Ivan, > Pavel, is it really true, that in .NET sync versions of libraries and tools > are completely eliminated?
Far from being eliminated, but there is a movement in this direction. For example, HttpClient [1] only provides async variants for most of the methods. Exposing sync wrappers for async methods is not recommended [2]. There is a good explanation of potential threading issues there, and it can be applied to Java too. > you cannot mix both functions easily You can mix them easily. C#: table.GetAsync(k).Result or table.GetAsync(k).GetAwaiter().GetResult() (different exception handling) Java: table.getAsync(k).get() The same thing we do in sync wrapper for async method is now in the user code. Which is better for two reasons: - users won't accidentally use sync API when async API should be used - when they really have to use sync API, potentially dangerous behavior is not hidden [1] https://docs.microsoft.com/en-us/dotnet/api/system.net.http.httpclient?view=net-5.0#methods [2] https://devblogs.microsoft.com/pfxteam/should-i-expose-synchronous-wrappers-for-asynchronous-methods/ On Thu, Sep 9, 2021 at 11:16 AM Ivan Daschinsky <ivanda...@gmail.com> wrote: > >> 2. In languages with proper async support (async-await, etc.), we can > skip sync API altogether. > It sounds pretty strange, as for me. Usually you cannot mix both functions > easily, it is called blue-red functions problem [1] > In python you definitely cannot do sync over async, for example > (principally can, but nobody do that because of mediocre performance of > that solution). And many developers > still prefer writing code withou asyncio at all. > > Pavel, is it really true, that in .NET sync versions of libraries and tools > are completely eliminated? > > [1] -- > https://elizarov.medium.com/how-do-you-color-your-functions-a6bb423d936d > > ср, 8 сент. 2021 г. в 22:33, Pavel Tupitsyn <ptupit...@apache.org>: > > > To put it another way: > > - true sync operation completes by itself > > - sync-over-async operation requires another thread to complete > > > > On Wed, Sep 8, 2021 at 10:15 PM Pavel Tupitsyn <ptupit...@apache.org> > > wrote: > > > > > Val, > > > > > > That's exactly what I have in mind. > > > Yes, we block the user thread, but then we should unblock it by > > completing > > > the future. > > > We can't complete the future from a Netty thread [1], so we'll need > some > > > other thread from some executor. > > > If there are no threads available (because they are blocked by the sync > > > API above), the future won't complete => deadlock. > > > > > > [1] > > > > > > https://lists.apache.org/thread.html/r528659381d983a177d779f56ef3d7da6fe17eb3504383f5f87727514%40%3Cdev.ignite.apache.org%3E > > > > > > On Wed, Sep 8, 2021 at 9:40 PM Valentin Kulichenko < > > > valentin.kuliche...@gmail.com> wrote: > > > > > >> Pavel, > > >> > > >> I might be missing something - could you please elaborate a little > more? > > >> > > >> When I say "sync on top of async", I basically mean that (for example) > > >> 'insert(..)' is equivalent to 'insertAsync(..).join()'. In my > > >> understanding, it only blocks the user's thread. > > >> > > >> Am I wrong? Or you have a different implementation in mind? > > >> > > >> -Val > > >> > > >> On Wed, Sep 8, 2021 at 12:50 AM Pavel Tupitsyn <ptupit...