Commit bd798764 authored by Nick Mathewson's avatar Nick Mathewson 🦀
Browse files

circmgr: limit circuit attempts when launch_parallelism > 1. 

Previously, if we had launch_parallelism > 1, and we were willing to
retry building a circuit max_retries times, then we'd launch up to
max_retries * launch_parallelism circuits before giving up.  Ouch!

With this patch, we try to keep the total number of circuits
planned and attempted to the actual max_retries limit.

Part of #329; found with arti-testing.
parent 6e8c982a

crates/tor-circmgr/src/mgr.rs

+21 −1
Original line number Diff line number Diff line
@@ -742,14 +742,34 @@ impl<B: AbstractCircBuilder + 'static, R: Runtime> AbstractCircMgr<B, R> { 
        usage: &<B::Spec as AbstractSpec>::Usage,

        dir: DirInfo<'_>,

    ) -> Result<B::Circ> {

        /// Return CEIL(a/b).

        ///

        /// Requires that a+b is less than usize::MAX.

        ///

        /// This can be removed once usize::div_ceil is stable.

        ///

        /// # Panics

        ///

        /// Panics if b is 0.

        fn div_ceil(a: usize, b: usize) -> usize {

            (a + b - 1) / b

        }



        let circuit_timing = self.circuit_timing();

        let wait_for_circ = circuit_timing.request_timeout;

        let timeout_at = self.runtime.now() + wait_for_circ;

        let max_tries = circuit_timing.request_max_retries;

        // We compute the maximum number of times through this loop by dividing

        // the maximum number of circuits to attempt by the number that will be

        // launched in parallel for each iteration.

        let max_iterations = div_ceil(

            max_tries as usize,

            std::cmp::max(1, self.builder.launch_parallelism(usage)),

        );



        let mut retry_err = RetryError::<Box<Error>>::in_attempt_to("find or build a circuit");



        for n in 1..(max_tries + 1) {

        for n in 1..(max_iterations + 1) {

            // How much time is remaining?

            let remaining = match timeout_at.checked_duration_since(self.runtime.now()) {

                None => {