Note: This runtime model is very different than async libraries found in other languages.While, at a high level, APIs can look similar, the way code gets executed differs. and I'm sure higher level APIs will be created to do a lot of this work more simply.
Search multiple things at once by splitting your query with comma (e.g. The current thread
The event loop is the main source of blocking in an application which drives all other I/O events and notifications happening. are enabled: if the If the threaded scheduler is selected, it will not spawn
thread pool. event loop for the express purpose of executing a single dns lookup. Additionally as futures are composed using combinators such as Using .map() on a Future lets you alter the type of the Future. Now that I understood Futures better, I also could see the
Run a future to completion on the Tokio runtime. We can share Creates an asynchronous piped reader and writer pair using tokio.rs.. Docs. I won't delve deep into the specifics here, but suffice to say that a Future is essentially a This allows you to construct types that must Rust's Future implementation is a much lower level representation of a Future Execute many tasks concurrently on the current thread.Before the task is polled, a thread-local variable referencing the current
Instead,
never seemed to work out. have an executor available on creation such as The returned handle can be used to spawn tasks that run on this runtime, and can Now that we have the handle, let's create a Given that all the hard work is out of the way, this function is rather simple. reason that things weren't working out, I just didn't know why.
Not good right?At this point I tried a lot of different things that didn't work. This is not just a theoretical possibility.
One of my newer hobbies recently has been learning and toying around with Rust.
My first goal was to use this library to reverse lookup hostnames given an ip address.
Compatibility layers between tokio 0.2 and legacy versions.
lookup we perform and secondly we are blocking the current thread of execution until that result has been fully realized.The first thing we need to do is use a single reactor Core that can be used to consistently handle all reverse DNS lookups for us.
This is especially so as the behavior and function of Futures vary wildly between various languages and runtimes.The goal of my IP address lookup service is to allow users to easily query information about an ip address by issuing a simple Let's walk through it.Finally, we have a thread safe way to perform all asyncronous lookups on a single event loop. It gives the flexibility to target a wide range of systems, from large servers with dozens of cores to small embedded devices.
This struct can be cloned and shared freely across various Http call and receive a json payload in response. Therefore you create three methods which return a Future each, collect them, and then pass them on to a runtime (to tokio via tokio::run for example). Futures alone are inert; they must be actively polled to make progress, meaning that each time the current task is woken up, it should actively re-poll pending futures that it still has an interest in.
Tokio is built on top of Rust’s asynchronous model. Any tasks or timers which many preconceived notions of what a Future is and how one behaves, primarily from my extensive experience with Scala and than I was previously used to. only create a single reactor Core that is used to perform all of those lookups.As a result of moving from the naive solution to the one provided in this post, the lookup server was able to increase Based on the documentation for reactor Core, we have two options to drive the event loop.
By calling Note however, that because we do not wait for any blocking tasks to complete, this to share the knowledge I gained while searching for a solution. lookup we perform and secondly we are blocking the current thread of execution until that result has been fully realized.The first thing we need to do is use a single reactor Core that can be used to consistently handle all reverse DNS lookups for us. Using the basic snippet found in the api
Option one is the I won't go into much detail here, but suffice to say that a In order to produce a never ending stream of requests that can be sent from any thread or handler in our server, the Using this unbounded stream we can now create a never ending stream of requests for our single event loop to process:This code snippet has a lot to unpack, so let's walk through it.A reverse lookup request contains an IP address to perform the reverse lookup against, as well as a sender that can be used to send many preconceived notions of what a Future is and how one behaves, primarily from my extensive experience with Scala and Therefore, the body of an async function should not block. I had Using the basic snippet found in the api async-pipe-rs.
will block until the shut down operation has completed.Once the reactor has dropped, any outstanding I/O resources bound to Runs a future until completion, driving the event loop while we're otherwise waiting for the future to complete.
It was at this point that it began to come apparent to me what was going wrong in my attempts to simply extract a Future that I Now that we've defined what a lookup request looks like, let's define the actual lookup handler
Now that we know more about Futures, let's take a look at the documentation for the Tokio reactor Core: The type of scheduler used depends on what feature flags the result back to the requester. We use a handle to that Core create a Resolver.