caddyconfig: dependency-free http config loading retries

caddyconfig/httploader.go

@@ -15,17 +15,16 @@
 package caddyconfig
 
 import (
-	"context"
 	"crypto/tls"
 	"crypto/x509"
 	"fmt"
 	"io"
+	"math"
 	"net/http"
 	"os"
 	"time"
 
 	"github.com/caddyserver/caddy/v2"
-	"github.com/hashicorp/go-retryablehttp"
 )
 
 func init() {
@@ -47,7 +46,8 @@ type HTTPLoader struct {
 	// Maximum time allowed for a complete connection and request.
 	Timeout caddy.Duration `json:"timeout,omitempty"`
 
-	// Maximum number of retries for a successful call to URL. Defaults to 0.
+	// Maximum number of retries for a successful call to URL.
+	// Does exponential back-offs (2...4...8...16... seconds) between retries. Defaults to 0.
 	MaxRetries int `json:"max_retries,omitempty"`
 
 	TLS *struct {
@@ -99,7 +99,7 @@ func (hl HTTPLoader) LoadConfig(ctx caddy.Context) ([]byte, error) {
 		}
 	}
 
-	resp, err := client.Do(req)
+	resp, err := doHttpCallWithRetries(client, req, hl.MaxRetries)
 	if err != nil {
 		return nil, err
 	}
@@ -124,25 +124,34 @@ func (hl HTTPLoader) LoadConfig(ctx caddy.Context) ([]byte, error) {
 	return result, nil
 }
 
-func getRetryClient(ctx caddy.Context, maxRetries int, timeout caddy.Duration) (*http.Client, error) {
-	retryClient := retryablehttp.NewClient()
-	retryClient.RetryMax = maxRetries
-
-	retryClient.CheckRetry = func(ctx context.Context, resp *http.Response, err error) (bool, error) {
-		if err != nil || (resp.StatusCode < 200 || resp.StatusCode > 499) {
-			return true, err
+// Reattempts the http call using exponential back off when maxRetries is greater than 0.
+func doHttpCallWithRetries(client *http.Client, request *http.Request, maxRetries int) (*http.Response, error) {
+	var resp *http.Response
+	var err error
+
+	for retry := 0; retry <= maxRetries; retry++ {
+		if retry > 0 {
+			caddy.Log().Error(err.Error())
+			exponentialBackOff := math.Pow(2, float64(retry))
+			caddy.Log().Sugar().Infof("reattempting http load in %g seconds (%v retries remain)", exponentialBackOff, maxRetries-retry)
+			time.Sleep(time.Duration(exponentialBackOff) * time.Second)
+		}
+		resp, err = client.Do(request)
+		if err != nil {
+			err = fmt.Errorf("problem calling http loader url: %v", err)
+		} else if resp.StatusCode < 200 || resp.StatusCode > 499 {
+			err = fmt.Errorf("bad response status code from http loader url: %v", resp.StatusCode)
+		} else {
+			return resp, nil
 		}
-		return false, err
 	}
-	retryClient.HTTPClient.Timeout = time.Duration(timeout)
 
-	return retryClient.StandardClient(), nil
+	return resp, err
 }
 
 func (hl HTTPLoader) makeClient(ctx caddy.Context) (*http.Client, error) {
-	client, err := getRetryClient(ctx, hl.MaxRetries, hl.Timeout)
-	if err != nil {
-		return nil, err
+	client := &http.Client{
+		Timeout: time.Duration(hl.Timeout),
 	}
 
 	if hl.TLS != nil {

go.mod

@@ -41,7 +41,6 @@ require (
 
 require (
 	github.com/golang/mock v1.6.0 // indirect
-	github.com/hashicorp/go-cleanhttp v0.5.2 // indirect
 	golang.org/x/exp v0.0.0-20220722155223-a9213eeb770e // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 )
@@ -74,7 +73,6 @@ require (
 	github.com/golang/protobuf v1.5.2 // indirect
 	github.com/golang/snappy v0.0.4 // indirect
 	github.com/grpc-ecosystem/grpc-gateway v1.16.0 // indirect
-	github.com/hashicorp/go-retryablehttp v0.7.1
 	github.com/huandu/xstrings v1.3.2 // indirect
 	github.com/imdario/mergo v0.3.12 // indirect
 	github.com/inconshreveable/mousetrap v1.0.0 // indirect

go.sum

@@ -398,7 +398,6 @@ github.com/hashicorp/errwrap v1.0.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brv
 github.com/hashicorp/errwrap v1.1.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
 github.com/hashicorp/go-cleanhttp v0.5.0/go.mod h1:JpRdi6/HCYpAwUzNwuwqhbovhLtngrth3wmdIIUrZ80=
 github.com/hashicorp/go-cleanhttp v0.5.1/go.mod h1:JpRdi6/HCYpAwUzNwuwqhbovhLtngrth3wmdIIUrZ80=
-github.com/hashicorp/go-cleanhttp v0.5.2 h1:035FKYIWjmULyFRBKPs8TBQoi0x6d9G4xc9neXJWAZQ=
 github.com/hashicorp/go-cleanhttp v0.5.2/go.mod h1:kO/YDlP8L1346E6Sodw+PrpBSV4/SoxCXGY6BqNFT48=
 github.com/hashicorp/go-hclog v0.9.2/go.mod h1:5CU+agLiy3J7N7QjHK5d05KxGsuXiQLrjA0H7acj2lQ=
 github.com/hashicorp/go-hclog v0.14.1/go.mod h1:whpDNt7SSdeAju8AWKIWsul05p54N/39EeqMAyrmvFQ=
@@ -412,8 +411,6 @@ github.com/hashicorp/go-multierror v1.1.1/go.mod h1:iw975J/qwKPdAO1clOe2L8331t/9
 github.com/hashicorp/go-plugin v1.4.3/go.mod h1:5fGEH17QVwTTcR0zV7yhDPLLmFX9YSZ38b18Udy6vYQ=
 github.com/hashicorp/go-retryablehttp v0.5.3/go.mod h1:9B5zBasrRhHXnJnui7y6sL7es7NDiJgTc6Er0maI1Xs=
 github.com/hashicorp/go-retryablehttp v0.6.6/go.mod h1:vAew36LZh98gCBJNLH42IQ1ER/9wtLZZ8meHqQvEYWY=
-github.com/hashicorp/go-retryablehttp v0.7.1 h1:sUiuQAnLlbvmExtFQs72iFW/HXeUn8Z1aJLQ4LJJbTQ=
-github.com/hashicorp/go-retryablehttp v0.7.1/go.mod h1:vAew36LZh98gCBJNLH42IQ1ER/9wtLZZ8meHqQvEYWY=
 github.com/hashicorp/go-rootcerts v1.0.0/go.mod h1:K6zTfqpRlCUIjkwsN4Z+hiSfzSTQa6eBIzfwKfwNnHU=
 github.com/hashicorp/go-rootcerts v1.0.2/go.mod h1:pqUvnprVnM5bf7AOirdbb01K4ccR319Vf4pU3K5EGc8=
 github.com/hashicorp/go-secure-stdlib/base62 v0.1.1/go.mod h1:EdWO6czbmthiwZ3/PUsDV+UD1D5IRU4ActiaWGwt0Yw=