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wrap.go
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wrap.go
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// Copyright (c) 2021 6 River Systems
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
// IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
package services
import (
"context"
"errors"
"sync/atomic"
"go.uber.org/fx"
"golang.org/x/sync/errgroup"
"go.6river.tech/mmmbbb/ent"
)
type Service interface {
// Name describes the specific service for use in logging and status reports
Name() string
// Initialize should do any prep work for the service, but not actually start
// it yet. The context should only be used for the duration of the initialization.
Initialize(context.Context, *ent.Client) error
// Start runs the service. It will be invoked on a goroutine, so it should
// block and not return until the context is canceled, which is how the
// service is requested to stop. The service must close the ready channel once
// it is operational, so that any dependent services can know when they are OK
// to proceed.
Start(context.Context, chan<- struct{}) error
// Cleanup should release any resources acquired during Initialize. If another
// service fails during Initialize, Cleanup may be called without Start ever
// being called. If Start is called, Cleanup will not be called until after it
// returns.
Cleanup(context.Context) error
}
type serviceResults struct {
fx.Out
Service Service `group:"services"`
Ready ReadyCheck `group:"ready"`
}
func asService(service Service) fx.Option {
return fx.Provide(func(
ctx context.Context,
eg *errgroup.Group,
l fx.Lifecycle,
client *ent.Client,
) (serviceResults, error) {
return WrapService(ctx, eg, service, l, client)
})
}
func WrapService(
ctx context.Context,
eg *errgroup.Group,
service Service,
l fx.Lifecycle,
client *ent.Client,
) (serviceResults, error) {
readyCh := make(chan struct{})
ready := &serviceReady{ch: readyCh}
res := serviceResults{
Service: service,
Ready: ready,
}
if err := service.Initialize(ctx, client); err != nil {
return res, err
}
l.Append(fx.StartStopHook(
func() {
go ready.watch(ctx)
eg.Go(func() error {
return service.Start(ctx, readyCh)
})
<-readyCh
},
func(stopCtx context.Context) error {
return service.Cleanup(stopCtx)
},
))
return res, nil
}
type serviceReady struct {
ch <-chan struct{}
ready atomic.Bool
}
func (r *serviceReady) watch(ctx context.Context) {
select {
case <-ctx.Done():
return
case <-r.ch:
r.ready.Store(true)
}
}
func (r *serviceReady) Ready() error {
if r.ready.Load() {
return nil
}
return ErrNotReady
}
var ErrNotReady = errors.New("service not ready")