Stack overflow on a recursive query

[BrynCooke]

Discussed in #4426

The following query will cause the router to core dump:

query Recursion {
  topProducts {
    reviews {
      author {
        ...UserFragment @defer
      }
    }
  }
}

fragment UserFragment on User {
  reviews {
      author {
        ...UserFragment @defer
      }
  }
}

Run this against the starstuff graph to reproduce.

[BrynCooke]

Stack trace:

apollo_router::spec::query::subselections::collect_from_selection_set subselections.rs:242
apollo_router::spec::query::subselections::collect_from_selection_set subselections.rs:242
apollo_router::spec::query::subselections::collect_from_selection_set subselections.rs:242
apollo_router::spec::query::subselections::collect_subselections subselections.rs:127
apollo_router::query_planner::bridge_query_planner::BridgeQueryPlanner::parse_selections::{{closure}} bridge_query_planner.rs:304
apollo_router::query_planner::bridge_query_planner::BridgeQueryPlanner::get::{{closure}} bridge_query_planner.rs:644
<apollo_router::query_planner::bridge_query_planner::BridgeQueryPlanner as tower_service::Service<apollo_router::services::query_planner::Request>>::call::{{closure}} bridge_query_planner.rs:566
<core::pin::Pin<P> as core::future::future::Future>::poll future.rs:125
apollo_router::query_planner::caching_query_planner::CachingQueryPlanner<T>::plan::{{closure}}::{{closure}} caching_query_planner.rs:353
<tracing::instrument::Instrumented<T> as core::future::future::Future>::poll instrument.rs:272
<core::pin::Pin<P> as core::future::future::Future>::poll future.rs:125
tokio::runtime::task::core::Core<T,S>::poll::{{closure}} core.rs:328
[Inlined] tokio::loom::std::unsafe_cell::UnsafeCell<T>::with_mut unsafe_cell.rs:16
tokio::runtime::task::core::Core<T,S>::poll core.rs:317
tokio::runtime::task::harness::poll_future::{{closure}} harness.rs:485
<core::panic::unwind_safe::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once unwind_safe.rs:271
std::panicking::try::do_call panicking.rs:504
__rust_try 0x000055a7d9dd4a1b
std::panicking::try panicking.rs:468
std::panic::catch_unwind panic.rs:142
tokio::runtime::task::harness::poll_future harness.rs:473
tokio::runtime::task::harness::Harness<T,S>::poll_inner harness.rs:208
tokio::runtime::task::harness::Harness<T,S>::poll harness.rs:153
tokio::runtime::task::raw::poll raw.rs:271
tokio::runtime::task::raw::RawTask::poll raw.rs:201
tokio::runtime::task::LocalNotified<S>::run mod.rs:416
tokio::runtime::scheduler::multi_thread::worker::Context::run_task::{{closure}} worker.rs:639
[Inlined] tokio::runtime::coop::with_budget coop.rs:107
[Inlined] tokio::runtime::coop::budget coop.rs:73
tokio::runtime::scheduler::multi_thread::worker::Context::run_task worker.rs:575
tokio::runtime::scheduler::multi_thread::worker::Context::run worker.rs:526
tokio::runtime::scheduler::multi_thread::worker::run::{{closure}}::{{closure}} worker.rs:491
tokio::runtime::context::scoped::Scoped<T>::set scoped.rs:40
tokio::runtime::context::set_scheduler::{{closure}} context.rs:176
std::thread::local::LocalKey<T>::try_with local.rs:270
std::thread::local::LocalKey<T>::with local.rs:246
tokio::runtime::context::set_scheduler context.rs:176
tokio::runtime::scheduler::multi_thread::worker::run::{{closure}} worker.rs:486
tokio::runtime::context::runtime::enter_runtime runtime.rs:65
tokio::runtime::scheduler::multi_thread::worker::run worker.rs:478
tokio::runtime::scheduler::multi_thread::worker::Launch::launch::{{closure}} worker.rs:447
<tokio::runtime::blocking::task::BlockingTask<T> as core::future::future::Future>::poll task.rs:42
tokio::runtime::task::core::Core<T,S>::poll::{{closure}} core.rs:328
[Inlined] tokio::loom::std::unsafe_cell::UnsafeCell<T>::with_mut unsafe_cell.rs:16
tokio::runtime::task::core::Core<T,S>::poll core.rs:317
tokio::runtime::task::harness::poll_future::{{closure}} harness.rs:485
<core::panic::unwind_safe::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once unwind_safe.rs:271
std::panicking::try::do_call panicking.rs:504
__rust_try 0x000055a7df2c1e9b
std::panicking::try panicking.rs:468
std::panic::catch_unwind panic.rs:142
tokio::runtime::task::harness::poll_future harness.rs:473
tokio::runtime::task::harness::Harness<T,S>::poll_inner harness.rs:208
tokio::runtime::task::harness::Harness<T,S>::poll harness.rs:153
tokio::runtime::task::raw::poll raw.rs:271
tokio::runtime::task::raw::RawTask::poll raw.rs:201
tokio::runtime::task::UnownedTask<S>::run mod.rs:453
tokio::runtime::blocking::pool::Task::run pool.rs:159
tokio::runtime::blocking::pool::Inner::run pool.rs:513
tokio::runtime::blocking::pool::Spawner::spawn_thread::{{closure}} pool.rs:471
std::sys_common::backtrace::__rust_begin_short_backtrace backtrace.rs:154
std::thread::Builder::spawn_unchecked_::{{closure}}::{{closure}} mod.rs:529
<core::panic::unwind_safe::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once unwind_safe.rs:271
std::panicking::try::do_call panicking.rs:504
__rust_try 0x000055a7df2c1e9b
std::panicking::try panicking.rs:468
[Inlined] std::panic::catch_unwind panic.rs:142
std::thread::Builder::spawn_unchecked_::{{closure}} mod.rs:528
core::ops::function::FnOnce::call_once{{vtable.shim}} function.rs:250
[Inlined] <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once boxed.rs:2007
[Inlined] <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once boxed.rs:2007
std::sys::unix::thread::Thread::new::thread_start thread.rs:108
start_thread 0x00007f7dc7894ac3
__clone3 0x00007f7dc7926660

[BrynCooke]

This will be fixed when validation via apollo-rs is switched on by default later this week.