@apache.org> > > >> wrote: > > >> > > >> > Val, > > >> > > > >> > Agree with your points. > > >> > > > >> > > > >> > > async API should be primary > > >> > > > >> > It should be noted that all our APIs are inherently async, > > >> > because thin client is implemented asynchronously. > > >> > > > >> > > > >> > > with the sync version build on top > > >> > > > >> > We should document somehow that sync APIs are based on async ones, > > >> > because this may be dangerous in some use cases. > > >> > > > >> > For example, as a user, I may have a thread pool of 4 threads for > > >> > Ignite-related usage, that is also set as asyncContinuationExecutor > > [1]. > > >> > Now if I run a lot of concurrent Ignite requests using sync API, > all 4 > > >> > threads will end up blocked on CompletableFutures. > > >> > When one of the operations completes, we enqueue the completion to > > that > > >> > same thread pool, but all threads are blocked on sync APIs, > resulting > > >> in a > > >> > deadlock. > > >> > > > >> > This can be prevented by using a different > asyncContinuationExecutor, > > >> but > > >> > sync API users won't be usually aware of this. > > >> > > > >> > > > >> > [1] https://issues.apache.org/jira/browse/IGNITE-15359 > > >> > > > >> > On Wed, Sep 8, 2021 at 10:04 AM Courtney Robinson < > > >> > courtney.robin...@hypi.io> > > >> > wrote: > > >> > > > >> > > Hi Val, > > >> > > > > >> > > I'd highly support an async first API based on CompletionStage > > >> > > < > > >> > > > > >> > > > >> > > > https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletionStage.html > > >> > > > > > >> > > or > > >> > > its subtypes like CompletableFuture. > > >> > > In Ignite 2 we've written a wrapper library around IgniteFuture to > > >> > provide > > >> > > CompletionStage instead because many of the newer libs we use > > support > > >> > this. > > >> > > If Ignite 3 went this way it'd remove a lot of boiler > plate/wrapper > > >> that > > >> > we > > >> > > wrote to get what you're suggesting here. > > >> > > > > >> > > Regards, > > >> > > Courtney Robinson > > >> > > Founder and CEO, Hypi > > >> > > Tel: ++44 208 123 2413 (GMT+0) <https://hypi.io> > > >> > > > > >> > > <https://hypi.io> > > >> > > https://hypi.io > > >> > > > > >> > > > > >> > > On Wed, Sep 8, 2021 at 12:44 AM Valentin Kulichenko < > > >> > > valentin.kuliche...@gmail.com> wrote: > > >> > > > > >> > > > Igniters, > > >> > > > > > >> > > > I would like to gather some opinions on whether we want to focus > > on > > >> > sync > > >> > > vs > > >> > > > async APIs in Ignite 3. > > >> > > > > > >> > > > Here are some initial considerations that I have: > > >> > > > 1. Ignite 2.x is essentially "sync first". Async APIs exist, but > > >> they > > >> > use > > >> > > > non-standard IgniteFuture and provide counterintuitive > guarantees. > > >> In > > >> > my > > >> > > > experience, they significantly lack usability, and because of > that > > >> are > > >> > > > rarely used. > > >> > > > 2. In general, however, async execution becomes more and more > > >> > prominent. > > >> > > > Something we can't ignore if we want to create a modern > framework. > > >> > > > 3. Still, async support in Java is very limited (especially if > > >> compared > > >> > > to > > >> > > > other languages, like C# for example). > > >> > > > > > >> > > > My current position is the following (happy to discuss): > > >> > > > 1. We should pay more attention to async APIs. As a general > rule, > > >> async > > >> > > API > > >> > > > should be primary, with the sync version build on top. > > >> > > > 2. In languages with proper async support (async-await, etc.), > we > > >> can > > >> > > skip > > >> > > > sync API altogether. As an example of this, you can look at the > > >> first > > >> > > > version of the .NET client [1]. It exposes only async methods, > and > > >> it > > >> > > > doesn't look like sync counterparts are really needed. > > >> > > > 3. In Java (as well as other languages where applicable), we > will > > >> add > > >> > > sync > > >> > > > APIs that simply delegate to async APIs. This will help users to > > >> avoid > > >> > > > CompletableFuture if they don't want to use it. > > >> > > > > > >> > > > [1] https://github.com/apache/ignite-3/pull/306 > > >> > > > > > >> > > > Please share your thoughts. > > >> > > > > > >> > > > -Val > > >> > > > > > >> > > > > >> > > > >> > > > > > > > > -- > Sincerely yours, Ivan Daschinskiy >
