The question of "why not 1.0?" has come up a few times. After all, Tokio 0.1 has been stable for three years. The short answer: because it isn't time. There is nobody who would rather ship a Tokio 1.0 than us. It also isn't something to rush.
After all, async / await only landed in the stable Rust channel weeks ago.
There has been no significant production validation yet, except maybe fuchsia
and that seems like a fairly specialized use case. This release of Tokio
includes significant new code and new strategies with feature flags. Also, there
are still big open questions, such as the proposed changes to
AsyncRead and AsyncWrite.
Tokio 1.0 will be released as soon as the APIs are proven to handle real-world production cases.
The Tokio 1.0 release will be no later than Q3 2020. It will also come with "long-term support" guarantees:
- A minimum of 5 years of maintenance.
- A minimum of 3 years before a hypothetical 2.0 release.
When Tokio 1.0 is released in Q3 2020, on-going support, security fixes, and critical bug fixes are guaranteed until at least Q3 2025. Tokio 2.0 will not be released until at least Q3 2023 (though, ideally there will never be a Tokio 2.0 release).
While Tokio 0.1 probably should have been a 1.0, Tokio 0.2 will be a true 0.2 release. There will be breaking change releases every 2 ~ 3 months until 1.0. These changes will be much smaller than going from 0.1 -> 0.2. It is expected that the 1.0 release will look a lot like 0.2.
The biggest change will be the AsyncRead and AsyncWrite traits. Based on
experience gained over the past 3 years, there are a couple of issues to
address:
- Be able to safely use uninitialized memory as a read buffer.
- Practical read vectored and write vectored APIs.
There are a few strategies to solve these problems. These strategies need to be investigated and the solution validated. You can see this comment for a detailed statement of the problem.
The other major change, which has been in the works for a while, is updating Mio. Mio 0.6 was first released almost 4 years ago and has not had a breaking change since. Mio 0.7 has been in the works for a while. It includes a full rewrite of the windows support as well as a refined API. More will be written about this shortly.
Finally, now that the API is starting to stabilize, effort will be put into documentation. Tokio 0.2 is being released before updating the website and many of the old content will no longer be relevant. In the coming weeks, expect to see updates there.
So, we have our work cut out for us. We hope you enjoy this 0.2 release and are looking forward to your feedback and help.