feat: add backoff/retry to all client operations

injected retry with backoff and jitter for all client operations
extended ListModules server handler to include the latest version in the result

internal/server/connect.go

@@ -76,6 +76,31 @@ func (s *connectServer) ListModules(ctx context.Context, req *connect.Request[pe
 		mod := &perseusapi.Module{
 			Name: m.Name,
 		}
+		// include the latest version for each matched module
+		versionQ := store.ModuleVersionQuery{
+			ModuleFilter:      m.Name,
+			LatestOnly:        true,
+			IncludePrerelease: false,
+		}
+		vers, _, err := s.store.QueryModuleVersions(ctx, versionQ)
+		if err != nil {
+			log.Error(err, "unable to query for latest module version", "moduleFilter", m.Name, "latestOnly", true, "includePrerelease", false)
+			return nil, connect.NewError(connect.CodeInternal, fmt.Errorf("Unable to determine latest version for module %s: a database operation failed", m.Name))
+		}
+		// if no stable version exists, try to find a pre-release
+		if len(vers) == 0 {
+			versionQ.IncludePrerelease = true
+			vers, _, err = s.store.QueryModuleVersions(ctx, versionQ)
+			if err != nil {
+				log.Error(err, "unable to query for latest module version", "moduleFilter", m.Name, "latestOnly", true, "includePrerelease", true)
+				return nil, connect.NewError(connect.CodeInternal, fmt.Errorf("Unable to determine latest version for module %s: a database operation failed", m.Name))
+			}
+		}
+		// assign the latest version of the module, if found
+		if len(vers) > 0 {
+			mod.Versions = []string{"v" + vers[0].Version}
+		}
+
 		resp.Modules = append(resp.Modules, mod)
 	}
 	return connect.NewResponse(resp), nil

query.go

@@ -348,7 +348,9 @@ func lookupLatestModuleVersion(ctx context.Context, c perseusapiconnect.PerseusS
 		ModuleName:    modulePath,
 		VersionOption: perseusapi.ModuleVersionOption_latest,
 	})
-	resp, err := c.ListModuleVersions(ctx, req)
+	resp, err := retryOp(func() (*connect.Response[perseusapi.ListModuleVersionsResponse], error) {
+		return c.ListModuleVersions(ctx, req)
+	})
 	if err != nil {
 		return "", err
 	}
@@ -391,7 +393,9 @@ func walkDependencies(ctx context.Context, client perseusapiconnect.PerseusServi
 		Direction:  direction,
 	})
 	for done := false; !done; done = (req.Msg.PageToken != "") {
-		resp, err := client.QueryDependencies(ctx, req)
+		resp, err := retryOp(func() (*connect.Response[perseusapi.QueryDependenciesResponse], error) {
+			return client.QueryDependencies(ctx, req)
+		})
 		if err != nil {
 			return dependencyTreeNode{}, err
 		}
@@ -424,43 +428,21 @@ func listModules(ctx context.Context, ps perseusapiconnect.PerseusServiceClient,
 	})
 	for done := false; !done; {
 		status("retrieving modules")
-		resp, err := ps.ListModules(ctx, req)
+		resp, err := retryOp(func() (*connect.Response[perseusapi.ListModulesResponse], error) {
+			return ps.ListModules(ctx, req)
+		})
 		if err != nil {
-			return nil, fmt.Errorf("todo: %w", err)
+			return nil, fmt.Errorf("Unable to list modules matching the provided filter: %w", err)
 		}
 		for _, mod := range resp.Msg.Modules {
-			status(fmt.Sprintf("determining latest version for %s", mod.GetName()))
-			req2 := connect.NewRequest(&perseusapi.ListModuleVersionsRequest{
-				ModuleName:    mod.GetName(),
-				VersionOption: perseusapi.ModuleVersionOption_latest,
-			})
-			resp2, err := ps.ListModuleVersions(ctx, req2)
-			switch {
-			case err != nil:
-				return nil, fmt.Errorf("Unable to determine the current version for %s: %w", mod.GetName(), err)
-
-			case len(resp2.Msg.Modules) == 0 || len(resp2.Msg.Modules[0].Versions) == 0:
-				status(fmt.Sprintf("no stable version found for %s, trying to find a pre-release", mod.GetName()))
-				req2.Msg.IncludePrerelease = true
-				resp2, err = ps.ListModuleVersions(ctx, req2)
-				switch {
-				case err != nil:
-					return nil, fmt.Errorf("Unable to determine the current version for %s: %w", mod.GetName(), err)
-
-				case len(resp2.Msg.Modules) == 0 || len(resp2.Msg.Modules[0].Versions) == 0:
-					return nil, fmt.Errorf("No versions found for %s", mod.GetName())
-
-				default:
-					// got it
-				}
-			default:
-				// got it
-			}
-
-			results = append(results, dependencyItem{
+			item := dependencyItem{
 				Path:    mod.GetName(),
-				Version: resp2.Msg.Modules[0].Versions[0],
-			})
+				Version: "-", // show a dash if we don't have a version
+			}
+			if vers := mod.GetVersions(); len(vers) > 0 {
+				item.Version = vers[0]
+			}
+			results = append(results, item)
 		}
 		req.Msg.PageToken = resp.Msg.GetNextPageToken()
 		done = (req.Msg.PageToken != "")
@@ -493,7 +475,9 @@ func listModuleVersions(ctx context.Context, ps perseusapiconnect.PerseusService
 			apiRequest.Msg.VersionOption = perseusapi.ModuleVersionOption_latest
 		}
 		req.updateStatus(fmt.Sprintf("retreiving versions for modules matching %q", req.modulePattern))
-		resp, err := ps.ListModuleVersions(ctx, apiRequest)
+		resp, err := retryOp(func() (*connect.Response[perseusapi.ListModuleVersionsResponse], error) {
+			return ps.ListModuleVersions(ctx, apiRequest)
+		})
 		if err != nil {
 			return nil, fmt.Errorf("todo: %w", err)
 		}

