Hi,
I have been learning Golang for some few months now but still find it
difficult to design some applications. I have two HTTP servers A and B and
would like to do the following
1. server A send an HTTP PUT request with JSON body to server B.
2. If server B is not available, server A retry until server B is up and
respond to the request
3. In server B response body is a timer value received by server A
4. Server B uses the timer value (eg 45) to send a PATCH request using the
value as interval. For example in this case, server A send the PATCH
request to server B every 45 seconds.
5. Server B respond to the PATCH request with either HTTP status code 204
or status code 404.
6. If status code is 204, that is OK, server A continues to send the PATCH
request using the 45 seconds interval.
7. If the response status is 404, server A have to start the process again
from step 1 again to step 6 when 204 status code is received.
I have tried to write some code which works but restarting from step 1 when
404 status code is received does not work. Also am not sure if my
application design is good enough. Any help and comments about my
application design. Below is my code
var (
ContentLocation string
Timer int32
mu sync.Mutex
)
func SendPUTMessageToServerB() {
msgbytes, err := ioutil.ReadFile("./msg.json")
...
locProfilebytes, err := json.Marshal(pcfprofile)
...
locVarNRFUrl := "server B url"
profile, resp, err := HandlePUTMessage(locProfilebytes, locVarNRFUrl)
status := resp.StatusCode
if status == http.StatusOK {
logrus.Println("PUT mesage Update SUCCESS")
} else if status == http.StatusCreated {
logrus.Println("PUT message SUCCESS")
} else {
logrus.Println(fmt.Errorf("Wrong status code returned by server B
%d", status))
}
ContentLocation = resp.Header.Get("Location")
Timer = profile.TimerValue
}
func HandlePUTMessage(filebyte []byte, VarPath string) (Profile,
*http.Response, error) {
var (
// Set client and set url
localVarHTTPMethod = http.MethodPut
nfp Profile
)
req, err := http.NewRequest(localVarHTTPMethod, VarPath,
bytes.NewBuffer(filebyte))
if err != nil {
logrus.Error(err)
}
req.Close = true
req.Header.Set("Content-Type", "application/json")
backoff := 1
for {
res, err := Client.Do(req)
if err != nil || res == nil {
logrus.Println("Server A Trying to send PUT request ...")
backoff *= 2
if backoff > 20 {
backoff = 20
}
time.Sleep(time.Duration(backoff) * time.Second)
continue
}
defer func() {
if resCloseErr := res.Body.Close(); resCloseErr != nil {
logrus.Errorf("Response body cannot close: %+v",
resCloseErr)
}
}()
bodybytes, err := ioutil.ReadAll(res.Body)
//localVarHTTPResponse.Body.Close()
if err != nil {
logrus.Error(err)
return nfp, res, err
}
json.Unmarshal(bodybytes, &nfp)
return nfp, res, nil
}
}
// Send PATCH message to server B
func PATCHMessage() (err error) {
...
patchitembytes, err := json.Marshal(patchitem)
...
req, err := http.NewRequest("PATCH", ContentLocation,
bytes.NewBuffer(patchitembytes))
req.Header.Set("Content-Type", "application/json-patch+json")
response, err := transport.Client.Do(req) // for dev
defer response.Body.Close()
status := response.StatusCode
if status == http.StatusNoContent {
logrus.Info("PATCH message SUCCESS")
} else if status == http.StatusNotFound {
// Here I would like to restart PUT message if status code is 404
logrus.Println("Heart-Beat Message FAILED")
}
return err
}
// Send a patch message every Timer value
func SendPATCHMessageEveryTimerValue() {
for {
ticker := time.NewTicker(time.Duration(Timer) * time.Second)
mu.Lock()
for _ = range ticker.C {
err := PATCHMessage()
if err != nil {
SendPUTMessage()
}
}
mu.Unlock()
}
}
func main() {
SendPUTMessageToServerB()
go SendPATCHMessageEveryTimerValue()
}
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