## Problem
Splits of large tenants (several TB) can cause a huge amount of shard
ancestor compaction work, which can overload Pageservers.
Touches https://github.com/neondatabase/cloud/issues/22532.
## Summary of changes
Add a setting `compaction_shard_ancestor` (default `true`) to disable
shard ancestor compaction on a per-tenant basis.
## Problem
Metrics are saved in https://github.com/neondatabase/neon/pull/11559,
but the file is not matched by the attachment regex.
## Summary of changes
Make attachment regex match the metrics file.
## Problem
The information in the README.md contained errors, and some information
was missing.
## Summary of changes
Found errors are fixed, and new information is added.
---------
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
## Problem
Benchmarks results are inconsistent on existing small-metal runners
## Summary of changes
Introduce new `unit-perf` runners, and lets run benchmark on them.
The new hardware has slower, but consistent, CPU frequency - if run with
default governor schedutil.
Thus we needed to adjust some testcases' timeouts and add some retry
steps where hard-coded timeouts couldn't be increased without changing
the system under test.
-
[wait_for_last_record_lsn](6592d69a67/test_runner/fixtures/pageserver/utils.py (L193))
1000s -> 2000s
-
[test_branch_creation_many](https://github.com/neondatabase/neon/pull/11409/files#diff-2ebfe76f89004d563c7e53e3ca82462e1d85e92e6d5588e8e8f598bbe119e927)
1000s
-
[test_ingest_insert_bulk](https://github.com/neondatabase/neon/pull/11409/files#diff-e90e685be4a87053bc264a68740969e6a8872c8897b8b748d0e8c5f683a68d9f)
- with back throttling disabled compute becomes unresponsive for more
than 60 seconds (PG hard-coded client authentication connection timeout)
-
[test_sharded_ingest](https://github.com/neondatabase/neon/pull/11409/files#diff-e8d870165bd44acb9a6d8350f8640b301c1385a4108430b8d6d659b697e4a3f1)
600s -> 1200s
Right now there are only 2 runners of that class, and if we decide to go
with them, we have to check how much that type of runners we need, so
jobs not stuck with waiting for that type of runners available.
However we now decided to run those runners with governor performance
instead of schedutil.
This achieves almost same performance as previous runners but still
achieves consistent results for same commit
Related issue to activate performance governor on these runners
https://github.com/neondatabase/runner/pull/138
## Verification that it helps
### analyze runtimes on new runner for same commit
Table of runtimes for the same commit on different runners in
[run](https://github.com/neondatabase/neon/actions/runs/14417589789)
| Run | Benchmarks (1) | Benchmarks (2) |Benchmarks (3) |Benchmarks (4)
| Benchmarks (5) |
|--------|--------|---------|---------|---------|---------|
| 1 | 1950.37s | 6374.55s | 3646.15s | 4149.48s | 2330.22s |
| 2 | - | 6369.27s | 3666.65s | 4162.42s | 2329.23s |
| Delta % | - | 0,07 % | 0,5 % | 0,3 % | 0,04 % |
| with governor performance | 1519.57s | 4131.62s | - | - | - |
| second run gov. perf. | 1513.62s | 4134.67s | - | - | - |
| Delta % | 0,3 % | 0,07 % | - | - | - |
| speedup gov. performance | 22 % | 35 % | - | - | - |
| current desktop class hetzner runners (main) | 1487.10s | 3699.67s | -
| - | - |
| slower than desktop class | 2 % | 12 % | - | - | - |
In summary, the runtimes for the same commit on this hardware varies
less than 1 %.
---------
Co-authored-by: BodoBolero <peterbendel@neon.tech>
## Problem
Sometimes it's useful to see the pageserver metrics after a test in
order to debug stuff.
For example, for https://github.com/neondatabase/neon/issues/11465 I'd
like to know
what the remote storage latencies are from the client.
## Summary of changes
When stopping the env, record the pageserver metrics into a file in the
pageserver's workdir.
