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fetcher.go
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fetcher.go
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package resource
import (
"errors"
"fmt"
"os"
"time"
"code.cloudfoundry.org/clock"
"code.cloudfoundry.org/lager"
"github.com/concourse/atc"
"github.com/concourse/atc/worker"
)
const GetResourceLockInterval = 5 * time.Second
var ErrFailedToGetLock = errors.New("failed-to-get-lock")
var ErrInterrupted = errors.New("interrupted")
//go:generate counterfeiter . Fetcher
type Fetcher interface {
Fetch(
logger lager.Logger,
session Session,
tags atc.Tags,
teamID int,
resourceTypes atc.VersionedResourceTypes,
resourceInstance ResourceInstance,
metadata Metadata,
imageFetchingDelegate worker.ImageFetchingDelegate,
resourceOptions ResourceOptions,
signals <-chan os.Signal,
ready chan<- struct{},
) (FetchSource, error)
}
//go:generate counterfeiter . ResourceOptions
type ResourceOptions interface {
IOConfig() IOConfig
Source() atc.Source
Params() atc.Params
Version() atc.Version
ResourceType() ResourceType
LockName(workerName string) (string, error)
}
func NewFetcher(
clock clock.Clock,
db LockDB,
fetchSourceProviderFactory FetchSourceProviderFactory,
) Fetcher {
return &fetcher{
clock: clock,
db: db,
fetchSourceProviderFactory: fetchSourceProviderFactory,
}
}
type fetcher struct {
clock clock.Clock
db LockDB
fetchSourceProviderFactory FetchSourceProviderFactory
}
func (f *fetcher) Fetch(
logger lager.Logger,
session Session,
tags atc.Tags,
teamID int,
resourceTypes atc.VersionedResourceTypes,
resourceInstance ResourceInstance,
metadata Metadata,
imageFetchingDelegate worker.ImageFetchingDelegate,
resourceOptions ResourceOptions,
signals <-chan os.Signal,
ready chan<- struct{},
) (FetchSource, error) {
sourceProvider := f.fetchSourceProviderFactory.NewFetchSourceProvider(
logger,
session,
metadata,
tags,
teamID,
resourceTypes,
resourceInstance,
resourceOptions,
imageFetchingDelegate,
)
ticker := f.clock.NewTicker(GetResourceLockInterval)
defer ticker.Stop()
fetchSource, err := f.fetchWithLock(logger, sourceProvider, resourceOptions.IOConfig(), signals, ready)
if err != ErrFailedToGetLock {
return fetchSource, err
}
for {
select {
case <-ticker.C():
fetchSource, err := f.fetchWithLock(logger, sourceProvider, resourceOptions.IOConfig(), signals, ready)
if err != nil {
if err == ErrFailedToGetLock {
break
}
return nil, err
}
return fetchSource, nil
case <-signals:
return nil, ErrInterrupted
}
}
}
func (f *fetcher) fetchWithLock(
logger lager.Logger,
sourceProvider FetchSourceProvider,
ioConfig IOConfig,
signals <-chan os.Signal,
ready chan<- struct{},
) (FetchSource, error) {
// This is supposed to be a fast-feedback kind of Get
//
// Will return back a volume in any kind of state
// so that if it's already initialized
// we can use the initialized volume
source, err := sourceProvider.Get()
if err != nil {
return nil, err
}
isInitialized, err := source.IsInitialized()
if err != nil {
return nil, err
}
if isInitialized {
if ioConfig.Stdout != nil {
fmt.Fprintf(ioConfig.Stdout, "using version of resource found in cache\n")
}
close(ready)
return source, nil
}
lockName, err := source.LockName()
if err != nil {
return nil, err
}
lockLogger := logger.Session("lock-task", lager.Data{"lock-name": lockName})
lock, acquired, err := f.db.GetTaskLock(lockLogger, lockName)
if err != nil {
lockLogger.Error("failed-to-get-lock", err)
return nil, ErrFailedToGetLock
}
if !acquired {
lockLogger.Debug("did-not-get-lock")
return nil, ErrFailedToGetLock
}
defer lock.Release()
err = source.Initialize(signals, ready)
if err != nil {
return nil, err
}
return source, nil
}