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# Tips
## Implementing default logging and re-authentication attempts
You can implement custom logging and/or limit re-auth attempts by creating a custom HTTP client
like the following and setting it as the provider client's HTTP Client (via the
`gophercloud.ProviderClient.HTTPClient` field):
```go
//...
// LogRoundTripper satisfies the http.RoundTripper interface and is used to
// customize the default Gophercloud RoundTripper to allow for logging.
type LogRoundTripper struct {
rt http.RoundTripper
numReauthAttempts int
}
// newHTTPClient return a custom HTTP client that allows for logging relevant
// information before and after the HTTP request.
func newHTTPClient() http.Client {
return http.Client{
Transport: &LogRoundTripper{
rt: http.DefaultTransport,
},
}
}
// RoundTrip performs a round-trip HTTP request and logs relevant information about it.
func (lrt *LogRoundTripper) RoundTrip(request *http.Request) (*http.Response, error) {
glog.Infof("Request URL: %s\n", request.URL)
response, err := lrt.rt.RoundTrip(request)
if response == nil {
return nil, err
}
if response.StatusCode == http.StatusUnauthorized {
if lrt.numReauthAttempts == 3 {
return response, fmt.Errorf("Tried to re-authenticate 3 times with no success.")
}
lrt.numReauthAttempts++
}
glog.Debugf("Response Status: %s\n", response.Status)
return response, nil
}
endpoint := "https://127.0.0.1/auth"
pc := openstack.NewClient(endpoint)
pc.HTTPClient = newHTTPClient()
//...
```
## Implementing custom objects
OpenStack request/response objects may differ among variable names or types.
### Custom request objects
To pass custom options to a request, implement the desired `<ACTION>OptsBuilder` interface. For
example, to pass in
```go
type MyCreateServerOpts struct {
Name string
Size int
}
```
to `servers.Create`, simply implement the `servers.CreateOptsBuilder` interface:
```go
func (o MyCreateServeropts) ToServerCreateMap() (map[string]interface{}, error) {
return map[string]interface{}{
"name": o.Name,
"size": o.Size,
}, nil
}
```
create an instance of your custom options object, and pass it to `servers.Create`:
```go
// ...
myOpts := MyCreateServerOpts{
Name: "s1",
Size: "100",
}
server, err := servers.Create(computeClient, myOpts).Extract()
// ...
```
### Custom response objects
Some OpenStack services have extensions. Extensions that are supported in Gophercloud can be
combined to create a custom object:
```go
// ...
type MyVolume struct {
volumes.Volume
tenantattr.VolumeExt
}
var v struct {
MyVolume `json:"volume"`
}
err := volumes.Get(client, volID).ExtractInto(&v)
// ...
```
## Overriding default `UnmarshalJSON` method
For some response objects, a field may be a custom type or may be allowed to take on
different types. In these cases, overriding the default `UnmarshalJSON` method may be
necessary. To do this, declare the JSON `struct` field tag as "-" and create an `UnmarshalJSON`
method on the type:
```go
// ...
type MyVolume struct {
ID string `json: "id"`
TimeCreated time.Time `json: "-"`
}
func (r *MyVolume) UnmarshalJSON(b []byte) error {
type tmp MyVolume
var s struct {
tmp
TimeCreated gophercloud.JSONRFC3339MilliNoZ `json:"created_at"`
}
err := json.Unmarshal(b, &s)
if err != nil {
return err
}
*r = Volume(s.tmp)
r.TimeCreated = time.Time(s.CreatedAt)
return err
}
// ...
```
|
