Callbacks don't run if they don't have the right arity

[branliu0]

If the arity of the callback is not right, then an ArgumentError: wrong number of arguments gets thrown, but instance_exec swallows all exceptions so basically the effect is that the callback doesn't get run.

[lantins]

Are you able to look at this issue before we look at #129

[branliu0]

Sure thing. So what do you think would be a good solution? Here are some thoughts:

1. We could do an arity check when the callback is registered, and throw an exception if the arity is 0, since that would probably catch most cases. I think it gets a bit more complicated if we want to have a tighter guarantee on the correct arity (by matching the arity of self.perform with the callback)
2. We can print a warning for all the exceptions we get, instead of just silently suppressing them

[jzaleski]

I think that the second approach might actually be favorable. Unless of course there is a reliable/easy way to do the arity check up front, during the registration process. If we dump something into the Resque log it will likely give enough context to the person{,s} trouble-shooting so that they can remedy the issue on their side, we can, and should, only guard against so much. What do you think @lantins?

[lantins]

We need to let things blow up, as early as possible by letting the exceptions bubble through.

I guess the question is, are callbacks 'best effort' or 'job fails if callback fails'?

[jzaleski]

My concern here was allowing callbacks to blow up within the internals of
resque-retry. I am all for blowin up early if we can do it with 100%
confidence. Perhaps we can enforce the call signature for these rather than
letting them be varargs? If neither seems feasible I think the best
solution here is to make it a best attempt and log when there is a failure.
On Nov 3, 2015 6:24 PM, "Luke Antins" notifications@github.com wrote:

We need to let things blow up, as early as possible by letting the
exceptions bubble through.

I guess the question is, are callbacks 'best effort' or 'job fails if
callback fails'?

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#127 (comment)
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[lantins]

Best attempts to log the failure is a good place to start.

[jzaleski]

Excellent. Glad we're in agreement.

[lantins]

👍