Trait Stage
pub trait Stage<Provider>: Send + Sync {
// Required methods
fn id(&self) -> StageId;
fn execute(
&mut self,
provider: &Provider,
input: ExecInput,
) -> Result<ExecOutput, StageError>;
fn unwind(
&mut self,
provider: &Provider,
input: UnwindInput,
) -> Result<UnwindOutput, StageError>;
// Provided methods
fn poll_execute_ready(
&mut self,
_cx: &mut Context<'_>,
_input: ExecInput,
) -> Poll<Result<(), StageError>> { ... }
fn post_execute_commit(&mut self) -> Result<(), StageError> { ... }
fn post_unwind_commit(&mut self) -> Result<(), StageError> { ... }
}Expand description
A stage is a segmented part of the syncing process of the node.
Each stage takes care of a well-defined task, such as downloading headers or executing transactions, and persist their results to a database.
Stages must have a unique ID and implement a way to “roll forwards” (Stage::execute) and a way to “roll back” (Stage::unwind).
Stages are executed as part of a pipeline where they are executed serially.
Stages receive DBProvider.
Required Methods§
fn execute(
&mut self,
provider: &Provider,
input: ExecInput,
) -> Result<ExecOutput, StageError>
fn execute( &mut self, provider: &Provider, input: ExecInput, ) -> Result<ExecOutput, StageError>
Execute the stage. It is expected that the stage will write all necessary data to the database upon invoking this method.
fn unwind(
&mut self,
provider: &Provider,
input: UnwindInput,
) -> Result<UnwindOutput, StageError>
fn unwind( &mut self, provider: &Provider, input: UnwindInput, ) -> Result<UnwindOutput, StageError>
Unwind the stage.
Provided Methods§
fn poll_execute_ready(
&mut self,
_cx: &mut Context<'_>,
_input: ExecInput,
) -> Poll<Result<(), StageError>>
fn poll_execute_ready( &mut self, _cx: &mut Context<'_>, _input: ExecInput, ) -> Poll<Result<(), StageError>>
Returns Poll::Ready(Ok(())) when the stage is ready to execute the given range.
This method is heavily inspired by tower’s Service trait.
Any asynchronous tasks or communication should be handled in poll_execute_ready, e.g.
moving downloaded items from downloaders to an internal buffer in the stage.
If the stage has any pending external state, then Poll::Pending is returned.
If Poll::Ready(Err(_)) is returned, the stage may not be able to execute anymore
depending on the specific error. In that case, an unwind must be issued instead.
Once Poll::Ready(Ok(())) is returned, the stage may be executed once using execute.
Until the stage has been executed, repeated calls to poll_execute_ready must return either
Poll::Ready(Ok(())) or Poll::Ready(Err(_)).
Note that poll_execute_ready may reserve shared resources that are consumed in a
subsequent call of execute, e.g. internal buffers. It is crucial for implementations
to not assume that execute will always be invoked and to ensure that those resources
are appropriately released if the stage is dropped before execute is called.
For the same reason, it is also important that any shared resources do not exhibit
unbounded growth on repeated calls to poll_execute_ready.
Unwinds may happen without consulting poll_execute_ready first.
fn post_execute_commit(&mut self) -> Result<(), StageError>
fn post_execute_commit(&mut self) -> Result<(), StageError>
Post execution commit hook.
This is called after the stage has been executed and the data has been committed by the
provider. The stage may want to pass some data from Self::execute via the internal
field.
fn post_unwind_commit(&mut self) -> Result<(), StageError>
fn post_unwind_commit(&mut self) -> Result<(), StageError>
Post unwind commit hook.
This is called after the stage has been unwound and the data has been committed by the
provider. The stage may want to pass some data from Self::unwind via the internal
field.