backend/http: implement retries for the http backend (#19702)

Fixes #19619

backend/remote-state/http/backend.go

@@ -6,8 +6,10 @@ import (
 	"fmt"
 	"net/http"
 	"net/url"
+	"time"
 
-	cleanhttp "github.com/hashicorp/go-cleanhttp"
+	"github.com/hashicorp/go-cleanhttp"
+	"github.com/hashicorp/go-retryablehttp"
 	"github.com/hashicorp/terraform/backend"
 	"github.com/hashicorp/terraform/helper/schema"
 	"github.com/hashicorp/terraform/state"
@@ -66,6 +68,24 @@ func New() backend.Backend {
 				Default:     false,
 				Description: "Whether to skip TLS verification.",
 			},
+			"retry_max": &schema.Schema{
+				Type:        schema.TypeInt,
+				Optional:    true,
+				Default:     2,
+				Description: "The number of HTTP request retries.",
+			},
+			"retry_wait_min": &schema.Schema{
+				Type:        schema.TypeInt,
+				Optional:    true,
+				Default:     1,
+				Description: "The minimum time in seconds to wait between HTTP request attempts.",
+			},
+			"retry_wait_max": &schema.Schema{
+				Type:        schema.TypeInt,
+				Optional:    true,
+				Default:     30,
+				Description: "The maximum time in seconds to wait between HTTP request attempts.",
+			},
 		},
 	}
 
@@ -131,6 +151,12 @@ func (b *Backend) configure(ctx context.Context) error {
 		}
 	}
 
+	rClient := retryablehttp.NewClient()
+	rClient.HTTPClient = client
+	rClient.RetryMax = data.Get("retry_max").(int)
+	rClient.RetryWaitMin = time.Duration(data.Get("retry_wait_min").(int)) * time.Second
+	rClient.RetryWaitMax = time.Duration(data.Get("retry_wait_max").(int)) * time.Second
+
 	b.client = &httpClient{
 		URL:          updateURL,
 		UpdateMethod: updateMethod,
@@ -144,7 +170,7 @@ func (b *Backend) configure(ctx context.Context) error {
 		Password: data.Get("password").(string),
 
 		// accessible only for testing use
-		Client: client,
+		Client: rClient,
 	}
 	return nil
 }

backend/remote-state/http/backend_test.go

@@ -2,6 +2,7 @@ package http
 
 import (
 	"testing"
+	"time"
 
 	"github.com/hashicorp/terraform/configs"
 	"github.com/zclconf/go-cty/cty"
@@ -51,6 +52,9 @@ func TestHTTPClientFactory(t *testing.T) {
 		"unlock_method":  cty.StringVal("BLOOP"),
 		"username":       cty.StringVal("user"),
 		"password":       cty.StringVal("pass"),
+		"retry_max":      cty.StringVal("999"),
+		"retry_wait_min": cty.StringVal("15"),
+		"retry_wait_max": cty.StringVal("150"),
 	}
 
 	b = backend.TestBackendConfig(t, New(), configs.SynthBody("synth", conf)).(*Backend)
@@ -74,4 +78,13 @@ func TestHTTPClientFactory(t *testing.T) {
 		t.Fatalf("Unexpected username \"%s\" vs \"%s\" or password \"%s\" vs \"%s\"", client.Username, conf["username"],
 			client.Password, conf["password"])
 	}
+	if client.Client.RetryMax != 999 {
+		t.Fatalf("Expected retry_max \"%d\", got \"%d\"", 999, client.Client.RetryMax)
+	}
+	if client.Client.RetryWaitMin != 15*time.Second {
+		t.Fatalf("Expected retry_wait_min \"%s\", got \"%s\"", 15*time.Second, client.Client.RetryWaitMin)
+	}
+	if client.Client.RetryWaitMax != 150*time.Second {
+		t.Fatalf("Expected retry_wait_max \"%s\", got \"%s\"", 150*time.Second, client.Client.RetryWaitMax)
+	}
 }

backend/remote-state/http/client.go

@@ -11,6 +11,7 @@ import (
 	"net/http"
 	"net/url"
 
+	"github.com/hashicorp/go-retryablehttp"
 	"github.com/hashicorp/terraform/state"
 	"github.com/hashicorp/terraform/state/remote"
 )
@@ -28,7 +29,7 @@ type httpClient struct {
 	UnlockMethod string
 
 	// HTTP
-	Client   *http.Client
+	Client   *retryablehttp.Client
 	Username string
 	Password string
 
@@ -44,7 +45,7 @@ func (c *httpClient) httpRequest(method string, url *url.URL, data *[]byte, what
 	}
 
 	// Create the request
-	req, err := http.NewRequest(method, url.String(), reader)
+	req, err := retryablehttp.NewRequest(method, url.String(), reader)
 	if err != nil {
 		return nil, fmt.Errorf("Failed to make %s HTTP request: %s", what, err)
 	}

backend/remote-state/http/client_test.go

@@ -10,7 +10,7 @@ import (
 	"reflect"
 	"testing"
 
