tests/odb/backend/nonrefreshing.c


Log

Author Commit Date CI Message
Patrick Steinhardt 28a0741f 2017-04-10T09:30:08 odb: verify object hashes The upstream git.git project verifies objects when looking them up from disk. This avoids scenarios where objects have somehow become corrupt on disk, e.g. due to hardware failures or bit flips. While our mantra is usually to follow upstream behavior, we do not do so in this case, as we never check hashes of objects we have just read from disk. To fix this, we create a new error class `GIT_EMISMATCH` which denotes that we have looked up an object with a hashsum mismatch. `odb_read_1` will then, after having read the object from its backend, hash the object and compare the resulting hash to the expected hash. If hashes do not match, it will return an error. This obviously introduces another computation of checksums and could potentially impact performance. Note though that we usually perform I/O operations directly before doing this computation, and as such the actual overhead should be drowned out by I/O. Running our test suite seems to confirm this guess. On a Linux system with best-of-five timings, we had 21.592s with the check enabled and 21.590s with the ckeck disabled. Note though that our test suite mostly contains very small blobs only. It is expected that repositories with bigger blobs may notice an increased hit by this check. In addition to a new test, we also had to change the odb::backend::nonrefreshing test suite, which now triggers a hashsum mismatch when looking up the commit "deadbeef...". This is expected, as the fake backend allocated inside of the test will return an empty object for the OID "deadbeef...", which will obviously not hash back to "deadbeef..." again. We can simply adjust the hash to equal the hash of the empty object here to fix this test.
Patrick Steinhardt e29e8029 2017-04-10T10:31:22 tests: odb: make hash of fake backend configurable In the odb::backend::nonrefreshing test suite, we set up a fake backend so that we are able to determine if backend functions are called correctly. During the setup, we also parse an OID which is later on used to read out the pseudo-object. While this procedure works right now, it will create problems later when we implement hash verification for looked up objects. The current OID ("deadbeef") will not match the hash of contents we give back to the ODB layer and thus cannot be verified. Make the hash configurable so that we can simply switch the returned for single tests.
Ben Straub 17820381 2013-11-14T14:05:52 Rename tests-clar to tests