mediocre-go-lib/m/m.go

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// Package m is the glue which holds all the other packages in this project
// together. While other packages in this project are intended to be able to be
// used separately and largely independently, this package combines them in ways
// which I specifically like.
package m
import (
"context"
"os"
"os/signal"
"github.com/mediocregopher/mediocre-go-lib/mcfg"
"github.com/mediocregopher/mediocre-go-lib/merr"
"github.com/mediocregopher/mediocre-go-lib/mlog"
"github.com/mediocregopher/mediocre-go-lib/mrun"
)
// CfgSource returns an mcfg.Source which takes in configuration info from the
// environment and from the CLI.
func CfgSource() mcfg.Source {
return mcfg.Sources{
mcfg.SourceEnv{},
mcfg.SourceCLI{},
}
}
// NewServiceCtx returns a Context which should be used as the root Context when
// creating long running services, such as an RPC service or database.
//
// The returned Context will automatically handle setting up global
// configuration parameters like "log-level", as well as an http endpoint where
// debug information about the running process can be accessed.
//
// TODO set up the debug endpoint.
func NewServiceCtx() context.Context {
ctx := context.Background()
// set up log level handling
logger := mlog.NewLogger()
ctx = mlog.Set(ctx, logger)
ctx, logLevelStr := mcfg.String(ctx, "log-level", "info", "Maximum log level which will be printed.")
ctx = mrun.OnStart(ctx, func(context.Context) error {
logLevel := mlog.LevelFromString(*logLevelStr)
if logLevel == nil {
return merr.New("invalid log level", "log-level", *logLevelStr)
}
logger.SetMaxLevel(logLevel)
return nil
})
return ctx
}
// Run performs the work of populating configuration parameters, triggering the
// start event, waiting for an interrupt, and then triggering the stop event.
// Run will block until the stop event is done. If any errors are encountered a
// fatal is thrown.
func Run(ctx context.Context) {
log := mlog.From(ctx)
if err := mcfg.Populate(ctx, CfgSource()); err != nil {
log.Fatal(ctx, "error populating configuration", merr.KV(err))
} else if err := mrun.Start(ctx); err != nil {
log.Fatal(ctx, "error triggering start event", merr.KV(err))
}
{
ch := make(chan os.Signal, 1)
signal.Notify(ch, os.Interrupt)
s := <-ch
log.Info(ctx, "signal received, stopping", mlog.KV{"signal": s})
}
if err := mrun.Stop(ctx); err != nil {
log.Fatal(ctx, "error triggering stop event", merr.KV(err))
}
log.Info(ctx, "exiting process")
}