log: Drop `Debugf()` function from `Logger` interface

Next to `Debug()` and related functions our `Logger` interface also
provides `Debugf()` and related functions that takes a formatting string
as well as a set of arguments for it. There are multiple reasons though
why we don't want to expose these functions:

    - They do not exist in the `slog` package, which thus causes our own
      internal interface to diverge from our desired target solution.

    - It is discouraged to put variable data into the message itself.
      Instead, callsites are encouraged to add any variable data as
      structured log data.

    - It often gets abused in contexts where it's not required at all to
      call the formatting variant as all we pass in is a static string.

    - We have a pending addition of logging functions that also take a
      context parameter as input. The formatting family would cause us
      to require four more functions that take such a context as input.

Let's remove `Debugf()` in favor of `Debug()`. Most of the existing
callsites are converted to instead use structured logging data.

6 files changed, 20 insertions, 11 deletions

diff --git a/internal/cli/praefect/subcmd_list_untracked_repositories.go b/internal/cli/praefect/subcmd_list_untracked_repositories.go
index 289ede89f..af356deba 100644
--- a/internal/cli/praefect/subcmd_list_untracked_repositories.go
+++ b/internal/cli/praefect/subcmd_list_untracked_repositories.go
@@ -77,7 +77,7 @@ func listUntrackedRepositoriesAction(appCtx *cli.Context) error {
 	ctx = metadata.AppendToOutgoingContext(ctx, "client_name", appCtx.Command.Name)
 
 	logger = logger.WithField("correlation_id", correlation.ExtractFromContext(ctx))
-	logger.Debugf("starting %s command", appCtx.App.Name)
+	logger.Debug(fmt.Sprintf("starting %s command", appCtx.App.Name))
 
 	logger.Debug("dialing to gitaly nodes...")
 	nodeSet, err := dialGitalyStorages(ctx, conf, defaultDialTimeout)
@@ -107,7 +107,11 @@ func listUntrackedRepositoriesAction(appCtx *cli.Context) error {
 	}
 	for _, vs := range conf.VirtualStorages {
 		for _, node := range vs.Nodes {
-			logger.Debugf("check %q/%q storage repositories", vs.Name, node.Storage)
+			logger.WithFields(log.Fields{
+				"virtual_storage": vs.Name,
+				"storage_node":    node.Storage,
+			}).Debug("checking storage repositories")
+
 			if err := walker.ExecOnRepositories(ctx, vs.Name, node.Storage, reporter.Report); err != nil {
 				return fmt.Errorf("exec on %q/%q: %w", vs.Name, node.Storage, err)
 			}
diff --git a/internal/cli/praefect/subcmd_track_repository.go b/internal/cli/praefect/subcmd_track_repository.go
index 98bb40fcc..207d89542 100644
--- a/internal/cli/praefect/subcmd_track_repository.go
+++ b/internal/cli/praefect/subcmd_track_repository.go
@@ -336,7 +336,12 @@ func (req *trackRepositoryRequest) authoritativeRepositoryExists(ctx context.Con
 
 		for _, node := range vs.Nodes {
 			if node.Storage == nodeName {
-				logger.Debugf("check if repository %q exists on gitaly %q at %q", req.ReplicaPath, node.Storage, node.Address)
+				logger.WithFields(log.Fields{
+					"replica_path": req.ReplicaPath,
+					"storage_node": node.Storage,
+					"node_address": node.Address,
+				}).Debug("check if repository exists on Gitaly node")
+
 				repo := &gitalypb.Repository{
 					StorageName:  node.Storage,
 					RelativePath: req.ReplicaPath,
diff --git a/internal/gitaly/storage/storagemgr/database.go b/internal/gitaly/storage/storagemgr/database.go
index 526c7eda6..66913f846 100644
--- a/internal/gitaly/storage/storagemgr/database.go
+++ b/internal/gitaly/storage/storagemgr/database.go
@@ -1,6 +1,8 @@
 package storagemgr
 
 import (
+	"fmt"
+
 	"github.com/dgraph-io/badger/v4"
 	"gitlab.com/gitlab-org/gitaly/v16/internal/log"
 )
@@ -20,6 +22,10 @@ type badgerLogger struct {
 	log.Logger
 }
 
+func (l badgerLogger) Debugf(msg string, args ...any) {
+	l.Debug(fmt.Sprintf(msg, args...))
+}
+
 func (l badgerLogger) Warningf(msg string, args ...any) {
 	l.Warnf(msg, args...)
 }
diff --git a/internal/limiter/adaptive_calculator.go b/internal/limiter/adaptive_calculator.go
index ebb7526e0..97a273c2a 100644
--- a/internal/limiter/adaptive_calculator.go
+++ b/internal/limiter/adaptive_calculator.go
@@ -259,7 +259,7 @@ func (c *AdaptiveCalculator) calibrateLimits(ctx context.Context) {
 			logger.WithFields(map[string]interface{}{
 				"previous_limit": limit.Current(),
 				"new_limit":      newLimit,
-			}).Debugf("Additive increase")
+			}).Debug("Additive increase")
 		} else {
 			// Multiplicative decrease
 			newLimit = int(math.Floor(float64(limit.Current()) * setting.BackoffFactor))
diff --git a/internal/log/logger.go b/internal/log/logger.go
index a1baac5c8..9fafeaa1c 100644
--- a/internal/log/logger.go
+++ b/internal/log/logger.go
@@ -18,7 +18,6 @@ type Logger interface {
 	WithFields(fields Fields) Logger
 	WithError(err error) Logger
 
-	Debugf(format string, args ...any)
 	Infof(format string, args ...any)
 	Warnf(format string, args ...any)
 	Errorf(format string, args ...any)
@@ -66,11 +65,6 @@ func (l LogrusLogger) WithError(err error) Logger {
 	return LogrusLogger{entry: l.entry.WithError(err)}
 }
 
-// Debugf writes a formatted log message at debug level.
-func (l LogrusLogger) Debugf(format string, args ...any) {
-	l.entry.Debugf(format, args...)
-}
-
 // Infof writes a formatted log message at info level.
 func (l LogrusLogger) Infof(format string, args ...any) {
 	l.entry.Infof(format, args...)
diff --git a/internal/praefect/coordinator.go b/internal/praefect/coordinator.go
index a95bab79b..e2a8875e4 100644
--- a/internal/praefect/coordinator.go
+++ b/internal/praefect/coordinator.go
@@ -665,7 +665,7 @@ func streamParametersContext(ctx context.Context) context.Context {
 func (c *Coordinator) StreamDirector(ctx context.Context, fullMethodName string, peeker proxy.StreamPeeker) (*proxy.StreamParameters, error) {
 	// For phase 1, we need to route messages based on the storage location
 	// to the appropriate Gitaly node.
-	log.FromContext(ctx).Debugf("Stream director received method %s", fullMethodName)
+	log.FromContext(ctx).WithField("method", fullMethodName).Debug("Stream director received method")
 
 	mi, err := c.registry.LookupMethod(fullMethodName)
 	if err != nil {