The `CRITICAL_OPS_BUCKETS` is not useful for getting an accurate
picture of basebackup latency because all the observations
that negatively affect our SLI fall into one bucket, i.e., 100ms-1s.
Use the same buckets as control plane instead.
## Problem
`cargo +nightly doc` is giving a lot of warnings: broken links, naked
URLs, etc.
## Summary of changes
* update the `proc-macro2` dependency so that it can compile on latest
Rust nightly, see https://github.com/dtolnay/proc-macro2/pull/391 and
https://github.com/dtolnay/proc-macro2/issues/398
* allow the `private_intra_doc_links` lint, as linking to something
that's private is always more useful than just mentioning it without a
link: if the link breaks in the future, at least there is a warning due
to that. Also, one might enable
[`--document-private-items`](https://doc.rust-lang.org/cargo/commands/cargo-doc.html#documentation-options)
in the future and make these links work in general.
* fix all the remaining warnings given by `cargo +nightly doc`
* make it possible to run `cargo doc` on stable Rust by updating
`opentelemetry` and associated crates to version 0.19, pulling in a fix
that previously broke `cargo doc` on stable:
https://github.com/open-telemetry/opentelemetry-rust/pull/904
* Add `cargo doc` to CI to ensure that it won't get broken in the
future.
Fixes#2557
## Future work
* Potentially, it might make sense, for development purposes, to publish
the generated rustdocs somewhere, like for example [how the rust
compiler does
it](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver/index.html).
I will file an issue for discussion.
Handle test failures like:
```
AssertionError: assert not ['$ts WARN delete_timeline{tenant_id=X timeline_id=Y}: About to remove 1 files\n']
```
Instead of logging:
```
WARN delete_timeline{tenant_id=X timeline_id=Y}: Found 1 files not bound to index_file.json, proceeding with their deletion
WARN delete_timeline{tenant_id=X timeline_id=Y}: About to remove 1 files
```
For each one operation of timeline deletion, list all unref files with
`info!`, and then continue to delete them with the added spice of
logging the rare/never happening non-utf8 name with `warn!`.
Rationale for `info!` instead of `warn!`: this is a normal operation;
like we had mentioned in `test_import.py` -- basically whenever we
delete a timeline which is not idle.
Rationale for N * (`ìnfo!`|`warn!`): symmetry for the layer deletions;
if we could ever need those, we could also need these for layer files
which are not yet mentioned in `index_part.json`.
---------
Co-authored-by: Christian Schwarz <christian@neon.tech>
Tests cannot be ran without configuring tracing. Split from #4678.
Does not nag about the span checks when there is no subscriber
configured, because then the spans will have no links and nothing can be
checked. Sadly the `SpanTrace::status()` cannot be used for this.
`tracing` is always configured in regress testing (running with
`pageserver` binary), which should be enough.
Additionally cleans up the test code in span checks to be in the test
code. Fixes a `#[should_panic]` test which was flaky before these
changes, but the `#[should_panic]` hid the flakyness.
Rationale for need: Unit tests might not be testing only the public or
`feature="testing"` APIs which are only testable within `regress` tests
so not all spans might be configured.
## Problem
ref https://github.com/neondatabase/neon/issues/4373
## Summary of changes
A step towards immutable layer map. I decided to finish the refactor
with this new approach and apply
https://github.com/neondatabase/neon/pull/4455 on this patch later.
In this PR, we moved all modifications of the layer map to one place
with semantic operations like `initialize_local_layers`,
`finish_compact_l0`, `finish_gc_timeline`, etc, which is now part
of `LayerManager`. This makes it easier to build new features upon
this PR:
* For immutable storage state refactor, we can simply replace the layer
map with `ArcSwap<LayerMap>` and remove the `layers` lock. Moving
towards it requires us to put all layer map changes in a single place as
in https://github.com/neondatabase/neon/pull/4455.
* For manifest, we can write to manifest in each of the semantic
functions.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
Co-authored-by: Christian Schwarz <christian@neon.tech>
This addresses the issue in #4526 by adding a test that reproduces the
race condition that gave rise to the bug (or at least *a* race condition
that gave rise to the same error message), and then implementing a fix
that just prints a message to the log if a file could not been found for
uploading. Even though the underlying race condition is not fixed yet,
this will un-block the upload queue in that situation, greatly reducing
the impact of such a (rare) race.
