uptimerobot/api: wait and retry when API responds with 429 TooManyReq…

…uests

To make provider more robust against recently introduced API calls
limits of 10 calls per minute for free accounts.

Closes louy#106

Signed-off-by: Mateusz Gozdek <[email protected]>

uptimerobot/api/client.go

@@ -6,13 +6,17 @@ import (
 	"fmt"
 	"io/ioutil"
 	"log"
+	"math/rand"
 	"net/http"
 	"strings"
+	"time"
 
 	"github.com/hashicorp/terraform-plugin-sdk/helper/logging"
 )
 
 func New(apiKey string) UptimeRobotApiClient {
+	rand.Seed(time.Now().UnixNano())
+
 	return UptimeRobotApiClient{apiKey}
 }
 
@@ -32,17 +36,34 @@ func (client UptimeRobotApiClient) MakeCall(
 
 	requestBody := fmt.Sprintf("api_key=%s&format=json&%s", client.apiKey, params)
 
-	req, err := http.NewRequest("POST", url, strings.NewReader(requestBody))
-	if err != nil {
-		return nil, fmt.Errorf("contructing request: %w", err)
-	}
+	var res *http.Response
 
-	req.Header.Add("cache-control", "no-cache")
-	req.Header.Add("content-type", "application/x-www-form-urlencoded")
+	for {
+		req, err := http.NewRequest("POST", url, strings.NewReader(requestBody))
+		if err != nil {
+			return nil, fmt.Errorf("contructing request: %w", err)
+		}
 
-	res, err := httpClient.Do(req)
-	if err != nil {
-		return nil, fmt.Errorf("performing API request: %w", err)
+		req.Header.Add("cache-control", "no-cache")
+		req.Header.Add("content-type", "application/x-www-form-urlencoded")
+
+		resCandidate, err := httpClient.Do(req)
+		if err != nil {
+			return nil, fmt.Errorf("performing API request: %w", err)
+		}
+
+		switch resCandidate.StatusCode {
+		case http.StatusTooManyRequests:
+			log.Printf("[DEBUG] Got response code %d, waiting...", http.StatusTooManyRequests)
+			waitForRetryAfter(resCandidate)
+		default:
+			log.Printf("[DEBUG] Got regular response code %d, proceeding", resCandidate.StatusCode)
+			res = resCandidate
+		}
+
+		if res != nil {
+			break
+		}
 	}
 
 	defer func() {
@@ -66,3 +87,23 @@ func (client UptimeRobotApiClient) MakeCall(
 
 	return result, nil
 }
+
+func waitForRetryAfter(res *http.Response) {
+	retryAfterRaws, ok := res.Header["Retry-After"]
+	if !ok || len(retryAfterRaws) > 1 {
+		log.Printf("[DEBUG] Retry-After header is missing, waiting 1 second for next request attempt")
+		retryAfterRaws = []string{"1"}
+	}
+
+	waitTime, err := time.ParseDuration(retryAfterRaws[0] + "s")
+	if err != nil {
+		log.Printf("[DEBUG] Parsing %q as Retry-After header value in seconds, waiting 1 second for next request: %v", retryAfterRaws, err)
+		waitTime = time.Second
+	}
+
+	waitTime = waitTime + 2*time.Second + time.Duration(rand.Float64())*time.Second
+
+	log.Printf("[DEBUG] Rate limit exceeded, waiting %v seconds to send next request", waitTime.Seconds())
+
+	time.Sleep(waitTime)
+}