## Problem
Part of https://github.com/neondatabase/neon/issues/11486
## Summary of changes
50% of the test instability of `test_create_churn_during_restart` are
due to error message gets changed. Allow the new error message.
Still need to fix other errors due to failure to acquire semaphore in
this or the next patch.
Signed-off-by: Alex Chi Z <chi@neon.tech>
## Problem
Pageservers now ignore unknown config fields, so this config tweaking is
no longer needed.
## Summary of changes
Get rid of the hack.
Closes https://github.com/neondatabase/neon/issues/11524
## Problem
https://github.com/neondatabase/neon/pull/11494 changes the batching
logic, but we don't have a way to evaluate it.
## Summary of changes
This PR introduces a global and per timeline metric which tracks the
reason for
which a batch was broken.
## Problem
Get page batching stops when we encounter requests at different LSNs.
We are leaving batching factor on the table.
## Summary of changes
The goal is to support keys with different LSNs in a single batch and
still serve them with a single vectored get.
Important restriction: the same key at different LSNs is not supported
in one batch. Returning different key
versions is a much more intrusive change.
Firstly, the read path is changed to support "scattered" queries. This
is a conceptually simple step from
https://github.com/neondatabase/neon/pull/11463. Instead of initializing
the fringe for one keyspace,
we do it for multiple at different LSNs and let the logic already
present into the fringe handle selection.
Secondly, page service code is updated to support batching at different
LSNs. Eeach request parsed from the wire determines its effective
request LSN and keeps it in mem for the batcher toinspect. The batcher
allows keys at
different LSNs in one batch as long one key is not requested at
different LSNs.
I'd suggest doing the first pass commit by commit to get a feel for the
changes.
## Results
I used the batching test from [Christian's
PR](https://github.com/neondatabase/neon/pull/11391) which increases the
change of batch breaks. Looking at the logs I think the new code is at
the max batching factor for the workload (we
only break batches due to them being oversized or because the executor
is idle).
```
Main:
Reasons for stopping batching: {'LSN changed': 22843, 'of batch size': 33417}
test_throughput[release-pg16-50-pipelining_config0-30-100-128-batchable {'max_batch_size': 32, 'execution': 'concurrent-futures', 'mode': 'pipelined'}].perfmetric.batching_factor: 14.6662
My branch:
Reasons for stopping batching: {'of batch size': 37024}
test_throughput[release-pg16-50-pipelining_config0-30-100-128-batchable {'max_batch_size': 32, 'execution': 'concurrent-futures', 'mode': 'pipelined'}].perfmetric.batching_factor: 19.8333
```
Related: https://github.com/neondatabase/neon/issues/10765
## Problem
See https://github.com/neondatabase/neon/issues/10652
Neon extension launches 2 BGW which reduce limit for parallel workers
and so affecting parallel_deadlock isolation test.
## Summary of changes
Increase `max_worker_processes` from default 8 to 16 for isolation test.
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
## Problem
Part of #9114
There was a debug-mode verification mode that verifies at every
retain_lsn. However, the code was tangled within the actual history
generation itself and it's hard to reason about correctness. This patch
adds a separate post-verification of the gc-compaction result that redos
logs at every retain_lsn and every record above the GC horizon. This
ensures that all key history we produce with gc-compaction is readable,
and if there're read errors after gc-compaction, it can only be
read-path errors instead of gc-compaction bugs.
## Summary of changes
* Add gc_compaction_verification flag, default to true.
* Implement a post-verification process.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
Previously, the structure of the spec file was just the compute spec.
However, the response from the control plane get spec request included
the compute spec and the compute_ctl config. This divergence was
hindering other work such as adding regression tests for compute_ctl
HTTP authorization.
Signed-off-by: Tristan Partin <tristan@neon.tech>
## Problem
The `pagebench` benchmarks set up an initial dataset by creating a
template tenant, copying the remote storage to a bunch of new tenants,
and attaching them to Pageservers.
