branch-4.1: [fix](cloud) fix segment footer CORRUPTION not triggering file cache retry #61386#61426
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…retry (#61386) ## Proposed changes The three-tier retry logic in `Segment::_open()` (static method) was structured as `if-else-if`, so when `open_file()` succeeded but `_parse_footer()` returned `CORRUPTION`, the retry branch was unreachable. ### Root cause ```cpp // Before: if-else-if structure auto st = fs->open_file(path, &file_reader, &reader_options); if (st) { // open_file succeeded (almost always) segment->_file_reader = ...; st = segment->_open(stats); // _parse_footer() → CORRUPTION stored in st } else if (st.is<CORRUPTION>() && ...) { // UNREACHABLE: already entered `if` branch // Tier 1: clear cache, retry // Tier 2: bypass cache, read remote directly } RETURN_IF_ERROR(st); // CORRUPTION returned without any retry ``` `open_file()` only opens a file handle and rarely returns `CORRUPTION`. The actual footer checksum validation happens inside `_parse_footer()` (called via `segment->_open()`). Because the retry was in an `else if` guarded by the same `st` from `open_file()`, it was never reachable for the common `_parse_footer()` corruption case. ### Fix Change `else if` to a separate `if` block, so CORRUPTION from either `open_file()` or `_parse_footer()` triggers the three-tier retry: ```cpp // After: independent if blocks if (st) { segment->_file_reader = ...; st = segment->_open(stats); // _parse_footer() → CORRUPTION stored in st } // NOW reachable regardless of where CORRUPTION came from if (st.is<CORRUPTION>() && reader_options.cache_type == FILE_BLOCK_CACHE) { // Tier 1: clear file cache, re-download from remote // Tier 2: bypass cache entirely, read remote directly // Tier 3: remote source itself corrupt (logs warning) } ``` ### Issue Observed in cloud (S3) deployments: schema change fails with `CORRUPTION: Bad segment file footer checksum not match`. Log analysis confirmed that no retry log messages were ever emitted, consistent with this code bug. ## Tests - Added `TestFooterCorruptionTriggersRetry` to `segment_corruption_test.cpp` - Uses the existing `Segment::parse_footer:magic_number_corruption` sync point to corrupt the footer magic number on the first `_parse_footer()` call only (simulating file cache corruption) - Verifies the segment opens successfully via the retry path
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Cherry-picked from #61386