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ExpvarMon

TermUI based Go apps monitor using expvars variables (/debug/vars). Quickest way to monitor your Go app.

Introduction

Go apps console monitoring tool. Minimal configuration efforts. Quick and fast monitoring solution for one or multiple services.

Features

Single- and multi-apps mode
Local and remote apps support
Arbitrary number of apps and vars to monitor (from 1 to 30+, depends on size of your terminal)
Track restarted/failed apps
Show maximum value
Supports: Integer, float, duration, memory, string, bool variables
Sparkline charts for integer, duration and memory data
Auto-resize on font-size change or window resize
Uses amazing TermUI library by gizak

Demo

Multiple apps mode

Single app mode

You can monitor arbitrary number of services and variables:

Purpose

This app targets debug/develop sessions when you need an instant way to monitor you app(s). It's not intended to monitor apps in production (though it may be convenient). Also it doesn't use any storage engines and doesn't send notifications.

Install

Just run go install:

go get github.com/divan/expvarmon
go install github.com/divan/expvarmon

Usage

Prepare your app

First, you have to add expvars support into your Go program. It's as simple as:

import _ "expvar"

and note the port your app is listening on. It it's not, just add two lines:

import "net/http"
...
http.ListenAndServe(":1234", nil)

and expvar will add handler for "localhost:1234/debug/vars" to your app.

By default, expvars adds to variables: memstats and cmdline. It's enough to monitor memory and garbage collector status in your app.

Run expvarmon

Just run expvarmon with -ports="1234" parameter:

expvarmon -ports="1234"

That's it.

Advanced usage

If you need to monitor more (or less) vars, you can specify them with -vars command line flag.

$ expvarmon -help
Usage of ./expvarmon:
-dummy=false: Use dummy (console) output
-i=5s: Polling interval
-ports="": Ports for accessing services expvars (start-end,port2,port3)
-self=false: Monitor itself
-vars="mem:memstats.Alloc,mem:memstats.Sys,mem:memstats.HeapAlloc,mem:memstats.HeapInuse,memstats.EnableGC,memstats.NumGC,duration:memstats.PauseTotalNs": Vars to monitor (comma-separated)
Examples:
    ./expvarmon -ports="80"
    ./expvarmon -ports="23000-23010,80" -i=1m
    ./expvarmon -ports="80,remoteapp:80" -vars="mem:memstats.Alloc,duration:Response.Mean,Counter"
    ./expvarmon -ports="1234-1236" -vars="Goroutines" -self
For more details and docs, see README: http://github.com/divan/expvarmon

So, yes, you can specify multiple ports, using '-' for ranges, and specify host(s) for remote apps.

You can also monitor expvarmon itself, using -self flag.

Vars

Expvar allows to export only basic types - structs, ints, floats, bools and strings. Ints are used for sparklines, and displayed as is. But you can spefify modifier to make sure it will be rendered properly.

Vars are specified as a comma-separated list of var identifiers with (optional) modifiers.

Modifier	Description
mem:	renders int64 as memory string (KB, MB, etc)
duration:	renders int64 as time.Duration (1s, 2ms, 12h23h)
str:	doesn't display sparklines chart for this value, just display as string

TODO

ports autodiscovery for given hostname
more tests coverage
better usage of color highligting (for max values or failed apps), after relevant patches will be merged to TermUI

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