* Do not hold timelines lock during GC
refer #1087
* Add gc_cs mutex for preveting creation of new timelines during GC
* Make clippy happy
* Use Mutex<()> instead of Mutex<i32> for GC critical section
Introduce the concept of a "ZenithWalRecord", which can be a Postgres WAL
record that is replayed with the Postgres WAL redo process, or a built-in
type that is handled entirely by pageserver code.
Replace the special code to replay Postgres XACT commit/abort records
with new Zenith WAL records. A separate zenith WAL record is created for
each modified CLOG page. This allows removing the 'main_data_offset'
field from stored PostgreSQL WAL records, which saves some memory and
some disk space in delta layers.
Introduce zenith WAL records for updating bits in the visibility map.
Previously, when e.g. a heap insert cleared the VM bit, we duplicated the
heap insert WAL record for the affected VM page. That was very wasteful.
The heap WAL record could be massive, containing a full page image in
the worst case. This addresses github issue #941.
The first COPY generates about 230 MB of write I/O, but the second
COPY, after deleting most of the rows and vacuuming the rows away,
generates 370 MB of writes. Both COPYs insert the same amount of data,
so they should generate roughly the same amount of I/O. This commit
doesn't try to fix the issue, just adds a test case to demonstrate it.
Add a new 'checkpoint' command to the pageserver API. Previously,
we've used 'do_gc' for that, but many tests, including this new one,
really only want to perform a checkpoint and don't care about GC. For
now, I only used the command in the new test, though, and didn't
convert any existing tests to use it.
This patch allows to shutdown wal receiver when there are no messages
and wal receiver is blocked inside tokio-postgres. In this case it
cannot check the shutdown flag.
This patch switches to use async interface of tokio-postgres directly
without sync wrappers. It opens the possibility to use tokio::select!
between the phsycal_stream.next() and a shutdown channel readiness to
interrupt replication process.
Also this allows to shutdown only particular wal receiver without
using global shutdown_requested flag.
Do it separately with SafekeeperPostgresCommand enum as a result. Since query is
always C string, switch postgres_backend process_query argument from Bytes to
&str.
Make passing ztli/ztenant id in safekeeper connection string optional; this is
needed for upcoming intra-safekeeper heartbeat cmd which is not bound to any
timeline.
Change meaning of lsns in HOT_STANDBY_FEEDBACK:
flush_lsn = disk_consistent_lsn,
apply_lsn = remote_consistent_lsn
Update compute node backpressure configuration respectively.
Update compute node configuration:
set 'synchronous_commit=remote_write' in setup without safekeepers.
This way compute node doesn't have to wait for data checkpoint on pageserver.
This doesn't guarantee data durability, but we only use this setup for tests, so it's fine.
Introduce builder objects, DeltaLayerWriter and ImageLayerWriter.
This gives more flexibility, as the DeltaLayer::create and
ImageLayer::create functions don't need to know about the details of
the format of where the page versions are coming from. This allows us
to change the format used in InMemoryLayer more easily, without having
to modify Delta- and ImageLayer code.
Also refactor the code in InMemoryLayer::write_to_disk for clarity.
Previously, the 'blknum' argument of various Layer functions was the
block number within the overall relation. That was pretty confusing,
because an individual layer only holds data from a one segment of the
relation. Furthermore, the 'put_truncation' function already dealt
with per-segment size, not overall relation size, adding to the
confusion.
Change the meaning of the 'blknum' argument to mean the block number
within the segment, not the overall relation.
If a commit record contains XIDs that are stored on different CLOG pages,
we duplicate the commit record for each affected CLOG page. In the redo
routine, we must only apply the parts of the record that apply to the
CLOG page being restored. We got that right in the loop that handles the
sub-XIDs, but incorrectly always set the bit that corresponds to the main
XID.
The logic to compute the page number was broken, and as a result, only
the first page of multixact members was updated correctly. All the
rest were left as zeros. Improve test_multixact.py to generate more
multixacts, to cover this case.
Also fix the check that the restored PG data directory matches the
original one. Previously, the test compared the 'pg_new' cluster,
which is a bit silly because the test restored the 'pg_new' cluster
only a few lines earlier, so if the multixact WAL redo is somehow
broken, the comparison will just compare two broken data directories
and report success. Change it to compare the original datadir, the one
where the multixacts were originally created, with a restored image of
the same.
The ephemeral files are not usable after restart, so just delete them.
Before this, you got "unrecognized filename in timeline dir" warnings
about them, as Konstantin noted at:
https://github.com/zenithdb/zenith/issues/906#issuecomment-995530870.
While we're at it, refactor away the list_files() function, moving the
logic fully into the caller. Seems more straightforward.
Rename save_decoded_record() to ingest_record(), and move the
responsibility for decoding the record into ingest_record().
Also move the responsibility of updating the CheckPoint relish to
ingest_record(). Put it in a new WalIngest struct, to help with tracking
that.
