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Less anxiety-inducing return values #771

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merged 2 commits into from
Sep 30, 2024
Merged

Less anxiety-inducing return values #771

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81de422
Less anxiety-inducing `Vm::{get, state_watcher}`
hawkw Sep 30, 2024
ce6bb51
Make PUT /instance/state 503 when waiting to init
hawkw Sep 30, 2024
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34 changes: 7 additions & 27 deletions bin/propolis-server/src/lib/server.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -343,14 +343,7 @@ async fn instance_get_common(
rqctx: &RequestContext<Arc<DropshotEndpointContext>>,
) -> Result<api::InstanceSpecGetResponse, HttpError> {
let ctx = rqctx.context();
ctx.vm.get().await.map_err(|e| match e {
VmError::NotCreated | VmError::WaitingToInitialize => {
not_created_error()
}
_ => HttpError::for_internal_error(format!(
"unexpected error from VM controller: {e}"
)),
})
ctx.vm.get().await.ok_or_else(not_created_error)
}

#[endpoint {
Expand Down Expand Up @@ -393,14 +386,7 @@ async fn instance_state_monitor(
let ctx = rqctx.context();
let gen = request.into_inner().gen;
let mut state_watcher =
ctx.vm.state_watcher().await.map_err(|e| match e {
VmError::NotCreated | VmError::WaitingToInitialize => {
not_created_error()
}
_ => HttpError::for_internal_error(format!(
"unexpected error from VM controller: {e}"
)),
})?;
ctx.vm.state_watcher().await.ok_or_else(not_created_error)?;

loop {
let last = state_watcher.borrow().clone();
Expand Down Expand Up @@ -440,9 +426,10 @@ async fn instance_state_put(
.put_state(requested_state)
.map(|_| HttpResponseUpdatedNoContent {})
.map_err(|e| match e {
VmError::NotCreated | VmError::WaitingToInitialize => {
not_created_error()
}
VmError::WaitingToInitialize => HttpError::for_unavail(
None,
"instance is still initializing".to_string(),
),
VmError::ForbiddenStateChange(reason) => HttpError::for_status(
Some(format!("instance state change not allowed: {}", reason)),
hyper::StatusCode::FORBIDDEN,
Expand Down Expand Up @@ -614,14 +601,7 @@ async fn instance_migrate_status(
.state_watcher()
.await
.map(|rx| HttpResponseOk(rx.borrow().migration.clone()))
.map_err(|e| match e {
VmError::NotCreated | VmError::WaitingToInitialize => {
not_created_error()
}
_ => HttpError::for_internal_error(format!(
"unexpected error from VM controller: {e}"
)),
})
.ok_or_else(not_created_error)
}

/// Issues a snapshot request to a crucible backend.
Expand Down
33 changes: 20 additions & 13 deletions bin/propolis-server/src/lib/vm/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -165,9 +165,6 @@ pub(crate) enum VmError {
#[error("VM operation result channel unexpectedly closed")]
ResultChannelClosed,

#[error("VM not created")]
NotCreated,

#[error("VM is currently initializing")]
WaitingToInitialize,

Expand Down Expand Up @@ -317,18 +314,23 @@ impl Vm {

/// Returns the state, properties, and instance spec for the instance most
/// recently wrapped by this `Vm`.
pub(super) async fn get(&self) -> Result<InstanceSpecGetResponse, VmError> {
///
/// # Returns
///
/// - `Some` if the VM has been created.
/// - `None` if no VM has ever been created.
pub(super) async fn get(&self) -> Option<InstanceSpecGetResponse> {
let guard = self.inner.read().await;
match &guard.state {
// If no VM has ever been created, there's nothing to get.
VmState::NoVm => Err(VmError::NotCreated),
VmState::NoVm => None,

// If the VM is active, pull the required data out of its objects.
VmState::Active(vm) => {
let spec =
vm.objects().lock_shared().await.instance_spec().clone();
let state = vm.external_state_rx.borrow().clone();
Ok(InstanceSpecGetResponse {
Some(InstanceSpecGetResponse {
properties: vm.properties.clone(),
spec: VersionedInstanceSpec::V0(spec.into()),
state: state.state,
Expand All @@ -340,7 +342,7 @@ impl Vm {
// machine.
VmState::WaitingForInit(vm)
| VmState::Rundown(vm)
| VmState::RundownComplete(vm) => Ok(InstanceSpecGetResponse {
| VmState::RundownComplete(vm) => Some(InstanceSpecGetResponse {
properties: vm.properties.clone(),
state: vm.external_state_rx.borrow().state,
spec: VersionedInstanceSpec::V0(vm.spec.clone().into()),
Expand All @@ -350,16 +352,21 @@ impl Vm {

/// Yields a handle to the most recent instance state receiver wrapped by
/// this `Vm`.
pub(super) async fn state_watcher(
&self,
) -> Result<InstanceStateRx, VmError> {
///
/// # Returns
///
/// - `Some` if the VM has been created.
/// - `None` if no VM has ever been created.
pub(super) async fn state_watcher(&self) -> Option<InstanceStateRx> {
let guard = self.inner.read().await;
match &guard.state {
VmState::NoVm => Err(VmError::NotCreated),
VmState::Active(vm) => Ok(vm.external_state_rx.clone()),
VmState::NoVm => None,
VmState::Active(vm) => Some(vm.external_state_rx.clone()),
VmState::WaitingForInit(vm)
| VmState::Rundown(vm)
| VmState::RundownComplete(vm) => Ok(vm.external_state_rx.clone()),
| VmState::RundownComplete(vm) => {
Some(vm.external_state_rx.clone())
}
}
}

Expand Down
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