In #11420, we found that
`test_pageserver_characterize_throughput_with_n_tenants` had degraded
performance because it set a custom tenant config in Pageservers that
was then replaced with the default tenant config by the storage
controller.
The initial fix was to register the tenants directly in the storage
controller, but this created the tenants with generation 1. This broke
`test_basebackup_with_high_slru_count`, where the template tenant was at
generation 2, leading to all layer files at generation 2 being ignored.
Resolves#11485.
Touches #11381.
## Summary of changes
This patch addresses both test issues by modifying `attach_hook` to also
take a custom tenant config. This allows attaching tenants to
Pageservers from pre-existing remote storage, specifying both the
generation and tenant config when registering them in the storage
controller.
The batching perf test workload is currently read-only sequential scans.
However, realistic workloads have concurrent writes (to other pages)
going on.
This PR simulates concurrent writes to other pages by emitting logical
replication messages.
These degrade the achieved batching factor, for the reason see
- https://github.com/neondatabase/neon/issues/10765
PR
- https://github.com/neondatabase/neon/pull/11494
will fix this problem and get batching factor back up.
---------
Co-authored-by: Vlad Lazar <vlad@neon.tech>
# Refs
- fixes https://github.com/neondatabase/neon/issues/11395
# Problem
Since 2025-03-10, we have observed increased flakiness of
`test_pageserver_getpage_throttle`.
The test is timing-dependent by nature, and was hitting the
```
assert duration_secs >= 10 * actual_smgr_query_seconds, (
"smgr metrics should not include throttle wait time"
)
```
quite frequently.
# Analysis
These failures are not reproducible.
In this PR's history is a commit that reran the test 100 times without
requiring a single retry.
In https://github.com/neondatabase/neon/issues/11395 there is a link to
a query to the test results database.
It shows that the flakiness was not constant, but rather episodic:
2025-03-{10,11,12,13} 2025-03-{19,20,21} 2025-03-31 and 2025-04-01.
To me, this suggests variability in available CPU.
# Solution
The point of the offending assertion is to ensure that most of the
request latency is spent on throttling, because testing of the
throttling mechanism is the point of the test.
The `10` magic number means at most 10% of mean latency may be spent on
request processing.
Ideally we would control the passage of time (virtual clock source) to
make this test deterministic.
But I don't see that happening in our regression test setup.
So, this PR de-flakes the test as follows:
- allot up to 66% of mean latency for request processing
- increase duration from 10s to 20s, hoping to get better protection
from momentary CPU spikes in noisy neighbor tests or VMs on the runner
host
As a drive-by, switch to `pytest.approx` and remove one self-test
assertion I can't make sense of anymore.
## Problem
We need to export some metrics about certs/connections to configure
alerts and make sure that all HTTP requests are gone before turning
https-only mode on.
- Closes: https://github.com/neondatabase/cloud/issues/25526
## Summary of changes
- Add started connection and connection error metrics to http/https
Server.
- Add certificate expiration time and reload metrics to
ReloadingCertificateResolver.
Because it wasn't recursive, there was a limit to the depth of updates.
This work is necessary because as we teach neon_local and compute_ctl
that the content in --spec-path should match a similar structure we get
from the control plane, the spec object itself will no longer be
toplevel. It will be under the "spec" key.
Signed-off-by: Tristan Partin <tristan@neon.tech>
## Problem
The graceful leadership transfer process involves calling step_down on
the old controller, but this was not waiting for shard splits to
complete, and the new controller could therefore end up trying to abort
a shard split while it was still going on.
We mitigated this already in #11256 by avoiding the case where shard
split completion would update the database incorrectly, but this was a
fragile fix because it assumes that is the only problematic part of the
split running concurrently.
Precursors:
- #11290
- #11256Closes: #11254
## Summary of changes
- Hold the reconciler gate from shard splits, so that step_down will
wait for them. Splits should always be fairly prompt, so it is okay to
wait here.
