## Problem
The existing behavior isn't exactly incorrect, but is operationally
risky: if the control plane compute hook breaks, then all the control
plane operations trying to call /location_config will end up retrying
forever, which could put more load on the system.
## Summary of changes
- Treat 404s as fatal errors to do fewer retries: a 404 either indicates
we have the wrong URL, or some control plane bug is failing to recognize
our tenant ID as existing.
- Do not return an error on reconcilation errors in a non-creating
/location_config response: this allows the control plane to finish its
Operation (and we will eventually retry the compute notification later)
## Problem
This is mainly to limit our concurrency, rather than to speed up
requests (I was doing some sanity checks on performance of the service
with thousands of shards)
## Summary of changes
- Enable the `diesel:r2d2` feature, which provides an async connection
pool
- Acquire a connection before entering spawn_blocking for a database
transaction (recall that diesel's interface is sync)
- Set a connection pool size of 99 to fit within default postgres limit
(100)
- Also set the tokio blocking thread count to accomodate the same number
of blocking tasks (the only thing we use spawn_blocking for is database
calls).
It's awkward to point to a file when doing some kinds of ad-hoc
deployment (like right now, when I'm hacking a helm chart having not
quite hooked up secrets properly yet). We take all the rest of the
secrets as CLI args directly, so let's do the same for public key.
## Problem
We don't have a neat way to carry around migration .sql files during
deploy, and in any case would prefer to avoid depending on diesel CLI to
deploy.
## Summary of changes
- Use `diesel_migrations` crate to embed migrations in our binary
- Run migrations on startup
- Drop the diesel dependency in the `neon_local` binary, as the
attachment_service binary just needs the database to exist. Do database
creation with a simple `createdb`.
Co-authored-by: Arpad Müller <arpad-m@users.noreply.github.com>
The solution we ended up for `backoff::retry` requires always cloning of
cancellation tokens even though there is just `.await`. Fix that, and
also turn the return type into `Option<Result<T, E>>` avoiding the need
for the `E::cancelled()` fn passed in.
Cc: #6096
## Problem
This change was left out of #6585 accidentally -- just forgot to push
the very last version of my branch.
Now that we can load database url from Secrets Manager, we don't always
need it on the CLI any more. We should let the user omit it instead of
passing `--database-url ""`
## Summary of changes
- Make `--database-url` optional
Cleanups from https://github.com/neondatabase/neon/pull/6394
- There was a rogue `*` breaking the `GET /tenant/:tenant_id`, which
passes through to shard zero
- There was a duplicate migrate endpoint
- There are un-prefixed API endpoints that were only needed for compat
tests and can now be removed.
## Problem
When we change which physical pageservers a tenant is attached to, we
must update the control plane so that it can update computes. This will
be done via an HTTP hook, as described in
https://www.notion.so/neondatabase/Sharding-Service-Control-Plane-interface-6de56dd310a043bfa5c2f5564fa98365#1fe185a35d6d41f0a54279ac1a41bc94
## Summary of changes
- Optional CLI args `--control-plane-jwt-token` and `-compute-hook-url`
are added. If these are set, then we will use this HTTP endpoint,
instead of trying to use neon_local LocalEnv to update compute
configuration.
- Implement an HTTP-driven version of ComputeHook that calls into the
configured URL
- Notify for all tenants on startup, to ensure that we don't miss
notifications if we crash partway through a change, and carry a
`pending_compute_notification` flag at runtime to allow notifications to
fail without risking never sending the update.
- Add a test for all this
One might wonder: why not do a "forever" retry for compute hook
notifications, rather than carrying a flag on the shard to call
reconcile() again later. The reason is that we will later limit
concurreny of reconciles, when dealing with larger numbers of shards,
and if reconcile is stuck waiting for the control plane to accept a
notification request, it could jam up the whole system and prevent us
making other changes. Anyway: from the perspective of the outside world,
we _do_ retry forever, but we don't retry forever within a given
Reconciler lifetime.
