Add support for creating Clients from a previously read settings file

[catsby]

This adds support for initializing a client from the contents of a settings file that's stored in memory. At present, clients are created by supplying a file path to a settings file, but for my use case I have the contents of the file stored elsewhere, either encrypted in a database or something like HashiCorp's Vault

I originally tried modifying ClientFromPublishSettingsFileWithConfig to check the filePath parameter supplied, to see if it's valid XML and not a file path, but settled on duplicating and modifying the ClientFromPublishSettingsFile and ClientFromPublishSettingsFileWithConfig methods into ClientFromPublishSettingsData and ClientFromPublishSettingsDataWithConfig, instead. There is duplication, but I felt it was simpler to reason about.

Example usage, borrowing from the snippet in the README:

package main

import (
    "encoding/base64"
    "fmt"
    "io/ioutil"
    "log"

    "github.com/Azure/azure-sdk-for-go/management"
    "github.com/Azure/azure-sdk-for-go/management/hostedservice"
    "github.com/Azure/azure-sdk-for-go/management/virtualmachine"
    "github.com/Azure/azure-sdk-for-go/management/vmutils"
)

func main() {
    dnsName := "cts-settings-data-ex"
    storageAccount := "terraformtesting"
    location := "West US"
    vmSize := "Small"
    vmImage := "b39f27a8b8c64d52b05eac6a62ebad85__Ubuntu-14_04-LTS-amd64-server-20140724-en-us-30GB"
    userName := "testuser"
    userPassword := "Test123"

    publishSettingsContent, err := ioutil.ReadFile("downloaded.publishsettings")
    if err != nil {
        panic(err)
    }

    client, err := management.ClientFromPublishSettingsData(publishSettingsContent, "")
    if err != nil {
        panic(err)
    }

    log.Println("Client created...")

    // create hosted service
    if err := hostedservice.NewClient(client).CreateHostedService(hostedservice.CreateHostedServiceParameters{
        ServiceName: dnsName,
        Location:    location,
        Label:       base64.StdEncoding.EncodeToString([]byte(dnsName))}); err != nil {
        panic(err)
    }

    log.Println("Service created...")

    // create virtual machine
    role := vmutils.NewVMConfiguration(dnsName, vmSize)
    vmutils.ConfigureDeploymentFromPlatformImage(
        &role,
        vmImage,
        fmt.Sprintf("http://%s.blob.core.windows.net/sdktest/%s.vhd", storageAccount, dnsName),
        "")
    vmutils.ConfigureForLinux(&role, dnsName, userName, userPassword)
    vmutils.ConfigureWithPublicSSH(&role)

    log.Println("Creating ...")
    operationID, err := virtualmachine.NewClient(client).
        CreateDeployment(role, dnsName, virtualmachine.CreateDeploymentOptions{})
    if err != nil {
        panic(err)
    }
    if err := client.WaitForOperation(operationID, nil); err != nil {
        panic(err)
    }
    log.Println("Done!")
}

Suggestions on naming and testing are welcome.
Thanks!

[msftclas]

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[ahmetb]

@catsby thanks for the pull request, looks like we need the CLA to be signed.

My only comment is you can totally call ClientFromPublishSettingsData from ClientFromPublishSettingsFile by first reading the file with ioutil.ReadFile and then passing the contents.

Having duplicated logic is something we usually really want to avoid as people usually forget maintaining both at the same time.

[msftclas]

@catsby, Thanks for signing the contribution license agreement so quickly! Actual humans will now validate the agreement and then evaluate the PR.

Thanks, MSBOT;

[catsby]

Hey @ahmetalpbalkan thanks for the reply

Having duplicated logic is something we usually really want to avoid as people usually forget maintaining both at the same time.

I've refactored some to consolidate and remove duplication, as well as preserve backwards compatibility. I think... can you take a look? Thanks!

[ahmetb]

@catsby I think we can even remove duplication in xml.Unmarshal. For now, by creating another method we have two paths that go like this:

func A()+---------+   
                  |   
                  v   
                func c()
                  ^   
                  |   
func B()+---------+   

However if you could call ClientFromPublishSettingsData from ClientFromPublishSettingsFile without creating another method (as in func c above), we'll have:

  +--------------------+           
  |      caller        |           
  +--+------------+----+           
     |            |                
     |            |                
     |            |                
     |            |                
     |            |                
     v            v                
func A()+--->func B()+------>func c()

which really enforces a single path. Both are equally OK, however I find latter easier to read. :-) If you could also fix that, the rest is LGTM.

[catsby]

Hey @ahmetalpbalkan , thanks for the continued help here. I hate to be difficult but I'm not sure I follow what you're suggesting, though I did just push 902e8bb to remove some duplication of xml.Unmarshall.

However if you could call ClientFromPublishSettingsData from ClientFromPublishSettingsFile without creating another method (as in func c above), we'll have

By this, do you mean for ClientFromPublishSettingsFile to determine if the filePath input is actually a file path, or contents of a file, and then choose ClientFromPublishSettingsFileWithConfig or ClientFromPublishSettingsData accordingly? I avoided this mostly because I didn't want to change the signature/purpose of any existing methods with this addition, specifically any exported methods.

With 902e8bb , both ClientFromPublishSettingsFile and ClientFromPublishSettingsData pass on a []byte slice to clientFromPublishData, which does the unmarshalling.

[ahmetb]

LGTM. Thanks!

[catsby]

Thanks so much @ahmetalpbalkan !