- Defense in depth: if step_down times out (hardcoded 10 second limit),
then fully terminate the controller process rather than letting it
continue running, potentially doing split-brainy things. This makes
sense because the new controller will always declare itself leader
unilaterally if step_down fails, so leaving an old controller running is
not beneficial.
- Tests: extend
`test_storage_controller_leadership_transfer_during_split` to separately
exercise the case of a split holding up step_down, and the case where
the overall timeout on step_down is hit and the controller terminates.
## Problem
`test_location_conf_churn` performs random location updates on
Pageservers. While doing this, it could instruct the compute to connect
to a stale generation and execute queries. This is invalid, and will
fail if a newer generation has removed layer files used by the stale
generation.
Resolves#11348.
## Summary of changes
Only connect to the latest generation when executing queries.
## Problem
Walproposer should get elected and commit WAL on safekeepers specified
by the membership configuration.
## Summary of changes
- Add to wp `members_safekeepers` and `new_members_safekeepers` arrays
mapping configuration members to connection slots. Establish this
mapping (by node id) when safekeeper sends greeting, giving its id and
when mconf becomes known / changes.
- Add to TermsCollected, VotesCollected,
GetAcknowledgedByQuorumWALPosition membership aware logic. Currently it
partially duplicates existing one, but we'll drop the latter eventually.
- In python, rename Configuration to MembershipConfiguration for
clarity.
- Add test_quorum_sanity testing new logic.
ref https://github.com/neondatabase/neon/issues/10851
## Problem
Part of #9114
## Summary of changes
Gc-compaction flag was not correctly set, causing it not getting
preempted by L0.
Signed-off-by: Alex Chi Z <chi@neon.tech>
## Problem
`test_location_conf_churn` often fails with `neither image nor delta
layer`, but doesn't say what the file actually is. However, past local
failures have indicated that it might be `.___temp` files.
Touches https://github.com/neondatabase/neon/issues/11348.
## Summary of changes
Ignore `.___temp` files when evicting local layers, and include the file
name in the error message.
## Problem
our large oltp benchmark runs very long - we want to remove the duration
of the reindex step.
we don't run concurrent workload anyhow but added "concurrently" only to
have a "prod-like" approach. But if it just doubles the time we report
because it requires two instead of one full table scan we can remove it
## Summary of changes
remove keyword concurrently from the reindex step
We'd like to run benchmarks starting from a steady state. To this end,
do a reconciliation round before proceeding with the benchmark.
This is useful for benchmarks that use tenant dir snapshots since a
non-standard tenant configuration is used to generate the snapshot. The
storage controller is not aware of the non default tenant configuration
and will reconcile while the bench is running.
## Problem
Now `get_timestamp_of_lsn` returns `404 NotFound` if there is no clog
pages for given LSN, and it's difficult to distinguish from other 404
errors. A separate status code for this error will allow the control
plane to handle this case.
- Closes: https://github.com/neondatabase/neon/issues/11439
- Corresponding PR in control plane:
https://github.com/neondatabase/cloud/pull/27125
## Summary of changes
- Return `412 PreconditionFailed` instead of `404 NotFound` if no
timestamp is fond for given LSN.
I looked briefly through the current error handling code in cloud.git
and the status code change should not affect anything for the existing
code. Change from the corresponding PR also looks fine and should work
with the current PS status code. Additionally, here is OK to merge it
from control plane team:
https://github.com/neondatabase/neon/issues/11439#issuecomment-2789327552
---------
Co-authored-by: John Spray <john@neon.tech>
## Problem
The current stripe size of 256 MB is a bit large, and can cause load
imbalances across shards. A stripe size of 16 MB appears more reasonable
to avoid hotspots, although we don't see evidence of this in benchmarks.
Resolves https://github.com/neondatabase/cloud/issues/25634.
Touches https://github.com/neondatabase/cloud/issues/21870.
## Summary of changes
* Change the default stripe size to 16 MB.
