scli

Extends cli to server main()s .

In addition to flags, usage and help output, arguments validation, scli abstracts the repetitive parts of a main() to setup a config directory watch for dynamic flags (configmap in kubernetes cases) and configuration endpoint/UI/api.

It also sets up standard library logger interception to log these under same JSON (or color console) format.

You can see real use example in a server like proxy.

Server Example

Server example sampleServer

Previous style (non structured json, no color log format):

% go run . -config-dir ./config -config-port 8888 -logger-no-color -logger-json=false a b
14:50:54 [I] updater.go:47> Configmap flag value watching on ./config
14:50:54 [I] updater.go:156> updating loglevel to "verbose\n"
14:50:54 [I] logger.go:183> Log level is now 1 Verbose (was 2 Info)
14:50:54 [I] updater.go:97> Now watching . and config
14:50:54 [I] updater.go:162> Background thread watching config now running
14:50:54 [I] scli.go:81> Fortio scli dev dflag config server listening on [::]:8888
14:50:54 [I] scli.go:90> Starting sampleServer dev  go1.20.3 arm64 darwin
14:50:55 [I] main.go:16> FD count 1s after start : 16
# When visiting the UI
14:51:10 [I] http_logging.go:73> ListFlags, method="GET", url="/", proto="HTTP/1.1", remote_addr="[::1]:59034",
14:51:15 [I] main.go:18> FD count 20s later      : 16
14:51:15 [I] main.go:21> FD count stability check: 16
14:51:15 [I] main.go:21> FD count stability check: 16
14:51:15 [I] main.go:21> FD count stability check: 16
14:51:15 [I] main.go:21> FD count stability check: 16
14:51:15 [I] main.go:21> FD count stability check: 16
14:51:15 [I] main.go:27> Running until interrupted (ctrl-c)...
# pkill -int sampleServer
14:51:20 [W] scli.go:101> Interrupt received.
14:51:20 [I] main.go:29> Normal exit
% echo $?
0

With the flags ui on http://localhost:8888

New default style of logging since 1.5 (JSON for servers):

$ go run . -config-dir ./config -config-port 8888 a b 2>&1 | cat # forces no color because stderr isn't a terminal

{"ts":1689985712.410200,"level":"info","r":1,"file":"updater.go","line":47,"msg":"Configmap flag value watching on ./config"}
{"ts":1689985712.411816,"level":"info","r":1,"file":"updater.go","line":156,"msg":"updating loglevel to \"verbose\\n\""}
{"ts":1689985712.411841,"level":"info","r":1,"file":"logger.go","line":245,"msg":"Log level is now 1 Verbose (was 2 Info)"}
{"ts":1689985712.412396,"level":"info","r":1,"file":"updater.go","line":97,"msg":"Now watching . and config"}
{"ts":1689985712.412539,"level":"info","r":19,"file":"updater.go","line":162,"msg":"Background thread watching config now running"}
{"ts":1689985712.412901,"level":"info","r":1,"file":"scli.go","line":104,"msg":"Fortio scli dev dflag config server listening on [::]:8888"}
{"ts":1689985712.412911,"level":"info","r":1,"file":"scli.go","line":113,"msg":"Starting sampleServer dev  go1.20.6 arm64 darwin"}
{"ts":1689985713.415586,"level":"info","r":1,"file":"main.go","line":16,"msg":"FD count 1s after start : 14"}
# list flag (curl localhost:8888)
{"ts":1689985717.703528,"level":"info","r":21,"file":"http_logging.go","line":73,"msg":"ListFlags","method":"GET","url":"/","proto":"HTTP/1.1","remote_addr":"127.0.0.1:57975","host":"localhost:8888","header.x-forwarded-proto":"","header.x-forwarded-for":"","user-agent":"curl/8.0.1","header.User-Agent":"curl/8.0.1","header.Accept":"*/*"}
{"ts":1689985733.418850,"level":"info","r":1,"file":"main.go","line":18,"msg":"FD count 20s later      : 14"}
{"ts":1689985733.419088,"level":"info","r":1,"file":"main.go","line":21,"msg":"FD count stability check: 14"}
{"ts":1689985733.419280,"level":"info","r":1,"file":"main.go","line":21,"msg":"FD count stability check: 14"}
{"ts":1689985733.419426,"level":"info","r":1,"file":"main.go","line":21,"msg":"FD count stability check: 14"}
{"ts":1689985733.419565,"level":"info","r":1,"file":"main.go","line":21,"msg":"FD count stability check: 14"}
{"ts":1689985733.419702,"level":"info","r":1,"file":"main.go","line":21,"msg":"FD count stability check: 14"}
{"ts":1689985733.419710,"level":"info","r":1,"file":"main.go","line":27,"msg":"Running until interrupted (ctrl-c)..."}
# Sending INT signal
{"ts":1689985903.623639,"level":"warn","r":1,"file":"scli.go","line":124,"msg":"Interrupt received."}
{"ts":1689985903.623682,"level":"info","r":1,"file":"main.go","line":29,"msg":"Normal exit"}

