats.io:8222/connz?limit=1&offset=1&subs=1.

Response

{
"server_id": "NACDVKFBUW4C4XA24OOT6L4MDP56MW76J5RJDFXG7HLABSB46DCMWCOW",
"now": "2019-06-24T14:28:16.520365-07:00",
"num_connections": 2,
"total": 2,
"offset": 0,
"limit": 1024,
"connections": [
{
"cid": 1,
"ip": "127.0.0.1",
"port": 49764,
"start": "2019-06-24T14:27:25.94611-07:00",
"last_activity": "2019-06-24T14:27:25.954046-07:00",
"rtt": "275µs",
"uptime": "50s",
"idle": "50s",
"pending_bytes": 0,
"in_msgs": 0,
"out_msgs": 0,
"in_bytes": 0,
"out_bytes": 0,
"subscriptions": 1,
"name": "NATS Sample Subscriber",
"lang": "go",
"version": "1.8.1",
"subscriptions_list": [
"hello.world"
]
},
{
"cid": 2,
"ip": "127.0.0.1",
"port": 49767,
"start": "2019-06-24T14:27:43.403923-07:00",
"last_activity": "2019-06-24T14:27:43.406568-07:00",
"rtt": "96µs",
"uptime": "33s",
"idle": "33s",
"pending_bytes": 0,
"in_msgs": 0,
"out_msgs": 0,
"in_bytes": 0,
"out_bytes": 0,
"subscriptions": 1,
"name": "NATS Sample Subscriber",
"lang": "go",
"version": "1.8.1",
"subscriptions_list": [
"foo.bar"
]
}
]
}

Route Information

The /routez endpoint reports information on active routes for a cluster. Routes are expected to be low, so there is no paging mechanism with this endpoint.

Endpoint: http://server:port/routez

Result

Return Code

Success

200 (OK)

Error

400 (Bad Request)

Arguments

Argument

Values

Description

subs

true, 1, false, 0 or detail

Include subscriptions. Default is false. When set to detail a list with more detailed subscription information will be returned.

As noted above, the routez endpoint does support the subs argument from the /connz endpoint. For example: http://demo.nats.io:8222/routez?subs=1

Example

Response

{
"server_id": "NACDVKFBUW4C4XA24OOT6L4MDP56MW76J5RJDFXG7HLABSB46DCMWCOW",
"now": "2019-06-24T14:29:16.046656-07:00",
"num_routes": 1,
"routes": [
{
"rid": 1,
"remote_id": "de475c0041418afc799bccf0fdd61b47",
"did_solicit": true,
"ip": "127.0.0.1",
"port": 61791,
"pending_size": 0,
"in_msgs": 0,
"out_msgs": 0,
"in_bytes": 0,
"out_bytes": 0,
"subscriptions": 0
}
]
}

Gateway Information

The /gatewayz endpoint reports information about gateways used to create a NATS supercluster. Like routes, the number of gateways are expected to be low, so there is no paging mechanism with this endpoint.

Endpoint: http://server:port/gatewayz

Result

Return Code

Success

200 (OK)

Error

400 (Bad Request)

Arguments

Argument

Values

Description

accs

true, 1, false, 0

Include account information. Default is false.

gw_name

string

Return only remote gateways with this name.

acc_name

string

Limit the list of accounts to this account name.