retry.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"crypto/rand"
+	"math/big"
+	"time"
+
+	"connectrpc.com/connect"
+)
+
+var (
+	// subsequent retry delays for retryOp()
+	// - use the first 5 Fibonacci numbers for semi-exponential growth
+	// - the extra 0 value is a sentinel so we don't do another wait after we've exhausted all 5 retries
+	backoffDelays = []time.Duration{
+		100 * time.Millisecond,
+		200 * time.Millisecond,
+		300 * time.Millisecond,
+		500 * time.Millisecond,
+		800 * time.Millisecond,
+		0,
+	}
+)
+
+// retryOp performs the specified operation, retrying up to 5 times if the request returns a 502-Unavailable
+// status to provide resiliency for transient failures due to LB flakiness (especially within K8S).
+func retryOp[T any](op func() (T, error)) (result T, err error) {
+	var zero T
+	for _, wait := range backoffDelays {
+		result, err = op()
+		switch {
+		case err == nil:
+			return result, nil
+		case connect.CodeOf(err) == connect.CodeUnavailable:
+			if wait > 0 {
+				// inject up to 20% jitter
+				maxJitter := big.NewInt(int64(float64(int64(wait)) * 0.2))
+				jitter, _ := rand.Int(rand.Reader, maxJitter)
+				wait += time.Duration(jitter.Int64())
+				<-time.After(wait)
+			}
+		default:
+			return zero, err
+		}
+	}
+	// if we get here, err is non-nil and from a 502 but we have exhausted all retries
+	return zero, err
+}

update.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"os"
 	"path"
+	"time"
 
 	"connectrpc.com/connect"
 	"github.com/spf13/cobra"
@@ -192,7 +193,10 @@ func getModuleInfoFromProxy(modulePath string) (moduleInfo, error) {
 // applyUpdates calls the Perseus server to update the dependencies of the specified module
 func applyUpdates(conf clientConfig, mod module.Version, deps []module.Version) (err error) {
 	// create the client and call the server
-	ctx := context.Background()
+	// . be sure we don't hang "forever".  5s is a bit over 2X the cumulative retry delays (1900 ms)
+	//   so this shouldn't generate any pre-mature aborts
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
 	client := conf.getClient()
 	req := connect.NewRequest(&perseusapi.UpdateDependenciesRequest{
 		ModuleName: mod.Path,
@@ -205,15 +209,17 @@ func applyUpdates(conf clientConfig, mod module.Version, deps []module.Version)
 			Versions: []string{d.Version},
 		}
 	}
-	if _, err = client.UpdateDependencies(ctx, req); err != nil {
-		return err
-	}
-	return nil
+
+	_, err = retryOp(func() (struct{}, error) {
+		_, err := client.UpdateDependencies(ctx, req)
+		return struct{}{}, err
+	})
+	return err
 }
 
 // moduleInfo represents the relevant Go module metadata for this application.
 //
-// This struct does not contain a version because the Go module library (golang.org/x/mod/modfile)
+// Values may not contain a version because the Go module library (golang.org/x/mod/modfile)
 // does not return a version for the "main" module even if it is a library package.
 type moduleInfo struct {
 	// the module name, ex: github.com/CrowdStrike/perseus