We depends on rustls in postgres_backend anyway, so might as well use it
for all TLS stuff. Seems better to depend on only one library both from a
security point of view, and because fewer dependencies means less code to
compile. With this commit, we no longer depend on OpenSSL.
Move the code for decoding a WAL stream into WAL records into
'postgres_ffi', and keep the code to parse the WAL records deeper in
'pageserver' crate, renamed to walrecord.rs.
This tidies up the dependencies a bit. 'walkeeper' reuses the same
waldecoder routines, and it used to depend on 'pageserver' because of
that. Now it only depends on 'postgres_ffi'.
(The comment in walkeeper/Cargo.toml that claimed that the dependency was
needed for ZTimelineId was obsolete. ZTimelineId is defined in
'zenith_utils', the dependency was actually needed for the waldecoder.)
0.28.0 includes two changes I submitted to upstream:
- Add support for older ListObjects API, needed to use rust-s3 with Google
Cloud Storage: https://github.com/durch/rust-s3/pull/229
- If file is smaller than one chunk, don't initiate multi-part upload.
https://github.com/durch/rust-s3/pull/228
These are not critical for Zenith right now, but let's stay up-to-date.
Currently, we return an all-zeros page if you request a block beyond end of
a relation. That has been implemented in LayeredTimeline::materialize_page,
so that if Layer::get_page_reconstruct_data returns Missing, it returns
and all-zeros page.
However InMemoryLayer and DeltaLayer would return Continue, not Missing,
in that case, and materialize_page would try to find the predecessor
layer. If there was a preceding image layer, then everything would still
work, but if there wasn't, it would return a "could not find predecessor
of layer" error. Fix that in InMemoryLayer and DeltaLayer, making them
check the size of the relation and return Missing in that case.
This is hard to reproduce at the moment, but it happened quickly with
pgbench when I modified InMemoryLayer::write_to_disk so that it didn't
always create a new ImageLayer.
This patch introduces fixes for several problems affecting
LLVM-based code coverage:
* Daemonizing parent processes should call _exit() to prevent
coverage data file corruption (*.profraw) due to concurrent writes.
* Implement proper shutdown handlers in safekeeper.
write_lsn - The last LSN received and processed by pageserver's walreceiver.
flush_lsn - same as write_lsn. At pageserver it doesn't guarantees data persistence, but it's fine. We rely on safekeepers.
apply_lsn - The LSN at which pageserver guaranteed persistence of all received data (disk_consistent_lsn).
While we're at it, reuse the Book and the VirtualFile that's backing
it even over unload() calls. Previously, we would keep the Book open,
but on load(), we would re-open it anyway, which didn't make much
sense. Now we reuse it it. Alternatively, perhaps we should close it
on unload() to save some memory, but this I'm not going to think too
hard about it right now as the whole load/unload thing is a bit of a
hack and needs to be rewritten.
This is hard to reproduce ATM, because the incorrect state would get
fixed by an unload(). A checkpoint creates the DeltaLayer, and it also
calls unload() afterwards, so the window is not very large. I hit it
occasionally with a scale 1000 pgbench test, after I had modified
InMemoryLayer::write_to_disk() to not write an image layer every time,
which made the DeltaLayers be accessed more often.
This doesnt show up at the moment, because we never create a delta
layer with end-LSN equal to the last LSN. We always create an image
layer at that LSN instead. For example, if the latest processed LSN is
100, we would create a delta layer with end LSN 100 (exclusive), and
an image layer at 100. But that's just how InMemoryLayer::write_to_disk
happens to work at the moment, there's no fundamental reason it needs
to always create that image layer. I noticed this bug when I tried to
change the logic in InMemoryLayer::write_to_disk to only create an
image layer after a few delta layers.
The "in-memory layer" is misnomer now, each in-memory layer is now actually
backed by a file. The files are ephemeral, in that they don't survive page
server crash or shutdown.
To avoid reading the file for every operation,
"ephemeral files" are cached in a page cache.
This includes changes from 'inmemory-layer-chunks' branch to serialize /
the page versions when they are added to the open layer. The difference is
that they are not serialized to the expandable in-memory "chunk buffer", but
written out to the file.
Out of scope LSNs include pre initdb LSNs, and LSNs prior to
latest_gc_cutoff.
To get there there was also two cleanups:
* Fix error handling in Execute message handler. This fixes behaviour
when basebackup retured an error. Previously pageserver thread just
died.
* Remove "ancestor" file which previously contained ancestor id and
branch lsn. Currently the same data can be obtained from metadata file.
And just the way we handled ancestor file in the code introduced the
case when branching fails timeline directory is created but there is no data in it
except ancestor file. And this confused gc because it scans
directories. So it is better to just remove ancestor file and clean up
this timeline directory creation so it happens after all validity
checks have passed
