fix(test suite) virtual_file_io_engine and get_vectored_impl patametrization doesn't work (#7113)

# Problem

While investigating #7124, I noticed that the benchmark was always using
the `DEFAULT_*` `virtual_file_io_engine` , i.e., `tokio-epoll-uring` as
of https://github.com/neondatabase/neon/pull/7077.

The fundamental problem is that the `control_plane` code has its own
view of `PageServerConfig`, which, I believe, will always be a subset of
the real pageserver's `pageserver/src/config.rs`.

For the `virtual_file_io_engine` and `get_vectored_impl` parametrization
of the test suite, we were constructing a dict on the Python side that
contained these parameters, then handed it to
`control_plane::PageServerConfig`'s derived `serde::Deserialize`.
The default in serde is to ignore unknown fields, so, the Deserialize
impl silently ignored the fields.
In consequence, the fields weren't propagated to the `pageserver --init`
call, and the tests ended up using the
`pageserver/src/config.rs::DEFAULT_` values for the respective options
all the time.

Tests that explicitly used overrides in `env.pageserver.start()` and
similar were not affected by this.

But, it means that all the test suite runs where with parametrization
didn't properly exercise the code path.

# Changes

- use `serde(deny_unknown_fields)` to expose the problem  
- With this change, the Python tests that override
`virtual_file_io_engine` and
`get_vectored_impl` fail on `pageserver --init`, exposing the problem.
- use destructuring to uncover the issue in the future
- fix the issue by adding the missing fields to the `control_plane`
crate's `PageServerConf`
- A better solution would be for control plane to re-use a struct
provided
    by the pageserver crate, so that everything is in one place in
    `pageserver/src/config.rs`, but, our config parsing code is (almost)
    beyond repair anyways.
- fix the `pageserver_virtual_file_io_engine` to be responsive to the
env var
  - => required to make parametrization work in benchmarks

# Testing

Before merging this PR, I re-ran the regression tests & CI with the full
matrix of `virtual_file_io_engine` and `tokio-epoll-uring`, see
9c7ea364e0

control_plane/src/local_env.rs

@@ -114,7 +114,7 @@ impl NeonBroker {
 }
 
 #[derive(Serialize, Deserialize, PartialEq, Eq, Clone, Debug)]
-#[serde(default)]
+#[serde(default, deny_unknown_fields)]
 pub struct PageServerConf {
     // node id
     pub id: NodeId,
@@ -126,6 +126,9 @@ pub struct PageServerConf {
     // auth type used for the PG and HTTP ports
     pub pg_auth_type: AuthType,
     pub http_auth_type: AuthType,
+
+    pub(crate) virtual_file_io_engine: String,
+    pub(crate) get_vectored_impl: String,
 }
 
 impl Default for PageServerConf {
@@ -136,6 +139,9 @@ impl Default for PageServerConf {
             listen_http_addr: String::new(),
             pg_auth_type: AuthType::Trust,
             http_auth_type: AuthType::Trust,
+            // FIXME: use the ones exposed by pageserver crate
+            virtual_file_io_engine: "tokio-epoll-uring".to_owned(),
+            get_vectored_impl: "sequential".to_owned(),
         }
     }
 }

control_plane/src/pageserver.rs

@@ -78,18 +78,31 @@ impl PageServerNode {
     ///
     /// These all end up on the command line of the `pageserver` binary.
     fn neon_local_overrides(&self, cli_overrides: &[&str]) -> Vec<String> {
-        let id = format!("id={}", self.conf.id);
         // FIXME: the paths should be shell-escaped to handle paths with spaces, quotas etc.
         let pg_distrib_dir_param = format!(
             "pg_distrib_dir='{}'",
             self.env.pg_distrib_dir_raw().display()
         );
 
-        let http_auth_type_param = format!("http_auth_type='{}'", self.conf.http_auth_type);
-        let listen_http_addr_param = format!("listen_http_addr='{}'", self.conf.listen_http_addr);
+        let PageServerConf {
+            id,
+            listen_pg_addr,
+            listen_http_addr,
+            pg_auth_type,
+            http_auth_type,
+            virtual_file_io_engine,
+            get_vectored_impl,
+        } = &self.conf;
 
-        let pg_auth_type_param = format!("pg_auth_type='{}'", self.conf.pg_auth_type);
-        let listen_pg_addr_param = format!("listen_pg_addr='{}'", self.conf.listen_pg_addr);
+        let id = format!("id={}", id);
+
+        let http_auth_type_param = format!("http_auth_type='{}'", http_auth_type);
+        let listen_http_addr_param = format!("listen_http_addr='{}'", listen_http_addr);
+
+        let pg_auth_type_param = format!("pg_auth_type='{}'", pg_auth_type);
+        let listen_pg_addr_param = format!("listen_pg_addr='{}'", listen_pg_addr);
+        let virtual_file_io_engine = format!("virtual_file_io_engine='{virtual_file_io_engine}'");
+        let get_vectored_impl = format!("get_vectored_impl='{get_vectored_impl}'");
 
         let broker_endpoint_param = format!("broker_endpoint='{}'", self.env.broker.client_url());
 
@@ -101,6 +114,8 @@ impl PageServerNode {
             listen_http_addr_param,
             listen_pg_addr_param,
             broker_endpoint_param,
+            virtual_file_io_engine,
+            get_vectored_impl,
         ];
 
         if let Some(control_plane_api) = &self.env.control_plane_api {
@@ -111,7 +126,7 @@ impl PageServerNode {
 
             // Storage controller uses the same auth as pageserver: if JWT is enabled
             // for us, we will also need it to talk to them.
-            if matches!(self.conf.http_auth_type, AuthType::NeonJWT) {
+            if matches!(http_auth_type, AuthType::NeonJWT) {
                 let jwt_token = self
                     .env
                     .generate_auth_token(&Claims::new(None, Scope::GenerationsApi))
@@ -129,8 +144,7 @@ impl PageServerNode {
             ));
         }
 
-        if self.conf.http_auth_type != AuthType::Trust || self.conf.pg_auth_type != AuthType::Trust
-        {
+        if *http_auth_type != AuthType::Trust || *pg_auth_type != AuthType::Trust {
             // Keys are generated in the toplevel repo dir, pageservers' workdirs
             // are one level below that, so refer to keys with ../
             overrides.push("auth_validation_public_key_path='../auth_public_key.pem'".to_owned());

test_runner/fixtures/parametrize.py

@@ -28,7 +28,7 @@ def platform() -> Optional[str]:
 
 @pytest.fixture(scope="function", autouse=True)
 def pageserver_virtual_file_io_engine() -> Optional[str]:
-    return None
+    return os.getenv("PAGESERVER_VIRTUAL_FILE_IO_ENGINE")
 
 
 def pytest_generate_tests(metafunc: Metafunc):