Re: [pbs-devel] [PATCH v3 proxmox-backup 2/5] fix #3847: datastore: test FixedIndexWriter

["Fabian Grünbichler" <f.gruenbichler@proxmox.com>]

On January 9, 2026 6:35 pm, Robert Obkircher wrote:
> Create a dummy chunk store and write fidx files with fixed and
> dynamically sized writers. Compare the resulting binary files directly
> (ignoring uuid and ctime) and also read them back using the reader.
> 
> The chunk hashes are made up and don't actually exist in the chunk
> store.
> 
> Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>
> ---
>  pbs-datastore/src/fixed_index.rs | 184 +++++++++++++++++++++++++++++++
>  1 file changed, 184 insertions(+)
> 
> diff --git a/pbs-datastore/src/fixed_index.rs b/pbs-datastore/src/fixed_index.rs
> index 8036a519..a20edc94 100644
> --- a/pbs-datastore/src/fixed_index.rs
> +++ b/pbs-datastore/src/fixed_index.rs
> @@ -530,3 +530,187 @@ impl FixedIndexWriter {
>          Ok(())
>      }
>  }
> +
> +#[cfg(test)]
> +mod tests {
> +    use super::*;
> +    use crate::chunk_store::ChunkStore;
> +    use pbs_api_types::DatastoreFSyncLevel;
> +    use std::fs;
> +    use std::sync::Arc;
> +
> +    const CS: usize = 4096;
> +
> +    #[test]
> +    fn test_fixed_index_writer() {

this should be a setup method, and not annotated as #[test]

> +        let mut testdir = fs::canonicalize(".").unwrap();

NACK, please use a tmpdir instead of writing to the current dir.. cargo
only provides a mechanism for this for integration tests, so for unit
tests you need to take care of it yourself, or move these to an
integration test..

we have discussed dropping the chunk store entirely in the past:

https://lore.proxmox.com/pbs-devel/1761822027.sm41v71zmk.astroid@yuna.none/

maybe we should do that and make unit testing here more
straight-forward? would still require a writable path though..

> +        testdir.push(".testdir_fixed_index");
> +
> +        if let Err(_e) = std::fs::remove_dir_all(&testdir) { /* ignore */ }
> +
> +        // this is a lot faster than ChunkStore::create, which takes almost 3 seconds
> +        let store = {
> +            let mut chunks = PathBuf::from(&testdir);
> +            chunks.push(".chunks");
> +            fs::create_dir_all(chunks).unwrap();
> +            Arc::new(ChunkStore::open("test", &testdir, DatastoreFSyncLevel::None).unwrap())
> +        };
> +
> +        test_empty(store.clone());
> +        test_smaller_than_initial_capacity(store.clone());
> +        test_grow_to_multiples_of_chunk_size(store.clone());
> +        test_grow_to_fixed_size(store);

these should not be called here, but rather call the setup method

> +
> +        std::fs::remove_dir_all(&testdir).unwrap();

and this should be handled with some kind of auto-cleanup-on-drop
mechanism, unless the whole thing is moved to an integration test, in
which case it will be somewhere under `target/` anyway..

> +    }
> +
> +    fn test_empty(store: Arc<ChunkStore>) {
> +        let path = Path::new("test_empty");
> +        let mut w = FixedIndexWriter::create(store, path, None, CS).unwrap();
> +
> +        assert_eq!(0, w.index_length(), "returns length, not capacity");

should also check the capacity and size?

> +        assert!(w.add_digest(0, &[1u8; 32]).is_err(), "out of bounds");
> +        assert!(w.close().is_err(), "should refuse to create empty file");
> +    }
> +
> +    fn test_smaller_than_initial_capacity(store: Arc<ChunkStore>) {

the test_grow_to_multiples_of_chunk_size also tests sizes smaller than
the initial capacity.. this tests a very special edge case - an index
made up of a single, partial chunk..

> +        let path = Path::new("test_smaller_than_initial_capacity");
> +        let mut w = FixedIndexWriter::create(store.clone(), path, None, CS).unwrap();
> +
> +        let size = CS - 1;
> +        let expected = test_data(size);
> +        w.grow_to_size(size).unwrap();
> +        expected[0].add_to(&mut w);
> +
> +        w.close().unwrap();
> +        drop(w);
> +
> +        check_with_reader(&store.relative_path(path), size, &expected);
> +        compare_to_known_size_writer(store, path, size, &expected);
> +    }
> +
> +    fn test_grow_to_multiples_of_chunk_size(store: Arc<ChunkStore>) {
> +        let path = Path::new("test_grow_to_multiples_of_chunk_size");
> +        let mut w = FixedIndexWriter::create(store.clone(), path, None, CS).unwrap();
> +
> +        let initial = FixedIndexWriter::INITIAL_CAPACITY;
> +        let steps = [1, 2, initial, initial + 1, 5 * initial, 10 * initial + 1];
> +        let expected = test_data(steps.last().unwrap() * CS);
> +
> +        let mut begin = 0;
> +        for chunk_count in steps {
> +            let last = &expected[chunk_count - 1];
> +            w.grow_to_size(last.end).unwrap();
> +            assert_eq!(last.index + 1, w.index_length());

if index_length is changed to capacity, then this needs to be adapted,
unless index_length() continues to return the length based on size and
chunk size

