fix(elasticsearch sink): Wrap provider call with a tokio runtime

[LucioFranco]

This change fixes the usage of rusoto's credentials
the issue arises when a user wants to fetch credentials
via the network with the InstanceMetadataProvider type.
This type sets a timer that depends on the tokio-timer
being set. Previously, this sink used the wait combinator
that does not wrap the future with a tokio timer. Thus,
when a user tried to run this it would fail out because
the timer was not set. This changes the code to allow
the credentials fetch future to be wrapped in a tokio
timer.

Closes #1093

Signed-off-by: Lucio Franco luciofranco14@gmail.com

[lukesteensen]

Can you explain why this will close the linked issue? It seems like this will just allow a timeout to happen, not a previously failing call to succeed.

[LucioFranco]

@lukesteensen This closes the issue because when InstanceMetadataProvider attempts to fetch the credentials it sets up a timer to time out the http request. This timer is not wrapped in any runtime and thus bails out because there is no tokio timer set in the TLS. I was able to reproduce the error on an ec2 instance with an IAM role and once wrapping the future and using Runtime::block_on I was able to fetch the credentials. What I noticed was that when calling the specific provider manually I was able to get the tokio error out of it but it seems that rusoto hides this and just spits out a generic error when using the ChainProvider.

This type of issue with the missing timer is a very common one so its just the fact that we were using Future::wait which is an issue if you're trying to use any of the tokio items.

[lukesteensen]

I was able to reproduce the error on an ec2 instance with an IAM role and once wrapping the future and using Runtime::block_on I was able to fetch the credentials.

Lead with this next time 😄

[lukesteensen]

I'm pretty sure we should just swap out wait() for sync() here.

[LucioFranco]

Not available with the https://docs.rs/rusoto_credential/0.41.1/rusoto_credential/trait.ProvideAwsCredentials.html trait.

[lukesteensen]

Oh. Weird that they're not using RusotoFuture. Carry on.