calypso/docs/BUGFIX-DISK-PARSING.md

Bug Fix: Disk Discovery JSON Parsing Issue

Problem

The disk listing endpoint was returning 500 Internal Server Error with the error:

failed to parse lsblk output: json: cannot unmarshal number into Go struct field .blockdevices.size of type string

Root Cause

The lsblk -J command returns JSON where the size field is a number, but the Go struct expected it as a string. This caused a JSON unmarshaling error.

Solution

Updated the struct to accept size as interface{} and added type handling to parse both string and number formats.

Changes Made

File: backend/internal/storage/disk.go

1. Updated struct definition to accept size as interface{}:

   var lsblkOutput struct {
       BlockDevices []struct {
           Name string      `json:"name"`
           Size interface{} `json:"size"` // Can be string or number
           Type string      `json:"type"`
       } `json:"blockdevices"`
   }
   

2. Updated size parsing logic to handle both string and number types:

   // Parse size (can be string or number)
   var sizeBytes int64
   switch v := device.Size.(type) {
   case string:
       if size, err := strconv.ParseInt(v, 10, 64); err == nil {
           sizeBytes = size
       }
   case float64:
       sizeBytes = int64(v)
   case int64:
       sizeBytes = v
   case int:
       sizeBytes = int64(v)
   }
   disk.SizeBytes = sizeBytes
   

Testing

After this fix, the disk listing endpoint should work correctly:

curl http://localhost:8080/api/v1/storage/disks \
  -H "Authorization: Bearer $TOKEN"

Expected Response: 200 OK with a list of physical disks.

Impact

• ✅ Disk discovery now works correctly
• ✅ Handles both string and numeric size values from lsblk
• ✅ More robust parsing that works with different lsblk versions
• ✅ No breaking changes to API response format

Related Files

• backend/internal/storage/disk.go - Disk discovery and parsing logic