Examples

Response

{
"server_id": "NANVBOU62MDUWTXWRQ5KH3PSMYNCHCEUHQV3TW3YH7WZLS7FMJE6END6",
"now": "2019-07-24T18:02:55.597398-06:00",
"name": "region1",
"host": "2601:283:4601:1350:1895:efda:2010:95a1",
"port": 4501,
"outbound_gateways": {
"region2": {
"configured": true,
"connection": {
"cid": 7,
"ip": "127.0.0.1",
"port": 5500,
"start": "2019-07-24T18:02:48.765621-06:00",
"last_activity": "2019-07-24T18:02:48.765621-06:00",
"uptime": "6s",
"idle": "6s",
"pending_bytes": 0,
"in_msgs": 0,
"out_msgs": 0,
"in_bytes": 0,
"out_bytes": 0,
"subscriptions": 0,
"name": "NCXBIYWT7MV7OAQTCR4QTKBN3X3HDFGSFWTURTCQ22ZZB6NKKJPO7MN4"
}
},
"region3": {
"configured": true,
"connection": {
"cid": 5,
"ip": "::1",
"port": 6500,
"start": "2019-07-24T18:02:48.764685-06:00",
"last_activity": "2019-07-24T18:02:48.764685-06:00",
"uptime": "6s",
"idle": "6s",
"pending_bytes": 0,
"in_msgs": 0,
"out_msgs": 0,
"in_bytes": 0,
"out_bytes": 0,
"subscriptions": 0,
"name": "NCVS7Q65WX3FGIL2YQRLI77CE6MQRWO2Y453HYVLNMBMTVLOKMPW7R6K"
}
}
},
"inbound_gateways": {
"region2": [
{
"configured": false,
"connection": {
"cid": 9,
"ip": "::1",
"port": 52029,
"start": "2019-07-24T18:02:48.76677-06:00",
"last_activity": "2019-07-24T18:02:48.767096-06:00",
"uptime": "6s",
"idle": "6s",
"pending_bytes": 0,
"in_msgs": 0,
"out_msgs": 0,
"in_bytes": 0,
"out_bytes": 0,
"subscriptions": 0,
"name": "NCXBIYWT7MV7OAQTCR4QTKBN3X3HDFGSFWTURTCQ22ZZB6NKKJPO7MN4"
}
}
],
"region3": [
{
"configured": false,
"connection": {
"cid": 4,
"ip": "::1",
"port": 52025,
"start": "2019-07-24T18:02:48.764577-06:00",
"last_activity": "2019-07-24T18:02:48.764994-06:00",
"uptime": "6s",
"idle": "6s",
"pending_bytes": 0,
"in_msgs": 0,
"out_msgs": 0,
"in_bytes": 0,
"out_bytes": 0,
"subscriptions": 0,
"name": "NCVS7Q65WX3FGIL2YQRLI77CE6MQRWO2Y453HYVLNMBMTVLOKMPW7R6K"
}
},
{
"configured": false,
"connection": {
"cid": 8,
"ip": "127.0.0.1",
"port": 52026,
"start": "2019-07-24T18:02:48.766173-06:00",
"last_activity": "2019-07-24T18:02:48.766999-06:00",
"uptime": "6s",
"idle": "6s",
"pending_bytes": 0,
"in_msgs": 0,
"out_msgs": 0,
"in_bytes": 0,
"out_bytes": 0,
"subscriptions": 0,
"name": "NCKCYK5LE3VVGOJQ66F65KA27UFPCLBPX4N4YOPOXO3KHGMW24USPCKN"
}
}
]
}
}

Leaf Nodes Information

The /leafz endpoint reports detailed information about the leaf node connections.

Endpoint: http://server:port/leafz

Result

Return Code

Success

200 (OK)

Error

400 (Bad Request)

Arguments

Argument

Values

Description

subs

true, 1, false, 0

Include internal subscriptions. Default is false.

As noted above, the leafz endpoint does support the subs argument from the /connz endpoint. For example: http://demo.nats.io:8222/leafz?subs=1

Example

Response

{
"server_id": "NC2FJCRMPBE5RI5OSRN7TKUCWQONCKNXHKJXCJIDVSAZ6727M7MQFVT3",
"now": "2019-08-27T09:07:05.841132-06:00",
"leafnodes": 1,
"leafs": [
{
"account": "$G",
"ip": "127.0.0.1",
"port": 6223,
"rtt": "200µs",
"in_msgs": 0,
"out_msgs": 10000,
"in_bytes": 0,
"out_bytes": 1280000,
"subscriptions": 1,
"subscriptions_list": [
"foo"
]
}
]
}

Subscription Routing Information

The /subsz endpoint reports detailed information about the current subscriptions and the routing data structure. It is not normally used.

Endpoint: http://server:port/subsz

Result

Return Code

Success

200 (OK)

Error

400 (Bad Request)

Arguments

Argument

Values

Description

subs

true, 1, false, 0

Include subscriptions. Default is false.

offset

integer > 0

Pagination offset. Default is 0.

limit

integer > 0

Number of results to return. Default is 1024.

test

subject

Test whether a subsciption exists.

Example

Response

{
"num_subscriptions": 2,
"num_cache": 0,
"num_inserts": 2,
"num_removes": 0,
"num_matches": 0,
"cache_hit_rate": 0,
"max_fanout": 0,
"avg_fanout": 0
}

Creating Monitoring Applications

NATS monitoring endpoints support JSONP and CORS. You can easily create single page web applications for monitoring. To do this you simply pass the callback query parameter to any endpoint.

For example:

http://demo.nats.io:8222/connz?callback=cb

Here is a JQuery example implementation:

$.getJSON('http://demo.nats.io:8222/connz?callback=?', function(data) {
console.log(data);
});

Monitoring Tools

In addition to writing custom monitoring tools, you can monitor nats-server in Prometheus. The Prometheus NATS Exporter allows you to configure the metrics you want to observe and store in Prometheus. There's a sample Grafana dashboard that you can use to visualize the server metrics.