Potential memory leak in services/api/index.ts

[jasnell]

In the connected function in https://github.com/covidgreen/covid-green-app/blob/current/services/api/index.ts#L47-L60 https://github.com/covidgreen/covid-green-app/blob/current/src/services/api/index.ts#L46-L59, when retry is true and the network is not available, the function recursively awaits on itself. This sets up a memory leak when the network is unavailable for a protracted period of time (memory leak in that the Promise chain will grow indefinitely while waiting for the network to become available.

The code in question is copied below:

const connected = async (retry = false): Promise<boolean> => {
  const networkState = await NetInfo.fetch();
  if (networkState.isInternetReachable && networkState.isConnected) {
    return true;
  }

  if (retry) {
    throw new Error('Network Unavailable');
  } else {
    await new Promise((r) => setTimeout(r, 1000));
    await connected(true);
    return true;
  }
};

This should be refactored to avoid the recursion.

[amis-shokoohi]

I don't know if I'm missing something but
when retry is true and networkState checks are falsy, the function throws an error but
when it's false, the function is gonna call itself with true arg, which again ends up throwing an error if network is unavailable.

[amis-shokoohi]

Uh everything's changed 😳
the link to index returns 404

[jasnell]

Updated the link. The source was restructured into the src directory.

[jasnell]

And yes, I saw the retry gating there... still better to avoid the recursion, as it's simply not necessary.

const checkNetworkState = async () : Promise<boolean> => {
  const networkState = await NetInfo.fetch();
  return networkState.isInternetReachable && networkState.isConnected;
};

const connected = async () : Promise<boolean> => {
  if (!(await checkNetworkState())) {
    await new Promise(r => setTimeout(r, 1000));
    if (!(await checkNetworkState()))
      throw new Error('Network unavailable');
  }
  return true;
};

[amis-shokoohi]

Thank you
This implementation is much better.
May I send your code as a PR?

[jasnell]

Certainly!