Add Alibaba Cloud Provider

[xianlubird]

Add Alibaba Cloud provided

[njuettner]

@xianlubird thanks for open the PR 🎉 and a new provider 🙂.
We'll have a look.

[xianlubird]

@njuettner
For the continuous-integration/travis-ci/pr fail message

!!! 'gofmt -s' needs to be run on the following files: 
./provider/google.go
./provider/google_test.go
FAILED   /home/travis/gopath/src/github.com/kubernetes-incubator/external-dns/vendor/github.com/kubernetes/repo-infra/verify/go-tools/verify-gofmt.sh	0s

I didn't change /provider/google.go and ./provider/google_test.go , and in my workspace, I run verify shell, it was fine.

SUCCESS  /go/src/github.com/kubernetes-incubator/external-dns/vendor/github.com/kubernetes/repo-infra/verify/go-tools/verify-gofmt.sh	1s

So cloud you give me some advice on how to fix it, thanks.

[njuettner]

It fails due to a change from go 1.10 to go 1.11. gofmt behaves differently.
If you have already go 1.11 could you run gofmt -s for those files (google.go, google_test.go)?

[njuettner]

I would recommend to change 0.4 to version 0.5.6. This would be the next version incl. Alibaba Cloud

[njuettner]

maybe this could be also configurable via flag or something. refreshing every 1 second sounds eager to me. WDTY?

[xianlubird]

• roleName is a Alibaba Cloud STS Token role, it can be fetch from ECS internal API, so it don't need to be config via flag.
• refreshStsToken, the first time is 1 second, but from the next time it will be turned to 9 minute.

func (p *AlibabaCloudProvider) refreshStsToken(sleepTime time.Duration) {
    for {
        time.Sleep(sleepTime)
        now := time.Now()
        sleepTime = p.nextExpire.Sub(nowTime)
        log.Infof("Distance expiration time %v", sleepTime)
        if sleepTime < time.Duration(10*time.Minute) {
	       sleepTime = time.Duration(time.Second * 1)
        } else {
	       sleepTime = time.Duration(9 * time.Minute)
       }
     }
}

So in most situation, the refresh loop time will be 9 minute. I think it's fine.

[njuettner]

Another question I just saw that your tests cover roughly 60% of your code, do you feel confident enough that everything works as expected?

Other than my small notes it looks good to me.

[xianlubird]

@njuettner

• I have already change version to 0.5.6 according to your comments
• Foe the test case, I add some, now it's 68.1%. It has cover most situation including add, update, delete public & private zone. And I also test it in product environment, we have support many users in Alibaba Cloud. I will also keep improve features & bug.

Thanks for your review. :-)

[njuettner]

Agreed, thanks for your hard work and offering Alibaba Cloud as new provider 🚀 .
As I've already mentioned it will released with v0.5.6.