The `pending_compute_notification` logic is predicated on later adding a
background task that just calls `Service::reconcile_all` on a schedule
to make sure that anything+everything that can fail a
Reconciler::reconcile call will eventually be retried.
## Problem
Passing secrets in via CLI/environment is awkward when using helm for
deployment, and not ideal for security (secrets may show up in ps,
/proc).
We can bypass these issues by simply connecting directly to the AWS
Secrets Manager service at runtime.
## Summary of changes
- Add dependency on aws-sdk-secretsmanager
- Update other aws dependencies to latest, to match transitive
dependency versions
- Add `Secrets` type in attachment service, using AWS SDK to load if
secrets are not provided on the command line.
## Problem
The `--path` argument is only used in testing, for compat tests that use
a JSON snapshot of state rather than the postgres database. In regular
deployments, it should be omitted (currently one has to specify `--path
""`)
## Summary of changes
Make `--path` optional.
Depends on: https://github.com/neondatabase/neon/pull/6468
## Problem
The sharding service will be used as a "virtual pageserver" by the
control plane -- so it needs the set of pageserver APIs that the control
plane uses, and to present them under identical URLs, including prefix
(/v1).
## Summary of changes
- Add missing APIs:
- Tenant deletion
- Timeline deletion
- Node list (used in test now, later in tools)
- `/location_config` API (for migrating tenants into the sharding
service)
- Rework attachment service URLs:
- `/v1` prefix is used for pageserver-compatible APIs
- `/upcall/v1` prefix is used for APIs that are called by the pageserver
(re-attach and validate)
- `/debug/v1` prefix is used for endpoints that are for testing
- `/control/v1` prefix is used for new sharding service APIs that do not
mimic a pageserver API, such as registering and configuring nodes.
- Add test_sharding_service. The sharding service already had some
collateral coverage from its use in general tests, but this is the first
dedicated testing for it.
## Problem
Spun off from https://github.com/neondatabase/neon/pull/6394 -- this PR
is just the persistence parts and the changes that enable it to work
nicely
## Summary of changes
- Revert #6444 and #6450
- In neon_local, start a vanilla postgres instance for the attachment
service to use.
- Adopt `diesel` crate for database access in attachment service. This
uses raw SQL migrations as the source of truth for the schema, so it's a
soft dependency: we can switch libraries pretty easily.
- Rewrite persistence.rs to use postgres (via diesel) instead of JSON.
- Preserve JSON read+write at startup and shutdown: this enables using
the JSON format in compatibility tests, so that we don't have to commit
to our DB schema yet.
- In neon_local, run database creation + migrations before starting
attachment service
- Run the initial reconciliation in Service::spawn in the background, so
that the pageserver + attachment service don't get stuck waiting for
each other to start, when restarting both together in a test.
## Problem
The API for detaching things wasn't implement yet, but one could hit
this case indirectly from tests when using attach-hook, and find tenants
unexpectedly attached again because their policy remained Single.
## Summary of changes
Add PlacementPolicy::Detached, and:
- add the behavior for it in schedule()
- in tenant_migrate, refuse if the policy is detached
- automatically set this policy in attach-hook if the caller has
specified pageserver=null.
The pagebench integration PR (#6214) issues attachment requests in
parallel.
We observed corrupted attachments.json from time to time, especially in
the test cases with high tenant counts.
The atomic overwrite added in #6444 exposed the root cause cleanly:
the `.commit()` calls of two request handlers could interleave or
be reordered.
See also:
https://github.com/neondatabase/neon/pull/6444#issuecomment-1906392259
This PR makes changes to the `persistence` module to fix above race:
- mpsc queue for PendingWrites
- one writer task performs the writes in mpsc queue order
- request handlers that need to do writes do it using the
new `mutating_transaction` function.
`mutating_transaction`, while holding the lock, does the modifications,
serializes the post-modification state, and pushes that as a
`PendingWrite` into the mpsc queue.
