What kind of change does this PR introduce?

Feature

Description

This PR prevents the supervisor from switching the user worker to the early drop state if there is a microtask (Promise) queued in the user worker.

Note that this does not track all promises, only those marked for tracking at runtime by extra typing, also, this support only works in the per_worker policy.

Type declaration

// its definition is found in `types/global.d.ts` in this PR.
declare function markAsBackgroundTask<T>(promise: Promise<T>): Promise<T>;

Usage

markAsBackgroundTask(new Promise(...));

Side note

This behavior will interact with the graceful shutdown.

In other words, even if runtime is during the graceful shutdown state, if there are background tasks left in the user worker, the supervisor will wait for them to be completed unless it is forced to terminate by the resource limit.

The timeout for the graceful shutdown specified by the flag in cli is respected, so the maximum time that the supervisor can wait for background tasks is limited to the graceful shutdown timeout. (For each user worker)

Future note

Today, I have made it so that this can only be done by extra typing, which is due to the limitation that we cannot get consistent promise counts that can determine whether all background tasks created by core scripts or our deno ext implementation have been resolved.

Most of these inconsistencies seem to occur in our HTTP request listener implementation (not sure), and if this is resolved, extra typing may not be necessary, so it should be reviewed later.