The previous default of 8 was a regression risk: cm_transfer_credit.py
uses ThreadPoolExecutor with CM_TRANSFER_MAX_THREADS (default 20 in
prod compose), so up to 20 threads concurrently call self.db.query().
With pool_size=8, the 9th-20th threads would hit PoolError, which
gets caught by 'except Error' and silently returns []/False — making
transfers fail with no obvious cause.
Default bumped to 24 (covers the 20-thread default with 4 in reserve).
mysql.connector caps pool_size at 32; clamping with a clear log line
so a future operator who pushes CM_TRANSFER_MAX_THREADS too high gets
a readable message instead of a library traceback.
Operator note: if you raise CM_TRANSFER_MAX_THREADS, also raise
DB_POOL_SIZE to at least the same value (max 32). At 32 threads with
4 services × 32 = 128 conns total, still well under MySQL's default
max_connections=151.
yiekheng
324c88e652