Fixes#4526.
## Problem
Postgres submodule can be changed unintentionally, and these changes are
easy to miss during the review.
Adding a check that should prevent this from happening, the check fails
`build-neon` job with the following message:
```
Expected postgres-v14 rev to be at '1414141414141414141414141414141414141414', but it is at '1144aee1661c79eec65e784a8dad8bd450d9df79'
Expected postgres-v15 rev to be at '1515151515151515151515151515151515151515', but it is at '1984832c740a7fa0e468bb720f40c525b652835d'
Please update vendors/revisions.json if these changes are intentional.
```
This is an alternative approach to
https://github.com/neondatabase/neon/pull/4603
## Summary of changes
- Add `vendor/revisions.json` file with expected revisions
- Add built-time check (to `build-neon` job) that Postgres submodules
match revisions from `vendor/revisions.json`
- A couple of small improvements for logs from
https://github.com/neondatabase/neon/pull/4603
- Fixed GitHub autocomment for no tests was run case
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
The comment referenced an issue that was already closed. Remove that
reference and replace it with an explanation why we already don't print
an error.
See discussion in
https://github.com/neondatabase/neon/issues/2934#issuecomment-1626505916
For the TOCTOU fixes, the two calls after the `.exists()` both didn't
handle the situation well where the file was deleted after the initial
`.exists()`: one would assume that the path wasn't a file, giving a bad
error, the second would give an accurate error but that's not wanted
either.
We remove both racy `exists` and `is_file` checks, and instead just look
for errors about files not being found.
## Problem
part of https://github.com/neondatabase/neon/pull/4340
## Summary of changes
Remove LayerDescriptor and remove `todo!`. At the same time, this PR
adds `AsLayerDesc` trait for all persistent layers and changed
`LayerFileManager` to have a generic type. For tests, we are now using
`LayerObject`, which is a wrapper around `PersistentLayerDesc`.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
Before this PR, during shutdown, we'd find naked logs like this one for every active page service connection:
```
2023-07-05T14:13:50.791992Z INFO shutdown request received in run_message_loop
```
This PR
1. adds a peer_addr span field to distinguish the connections in logs
2. sets the tenant_id / timeline_id fields earlier
It would be nice to have `tenant_id` and `timeline_id` directly on
the `page_service_conn_main` span (empty, initially), then set
them at the top of `process_query`.
The problem is that the debug asserts for `tenant_id` and
`timeline_id` presence in the tracing span doesn't support
detecting empty values [1].
So, I'm a bit hesitant about over-using `Span::record`.
[1] https://github.com/neondatabase/neon/issues/4676
We see the following log lines occasionally in prod:
```
kill_and_wait_impl{pid=1983042}: wait successful exit_status=signal: 9 (SIGKILL)
```
This PR makes it easier to find the tenant for the pid, by including the
tenant id as a field in the span.
It started from few config methods that have various orderings and
sometimes use references sometimes not. So I unified path manipulation
methods to always order tenant_id before timeline_id and use referenced
because we dont need owned values.
Similar changes happened to call-sites of config methods.
I'd say its a good idea to always order tenant_id before timeline_id so
it is consistent across the whole codebase.
## Problem
I was reading the code of the page server today and found these minor
things that I thought could be cleaned up.
## Summary of changes
* remove a redundant indentation layer and continue in the flushing loop
* use the builtin `PartialEq` check instead of hand-rolling a `range_eq`
function
* Add a missing `>` to a prominent doc comment
Does three things:
* add a `Display` impl for `LayerFileName` equal to the `short_id`
* based on that, replace the `Layer::short_id` function by a requirement
for a `Display` impl
* use that `Display` impl in the places where the `short_id` and `file_name()` functions were used instead
Fixes#4145
Looking at logs from staging and prod, I found there are a bunch of log
lines without tenant / timeline context.
Manully walk through all task_mgr::spawn lines and fix that using the
least amount of work required.
While doing it, remove some redundant `shutting down` messages.
refs https://github.com/neondatabase/neon/issues/4222
This renames the `pageserver_tenant_synthetic_size` metric to
`pageserver_tenant_synthetic_cached_size_bytes`, as was requested on
slack (link in the linked issue).