* Remove `ShardParameters::DEFAULT_STRIPE_SIZE`, and only use
`pageserver_api::shard::DEFAULT_STRIPE_SIZE`.
* Update a bunch of tests that assumed a certain stripe size.
## Problem
With the recent improvements to L0 compaction responsiveness,
`test_create_snapshot` now ends up generating 10,000 layer files
(compared to 1,000 in previous snapshots). This increases the snapshot
size by 4x, and significantly slows down tests.
## Summary of changes
Increase the target layer size from 128 KB to 256 KB, and the L0
compaction threshold from 1 to 5. This reduces the layer count from
about 10,000 to 1,000.
## Problem
`tenant_import`, used to import an existing tenant from remote storage
into a storage controller for support and debugging, assumed
`DEFAULT_STRIPE_SIZE` since this can't be recovered from remote storage.
In #11168, we are changing the stripe size, which will break
`tenant_import`.
Resolves#11175.
## Summary of changes
* Add `stripe_size` to the tenant manifest.
* Add `TenantScanRemoteStorageShard::stripe_size` and return from
`tenant_scan_remote` if present.
* Recover the stripe size during`tenant_import`, or fall back to 32768
(the original default stripe size).
* Add tenant manifest compatibility snapshot:
`2025-04-08-pgv17-tenant-manifest-v1.tar.zst`
There are no cross-version concerns here, since unknown fields are
ignored during deserialization where relevant.
Service targeted for storing and retrieving LFC prewarm data.
Can be used for proxying S3 access for Postgres extensions like
pg_mooncake as well.
Requests must include a Bearer JWT token.
Token is validated using a pemfile (should be passed in infra/).
Note: app is not tolerant to extra trailing slashes, see app.rs
`delete_prefix` test for comments.
Resolves: https://github.com/neondatabase/cloud/issues/26342
Unrelated changes: gate a `rename_noreplace` feature and disable it in
`remote_storage` so as `object_storage` can be built with musl
## Problem
`test_scrubber_tenant_snapshot` is flaky with `request was dropped`
errors. More details are in the issue.
- Closes: https://github.com/neondatabase/neon/issues/11278
## Summary of changes
- Disable shard scheduling during pageservers restart
- Add `reconcile_until_idle` in the end of the test
## Problem
If the local file cache is shrunk, so that we punch some holes in the
underlying file, the local_cache view displays the holes incorrectly.
See https://github.com/neondatabase/neon/issues/10770
## Summary of changes
Skip hole tags in the local_cache view.
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
## Problem
Currently, the tenant manifest is only uploaded if there are offloaded
timelines. The checks are also a bit loose (e.g. only checks number of
offloaded timelines). We want to start using the manifest for other
things too (e.g. stripe size).
Resolves#11271.
## Summary of changes
This patch ensures that a tenant manifest always exists. The lifecycle
is:
* During preload, fetch the existing manifest, if any.
* During attach, upload a tenant manifest if it differs from the
preloaded one (or does not exist).
* Upload a new manifest as needed, if it differs from the last-known
manifest (ignoring version number).
* On splits, pre-populate the manifest from the parent.
* During Pageserver physical GC, remove old manifests but keep the
latest 2 generations.
This will cause nearly all existing tenants to upload a new tenant
manifest on their first attach after this change. Attaches are
concurrency-limited in the storage controller, so we expect this will be
fine.
Also updates `make_broken` to automatically log at `INFO` level when the
tenant has been cancelled, to avoid spurious error logs during shutdown.
## Problem
We don't have metrics to exactly quantify the end user impact of
on-demand downloads.
Perf tracing is underway (#11140) to supply us with high-resolution
*samples*.
But it will also be useful to have some aggregate per-timeline and
per-instance metrics that definitively contain all observations.
## Summary of changes
This PR consists of independent commits that should be reviewed
independently.
However, for convenience, we're going to merge them together.
