Defering disk writes is still probably a good idea, but unfortunately
there are some tradeoffs with rust's async story that make it non-ideal.
Ideally we would defer writes, but have a Drop impl on DiskStorage that
waited for all the deferred writes to complete. While it's trival to
create a future that waits for all deferred writes to finish it's not
currently possible to write a Drop impl that waits on a future.
It would be possible to write an inherent async fn that takes self by
value and waits for the writes, but that method would need to be
propogated up all the way to users of the library and they would need to
remember to invoke it before dropping the Authenticator.
Remove expires_in in favor of only having an expires_at DateTime field.
Add a from_json method that deserializes from json data into the
appropriate Token (or Error) and use that consistently throughout the
codebase.
DefaultHasher is not documented as being consistent. It's best to not
trust that the resulting hash value is consistent even across different
executions of the same binary and even more so across different
versions.
These appear to only be used by examples in the old/ directory which has
not compiled for a long time. Not sure why the contents of that
directory are still around.
No more need to macro_use serde. Order the imports consistently (albeit
somewhat arbitrary), starting with items from this crate, followed by
std, followed by external crates.
The current code uses standard blocking i/o operations (std::fs::*) this
is problematic as it would block the entire futures executor waiting for
i/o.
This change is a major refactoring to make the token storage mechansim
async i/o friendly. The first major decision was to abandon the GetToken
trait. The trait is only implemented internally and there was no
mechanism for users to provide their own, but async fn's are not
currently supported in trait impls so keeping the trait would have
required Boxing futures. This probably would have been fine, but seemed
unnecessary. Instead of a trait the storage mechanism is just an enum
with a choice between Memory and Disk storage.
The DiskStorage works primarily as it did before, rewriting the entire
contents of the file on every set() invocation. The only difference is
that we now defer the actual writing to a separate task so that it does
not block the return of the Token to the user. If disk i/o is too slow
to keep up with the rate of incoming writes it will push back and
will eventually block the return of tokens, this is to prevent a buildup
of in-flight requests. One major drawback to this approach is that any
errors that happen on write are simply logged and no delegate function
is invoked on error because the delegate no longer has the ability to
say to sleep, retry, etc.
