fix(state): Write database format version to disk atomically to avoid a rare panic #8795
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… directories with `default_cache_dir()`
…spawn_atomic_write_to_tmp_file` for use in async environments.
…s callsite to avoid adding tokio as a dependency of zebra-chain.
upbqdn
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Aug 26, 2024
arya2
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arya2
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Aug 28, 2024
Co-authored-by: Marek <[email protected]>
upbqdn
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Aug 29, 2024
dmidem
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Oct 29, 2024
… a rare panic (ZcashFoundation#8795) * Splits `atomic_write_to_tmp_file` out of `zebra_network::Config::update_peer_cache` * Uses the new `atomic_write_to_tmp_file` fn in `update_peer_cache()` * Replaces repetitive code for getting the default peer and state cache directories with `default_cache_dir()` * Converts `atomic_write_to_tmp_file` to a blocking function and adds `spawn_atomic_write_to_tmp_file` for use in async environments. * Uses `atomic_write_to_tmp_file` to write database versions to disk * Removes `spawn_atomic_write_to_tmp_file()` and inlines its body at its callsite to avoid adding tokio as a dependency of zebra-chain. * Apply suggestions from code review Co-authored-by: Marek <[email protected]> --------- Co-authored-by: Marek <[email protected]>
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Motivation
We want to avoid potentially corrupting the database format version file when updating it.
Closes #8793.
Solution
atomic_write_to_tmp_file()fn.fs::write()inwrite_database_format_version_to_disk()with a call toatomic_write_to_tmp_file().Tests
Parts of this change are covered by existing tests for
update_peer_cache().We could also add a test for the atomic file write that interrupts a very expensive file system operation and checks that nothing has been written to the target file path, though I would prefer to leave that as follow-up work.
Follow-up Work
atomic_write_to_tmp_file()doesn't write anything to the target file path when interrupted.PR Author's Checklist
PR Reviewer's Checklist