## Problem
This is a follow-up to TODO, as part
of the effort to rewire the compute reconfiguration/notification
mechanism to make it more robust. Please refer to that commit or ticket
BRC-1778 for full context of the problem.
## Summary of changes
The previous change added mechanism in `compute_ctl` that makes it
possible to refresh the configuration of PG on-demand by having
`compute_ctl` go out to download a new config from the control
plane/HCC. This change wired this mechanism up with PG so that PG will
signal `compute_ctl` to refresh its configuration when it suspects that
it could be talking to incorrect pageservers due to a stale
configuration.
PG will become suspicious that it is talking to the wrong pageservers in
the following situations:
1. It cannot connect to a pageserver (e.g., getting a network-level
connection refused error)
2. It can connect to a pageserver, but the pageserver does not return
any data for the GetPage request
3. It can connect to a pageserver, but the pageserver returns a
malformed response
4. It can connect to a pageserver, but there is an error receiving the
GetPage request response for any other reason
This change also includes a minor tweak to `compute_ctl`'s config
refresh behavior. Upon receiving a request to refresh PG configuration,
`compute_ctl` will reach out to download a config, but it will not
attempt to apply the configuration if the config is the same as the old
config is it replacing. This optimization is added because the act of
reconfiguring itself requires working pageserver connections. In many
failure situations it is likely that PG detects an issue with a
pageserver before the control plane can detect the issue, migrate
tenants, and update the compute config. In this case even the latest
compute config won't point PG to working pageservers, causing the
configuration attempt to hang and negatively impact PG's
time-to-recovery. With this change, `compute_ctl` only attempts
reconfiguration if the refreshed config points PG to different
pageservers.
## How is this tested?
The new code paths are exercised in all existing tests because this
mechanism is on by default.
Explicitly tested in `test_runner/regress/test_change_pageserver.py`.
Co-authored-by: William Huang <william.huang@databricks.com>
## Problem
`TYPE_CHECKING` is used inconsistently across Python tests.
## Summary of changes
- Update `ruff`: 0.7.0 -> 0.11.2
- Enable TC (flake8-type-checking):
https://docs.astral.sh/ruff/rules/#flake8-type-checking-tc
- (auto)fix all new issues
## Problem
Previously, Workload was reconfiguring the compute before each run of
writes, which was meant to be a no-op when nothing changed, but was
actually writing extra data due to an issue being fixed in
https://github.com/neondatabase/neon/pull/10696.
The row counts in tests were too low in some cases, these tests were
only working because of those extra writes that shouldn't have been
happening, and moreover were relying on checkpoints happening.
## Summary of changes
- Only reconfigure compute if the attached pageserver actually changed.
If pageserver is set to None, that means controller is managing
everything, so never reconfigure compute.
- Update tests that wrote too few rows.
---------
Co-authored-by: Alexey Kondratov <kondratov.aleksey@gmail.com>
## Problem
part of https://github.com/neondatabase/neon/issues/9114
part of investigation of
https://github.com/neondatabase/neon/issues/10049
## Summary of changes
* If `cfg!(test) or cfg!(feature = testing)`, then we will always try
generating an image to ensure the history is replayable, but not put the
image layer into the final layer results, therefore discovering wrong
key history before we hit a read error.
* I suspect it's easier to trigger some races if gc-compaction is
continuously run on a timeline, so I increased the frequency to twice
per 10 churns.
* Also, create branches in gc-compaction smoke tests to get more test
coverage.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
Co-authored-by: Arpad Müller <arpad@neon.tech>
## Problem
LFC is not enabled by default in tests, but it is enabled in production.
This increases the risk of errors in the production environment, which
were not found during the routine workflow.
However, enabling LFC for all the tests may overload the disk on our
servers and increase the number of failures.
So, we try enabling LFC in one case to evaluate the possible risk.
## Summary of changes
A new environment variable, USE_LFC is introduced. If it is set to true,
LFC is enabled by default in all the tests.
In our workflow, we enable LFC for PG17, release, x86-64, and disabled
for all other combinations.
---------
Co-authored-by: Alexey Masterov <alexeymasterov@neon.tech>
Co-authored-by: a-masterov <72613290+a-masterov@users.noreply.github.com>
## Problem
Follow up to https://github.com/neondatabase/neon/pull/9682, hopefully
we can detect some issues or assure ourselves that this is ready for
production.
## Summary of changes
* Add a compaction-detach-ancestor smoke test.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
## Problem
We use a pretty old version of `mypy` 1.3 (released 1.5 years ago), it
produces false positives for `typing.Self`.
## Summary of changes
- Bump `mypy` from 1.3 to 1.13
- Fix new warnings and errors
- Use `typing.Self` whenever we `return self`
## Problem
On Debian 12 (Bookworm), Python 3.11 is the latest available version.