* `_cached` to hint that it is not incrementally calculated
* `_bytes` to indicate the unit the size is measured in
Fixes#3748
## Problem
#4528
## Summary of changes
Add a 60 seconds default timeout to the reqwest client
Add retries for up to 3 times to call into the metric consumption
endpoint
---------
Co-authored-by: Christian Schwarz <christian@neon.tech>
## Problem
part of https://github.com/neondatabase/neon/issues/4392, continuation
of https://github.com/neondatabase/neon/pull/4408
## Summary of changes
This PR removes all layer objects from LayerMap and moves it to the
timeline struct. In timeline struct, LayerFileManager maps a layer
descriptor to a layer object, and it is stored in the same RwLock as
LayerMap to avoid behavior difference.
Key changes:
* LayerMap now does not have generic, and only stores descriptors.
* In Timeline, we add a new struct called layer mapping.
* Currently, layer mapping is stored in the same lock with layer map.
Every time we retrieve data from the layer map, we will need to map the
descriptor to the actual object.
* Replace_historic is moved to layer mapping's replace, and the return
value behavior is different from before. I'm a little bit unsure about
this part and it would be good to have some comments on that.
* Some test cases are rewritten to adapt to the new interface, and we
can decide whether to remove it in the future because it does not make
much sense now.
* LayerDescriptor is moved to `tests` module and should only be intended
for unit testing / benchmarks.
* Because we now have a usage pattern like "take the guard of lock, then
get the reference of two fields", we want to avoid dropping the
incorrect object when we intend to unlock the lock guard. Therefore, a
new set of helper function `drop_r/wlock` is added. This can be removed
in the future when we finish the refactor.
TODOs after this PR: fully remove RemoteLayer, and move LayerMapping to
a separate LayerCache.
all refactor PRs:
```
#4437 --- #4479 ------------ #4510 (refactor done at this point)
\-- #4455 -- #4502 --/
```
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
There is a magic number about how often we repartition and therefore
affecting how often we compact. This PR makes this number `10` a global
constant and add docs.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
## Problem
Lets keep 500 for unusual stuff that is not considered normal. Came up
during one of the discussions around console logs now seeing this 500's.
## Summary of changes
- Return 409 Conflict instead of 500
- Remove 200 ok status because it is not used anymore
This PR concludes the "async `Layer::get_value_reconstruct_data`"
project.
The problem we're solving is that, before this patch, we'd execute
`Layer::get_value_reconstruct_data` on the tokio executor threads.
This function is IO- and/or CPU-intensive.
The IO is using VirtualFile / std::fs; hence it's blocking.
This results in unfairness towards other tokio tasks, especially under
(disk) load.
Some context can be found at
https://github.com/neondatabase/neon/issues/4154
where I suspect (but can't prove) load spikes of logical size
calculation to
cause heavy eviction skew.
Sadly we don't have tokio runtime/scheduler metrics to quantify the
unfairness.
But generally, we know blocking the executor threads on std::fs IO is
bad.
So, let's have this change and watch out for severe perf regressions in
staging & during rollout.
## Changes
* rename `Layer::get_value_reconstruct_data` to
`Layer::get_value_reconstruct_data_blocking`
* add a new blanket impl'd `Layer::get_value_reconstruct_data`
`async_trait` method that runs `get_value_reconstruct_data_blocking`
inside `spawn_blocking`.
* The `spawn_blocking` requires `'static` lifetime of the captured
variables; hence I had to change the data flow to _move_ the
`ValueReconstructState` into and back out of get_value_reconstruct_data
instead of passing a reference. It's a small struct, so I don't expect a
big performance penalty.
## Performance
Fundamentally, the code changes cause the following performance-relevant
changes:
* Latency & allocations: each `get_value_reconstruct_data` call now
makes a short-lived allocation because `async_trait` is just sugar for
boxed futures under the hood
* Latency: `spawn_blocking` adds some latency because it needs to move
the work to a thread pool
* using `spawn_blocking` plus the existing synchronous code inside is
probably more efficient better than switching all the synchronous code
to tokio::fs because _each_ tokio::fs call does `spawn_blocking` under
the hood.
* Throughput: the `spawn_blocking` thread pool is much larger than the
async executor thread pool. Hence, as long as the disks can keep up,
which they should according to AWS specs, we will be able to deliver
higher `get_value_reconstruct_data` throughput.
