"top" command for Node apps
The idea is to be able to quickly see the heaviest currently running Node functions using a single command in the terminal just like with "top" for regular processes. Another major point is only attaching the inspector for the time of the profiling so the tool can be always available in a production server without causing any overhead.
Once this is enabled there's no need to restart the app with "--profile" flag so any unexpected high CPU usage can be debugged more easily.
Usage - with no code changes required(Linux only)
npm i -g ntop ntop inject 12345 // where 12345 is the process id ntop 12345
Usage with includes in a project
Add to the script to enable communication with CLI tool
const ntop = require('ntop') ntop()
Then run the CLI. It will find all processes enabled for ntop communication
You'll see a list of ntop-enabled Node processes and their corresponding PIDs for convenience. Now you can see the list of functions for any process with
Example output:
- (garbage collector) | 11.703ms |
- utils.bulkPreparePacket | 1.53ms | file:///home/app/src/Utils.js:91:26
- (anonymous) | 1.181ms | evalmachine.:3:14
- (anonymous) | 1.126ms | file:///home/app/node_modules/lodash/lodash.js:1223:19
Custom sampling time 5s
Verbose output showing breadcrumbs i.e. to see what called (anonymous)
Example output with "breadcrumbs":
-
(garbage collector) | 4.191ms |
-
utils.bulkPreparePacket | 3.034ms | file:///home/app/src/Utils.js:91:26
< prepareBulkData < (anonymous) < update < emit < update < processTick < (anonymous) < listOnTimeout < processTimers -
(anonymous) | 2.574ms | evalmachine.:3:14
< listOnTimeout < processTimers -
prepareBulkData | 1.516ms | file:///home/app/src/controllers/Map.js:672:17
< (anonymous) < update < emit < update < processTick < (anonymous) < listOnTimeout < processTimers -
hasCallback | 1.141ms | file:///home/app/src/Scripting.js:271:13
< update < emit < update < processTick < (anonymous) < listOnTimeout < processTimers
Experimental flame chart
"Flame chart" (initial experiment):
- (root) 3056.191ms
-- processTimers 0.661ms
--- listOnTimeout 0.661ms
---- (anonymous function) 0.661ms
----- processTick 0.661ms
------ queueNextAction 0.661ms
------- setImmediate 0.661ms
-------- Immediate 0.661ms
--------- initAsyncResource 0.661ms
-- processTimers 1.305ms
--- listOnTimeout 1.305ms
---- (anonymous function) 1.305ms
----- processTick 1.305ms
------ update 1.305ms
------- emit 1.305ms
-------- update 1.305ms
--------- (anonymous function) 1.305ms
-- (garbage collector) 2.185ms
-- processTimers 1.118ms
--- listOnTimeout 1.118ms
---- (anonymous function) 1.118ms
----- processTick 1.118ms
------ update 1.118ms
------- emit 1.118ms
-------- update 1.118ms
--------- (anonymous function) 1.118ms
---------- prepareBulkData 1.118ms
----------- utils.bulkPreparePacket 1.118ms
-- processTimers 1.471ms
--- listOnTimeout 1.471ms
---- (anonymous function) 1.471ms
----- processTick 1.471ms
------ update 1.471ms
------- emit 1.471ms
-------- update 1.471ms
--------- (anonymous function) 1.471ms
---------- prepareBulkData 1.471ms
----------- utils.bulkPreparePacket 1.471ms
------------ preparePacket 1.471ms