-	cleanhttp "github.com/hashicorp/go-cleanhttp"
+	"github.com/hashicorp/go-retryablehttp"
 	"github.com/hashicorp/terraform/state/remote"
 )
 
@@ -30,14 +30,14 @@ func TestHTTPClient(t *testing.T) {
 	}
 
 	// Test basic get/update
-	client := &httpClient{URL: url, Client: cleanhttp.DefaultClient()}
+	client := &httpClient{URL: url, Client: retryablehttp.NewClient()}
 	remote.TestClient(t, client)
 
 	// test just a single PUT
 	p := &httpClient{
 		URL:          url,
 		UpdateMethod: "PUT",
-		Client:       cleanhttp.DefaultClient(),
+		Client:       retryablehttp.NewClient(),
 	}
 	remote.TestClient(t, p)
 
@@ -49,7 +49,7 @@ func TestHTTPClient(t *testing.T) {
 		LockMethod:   "LOCK",
 		UnlockURL:    url,
 		UnlockMethod: "UNLOCK",
-		Client:       cleanhttp.DefaultClient(),
+		Client:       retryablehttp.NewClient(),
 	}
 	b := &httpClient{
 		URL:          url,
@@ -58,7 +58,7 @@ func TestHTTPClient(t *testing.T) {
 		LockMethod:   "LOCK",
 		UnlockURL:    url,
 		UnlockMethod: "UNLOCK",
-		Client:       cleanhttp.DefaultClient(),
+		Client:       retryablehttp.NewClient(),
 	}
 	remote.TestRemoteLocks(t, a, b)
 
@@ -68,13 +68,23 @@ func TestHTTPClient(t *testing.T) {
 	defer ts.Close()
 
 	url, err = url.Parse(ts.URL)
-	c := &httpClient{
+	client = &httpClient{
 		URL:          url,
 		UpdateMethod: "PUT",
-		Client:       cleanhttp.DefaultClient(),
+		Client:       retryablehttp.NewClient(),
 	}
-	remote.TestClient(t, c) // first time through: 201
-	remote.TestClient(t, c) // second time, with identical data: 204
+	remote.TestClient(t, client) // first time through: 201
+	remote.TestClient(t, client) // second time, with identical data: 204
+
+	// test a broken backend
+	brokenHandler := new(testBrokenHTTPHandler)
+	brokenHandler.handler = new(testHTTPHandler)
+	ts = httptest.NewServer(http.HandlerFunc(brokenHandler.Handle))
+	defer ts.Close()
+
+	url, err = url.Parse(ts.URL)
+	client = &httpClient{URL: url, Client: retryablehttp.NewClient()}
+	remote.TestClient(t, client)
 }
 
 func assertError(t *testing.T, err error, expected string) {
@@ -149,3 +159,18 @@ func (h *testHTTPHandler) HandleWebDAV(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte(fmt.Sprintf("Unknown method: %s", r.Method)))
 	}
 }
+
+type testBrokenHTTPHandler struct {
+	lastRequestWasBroken bool
+	handler              *testHTTPHandler
+}
+
+func (h *testBrokenHTTPHandler) Handle(w http.ResponseWriter, r *http.Request) {
+	if h.lastRequestWasBroken {
+		h.lastRequestWasBroken = false
+		h.handler.Handle(w, r)
+	} else {
+		h.lastRequestWasBroken = true
+		w.WriteHeader(500)
+	}
+}

command/apply_test.go

@@ -677,6 +677,9 @@ func TestApply_plan_remoteState(t *testing.T) {
 		"username":               cty.NullVal(cty.String),
 		"password":               cty.NullVal(cty.String),
 		"skip_cert_verification": cty.NullVal(cty.Bool),
+		"retry_max":              cty.NullVal(cty.String),
+		"retry_wait_min":         cty.NullVal(cty.String),
+		"retry_wait_max":         cty.NullVal(cty.String),
 	})
 	backendConfigRaw, err := plans.NewDynamicValue(backendConfig, backendConfig.Type())
 	if err != nil {

website/docs/backends/types/http.html.md

@@ -60,3 +60,8 @@ The following configuration options are supported:
  * `password` - (Optional) The password for HTTP basic authentication
  * `skip_cert_verification` - (Optional) Whether to skip TLS verification.
    Defaults to `false`.
+ * `retry_max` – (Optional) The number of HTTP request retries. Defaults to `2`.
+ * `retry_wait_min` – (Optional) The minimum time in seconds to wait between HTTP request attempts.
+   Defaults to `1`.
+ * `retry_wait_max` – (Optional) The maximum time in seconds to wait between HTTP request attempts.
+   Defaults to `30`.