* Disk IOPS utilization: we will see higher disk utilization if we get
more throughput. Not a problem because the disks in prod are currently
under-utilized, according to node_exporter metrics & the AWS specs.
* CPU utilization: at higher throughput, CPU utilization will be higher.
Slightly higher latency under regular load is acceptable given the
throughput gains and expected better fairness during disk load peaks,
such as logical size calculation peaks uncovered in #4154.
## Full Stack Of Preliminary PRs
This PR builds on top of the following preliminary PRs
1. Clean-ups
* https://github.com/neondatabase/neon/pull/4316
* https://github.com/neondatabase/neon/pull/4317
* https://github.com/neondatabase/neon/pull/4318
* https://github.com/neondatabase/neon/pull/4319
* https://github.com/neondatabase/neon/pull/4321
* Note: these were mostly to find an alternative to #4291, which I
thought we'd need in my original plan where we would need to convert
`Tenant::timelines` into an async locking primitive (#4333). In reviews,
we walked away from that, but these cleanups were still quite useful.
2. https://github.com/neondatabase/neon/pull/4364
3. https://github.com/neondatabase/neon/pull/4472
4. https://github.com/neondatabase/neon/pull/4476
5. https://github.com/neondatabase/neon/pull/4477
6. https://github.com/neondatabase/neon/pull/4485
7. https://github.com/neondatabase/neon/pull/4441
The stats for `compact_level0_phase` that I added in #4527 show the
following breakdown (24h data from prod, only looking at compactions
with > 1 L1 produced):
* 10%ish of wall-clock time spent between the two read locks
* I learned that the `DeltaLayer::iter()` and `DeltaLayer::key_iter()`
calls actually do IO, even before we call `.next()`. I suspect that is
why they take so much time between the locks.
* 80+% of wall-clock time spent writing layer files
* Lock acquisition time is irrelevant (low double-digit microseconds at
most)
* The generation of the holes holds the read lock for a relatively long
time and it's proportional to the amount of keys / IO required to
iterate over them (max: 110ms in prod; staging (nightly benchmarks):
multiple seconds).
Find below screenshots from my ad-hoc spreadsheet + some graphs.
<img width="1182" alt="image"
src="https://github.com/neondatabase/neon/assets/956573/81398b3f-6fa1-40dd-9887-46a4715d9194">
<img width="901" alt="image"
src="https://github.com/neondatabase/neon/assets/956573/e4ac0393-f2c1-4187-a5e5-39a8b0c394c9">
<img width="210" alt="image"
src="https://github.com/neondatabase/neon/assets/956573/7977ade7-6aa5-4773-a0a2-f9729aecee0d">
## Changes In This PR
This PR makes the following changes:
* rearrange the `compact_level0_phase1` code such that we build the
`all_keys_iter` and `all_values_iter` later than before
* only grab the `Timeline::layers` lock once, and hold it until we've
computed the holes
* run compact_level0_phase1 in spawn_blocking, pre-grabbing the
`Timeline::layers` lock in the async code and passing it in as an
`OwnedRwLockReadGuard`.
* the code inside spawn_blocking drops this guard after computing the
holds
* the `OwnedRwLockReadGuard` requires the `Timeline::layers` to be
wrapped in an `Arc`. I think that's Ok, the locking for the RwLock is
more heavy-weight than an additional pointer indirection.
## Alternatives Considered
The naive alternative is to throw the entire function into
`spawn_blocking`, and use `blocking_read` for `Timeline::layers` access.
What I've done in this PR is better because, with this alternative,
1. while we `blocking_read()`, we'd waste one slot in the spawn_blocking
pool
2. there's deadlock risk because the spawn_blocking pool is a finite
resource
## Metadata
Fixes https://github.com/neondatabase/neon/issues/4492
This is follow-up to
```
commit 2252c5c282
Author: Alex Chi Z <iskyzh@gmail.com>
Date: Wed Jun 14 17:12:34 2023 -0400
metrics: convert some metrics to pageserver-level (#4490)
```
The consumption metrics synthetic size worker does logical size
calculation. Logical size calculation currently does synchronous disk
IO. This blocks the MGMT_REQUEST_RUNTIME's executor threads, starving
other futures.