## Summary of changes
- Update Python to 3.11 in build-tools
- Fix ruff check / format
- Fix mypy
- Use `StrEnum` instead of pair `str`, `Enum`
- Update docs
close https://github.com/neondatabase/neon/issues/9160
For whatever reason, pg17's WAL pattern seems different from others,
which triggers some flaky behavior within the compaction smoke test.
## Summary of changes
* Run L0 compaction before proceeding with the read benchmark.
* So that we can ensure the num of L0 layers is 0 and test the
compaction behavior only with L1 layers.
We have a threshold for triggering L0 compaction. In some cases, the
test case did not produce enough L0 layers to do a L0 compaction,
therefore leaving the layer map with 3+ L0 layers above the L1 layers.
This increases the average read depth for the timeline.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
Going through the list of recent flaky tests, trying to fix those
related to graceful shutdown.
- test_forward_compatibility: flush and wait for uploads to avoid
graceful shutdown
- test_layer_bloating: in the end the endpoint and vanilla are still up
=> immediate shutdown
- test_lagging_sk: pageserver shutdown is not related to the test =>
immediate shutdown
- test_lsn_lease_size: pageserver flushing is not needed => immediate
shutdown
Additionally:
- remove `wait_for_upload` usage from workload fixture
Cc: #8708Fixes: #8710
## Problem
Ingest filtering wasn't being applied to timeline creations, so a
timeline created on a sharded tenant would use 20MB+ on each shard (each
shard got a full copy). This didn't break anything, but is inefficient
and leaves the system in a harder-to-validate state where shards
initially have some data that they will eventually drop during
compaction.
Closes: https://github.com/neondatabase/neon/issues/6649
## Summary of changes
- in `import_rel`, filter block-by-block with is_key_local
- During test_sharding_smoke, check that per-shard physical sizes are as
expected
- Also extend the test to check deletion works as expected (this was an
outstanding tech debt task)
## Problem
In the test for https://github.com/neondatabase/neon/pull/6776, a test
cases uses tiny layer sizes and tiny stripe sizes. This hits a scenario
where a shard's checkpoint interval spans a region where none of the
content in the WAL is ingested by this shard. Since there is no layer to
flush, we do not advance disk_consistent_lsn, and this causes the test
to fail while waiting for LSN to advance.
## Summary of changes
- Pass an LSN through `layer_flush_start_tx`. This is the LSN to which
we have frozen at the time we ask the flush to flush layers frozen up to
this point.
- In the layer flush task, if the layers we flush do not reach
`frozen_to_lsn`, then advance disk_consistent_lsn up to this point.
- In `maybe_freeze_ephemeral_layer`, handle the case where
last_record_lsn has advanced without writing a layer file: this ensures
that disk_consistent_lsn and remote_consistent_lsn advance anyway.
The net effect is that the disk_consistent_lsn is allowed to advance
past regions in the WAL where a shard ingests no data, and that we
uphold our guarantee that remote_consistent_lsn always eventually
reaches the tip of the WAL.
The case of no layer at all is hard to test at present due to >0 shards
being polluted with SLRU writes, but I have tested it locally with a
branch that disables SLRU writes on shards >0. We can tighten up the
testing on this in future as/when we refine shard filtering (currently
shards >0 need the SLRU because they use it to figure out cutoff in GC
using timestamp-to-lsn).
Add shard_number to PageserverFeedback and parse it on the compute side.
When compute receives a new ps_feedback, it calculates min LSNs among
feedbacks from all shards, and uses those LSNs for backpressure.
Add `test_sharding_backpressure` to verify that backpressure slows down
compute to wait for the slowest shard.
## Problem
Shard splits worked, but weren't safe against failures (e.g. node crash
during split) yet.
Related: #6676
## Summary of changes
- Introduce async rwlocks at the scope of Tenant and Node:
- exclusive tenant lock is used to protect splits
- exclusive node lock is used to protect new reconciliation process that
happens when setting node active
- exclusive locks used in both cases when doing persistent updates (e.g.
node scheduling conf) where the update to DB & in-memory state needs to
be atomic.
- Add failpoints to shard splitting in control plane and pageserver
code.
- Implement error handling in control plane for shard splits: this
detaches child chards and ensures parent shards are re-attached.
- Crash-safety for storage controller restarts requires little effort:
we already reconcile with nodes over a storage controller restart, so as
long as we reset any incomplete splits in the DB on restart (added in
this PR), things are implicitly cleaned up.
- Implement reconciliation with offline nodes before they transition to
active:
- (in this context reconciliation means something like
startup_reconcile, not literally the Reconciler)
- This covers cases where split abort cannot reach a node to clean it
up: the cleanup will eventually happen when the node is marked active,
as part of reconciliation.
- This also covers the case where a node was unavailable when the
storage controller started, but becomes available later: previously this
allowed it to skip the startup reconcile.
- Storage controller now terminates on panics. We only use panics for
true "should never happen" assertions, and these cases can leave us in
an un-usable state if we keep running (e.g. panicking in a shard split).
