Use the write-and-rename paradigm for all JSON files.

This ensures that clients don't pick up partial writes for any JSON
files, including logs, manifests, summaries and so on.

utils.go

@@ -26,15 +26,45 @@ func newGlobalConfiguration(registry string) globalConfiguration {
     }
 }
 
-func dumpJson(path string, output interface{}) error {
-    str, err := json.MarshalIndent(output, "", "    ")
+func dumpJson(path string, content interface{}) error {
+    // Using the save-and-rename paradigm to avoid clients picking up partial writes.
+    temp, err := os.CreateTemp(filepath.Dir(path), ".temp*.json")
+    if err != nil {
+        return fmt.Errorf("failed to create temporary file when saving %q; %w", path, err)
+    }
+
+    is_closed := false
+    defer func() {
+        if !is_closed {
+            temp.Close()
+        }
+    }()
+
+    err = os.Chmod(temp.Name(), 0644)
     if err != nil {
-        return fmt.Errorf("failed to marshal JSON; %w", err)
+        return fmt.Errorf("failed to set temporary file permissions when saving %q; %w", path, err);
     }
 
-    err = os.WriteFile(path, str, 0644)
+    as_str, err := json.MarshalIndent(content, "", "    ")
     if err != nil {
-        return fmt.Errorf("failed to write to %q; %w", path, err)
+        return fmt.Errorf("failed to marshal JSON to save to %q; %w", path, err)
+    }
+
+    _, err = temp.Write(as_str)
+    if err != nil {
+        return fmt.Errorf("failed to write JSON to temporary file for %q; %w", path, err)
+    }
+
+    temp_name := temp.Name()
+    is_closed = true
+    err = temp.Close()
+    if err != nil {
+        return fmt.Errorf("failed to close temporary file when saving to %q; %w", path, err)
+    }
+
+    err = os.Rename(temp_name, path)
+    if err != nil {
+        return fmt.Errorf("failed to rename temporary file to %q; %w", path, err)
     }
 
     return nil
@@ -63,47 +93,11 @@ func isMissingOrBadName(name *string) error {
 
 const logDirName = "..logs"
 
-func dumpLog(registry string, output interface{}) error {
+func dumpLog(registry string, content interface{}) error {
     path := time.Now().Format(time.RFC3339) + "_" + strconv.Itoa(100000 + rand.Intn(900000))
-    return dumpJson(filepath.Join(registry, logDirName, path), output)
+    return dumpJson(filepath.Join(registry, logDirName, path), content)
 }
 
 func dumpResponse(response_dir, reqname string, content interface{}) error {
-    // Using the save-and-rename paradigm to avoid clients picking up partial writes.
-    temp, err := os.CreateTemp(response_dir, "TEMP")
-    if err != nil {
-        return fmt.Errorf("failed to create temporary file for response to %q; %w", reqname, err)
-    }
-
-    is_closed := false
-    defer func() {
-        if !is_closed {
-            temp.Close()
-        }
-    }()
-
-    as_str, err := json.MarshalIndent(content, "", "    ")
-    if err != nil {
-        return fmt.Errorf("failed to marshal JSON for response to %q; %w", reqname, err)
-    }
-
-    _, err = temp.Write(as_str)
-    if err != nil {
-        return fmt.Errorf("failed to write JSON for response to %q; %w", reqname, err)
-    }
-
-    temp_name := temp.Name()
-    is_closed = true
-    err = temp.Close()
-    if err != nil {
-        return fmt.Errorf("failed to close file for response to %q; %w", reqname, err)
-    }
-
-    logpath := filepath.Join(response_dir, reqname)
-    err = os.Rename(temp_name, logpath)
-    if err != nil {
-        return fmt.Errorf("failed to rename response to %q; %w", reqname, err)
-    }
-
-    return nil
+    return dumpJson(filepath.Join(response_dir, reqname), content)
 }