harmos-runtime 0.1.6

Harmos runtime: managed state, undo, recovery, background work and typed streams.
Documentation 
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/* ***
 *
 * Harmos
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * ***
 */

/* === Modules === */

/* === Re-Exports === */

pub use crate::config::DecodeSettings;

/* === Imports === */

// Standard Library Imports
use std::{marker::PhantomData, sync::Arc};

// Third Party Imports
use bytes::Buf;
use tokio::sync::Semaphore;
use tonic::{Status, codec::DecodeBuf};

// Local Imports
use super::codec::Wire;
use crate::{MemorySize, operations::StreamItem};
use harmos_sdk::grpc::DecodeInput;

/* === Constants === */

/* === Macros === */

/* === Type Aliases === */

/* === Structs === */

pub struct Decoder<W, T> {
    settings: DecodeSettings,
    budget: Arc<Semaphore>,
    failure: Option<Status>,
    message: PhantomData<fn() -> (W, T)>,
}

/* === Enums === */

/* === Traits === */

/* === Implementations === */

impl DecodeSettings {
    pub(super) fn validate(&self) -> Result<(), Status> {
        if self.message_bytes.get() > u32::MAX as usize
            || self.retained_bytes.get() > u32::MAX as usize
            || self.retained_bytes.get() > Semaphore::MAX_PERMITS
        {
            return Err(Status::invalid_argument("gRPC decode limit exceeds supported capacity"));
        }
        Ok(())
    }
}

impl<W: Wire<T>, T: MemorySize + 'static> Decoder<W, T> {
    pub(super) fn message_limit(&self) -> usize {
        self.settings.message_bytes.get()
    }

    pub(super) fn fork(&self) -> Self {
        Self { settings: self.settings, budget: self.budget.clone(), failure: None, message: PhantomData }
    }

    pub fn new(settings: DecodeSettings) -> Result<Self, Status> {
        settings.validate()?;
        Ok(Self { settings, budget: Arc::new(Semaphore::new(settings.retained_bytes.get())), failure: None, message: PhantomData })
    }

    pub fn request<B>(self, body: B) -> tonic::Streaming<StreamItem<T>>
    where
        B: tonic::codegen::Body + Send + 'static,
        B::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
    {
        let limit = self.settings.message_bytes.get();
        tonic::Streaming::new_request(self, body, None, Some(limit))
    }

    fn message(&mut self, encoded: &[u8]) -> Result<StreamItem<T>, Status> {
        if let Some(error) = &self.failure {
            return Err(error.clone());
        }
        let result = self.decode_message(encoded);
        if let Err(error) = &result {
            self.failure = Some(error.clone());
        }
        result
    }

    #[tracing::instrument(target = "harmos::grpc", name = "grpc.decode", level = "trace", skip_all, fields(wire_bytes = encoded.len()))]
    fn decode_message(&self, encoded: &[u8]) -> Result<StreamItem<T>, Status> {
        if encoded.len() > self.settings.message_bytes.get() {
            return Err(Status::resource_exhausted("gRPC message exceeds wire ceiling"));
        }
        let (value, claim) = W::decode_admitted(DecodeInput::new(encoded), |bytes| {
            let span = tracing::trace_span!(target: "harmos::grpc", "grpc.decode.admit", decoded_bytes = bytes);
            let _entered = span.enter();
            let bytes = bytes.max(std::mem::size_of::<T>()).max(1);
            if bytes > self.settings.retained_bytes.get() {
                return Err(Status::resource_exhausted("gRPC decoded message exceeds byte ceiling"));
            }
            self.budget
                .clone()
                .try_acquire_many_owned(bytes as u32)
                .map_err(|_| Status::resource_exhausted("gRPC decoded items retain byte capacity"))
        })?;
        StreamItem::charged(value, claim).map_err(|error| Status::internal(error.to_string()))
    }
}

impl<W: Wire<T>, T: MemorySize + 'static> tonic::codec::Decoder for Decoder<W, T> {
    type Item = StreamItem<T>;
    type Error = Status;

    fn decode(&mut self, source: &mut DecodeBuf<'_>) -> Result<Option<Self::Item>, Status> {
        let length = source.remaining();
        let value = self.message(source.chunk())?;
        source.advance(length);
        Ok(Some(value))
    }
}

/* === Public Functions === */

/* === Private Functions === */

/* === Tests === */