Introduce mc-util-lmdb crate containing a generic MetadataStore for lmdb database versioning #349
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…mdb database versioning
eranrund
commented
Aug 5, 2020
| /// Metadata store settings that are used for version control. | ||
| #[derive(Clone, Default, Debug)] | ||
| pub struct LedgerDbMetadataStoreSettings; | ||
| impl MetadataStoreSettings for LedgerDbMetadataStoreSettings { |
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This stuff is the main idea behind the work proposed in this PR. Each LMDB user would need to have this, instead of duplicating the entire metadata_store.rs file.
eranrund
commented
Aug 5, 2020
| /// release. | ||
| pub created_by_crate_version: String, | ||
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| _s: S, |
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Ideally this would've been PhantomData<S> instead, but Rust doesn't like that (rust-lang/rust#46969 might be related).
sugargoat
approved these changes
Aug 5, 2020
mfaulk
approved these changes
Aug 5, 2020
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Motivation
We implemented a simple versioning scheme for LedgerDB which allows us to prevent opening the database if it contains data that is incompatible with the code that is opening it. This behavior is desirable for other LMDB databases as well, such as mobilecoind's, watcher, etc.
In this PR
mc_ledger_db::MetadataStoreinto a generic one that lives inside a newmc_util_lmdbcrate. Its a pretty trivial implementation, so maybe we want to just duplicate https://github.com/mobilecoinofficial/mobilecoin/blob/68a7b65c9fe515825d95278e47371ce0bb926194/ledger/db/src/metadata.rs into each place we use LMDB in - I am not sure. On one hand, the const-configuration-using-a-trait feels a bit forced, and on the other hand it does reduce code duplication significantly (I expect this code to be used in at least 5 places, I think?). Happy to hear thoughts on this.Future Work