refactor: address code review feedback on comments and style

Fixed several code quality issues identified during review:

1. Corrected backoff algorithm description in filer_client.go:
   - Changed "Exponential backoff" to "Multiplicative backoff with 1.5x factor"
   - The formula waitTime * 3/2 produces 1s, 1.5s, 2.25s, not exponential 2^n
   - More accurate terminology prevents confusion

2. Removed redundant nil check in vidmap_client.go:
   - After the for loop, node is guaranteed to be non-nil
   - Loop either returns early or assigns non-nil value to node
   - Simplified: if node != nil { node.cache.Store(nil) } → node.cache.Store(nil)

3. Added startup logging to IAM server for consistency:
   - Log when master client connection starts
   - Matches pattern in S3ApiServer (line 100 in s3api_server.go)
   - Improves operational visibility during startup
   - Added missing glog import

4. Fixed indentation in filer/reader_at.go:
   - Lines 76-91 had incorrect indentation (extra tab level)
   - Line 93 also misaligned
   - Now properly aligned with surrounding code

5. Updated deprecation comment to follow Go convention:
   - Changed "DEPRECATED:" to "Deprecated:" (standard Go format)
   - Tools like staticcheck and IDEs recognize the standard format
   - Enables automated deprecation warnings in tooling
   - Better developer experience

All changes are cosmetic and do not affect functionality.

weed/filer/reader_at.go

@@ -28,7 +28,7 @@ var _ = io.Closer(&ChunkReadAt{})
 
 // LookupFn creates a basic volume location lookup function with simple caching.
 //
-// DEPRECATED: This function has several limitations compared to wdclient.FilerClient:
+// Deprecated: Use wdclient.FilerClient instead. This function has several limitations compared to wdclient.FilerClient:
 //   - Simple bounded cache (10k entries, no eviction policy or TTL for stale entries)
 //   - No singleflight deduplication (concurrent requests for same volume will duplicate work)
 //   - No cache history for volume moves (no fallback chain when volumes migrate)
@@ -73,22 +73,22 @@ func LookupFn(filerClient filer_pb.FilerClient) wdclient.LookupFileIdFunctionTyp
 						return err
 					}
 
-				locations = resp.LocationsMap[vid]
-				if locations == nil || len(locations.Locations) == 0 {
-					glog.V(0).InfofCtx(ctx, "failed to locate %s", fileId)
-					return fmt.Errorf("failed to locate %s", fileId)
-				}
-				vicCacheLock.Lock()
-				// Simple size limit to prevent unbounded growth
-				// For proper cache management, use wdclient.FilerClient instead
-				if cacheSize < maxCacheSize {
-					vidCache[vid] = locations
-					cacheSize++
-				} else if cacheSize == maxCacheSize {
-					glog.Warningf("filer.LookupFn cache reached limit of %d volumes, not caching new entries. Consider migrating to wdclient.FilerClient for bounded cache management.", maxCacheSize)
-					cacheSize++ // Only log once
-				}
-				vicCacheLock.Unlock()
+					locations = resp.LocationsMap[vid]
+					if locations == nil || len(locations.Locations) == 0 {
+						glog.V(0).InfofCtx(ctx, "failed to locate %s", fileId)
+						return fmt.Errorf("failed to locate %s", fileId)
+					}
+					vicCacheLock.Lock()
+					// Simple size limit to prevent unbounded growth
+					// For proper cache management, use wdclient.FilerClient instead
+					if cacheSize < maxCacheSize {
+						vidCache[vid] = locations
+						cacheSize++
+					} else if cacheSize == maxCacheSize {
+						glog.Warningf("filer.LookupFn cache reached limit of %d volumes, not caching new entries. Consider migrating to wdclient.FilerClient for bounded cache management.", maxCacheSize)
+						cacheSize++ // Only log once
+					}
+					vicCacheLock.Unlock()
 
 					return nil
 				})

weed/iamapi/iamapi_server.go

@@ -12,6 +12,7 @@ import (
 	"github.com/gorilla/mux"
 	"github.com/seaweedfs/seaweedfs/weed/credential"
 	"github.com/seaweedfs/seaweedfs/weed/filer"
+	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/pb"
 	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
 	"github.com/seaweedfs/seaweedfs/weed/pb/iam_pb"
@@ -68,6 +69,7 @@ func NewIamApiServerWithStore(router *mux.Router, option *IamServerOption, expli
 	// Start KeepConnectedToMaster for volume location lookups
 	// IAM config files are typically small and inline, but if they ever have chunks,
 	// ReadEntry→StreamContent needs masterClient for volume lookups
+	glog.V(0).Infof("IAM API starting master client connection for volume location lookups")
 	go masterClient.KeepConnectedToMaster(shutdownCtx)
 	
 	configure := &IamS3ApiConfigure{

weed/wdclient/filer_client.go

@@ -344,7 +344,7 @@ func (p *filerVolumeProvider) LookupVolumeIds(ctx context.Context, volumeIds []s
 			glog.V(1).Infof("FilerClient: all %d filer(s) failed with retryable error (attempt %d/%d), retrying in %v: %v",
 				n, retry+1, maxRetries, waitTime, lastErr)
 			time.Sleep(waitTime)
-			waitTime = waitTime * 3 / 2 // Exponential backoff: 1s, 1.5s, 2.25s
+			waitTime = waitTime * 3 / 2 // Multiplicative backoff with 1.5x factor: 1s, 1.5s, 2.25s
 		}
 	}
 

weed/wdclient/vidmap_client.go

@@ -336,7 +336,6 @@ func (vc *vidMapClient) resetVidMap() {
 		}
 		node = node.cache.Load()
 	}
-	if node != nil {
-		node.cache.Store(nil)
-	}
+	// node is guaranteed to be non-nil after the loop
+	node.cache.Store(nil)
 }