While there's work on the way to move the synchronous disk IO into
spawn_blocking, the quickfix here is to use the BACKGROUND_RUNTIME
instead of MGMT_REQUEST_RUNTIME.
Actually it's not just a quickfix. We simply shouldn't be blocking
MGMT_REQUEST_RUNTIME executor threads on CPU or sync disk IO.
That work isn't done yet, as many of the mgmt tasks still _do_ disk IO.
But it's not as intensive as the logical size calculations that we're
fixing here.
While we're at it, fix disk-usage-based eviction in a similar way. It
wasn't the culprit here, according to prod logs, but it can
theoretically be a little CPU-intensive.
More context, including graphs from Prod:
https://neondb.slack.com/archives/C03F5SM1N02/p1687541681336949
The histogram distinguishes by ok/err.
I took the liberty to create a small abstraction for such use cases.
It helps keep the label values inside `metrics.rs`, right next
to the place where the metric and its labels are declared.
* `compaction_threshold` should be an integer, not a string.
* uncomment `[section]` so that if a user needs to modify the config,
they can simply uncomment the corresponding line. Otherwise it's easy
for us to forget uncommenting the `[section]` when uncommenting the
config item we want to configure.
Signed-off-by: Alex Chi <iskyzh@gmail.com>
Commit
```
commit 472cc17b7a
Author: Dmitry Rodionov <dmitry@neon.tech>
Date: Thu Jun 15 17:30:12 2023 +0300
propagate lock guard to background deletion task (#4495)
```
did a drive-by fix, but, the drive-by had a typo.
```
gc_loop{tenant_id=2e2f2bff091b258ac22a4c4dd39bd25d}:update_gc_info{timline_id=837c688fd37c903639b9aa0a6dd3f1f1}:download_remote_layer{layer=000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000024DA0D1-000000000443FB51}:panic{thread=background op worker location=pageserver/src/tenant/timeline.rs:4843:25}: missing extractors: ["TimelineId"]
Stack backtrace:
0: utils::logging::tracing_panic_hook
at /libs/utils/src/logging.rs:166:21
1: <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call
at /rustc/9eb3afe9ebe9c7d2b84b71002d44f4a0edac95e0/library/alloc/src/boxed.rs:2002:9
2: std::panicking::rust_panic_with_hook
at /rustc/9eb3afe9ebe9c7d2b84b71002d44f4a0edac95e0/library/std/src/panicking.rs:692:13
3: std::panicking::begin_panic_handler::{{closure}}
at /rustc/9eb3afe9ebe9c7d2b84b71002d44f4a0edac95e0/library/std/src/panicking.rs:579:13
4: std::sys_common::backtrace::__rust_end_short_backtrace
at /rustc/9eb3afe9ebe9c7d2b84b71002d44f4a0edac95e0/library/std/src/sys_common/backtrace.rs:137:18
5: rust_begin_unwind
at /rustc/9eb3afe9ebe9c7d2b84b71002d44f4a0edac95e0/library/std/src/panicking.rs:575:5
6: core::panicking::panic_fmt
at /rustc/9eb3afe9ebe9c7d2b84b71002d44f4a0edac95e0/library/core/src/panicking.rs:64:14
7: pageserver::tenant::timeline::debug_assert_current_span_has_tenant_and_timeline_id
at /pageserver/src/tenant/timeline.rs:4843:25
8: <pageserver::tenant::timeline::Timeline>::download_remote_layer::{closure#0}::{closure#0}
at /pageserver/src/tenant/timeline.rs:4368:9
9: <tracing::instrument::Instrumented<<pageserver::tenant::timeline::Timeline>::download_remote_layer::{closure#0}::{closure#0}> as core::future::future::Future>::poll
at /.cargo/registry/src/github.com-1ecc6299db9ec823/tracing-0.1.37/src/instrument.rs:272:9
10: <pageserver::tenant::timeline::Timeline>::download_remote_layer::{closure#0}
at /pageserver/src/tenant/timeline.rs:4363:5
11: <pageserver::tenant::timeline::Timeline>::get_reconstruct_data::{closure#0}
at /pageserver/src/tenant/timeline.rs:2618:69
12: <pageserver::tenant::timeline::Timeline>::get::{closure#0}
at /pageserver/src/tenant/timeline.rs:565:13
13: <pageserver::tenant::timeline::Timeline>::list_slru_segments::{closure#0}
at /pageserver/src/pgdatadir_mapping.rs:427:42
14: <pageserver::tenant::timeline::Timeline>::is_latest_commit_timestamp_ge_than::{closure#0}
at /pageserver/src/pgdatadir_mapping.rs:390:13