It then release the lock and `await`s the completion of the write.
The writer tasks executes the `PendingWrites` in queue order.
Once the write has been executed, it wakes the writing tokio task.
The pagebench integration PR (#6214) is the first to SIGQUIT & then
restart attachment_service.
With many tenants (100), we have found frequent failures on restart in
the CI[^1].
[^1]:
[Allure](https://neon-github-public-dev.s3.amazonaws.com/reports/pr-6214/7615750160/index.html#suites/e26265675583c610f99af77084ae58f1/851ff709578c4452/)
```
2024-01-22T19:07:57.932021Z INFO request{method=POST path=/attach-hook request_id=2697503c-7b3e-4529-b8c1-d12ef912d3eb}: Request handled, status: 200 OK
2024-01-22T19:07:58.898213Z INFO Got SIGQUIT. Terminating
2024-01-22T19:08:02.176588Z INFO version: git-env:d56f31639356ed8e8ce832097f132f27ee19ac8a, launch_timestamp: 2024-01-22 19:08:02.174634554 UTC, build_tag build_tag-env:7615750160, state at /tmp/test_output/test_pageserver_max_throughput_getpage_at_latest_lsn[10-13-30]/repo/attachments.json, listening on 127.0.0.1:15048
thread 'main' panicked at /__w/neon/neon/control_plane/attachment_service/src/persistence.rs:95:17:
Failed to load state from '/tmp/test_output/test_pageserver_max_throughput_getpage_at_latest_lsn[10-13-30]/repo/attachments.json': trailing characters at line 1 column 8957 (maybe your .neon/ dir was written by an older version?)
stack backtrace:
0: rust_begin_unwind
at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/std/src/panicking.rs:645:5
1: core::panicking::panic_fmt
at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/panicking.rs:72:14
2: attachment_service::persistence::PersistentState::load_or_new::{{closure}}
at ./control_plane/attachment_service/src/persistence.rs:95:17
3: attachment_service::persistence::Persistence:🆕:{{closure}}
at ./control_plane/attachment_service/src/persistence.rs:103:56
4: attachment_service::main::{{closure}}
at ./control_plane/attachment_service/src/main.rs:69:61
5: tokio::runtime::park::CachedParkThread::block_on::{{closure}}
at ./.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/park.rs:282:63
6: tokio::runtime::coop::with_budget
at ./.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/coop.rs:107:5
7: tokio::runtime::coop::budget
at ./.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/coop.rs:73:5
8: tokio::runtime::park::CachedParkThread::block_on
at ./.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/park.rs:282:31
9: tokio::runtime::context::blocking::BlockingRegionGuard::block_on
at ./.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/context/blocking.rs:66:9
10: tokio::runtime::scheduler::multi_thread::MultiThread::block_on::{{closure}}
at ./.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/scheduler/multi_thread/mod.rs:87:13
11: tokio::runtime::context::runtime::enter_runtime
at ./.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/context/runtime.rs:65:16
12: tokio::runtime::scheduler::multi_thread::MultiThread::block_on
at ./.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/scheduler/multi_thread/mod.rs:86:9
13: tokio::runtime::runtime::Runtime::block_on
at ./.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/runtime.rs:350:50
14: attachment_service::main
at ./control_plane/attachment_service/src/main.rs:99:5
15: core::ops::function::FnOnce::call_once
at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
```
The attachment_service handles SIGQUIT by just exiting the process.
In theory, the SIGQUIT could come in while we're writing out the
`attachments.json`.
Now, in above log output, there's a 1 second gap between the last
request completing
and the SIGQUIT coming in. So, there must be some other issue.
But, let's have this change anyways, maybe it helps uncover the real
cause for the test failure.
Before this patch, we would update the `tenant_state.intent` in memory
but not persist the detachment to disk.
I noticed this in https://github.com/neondatabase/neon/pull/6214 where
we stop, then restart, the attachment service.
## 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>