And console output default colorized mode comes from log's 1.6.0 or newer:

Additional builtins

(coming from cli's base module)

buildinfo

e.g

$ go install fortio.org/scli/sampleServer@latest
go: downloading fortio.org/scli v1.7.0
$ sampleServer buildinfo
1.7.0 h1:NC3z2k+2NY5zTB+XoQGX2MKJulMq61gltK8OrkR3U9U= go1.20.5 arm64 darwin
go	go1.20.5
path	fortio.org/scli/sampleServer
mod	fortio.org/scli	v1.7.0	h1:NC3z2k+2NY5zTB+XoQGX2MKJulMq61gltK8OrkR3U9U=
dep	fortio.org/cli	v1.1.0	h1:ATIxi7DgA7WAexUCF8p5a0qlGYk48ZgkwSEDrvwXeN4=
dep	fortio.org/dflag	v1.5.2	h1:F9XVRj4Qr2IbJP7BMj7XZc9wB0Q/RZ61Ool+4YPVad8=
dep	fortio.org/log	v1.5.0	h1:0f/O7QPXQoDSnRjy8t0IyxTlQOYQsDOe0EO4Wnw8yCA=
dep	fortio.org/sets	v1.0.3	h1:HzewdGjH69YmyW06yzplL35lGr+X4OcqQt0qS6jbaO4=
dep	fortio.org/version	v1.0.2	h1:8NwxdX58aoeKx7T5xAPO0xlUu1Hpk42nRz5s6e6eKZ0=
dep	github.com/fsnotify/fsnotify	v1.6.0	h1:n+5WquG0fcWoWp6xPWfHdbskMCQaFnG6PfBrh1Ky4HY=
dep	golang.org/x/exp	v0.0.0-20230420155640-133eef4313cb	h1:rhjz/8Mbfa8xROFiH+MQphmAmgqRM0bOMnytznhWEXk=
dep	golang.org/x/sys	v0.9.0	h1:KS/R3tvhPqvJvwcKfnBHJwwthS11LRhmM5D59eEXa0s=
build	-buildmode=exe
build	-compiler=gc
build	CGO_ENABLED=1
build	CGO_CFLAGS=
build	CGO_CPPFLAGS=
build	CGO_CXXFLAGS=
build	CGO_LDFLAGS=
build	GOARCH=arm64
build	GOOS=darwin

help

sampleServer 1.8.0 usage:
	sampleServer [flags] arg1 arg2 [arg3...arg4]
or 1 of the special arguments
	sampleServer {help|version|buildinfo}
flags:
  -config-dir directory
    	Config directory to watch for dynamic flag changes
  -config-port port
    	Config port to open for dynamic flag UI/api
  -logger-file-line
    	Filename and line numbers emitted in JSON logs, use -logger-file-line=false to disable (default true)
  -logger-force-color
    	Force color output even if stderr isn't a terminal
  -logger-goroutine
    	GoroutineID emitted in JSON/color logs, use -logger-goroutine=false to disable (default true)
  -logger-json
    	Log in JSON format, use -logger-json=false to disable (default true)
  -logger-no-color
    	Prevent colorized output even if stderr is a terminal
  -logger-timestamp
    	Timestamps emitted in JSON logs, use -logger-timestamp=false to disable (default true)
  -loglevel level
    	log level, one of [Debug Verbose Info Warning Error Critical Fatal] (default Info)
  -quiet
    	Quiet mode, sets loglevel to Error (quietly) to reduces the output

version

Short 'numeric' version (v skipped, useful for docker image tags etc)

$ sampleServer version
1.7.0

envhelp

Will display a chain of fortio.org/struct2env environment variables<->config settings

$ sampleServer envhelp
# Environment variables recognized and current values:
# Logger environment variables:
LOGGER_LOG_PREFIX='> '
LOGGER_LOG_FILE_AND_LINE=true
LOGGER_FATAL_PANICS=true
LOGGER_JSON=true
LOGGER_NO_TIMESTAMP=false
LOGGER_CONSOLE_COLOR=true
LOGGER_FORCE_COLOR=false
LOGGER_GOROUTINE_ID=true
LOGGER_COMBINE_REQUEST_AND_RESPONSE=true
LOGGER_LEVEL='Info'

Server log diff'ing

When debugging in dev mode the differences between 2 log output, it's convenient to use the following flags

• -logger-timestamp=false so the timestamp is removed from the output as that would be different always
• -logger-file-line=false so code line numbers don't show as diffs either (if comparing different versions/releases)
• -logger-goroutine=false so Goroutine IDs don't show (which may or may not be desired)