In the unlikely event that we get into a crashloop as a result, we'll
rely on kubernetes to back us off.
- Add `test_sharding_split_failures` which exercises a variety of
failure cases during shard split.
## Problem
Where the stripe size is the same order of magnitude as the checkpoint
distance (such as with default settings), tenant shards can easily pass
through `checkpoint_distance` bytes of LSN without actually ingesting
anything. This results in emitting many tiny L0 delta layers.
## Summary of changes
- Multiply checkpoint distance by shard count before comparing with LSN
distance. This is a heuristic and does not guarantee that we won't emit
small layers, but it fixes the issue for typical cases where the writes
in a (checkpoint_distance * shard_count) range of LSN bytes are somewhat
distributed across shards.
- Add a test that checks the size of layers after ingesting to a sharded
tenant; this fails before the fix.
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
## Problem
The support for sharding in the pageserver was written before
https://github.com/neondatabase/neon/pull/6205 landed, so when it landed
we couldn't directly test sharding.
## Summary of changes
- Add `test_sharding_smoke` which tests the basics of creating a
sharding tenant, creating a timeline within it, checking that data
within it is distributed.
- Add modes to pg_regress tests for running with 4 shards as well as
with 1.
## Problem
To test sharding, we need something to control it. We could write python
code for doing this from the test runner, but this wouldn't be usable
with neon_local run directly, and when we want to write tests with large
number of shards/tenants, Rust is a better fit efficiently handling all
the required state.
This service enables automated tests to easily get a system with
sharding/HA without the test itself having to set this all up by hand:
existing tests can be run against sharded tenants just by setting a
shard count when creating the tenant.
## Summary of changes
Attachment service was previously a map of TenantId->TenantState, where
the principal state stored for each tenant was the generation and the
last attached pageserver. This enabled it to serve the re-attach and
validate requests that the pageserver requires.
In this PR, the scope of the service is extended substantially to do
overall management of tenants in the pageserver, including
tenant/timeline creation, live migration, evacuation of offline
pageservers etc. This is done using synchronous code to make declarative
changes to the tenant's intended state (`TenantState.policy` and
`TenantState.intent`), which are then translated into calls into the
pageserver by the `Reconciler`.
Top level summary of modules within
`control_plane/attachment_service/src`:
- `tenant_state`: structure that represents one tenant shard.
- `service`: implements the main high level such as tenant/timeline
creation, marking a node offline, etc.
- `scheduler`: for operations that need to pick a pageserver for a
tenant, construct a scheduler and call into it.
- `compute_hook`: receive notifications when a tenant shard is attached
somewhere new. Once we have locations for all the shards in a tenant,
emit an update to postgres configuration via the neon_local `LocalEnv`.
- `http`: HTTP stubs. These mostly map to methods on `Service`, but are
separated for readability and so that it'll be easier to adapt if/when
we switch to another RPC layer.
- `node`: structure that describes a pageserver node. The most important
attribute of a node is its availability: marking a node offline causes
tenant shards to reschedule away from it.
This PR is a precursor to implementing the full sharding service for
prod (#6342). What's the difference between this and a production-ready
controller for pageservers?
- JSON file persistence to be replaced with a database
- Limited observability.
- No concurrency limits. Marking a pageserver offline will try and
migrate every tenant to a new pageserver concurrently, even if there are
thousands.
- Very simple scheduler that only knows to pick the pageserver with
fewest tenants, and place secondary locations on a different pageserver
than attached locations: it does not try to place shards for the same
tenant on different pageservers. This matters little in tests, because
picking the least-used pageserver usually results in round-robin
placement.
- Scheduler state is rebuilt exhaustively for each operation that
requires a scheduler.
- Relies on neon_local mechanisms for updating postgres: in production
this would be something that flows through the real control plane.
---------
Co-authored-by: Arpad Müller <arpad-m@users.noreply.github.com>
These tests have been loitering on a branch of mine for a while: they
already provide value even without all the secondary mode bits landed
yet, and the Workload helper is handy for other tests too.
- `Workload` is a re-usable test workload that replaces some of the
arbitrary "write a few rows" SQL that I've found my self repeating, and
adds a systematic way to append data and check that reads properly
reflect the changes. This append+validate stuff is important when doing
migrations, as we want to detect situations where we might be reading
from a pageserver that has not properly seen latest changes.
- test_multi_attach is a validation of how the pageserver handles
attaching the same tenant to multiple pageservers, from a safety point
of view. This is intentionally separate from the larger testing of
migration, to provide an isolated environment for multi-attachment.
- test_location_conf_churn is a pseudo-random walk through the various
states that TenantSlot can be put into, with validation that attached
tenants remain externally readable when they should, and as a side
effect validating that the compute endpoint's online configuration
changes work as expected.
- test_live_migration is the reference implementation of how to drive a
pair of pageservers through a zero-downtime migration of a tenant.
---------
Co-authored-by: Arpad Müller <arpad-m@users.noreply.github.com>
