gRpc stream server gets conext canceled rpc error in streamServerInstance.Recv() function which leads to the stram connection getting dropped between the server and client. Could this be related to a simple timeout? Asking for help, clarification, or responding to other answers. To learn more, see our tips on writing great answers. info. Have a question about this project? i didn't use IDE so i cannot reproduce that. If this sounds familiar, let me introduce you to your new friend,errgroup.WithContext()found ingolang.org/x/sync/errgroup. Or maybe any DB error could fall into checking if the context has been canceled (ctx.Err() == context.Canceled)? Include clear steps. To get the actual details (like name, email, etc), we look up each friends id with the Profile service. debug information unconditionally. I don't think we always pass back the context error, esp with the closed rows. type Context interface { // Done returns a channel that is closed when this Context is canceled // or times out. do you use this code i share in current issue? GCCGO="gccgo" Continuous variant of the Chinese remainder theorem. We read every piece of feedback, and take your input very seriously. In the example above, we take care to ensure that writers always close the channels they control. We now have now seen another DB error that seems to be caused by context canceled and we're downgrading: Change https://golang.org/cl/145204 mentions this issue: database/sql: prefer to return Rows.lasterr rather then a static error. (3) if strings.Contains(err.Error(), anySubstring("dial tcp: operation was canceled") Asthe docstates: A Group is a collection of goroutines working on subtasks that are part of the same overall task. Edit: Could please explain you can't see a reasonable way to change it when surely all that would be needed would be to rename Done() to Cancelled() and then re-create Done() as wrapper to Cancelled() which is deprecated? The best we could perhaps do is retrofit a top-level func Cause(Context) error function into the context package, which would use Cause if defined or Err otherwise. But theres one particular interaction that we have to pay close attention to and manage ourselves: channel reads and writes. Making statements based on opinion; back them up with references or personal experience. The AWS SDK for Go v1.8.0 release adds support for the API operation request functional options, and the Context pattern. Regarding compatibility, my goal with this CL is to avoid breaking anything, including existing implementations of the Context interface. For example, if the user navigates away from the page and cancels the http request, we can stop immediately. Any of these individual network calls might fail, time out, or otherwise produce an error. Can YouTube (e.g.) Right now, all I see "Context cancelled" and have no idea why so. I've narrowed down the precise commit where things began to fail, and there are more vendor updates here than I'd previously thought. Or maybe any DB error could fall into checking are the rows closed? But I dont see an API for checking that (either in database/sql or pgx). // or the empty string if ctx.Done() is not closed. I had missed the developments around #28728 and their implications. We read every piece of feedback, and take your input very seriously. . A new context can be created using the context.Background(). Its methods are safe for simultaneous use by multiple // goroutines. ops ! If the connection between the client and server is lost, the transport should eventually fail all its streams, or the deadline of the RPC will be reached, and Recv will also return in those scenarios. GODRIVER-2037 Don't clear the connection pool on client-side connect timeout errors. Glad to hear this API is directionally correct. Please show us your code, or tell us how to recreate the problem. Context. Block artificially The first anti-pattern is the idea of blocking the main go routine without actually waiting on anything. I wonder if context.Context should record a bit of caller information (say, the PC of the immediate calling function) in context.WithTimeout and in calls to the CancelFunc returned by context.WithCancel. We have such a context implementation, but it's not a nice one because ctx.Err() still returns the vanilla context.Canceled error (as it also does in @Sajmani 's proposed patch). This comment section is from stream.go code CancelFunc ctx, = context. We iterate over a returned list of friend ids (collecting them in memory), look up each friends profile by id, and put the result in a response object. Have a question about this project? Also does Recv() block indefinitely ? they can delegate to Err()). Sign in The origin of the error suggests that theres no unique error type for rows are closed to compare against. The cases I'm thinking of are about a custom implementation of context that overrides the Done() channel - e.g. No other values for Err are defined. GOROOT="/usr/local/go" Sign in If a client provides an arbitrarily short deadline, you'll get context.DeadlineExceeded, but it's not the server's fault. I read the diff, but it's hard to intuit what rs.lasterr will be, as it seems to mostly come from the driver. We'd probably also want to make Cause(ctx) == ctx.Err() when the user hasn't provided a cause. I think you have it backwards. Its simple and straightforward (and probably fine for many use cases). If so, then indeed we'd need to make sure they are nil / not-nil at the same times. Yes, matching on error strings is typically bad practice. That could