15: <pageserver::tenant::timeline::Timeline>::find_lsn_for_timestamp::{closure#0}
at /pageserver/src/pgdatadir_mapping.rs:338:17
16: <pageserver::tenant::timeline::Timeline>::update_gc_info::{closure#0}::{closure#0}
at /pageserver/src/tenant/timeline.rs:3967:71
17: <tracing::instrument::Instrumented<<pageserver::tenant::timeline::Timeline>::update_gc_info::{closure#0}::{closure#0}> as core::future::future::Future>::poll
at /.cargo/registry/src/github.com-1ecc6299db9ec823/tracing-0.1.37/src/instrument.rs:272:9
18: <pageserver::tenant::timeline::Timeline>::update_gc_info::{closure#0}
at /pageserver/src/tenant/timeline.rs:3948:5
19: <pageserver::tenant::Tenant>::refresh_gc_info_internal::{closure#0}
at /pageserver/src/tenant.rs:2687:21
20: <pageserver::tenant::Tenant>::gc_iteration_internal::{closure#0}
at /pageserver/src/tenant.rs:2551:13
21: <pageserver::tenant::Tenant>::gc_iteration::{closure#0}
at /pageserver/src/tenant.rs:1490:13
22: pageserver::tenant::tasks::gc_loop::{closure#0}::{closure#0}
at /pageserver/src/tenant/tasks.rs:187:21
23: pageserver::tenant::tasks::gc_loop::{closure#0}
at /pageserver/src/tenant/tasks.rs:208:5
```
## Problem
## Summary of changes
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
## Problem
During timeline creation we create special mark file which presense
indicates that initialization didnt complete successfully. In case of a
crash restart we can remove such half-initialized timeline and following
retry from control plane side should perform another attempt.
So in case of a possible crash restart during initial loading we have
following picture:
```
timelines
| - <timeline_id>___uninit
| - <timeline_id>
| - | <timeline files>
```
We call `std::fs::read_dir` to walk files in `timelines` directory one
by one. If we see uninit file
we proceed with deletion of both, timeline directory and uninit file. If
we see timeline we check if uninit file exists and do the same cleanup.
But in fact its possible to get both branches to be true at the same
time. Result of readdir doesnt reflect following directory state
modifications. So you can still get "valid" entry on the next iteration
of the loop despite the fact that it was deleted in one of the previous
iterations of the loop.
To see that you can apply the following patch (it disables uninit mark
cleanup on successful timeline creation):
```diff
diff --git a/pageserver/src/tenant.rs b/pageserver/src/tenant.rs
index 4beb2664..b3cdad8f 100644
--- a/pageserver/src/tenant.rs
+++ b/pageserver/src/tenant.rs
@@ -224,11 +224,6 @@ impl UninitializedTimeline<'_> {
)
})?;
}
- uninit_mark.remove_uninit_mark().with_context(|| {
- format!(
- "Failed to remove uninit mark file for timeline {tenant_id}/{timeline_id}"
- )
- })?;
v.insert(Arc::clone(&new_timeline));
new_timeline.maybe_spawn_flush_loop();
```
And perform the following steps:
```bash
neon_local init
neon_local start
neon_local tenant create
neon_local stop
neon_local start
```
The error is:
```log
INFO load{tenant_id=X}:blocking: Found an uninit mark file .neon/tenants/X/timelines/Y.___uninit, removing the timeline and its uninit mark
2023-06-09T18:43:41.664247Z ERROR load{tenant_id=X}: load failed, setting tenant state to Broken: failed to load metadata
Caused by:
0: Failed to read metadata bytes from path .neon/tenants/X/timelines/Y/metadata
1: No such file or directory (os error 2)
```
So uninit mark got deleted together with timeline directory but we still
got directory entry for it and tried to load it.
The bug prevented tenant from being successfully loaded.
## Summary of changes
Ideally I think we shouldnt place uninit marks in the same directory as timeline directories but move them to separate directory and
gather them as an input to actual listing, but that would be sort of an
on-disk format change, so just check whether entries are still valid
before operating on them.