- refactor(metrics): measure_remote_op can use async traits
- impr(pageserver metrics): task_kind dimension for
remote_timeline_client latency histo
- implements https://github.com/neondatabase/cloud/issues/26800
- refs
https://github.com/neondatabase/cloud/issues/26193#issuecomment-2769705793
- use the opportunity to rename the metric and add a _global suffix;
checked grafana export, it's only used in two personal dashboards, one
of them mine, the other by Heikki
- log on-demand download latency for expensive-to-query but precise
ground truth
- metric for wall clock time spent waiting for on-demand downloads
## Refs
- refs https://github.com/neondatabase/cloud/issues/26800
- a bunch of minor investigations / incidents into latency outliers
# Refs
- refs https://github.com/neondatabase/neon/issues/8915
- discussion thread:
https://neondb.slack.com/archives/C033RQ5SPDH/p1742406381132599
- stacked atop https://github.com/neondatabase/neon/pull/11298
- corresponding internal docs update that illustrates how this PR
removes friction: https://github.com/neondatabase/docs/pull/404
# Problem
Rejecting `pageserver.toml`s with unknown fields adds friction,
especially when using `pageserver.toml` fields as feature flags that
need to be decommissioned.
See the added paragraphs on `pageserver_api::models::ConfigToml` for
details on what kind of friction it causes.
Also read the corresponding internal docs update linked above to see a
more imperative guide for using `pageserver.toml` flags as feature
flags.
# Solution
## Ignoring unknown fields
Ignoring is the serde default behavior.
So, just remove `serde(deny_unknown_fields)` from all structs in
`pageserver_api::config::ConfigToml`
`pageserver_api::config::TenantConfigToml`.
I went through all the child fields and verified they don't use
`deny_unknown_fields` either, including those shared with
`pageserver_api::models`.
## Warning about unknown fields
We still want to warn about unknown fields to
- be informed about typos in the config template
- be reminded about feature-flag style configs that have been cleaned up
in code but not yet in config templates
We tried `serde_ignore` (cf draft #11319) but it doesn't work with
`serde(flatten)`.
The solution we arrived at is to compare the on-disk TOML with the TOML
that we produce if we serialize the `ConfigToml` again.
Any key specified in the on-disk TOML but not present in the serialized
TOML is flagged as an ignored key.
The mechanism to do it is a tiny recursive decent visitor on the
`toml_edit::DocumentMut`.
# Future Work
Invalid config _values_ in known fields will continue to fail pageserver
startup.
See
- https://github.com/neondatabase/cloud/issues/24349
for current worst case impact to deployments & ideas to improve.
## Problem
https://github.com/neondatabase/neon/pull/11140 introduces performance
tracing with OTEL
and a pageserver config which configures the sampling ratio of get page
requests.
Enabling a non-zero sampling ratio on a per region basis is too
aggressive and comes with perf
impact that isn't very well understood yet.
## Summary of changes
Add a `sampling_ratio` tenant level config which overrides the
pageserver level config.
Note that we do not cache the config and load it on every get page
request such that changes propagate
timely.
Note that I've had to remove the `SHARD_SELECTION` span to get this to
work. The tracing library doesn't
expose a neat way to drop a span if one realises it's not needed at
runtime.
Closes https://github.com/neondatabase/neon/issues/11392
## Problem
IO metrics for secondary locations do not get deregistered when the
timeline is removed.
## Summary of changes
Stash the request context to be used for downloads in
`SecondaryTimelineDetail`. These objects match the lifetime of the
secondary timeline location pretty well.
When the timeline is removed, deregister the metrics too.
Closes https://github.com/neondatabase/neon/issues/11156
## Problem
There are some places in the code where we create `reqwest::Client`
without providing SSL CA certs from `ssl_ca_file`. These will break
after we enable TLS everywhere.
- Part of https://github.com/neondatabase/cloud/issues/22686
## Summary of changes
- Support `ssl_ca_file` in storage scrubber.
- Add `use_https_safekeeper_api` option to safekeeper to use https for
peer requests.
- Propagate SSL CA certs to storage_controller/client, storcon's
ComputeHook, PeerClient and maybe_forward.
