I didn't think this mattered, but it does: if you add a dependency to
zenith_utils, but forget to request a feature you need, the crate will
build from the workspace root, but not by itself.
It's probably better to pull in the whole dependency tree.
This leaves one problem unsolved: the missing feature above will now be
a latent bug. If that feature gets removed later by other crates, and
then the workspace_hack Cargo.toml is updated, this missing feature will
become a build failure.
Add fixes suggested in code review.
In a previous commit, I changed the NodeId field order and types to try
to preserve the exact serialization that was happening. Unfortunately,
that serialization was incorrect and the original struct was mostly
correct.
Change uuid to be a [u8; 16] as it was intended to be a byte array; that
will clearly indicate to serde serializers that no endian swaps will
ever be needed.
Replace XLogRecPtr with Lsn in wal_service.rs .
This removes the last use of XLogSegmentOffset and XLByteToSeg, so
delete them. (replaced by Lsn::segment_offset and Lsn::segment_number.)
The C memory representation is only needed if we want to guarantee the
same memory layout as some other program. Since we're using serde to
serialize these data structures, we can let the compiler do what it
wants.
This version validates on every call that our result is exactly the same
as the previous result.
NodeId is a strange corner case: one field is serialized little-endian
and one field is serialized big-endian. Hopefully we can fix that in the
future.
This module adds two traits that implement bincode-based serialization.
BeSer implements methods for big-endian encoding/decoding.
LeSer implements methods for little-endian encoding/decoding.
Right now, the BeSer and LeSer methods have the same names, meaning you
can't `use` them both at the same time. This is intended to be a safety
mechanism: mixing big-endian and little-endian encoding in the same file
is error-prone. There are ways around this, but the easiest fix is to
put the big-endian code and little-endian code in different files or
submodules.
This is a big async -> sync conversion. Most of it is a pretty
straightforward conversion of removing `async` and `.await` and swapping
in the right std modules.
I didn't find a thread-blocking version of `Notify` so I wrote one, and
then realized that there was already a Mutex being used there, so I
deleted my Notify and just used Condvar instead.
There is one part that seems odd to me: in `handle_start_replication`
there is a place where the previous code was doing a non-blocking read;
there is no TcpStream::try_read() so I fell back on manually flipping
the socket to non-blocking mode and then back again. This seems pretty
gross, but I'm not sure exactly what to replace this with: a background
thread? Extract the fd and run select() on it to first test if it's
readable?
Switch over to a newer version of rust-postgres PR752. A few
minor changes are required:
- PgLsn::UNDEFINED -> PgLsn::from(0)
- PgTimestamp -> SystemTime
Our builds can be a little inconsistent, because Cargo doesn't deal well
with workspaces where there are multiple crates which have different
dependencies that select different features. As a workaround, copy what
other big rust projects do: add a workspace_hack crate.
This crate just pins down a set of dependencies and features that
satisfies all of the workspace crates.
The benefits are:
- running `cargo build` from one of the workspace subdirectories now
works without rebuilding anything.
- running `cargo install` works (without rebuilding anything).
- making small dependency changes is much less likely to trigger large
dependency rebuilds.
A few things that Eric commented on at PR #96:
- Use thiserror to simplify the implemention of FilePathError
- Add unit tests
- Fix a few complaints from clippy
We should track the range of LSNs that are valid in a GetPage@LSN request
somehow, but currently this is just dead code. Remove, until we get around
to actually implement it.
https://github.com/zenithdb/zenith/issues/95 tracks that.
Currently, truncation is implemented in the RocksDB repository by storing
a special sentinel entry for each page that was truncated away. Hide that
implementation detail better in the abstract Repository interface, so
that caller doesn't need to construct the special sentinel WAL record.
While we're at it, refactor the CacheEntryContent struct to an enum.
This moves things around:
- The PageCache is split into two structs: Repository and Timeline. A
Repository holds multiple Timelines. In order to get a page version,
you must first get a reference to the Repository, then the Timeline
in the repository, and finally call the get_page_at_lsn() function
on the Timeline object. This sounds complicated, but because each
connection from a compute node, and each WAL receiver, only deals
with one timeline at a time, the callers can get the reference to
the Timeline object once and hold onto it. The Timeline corresponds
most closely to the old PageCache object.
- Repository and Timeline are now abstract traits, so that we can
support multiple implementations. I don't actually expect us to have
multiple implementations for long. We have the RocksDB
implementation now, but as soon as we have a different
implementation that's usable, I expect that we will retire the
RocksDB implementation. But I think this abstraction works as good
documentation in any case: it's now easier to see what the interface
for storing and loading pages from the repository is, by looking at
the Repository/Timeline traits. They abstract traits are in
repository.rs, and the RocksDB implementation of them is in
repository/rocksdb.rs.
- page_cache.rs is now a "switchboard" to get a handle to the
repository. Currently, the page server can only handle one
repository at a time, so there isn't much there, but in the future
we might do multi-tenancy there.
Mostly we're not testing python code, so verbose python tracebacks are
unhelpful. Add --tb=short to the pytest args to cut down on the noise.
To override this during testing, set the "extra_params" parameter on the
circleci job to "--tb=auto" or "--tb=long".
The local fork of rust-s3 has some code to support Google Cloud, but
that PR no longer applies upstream, and will need significant changes
before it can be re-submitted.
In the meantime, we might as well just use the most similar upstream
release. The benefit of switching is that it fixes a feature-resolution
bug that was causing us to build 24 more crates than needed (mostly
async-std and its dependencies).
The rust cache is growing dramatically. Change the cache key to start
over.
The weird "v98" was something I'd intended to reset before landing the
circleci config. Do the sane thing and start over at v01. The intent is
that we just increment the number each time something gets broken.
Since we are now calling the syscall directly, read_pidfile can now
parse an integer.
We also verify the pid is >= 1, because calling kill on 0 or negative
values goes straight to crazytown.
default(medium): 2 CPUs, 4GB RAM.
xlarge: 8 CPUs, 16GB RAM.
Some build jobs are getting killed with signal 9. I'm guessing that this
is probably an OOM condition...
I found I had a few other .zenith directories hanging around in odd
places. I doubt we intended those directories to collect in multiple
locations, so only hide the one in the git root directory.
If there isn't any version specified for a dependency crate, Cargo may
choose a newer version. This could happen when Cargo.lock is updated
("cargo update") but can also happen unexpectedly when adding or
changing other dependencies. This can allow API-breaking changes to be
picked up, breaking the build.
To prevent this, specify versions for all dependencies. Cargo is still
allowed to pick newer versions that are (hopefully) non-breaking, by
analyzing the semver version number.
There are two special cases here:
1. serde_derive::{Serialize, Deserialize} isn't really used any more. It
was only a separate crate in the past because of compiler limitations.
Nowadays, people turn on the "derive" feature of the serde crate and
use serde::{Serialize, Deserialize}.
2. parse_duration is unmaintained and has an open security issue. (gh
iss. 87) That issue probably isn't critical for us because of where we
use that crate, but it's probably still better to pin the version so we
can't get hit with an API-breaking change at an awkward time.
It's quite hard to get python2 to exit gracefully when the code was
intended for python3, because the interpreter will SyntaxError before
running a single line of code. Thankfully, the pytest developers put a
version check in their .ini config, so that should gracefully handle
both wrong-pytest-version and wrong-python-version.
Also document the woes of trying to run the pytest version shipped by
e.g. Debian or Ubuntu.
