From 1f66755fd87438dc85510c22be60f2a829d7d156 Mon Sep 17 00:00:00 2001
From: Jordan Sissel <jls@semicomplete.com>
Date: Wed, 16 Oct 2013 17:04:50 -0700
Subject: [PATCH] os.Rename fails on windows if the file exists. I can find no
 way to invoke ReplaceFile via Go, so lumberjack's registrar updates will not
 be atomic on Windows platform. On windows, the "old" registrar db is saved as
 ".lumberjack.old"

---
 harvester.go         |  2 ++
 registrar.go         | 19 ++-----------------
 registrar_other.go   | 23 +++++++++++++++++++++++
 registrar_windows.go | 24 ++++++++++++++++++++++++
 4 files changed, 51 insertions(+), 17 deletions(-)
 create mode 100644 registrar_other.go
 create mode 100644 registrar_windows.go

diff --git a/harvester.go b/harvester.go
index e44846b..98d6453 100644
--- a/harvester.go
+++ b/harvester.go
@@ -34,6 +34,8 @@ func (h *Harvester) Harvest(output chan *FileEvent) {
   // get current offset in file
   offset, _ := h.file.Seek(0, os.SEEK_CUR)
 
+  log.Printf("Current file offset: %d\n", offset)
+
   // TODO(sissel): Make the buffer size tunable at start-time
   reader := bufio.NewReaderSize(h.file, 16<<10) // 16kb buffer by default
 
diff --git a/registrar.go b/registrar.go
index cc01490..1999828 100644
--- a/registrar.go
+++ b/registrar.go
@@ -2,8 +2,6 @@ package main
 
 import (
   "log"
-  "os"
-  "encoding/json"
 )
 
 func Registrar(input chan []*FileEvent) {
@@ -28,25 +26,12 @@ func Registrar(input chan []*FileEvent) {
         Inode: ino,
         Device: dev,
       }
+      log.Printf("State %s: %d\n", *event.Source, event.Offset)
     }
 
     if len(state) > 0 {
-      write(state)
-      os.Rename(".lumberjack.new", ".lumberjack")
+      WriteRegistry(state, ".lumberjack")
     }
   }
 }
 
-func write(state map[string]*FileState) {
-  log.Printf("Saving registrar state.\n")
-  // Open tmp file, write, flush, rename
-  file, err := os.Create(".lumberjack.new")
-  if err != nil {
-    log.Printf("Failed to open .lumberjack.new for writing: %s\n", err)
-    return
-  }
-
-  encoder := json.NewEncoder(file)
-  encoder.Encode(state)
-  file.Close()
-}
diff --git a/registrar_other.go b/registrar_other.go
new file mode 100644
index 0000000..330dbb2
--- /dev/null
+++ b/registrar_other.go
@@ -0,0 +1,23 @@
+// +build !windows
+
+package main
+import (
+  "encoding/json"
+  "os"
+  "log"
+)
+
+func WriteRegistry(state map[string]*FileState, path string) {
+  // Open tmp file, write, flush, rename
+  file, err := os.Create(".lumberjack.new")
+  if err != nil {
+    log.Printf("Failed to open .lumberjack.new for writing: %s\n", err)
+    return
+  }
+  defer file.Close()
+
+  encoder := json.NewEncoder(file)
+  encoder.Encode(state)
+
+  os.Rename(".lumberjack.new", path)
+}
diff --git a/registrar_windows.go b/registrar_windows.go
new file mode 100644
index 0000000..ef8cf55
--- /dev/null
+++ b/registrar_windows.go
@@ -0,0 +1,24 @@
+package main
+
+import (
+  "encoding/json"
+  "os"
+  "log"
+)
+
+func WriteRegistry(state map[string]*FileState, path string) {
+  tmp := path + ".new"
+  file, err := os.Create(tmp)
+  if err != nil {
+    log.Printf("Failed to open .lumberjack.new for writing: %s\n", err)
+    return
+  }
+
+  encoder := json.NewEncoder(file)
+  encoder.Encode(state)
+  file.Close()
+
+  old := path + ".old"
+  os.Rename(path, old)
+  os.Rename(tmp, path)
+}
-- 
GitLab