Adds a test `test_storcon_create_delete_sk_down` which tests the
reconciler and pending op persistence if faced with a temporary
safekeeper downtime during timeline creation or deletion. This is in
contrast to `test_explicit_timeline_creation_storcon`, which tests the
happy path.
We also do some fixes:
* timeline and tenant deletion http requests didn't expect a body, but
`()` sent one.
* we got the tenant deletion http request's return type wrong: it's
supposed to be a hash map
* we add some logging to improve observability
* We fix `list_pending_ops` which had broken code meant to make it
possible to restrict oneself to a single pageserver. But diesel doesn't
support that sadly, or at least I couldn't figure out a way to make it
work. We don't need that functionality, so remove it.
* We add an info span to the heartbeater futures with the node id, so
that there is no context-free msgs like "Backoff: waiting 1.1 seconds
before processing with the task" in the storcon logs. we could also add
the full base url of the node but don't do it as most other log lines
contain that information already, and if we do duplication it should at
least not be verbose. One can always find out the base url from the node
id.
Successor of #11261
Part of #9011
Log the created project and endpoint IDs and improve typing in the
source code to improve readability.
Signed-off-by: Tristan Partin <tristan@neon.tech>
Based on https://github.com/neondatabase/neon/pull/11139
## Problem
We want to export performance traces from the pageserver in OTEL format.
End goal is to see them in Grafana.
## Summary of changes
https://github.com/neondatabase/neon/pull/11139 introduces the
infrastructure required to run the otel collector alongside the
pageserver.
### Design
Requirements:
1. We'd like to avoid implementing our own performance tracing stack if
possible and use the `tracing` crate if possible.
2. Ideally, we'd like zero overhead of a sampling rate of zero and be a
be able to change the tracing config for a tenant on the fly.
3. We should leave the current span hierarchy intact. This includes
adding perf traces without modifying existing tracing.
To satisfy (3) (and (2) in part) a separate span hierarchy is used.
`RequestContext` gains an optional `perf_span` member
that's only set when the request was chosen by sampling. All perf span
related methods added to `RequestContext` are no-ops for requests that
are not sampled.
This on its own is not enough for (3), so performance spans use a
separate tracing subscriber. The `tracing` crate doesn't have great
support for this, so there's a fair amount of boilerplate to override
the subscriber at all points of the perf span lifecycle.
### Perf Impact
[Periodic
pagebench](https://neonprod.grafana.net/d/ddqtbfykfqfi8d/e904990?orgId=1&from=2025-02-08T14:15:59.362Z&to=2025-03-10T14:15:59.362Z&timezone=utc)
shows no statistically significant regression with a sample ratio of 0.
There's an annotation on the dashboard on 2025-03-06.
### Overview of changes:
1. Clean up the `RequestContext` API a bit. Namely, get rid of the
`RequestContext::extend` API and use the builder instead.
2. Add pageserver level configs for tracing: sampling ratio, otel
endpoint, etc.
3. Introduce some perf span tracking utilities and expose them via
`RequestContext`. We add a `tracing::Span` wrapper to be used for perf
spans and a `tracing::Instrumented` equivalent for it. See doc comments
for reason.
4. Set up OTEL tracing infra according to configuration. A separate
runtime is used for the collector.
5. Add perf traces to the read path.
## Refs
- epic https://github.com/neondatabase/neon/issues/9873
---------
Co-authored-by: Christian Schwarz <christian@neon.tech>
## Problem
Previously, if the observed state was refreshed and matching the intent,
we wouldn't send
a compute notification. This is unsafe. There's no guarantee that the
location landed on the
pageserver _and_ a compute notification for it was delivered.
See
https://github.com/neondatabase/neon/issues/11291#issuecomment-2743205411
for one such example.
## Summary of changes
Add a reproducer and notify the compute if the correct observed state
required a refresh.
Closes https://github.com/neondatabase/neon/issues/11291