> +            assert!(w.add_digest(last.index + 1, &[1u8; 32]).is_err());
> +
> +            for c in expected[begin..chunk_count].iter().rev() {
> +                c.add_to(&mut w);
> +            }
> +            begin = chunk_count;
> +        }
> +        w.close().unwrap();
> +        drop(w);
> +
> +        let size = expected.len() * CS;
> +        check_with_reader(&store.relative_path(path), size, &expected);
> +        compare_to_known_size_writer(store, path, size, &expected);
> +    }
> +
> +    fn test_grow_to_fixed_size(store: Arc<ChunkStore>) {

s/fixed/misaligned/ ?

> +        let path = Path::new("test_grow_to_fixed_size");
> +        let mut w = FixedIndexWriter::create(store.clone(), path, None, CS).unwrap();
> +
> +        let size = (FixedIndexWriter::INITIAL_CAPACITY + 42) * CS - 1; // last is not full
> +        let expected = test_data(size);
> +
> +        w.grow_to_size(size).unwrap();
> +        assert!(w.grow_to_size(size + 1).is_err(), "size must be fixed now");
> +        assert_eq!(expected.len(), w.index_length());
> +        assert!(w.add_digest(expected.len(), &[1u8; 32]).is_err());
> +
> +        for c in expected.iter().rev() {
> +            c.add_to(&mut w);
> +        }
> +
> +        w.close().unwrap();
> +        drop(w);
> +
> +        check_with_reader(&store.relative_path(path), size, &expected);
> +        compare_to_known_size_writer(store, path, size, &expected);
> +    }
> +
> +    struct TestChunk {
> +        digest: [u8; 32],
> +        index: usize,
> +        size: usize,
> +        end: usize,
> +    }
> +
> +    impl TestChunk {
> +        fn add_to(&self, w: &mut FixedIndexWriter) {
> +            assert_eq!(
> +                self.index,
> +                w.check_chunk_alignment(self.end, self.size).unwrap()
> +            );
> +            w.add_digest(self.index, &self.digest).unwrap();
> +        }
> +    }
> +
> +    fn test_data(size: usize) -> Vec<TestChunk> {
> +        (0..size.div_ceil(CS))
> +            .map(|index| {
> +                let mut digest = [0u8; 32];
> +                let i = &(index as u64).to_le_bytes();
> +                for c in digest.chunks_mut(i.len()) {
> +                    c.copy_from_slice(i);
> +                }
> +                let size = if ((index + 1) * CS) <= size {
> +                    CS
> +                } else {
> +                    size % CS
> +                };
> +                TestChunk {
> +                    digest,
> +                    index,
> +                    size,
> +                    end: index * CS + size,
> +                }
> +            })
> +            .collect()
> +    }
> +
> +    fn check_with_reader(path: &Path, size: usize, chunks: &[TestChunk]) {
> +        let reader = FixedIndexReader::open(path).unwrap();
> +        assert_eq!(size as u64, reader.index_bytes());
> +        assert_eq!(chunks.len(), reader.index_count());
> +        for c in chunks {
> +            assert_eq!(&c.digest, reader.index_digest(c.index).unwrap());
> +        }
> +    }
> +
> +    fn compare_to_known_size_writer(
> +        store: Arc<ChunkStore>,
> +        name: &Path,
> +        size: usize,
> +        chunks: &[TestChunk],
> +    ) {
> +        let mut path = PathBuf::from(name);
> +        path.set_extension("reference");
> +        let mut w = FixedIndexWriter::create(store.clone(), &path, Some(size), CS).unwrap();
> +        for c in chunks {
> +            c.add_to(&mut w);
> +        }
> +        w.close().unwrap();
> +        drop(w);
> +
> +        let mut reference = fs::read(store.relative_path(&path)).unwrap();
> +        let mut tested = fs::read(store.relative_path(name)).unwrap();
> +
> +        // ignore uuid and ctime
> +        reference[8..32].fill(0);
> +        tested[8..32].fill(0);
> +
> +        assert_eq!(reference, tested);
> +    }
> +}
> -- 
> 2.47.3
> 
> 
> 
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