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:

• General Server Information

• Connections

• Routing

• Gateways

• Leaf Nodes

• Subscription Routing

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

• Get route information: http://demo.nats.io:8222/routez?subs=1

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

• Retrieve Gateway Information: http://demo.nats.io:8222/gatewayz

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

• Get leaf nodes information: http://demo.nats.io:8222/leafz?subs=1

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

• Get subscription routing information: http://demo.nats.io:8222/subsz

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.