Proper logging for invalid feeds

[c3ho]

What would you like to be added:
PR for #462 should land this week, the PR invalidates feeds and provides a reason. Problem is the reason is not working properly and will be outside of the scope of that PR. You can find the code responsible for invalidating feeds inside src/backend/index.js

Why would you like this to be added:
At the moment all feeds that error will have a value of unknown reason making it hard to inform users of what is wrong.

[chrispinkney]

This could be something that might want to be evaluated after PR #1828 lands.

[humphd]

Let's fix this. @manekenpix and I are trying to determine why our good friend @raygervais's blog feed constantly gets invalidated--it's not because we don't love his writing, we do!

We need to do a few things to make this debuggable:

1. When a feed parsing job fails we throw an error.
2. This error will get passed to the queue's failed event as the second arg, see docs, which says, "Errors will be passed as a second argument to the "failed" event)".
3. When that happens, we invalidate a feed here, but notice that we don't use the second arg error. This is a bug that needs to be fixed.
4. We should be passing that error on to the invalidate code here. Then we can update

   telescope/src/backend/index.js

   Lines 53 to 54 in 9582a0a

   	await feed.setInvalid('unknown reason');
   	logger.info(`Invalidating feed ${feed.url} for the following reason: ${'unknown reason'}`);

   to use the error, and store it in the database (e.g., we can JSON stringify it if we have to, or maybe the error.message is enough?).

I'm going to file another issue in order to allow us to see invalid feeds, and get the reason.

[joshuali7536]

Hi, I would like to take on this issue.

[humphd]

@joshuali7536 awesome, thank you! It's all yours.

[joshuali7536]

Hi @humphd,

So I took a look at the project trying to get a grasp of what things were doing to try and follow along with your steps. I'm not really sure if I'm doing this correctly. Could you take a look at this commit 5e1751e to see if I'm understanding properly?

[humphd]

@joshuali7536 yes, you're close:

  // TODO: we need to bubble up the reason for the failure
  await feed.setInvalid('unknown reason');

You need to update this bit too. Remove the TODO, and use error or error.message instead of 'unknown reason' so we put that in the db.