The PVF host is designed to avoid spawning tasks to minimize knowledge
of outer code. Using `async_std::task::spawn` (or Tokio's counterpart)
deemed unacceptable, `SpawnNamed` undesirable. Instead there is only one
task returned that is spawned by the candidate-validation subsystem.
The tasks from the sub-components are polled by that root task.
However, the way the tasks are bundled was incorrect. There was a giant
select that was polling those tasks. Particularly, that implies that as soon as
one of the arms of that select goes into await those sub-tasks stop
getting polled. This is a recipe for a deadlock which indeed happened
here.
Specifically, the deadlock happened during sending messages to the
execute queue by calling
[`send_execute`](https://github.com/paritytech/polkadot/blob/a68d9be35656dcd96e378fd9dd3d613af754d48a/node/core/pvf/src/host.rs#L601).
When the channel to the queue reaches the capacity, the control flow is
suspended until the queue handles those messages. Since this code is
essentially reached from [one of the select
arms](https://github.com/paritytech/polkadot/blob/a68d9be35656dcd96e378fd9dd3d613af754d48a/node/core/pvf/src/host.rs#L371),
the queue won't be given the control and thus no further progress can be
made.
This problem is solved by bundling the tasks one level higher instead,
by `selecting` over those long-running tasks.
We also stop treating returning from those long-running tasks as error
conditions, since that can happen during legit shutdown.
* Limit the number of PVF workers
In particular, limit the number of preparation workers to 1 (soft &
hard) and limit the number of execution workers to 2.
The reason why we are doing this is that it seems many workers launched
at the same time can cause problems. I.e. if there are more than 2
preparation workers, the time for preparation rises significantly to the
point of reaching the timeout.
This was mostly observed with parallel_compilation=true, so each worker
used `numcpu` threads and now we are looking to flip that parameter to
`false`. That said, we want to err on the safe side here and gradually
enable it later if our measurements show that we can do that safely.
* Adjust the test to accomodate the changed config value
* pvf: make execution timeout configurable
* guide: add timeouts to candidate validation params
* add timeouts to candidate validation messages
* fmt
* port backing to use the backing pvf timeout
* port approval-voting to use the execution timeout
* port dispute participation to use the correct timeout
* fmt
* address grumbles & test failure
* Use wasm-builder from git
This brings new features like compressed runtimes out of the box.
* chore: update wasm builder dep. from 3.0.0 to master
* Fix tests
* Update node/core/pvf/tests/it/main.rs
Co-authored-by: Sergei Shulepov <sergei@parity.io>
Co-authored-by: chevdor <chevdor@gmail.com>
Co-authored-by: Sergei Shulepov <sergei@parity.io>
* Implement PVF validation host
* WIP: Diener
* Increase the alloted compilation time
* Add more comments
* Minor clean up
* Apply suggestions from code review
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
* Fix pruning artifact removal
* Fix formatting and newlines
* Fix the thread pool
* Update node/core/pvf/src/executor_intf.rs
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
* Remove redundant test declaration
* Don't convert the path into an intermediate string
* Try to workaround the test failure
* Use the puppet_worker trick again
* Fix a blip
* Move `ensure_wasmtime_version` under the tests mod
* Add a macro for puppet_workers
* fix build for not real-overseer
* Rename the puppet worker for adder collator
* play it safe with the name of adder puppet worker
* Typo: triggered
* Add more comments
* Do not kill exec worker on every error
* Plumb Duration for timeouts
* typo: critical
* Add proofs
* Clean unused imports
* Revert "WIP: Diener"
This reverts commit b9f54e513366c7a6dfdd117ac19fbdc46b900b4d.
* Sync version of wasmtime
* Update cargo.lock
* Update Substrate
* Merge fixes still
* Update wasmtime version in test
* bastifmt
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
* Squash spaces
* Trailing new line for testing.rs
* Remove controversial code
* comment about biasing
* Fix suggestion
* Add comments
* make it more clear why unwrap_err
* tmpfile retry
* proper proofs for claim_idle
* Remove mutex from ValidationHost
* Add some more logging
* Extract exec timeout into a constant
* Add some clarifying logging
* Use blake2_256
* Clean up the merge
Specifically the leftovers after removing real-overseer
* Update parachain/test-parachains/adder/collator/Cargo.toml
Co-authored-by: Andronik Ordian <write@reusable.software>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Andronik Ordian <write@reusable.software>
Sergei Shulepov