When a Lua script containing a write command is executed against a
read-only replica in a Redis Cluster, the error may contain
"-READONLY You can't write against a read only replica" embedded
within a larger error message rather than starting with "READONLY ".
The existing code only checked for the "READONLY " prefix, missing
this format. This caused shouldRetry() and isReadOnlyError() to fail,
preventing automatic retry and connection pool cleanup.
The fix checks for the exact substring
"-READONLY You can't write against a read only replica" which is
specific enough to avoid false positives while catching the Lua
script error format.
Closes#2770
Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>
