monitr

Nodejs process monitoring tool.

This module currently works only on Linux operating systems. This module spawns a thread and begins monitoring the process.

It looks up /proc/* files on the system to report CPU Usage. It looks up /proc/pid/* files on the system to report its own stats. It calls the process.monitor.* methods to report total requests, open connections and total data transferred.

process.monitor.* methods are set by lib/monitor.js.

Here is the list of data the module reports periodically:

 { status: 
     { pid: <pid of the node process>,
       ts: <current time stamp>,
       cluster: <process group id>,
       reqstotal: <total requests processed by this node process server>,
       utcstart: <when the process was started>,
       events: <number of new reports being processed since last stats reporting>,,
       cpu: <cpu usage>,
       mem: <memory usage>,
       cpuperreq: <cpu usage per request>,
       oreqs: <current open requests count>,
       sys_cpu: <system cpu load>,
       oconns: <current open connections count>,
       user_cpu: <user cpu load>,
       rps: <requests per second>,
       kbs_out: <kbs of data transferred since last stats reporting>,
       elapsed: <time elapsed since last event>,
       kb_trans: <total kbs of data transferred>,
       jiffyperreq: <cpu usage in terms of ticks per request> 
    }
 }

This package is tested only with Node versions 10 and 12.

install

With npm do:

npm install monitr

methods

var monitor = require('monitr');

start()

monitor.start();

Spawns a thread and monitors the process. Writes process stats every second to the socket path.

stop()

monitor.stop();

Terminates the thread and closes the socket.

setIpcMonitorPath(socketPath)

monitor.setIpcMonitorPath('/tmp/my-process-stats.mon');

Sets the datagram socket name to write the stats. Defaults to /tmp/nodejs.mon

Health Status

Monitr now supports custom health functionality whereby the app can report its own health. The following methods are added to process.monitor to set and get the health information.

setHealthStatus(isDown, statusCode)
isDown()
getStatusCode()
getStatusTimestamp() - Return seconds when setHealthStatus was last called
getStatusDate() - Return Date object

Once setHealthStatus is invoked, the status json, described above, will have following additional fields.

health_status_timestamp: <timestamp when the setHealthStatus was invoked, in sec>,
health_is_down: <app is down or up, boolean>,
health_status_code: <health status code>

Handling HUP events

Monitr installs a custom SIGHUP handler which will optionally print out a NodeJS stack backtrace of the Javascript currently being executed. This can be useful for debugging where a NodeJS process may be stuck.

Due to the method by which the stack backtrace is obtained (installing a v8 Javascript engine debug event listener and simulating a debugger event), there is a performance slowdown for code running while the stack backtrace option is active.

By default the backtrace option is not enabled. You can enable it setting the showBacktrace property to true, e.g.

monitor.showBacktrace = true

Setting monitor.showBacktrace to false will restore the original performance by removing the debug event listener.

Example

Please refer to the examples/README.md for examples showing the use of these functions.

Build Status

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