chore: #64 add system hardening with retry logic for client (#68)

- implement RetryRoundTripper

Refs: #64

Reviewed-on: #68
Reviewed-by: Marcel_Henselin <marcel.henselin@stackit.cloud>
Co-authored-by: Andre Harms <andre.harms@stackit.cloud>
Co-committed-by: Andre Harms <andre.harms@stackit.cloud>

stackit/provider.go

@@ -6,6 +6,7 @@ import (
 	"context"
 	"fmt"
 	"strings"
+	"time"
 
 	"github.com/hashicorp/terraform-plugin-framework-validators/stringvalidator"
 	"github.com/hashicorp/terraform-plugin-framework/datasource"
@@ -45,6 +46,17 @@ var (
 	_ provider.Provider = &Provider{}
 )
 
+const (
+	// maxRetries is the maximum number of retries for a failed HTTP request.
+	maxRetries = 3
+	// initialDelay is the initial delay before the first retry attempt.
+	initialDelay = 2 * time.Second
+	// maxDelay is the maximum delay between retry attempts.
+	maxDelay = 90 * time.Second
+	// perTryTimeout is the timeout for each individual HTTP request attempt.
+	perTryTimeout = 30 * time.Second
+)
+
 // Provider is the provider implementation.
 type Provider struct {
 	version string
@@ -466,7 +478,7 @@ func (p *Provider) Configure(ctx context.Context, req provider.ConfigureRequest,
 		providerData.Experiments = experimentValues
 	}
 
-	roundTripper, err := sdkauth.SetupAuth(sdkConfig)
+	baseRoundTripper, err := sdkauth.SetupAuth(sdkConfig)
 	if err != nil {
 		core.LogAndAddError(
 			ctx,
@@ -477,6 +489,14 @@ func (p *Provider) Configure(ctx context.Context, req provider.ConfigureRequest,
 		return
 	}
 
+	roundTripper := core.NewRetryRoundTripper(
+		baseRoundTripper,
+		maxRetries,
+		initialDelay,
+		maxDelay,
+		perTryTimeout,
+	)
+
 	// Make round tripper and custom endpoints available during DataSource and Resource
 	// type Configure methods.
 	providerData.RoundTripper = roundTripper