Iterators are not always released

[penberg]

The Chisel.find_all() JavaScript function returns an iterator that is backed by a Rust QueryStreamResource object, which needs to be released at some point.

In JavaScript, you can implement a "return()" function for an iterator, which is called if the iterator is partially consumed.

For example, if you do the following (break out of iteration loop after first element):

let people = await Chisel.find_all("Person");
for await (let person of people) { 
  response += person.first_name;
  response += " ";
  break;
} 

The "return()" function is called to clean up. Our Chisel.find_all() iterator implements release() so this part is fine.

However, if you do:

let people = await Chisel.find_all("Person");

or even:

let people = await Chisel.find_all("Person");
people.next();

The "return()" function is not called, leaving the iterator alive. For us, this means that user can potentially leave QueryStream objects, for example, alive...

[espindola]

We should implement return(), and that is probably OK for version 0.1 or 0.2. The last line of defense is to use the GC, which can be used with:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/FinalizationRegistry

A good example is at https://github.com/denoland/deno/blob/main/ext/fetch/26_fetch.js#L95

[penberg]

@espindola We do implement return() already: https://github.com/chiselstrike/chiselstrike/blob/main/server/src/chisel.js#L39

The issue is about the corner cases it does not cover.

[espindola]

@espindola We do implement return() already: https://github.com/chiselstrike/chiselstrike/blob/main/server/src/chisel.js#L39

Nice, I missed that somehow. We should add a test to show that it is working :-)

[penberg]

We now explicitly iterate over all resources and close them in closeResources() after endpoint invocation so closing this issue.