work. 1 I think with your current patch that's not possible, because the key that Cause() looks for is not exported? This is whereerrgroup.WithContext()becomes our best friend. This context is a simple context that is never cancelled and does not carry any value. Println ( "trying", i ) try () } } func try () { mux := http. How does this impact our code? I assume you want to have a timeout per service call rather than across the Client use. This happens if I send a burst of data using the stream connection, happens usually after 1:30 minutes approxymately or roughly in between 40kto 60k data sent through the stream. rev2023.7.27.43548. The output of Cause(uc) and Cause(ctx2) is surprising to me. I believe this leaves 4 ways to act upon the error now. Golangcontextcontextcontextcontext context. Let's keep the discussion here for now, Capturing the stack trace at the cancel() call is likely to be uninteresting: usually cancel is called either via timer.AfterFunc (in the case of a deadline). Similarly, if the parent context is canceled (the request terminates early), the same thing will happen. That loses the error type and value identity. But that seems like it might mask real DB errors if the context was only coincidentally cancelled. / Left unchecked, leaked goroutines pin memory and process resources, eventually slowing down and then crashing the process. Do you mean a func net.IsCanceled(error) bool @jayconrod? I added test for cause vs. causeless cancels and more orderings. And there could be multiple streams in on HTTP2 connection. I would agree with what you saying, however a large amount documentation and existing guides I've encountered all talk about withTimeout ,withDeadline and withCancel all in the context of the Done() being called when the context has been cancelled. When a requesting client kills their connection while the server is processing the request, the request context is canceled. I do not know all the ways the http.ResponseWriter may be prematurely closed. Can you elaborate? GOOS="linux" That code spawns a new goroutine to propagate cancellation from a custom ctx to a stdlib one. Following is a Chi middleware example: func SetDBMiddleware(next http.Handler) http.Handler {. Have a question about this project? In the ServeHTTP method of ReverseProxy, it's quite clear that the context will only be canceled when the http.CloseNotifier detects that the underlying connection has gone away. Do you happen to have a record of which revision of the context package you were using previously, and which one you updated to? By clicking Sign up for GitHub, you agree to our terms of service and This is very expensive. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. If the server (or DB) is exceeding deadline, then that is a server error and I want it to be an error. It is one of the most important tools while working with concurrent programming in Go. CloseNotifier ); { var context. I think it would solve your issue. See #1229 (comment) for an example. To see all available qualifiers, see our documentation. case of a deadline) or via defer, which may make it harder to debug if (*) If I'd have my druthers, we would make Cause() a new method on ctx (even if that means that custom Ctx impls will need to add that method to compile under the new go version. Context () := rw . Ironically, Context.Value is O(N) with the depth of Context nesting, Would you agree? If youd like to play around with the various versions of the code yourself, heres the full runnable version ongolang playgroundandas a gist. My preference is to minimize API changes and improve debuggability in-place, but I understand performance concerns might make this difficult. Continuous session mode which might be helpful when handling API requests, for example, you can set up *gorm.DB with Timeout Context in middlewares, and then use the *gorm.DB when processing all requests. We read every piece of feedback, and take your input very seriously. To see all available qualifiers, see our documentation. We read every piece of feedback, and take your input very seriously. ctx1 is not canceled). There is a way of doing per-operation timeouts if you wish (killing the stream if the timeout is reached). My point about the extra context is that it is common for Go errors to be returned up the stack with extra information added. So if the callee has explicitly closed the context as shown above, this can result in a context cancelled error at caller. to your account. why context canceled? Theres one final piece of the puzzle: how do we know that all of our goroutines will exit in a timely manner? "revision": "f5079bd7f6f74e23c4d65efa0f4ce14cbd6a3c0f", => "revision": "1e491301e022f8f977054da4c2d852decd59571f", https://godoc.org/github.com/chromedp/chromedp#Evaluate, when i use this code with net/http and wrapping a http handler on it it makes unexpected end of JSON without IDE , and with IDE debug mode it returns context canceled. 1, Post http://ms-user-go.mp.online/user/listByIDs: context canceled, cancel contextcontext canceled, contextgin ContextRequest Context, 585338887server 1, 5, 58535server 18888server 2, server 2server 1server 2sleep, server 1server 1request contextreqeust contextclientcancelserver 1server 2http, go.1.17 & gin.1.3.0, forw.conn.r.startBackgroundRead(), cancelcontextcancelcontext, w.conn.r.startBackgroundRead(), startBackgroundRead -> backgroundRead -> handleReadErrorhandleReadErrorcontext cancel, context cancelcancel, backgroundReadEOFFIN, ICP18099781-6 context.DeadlineExceeded, or any error defined by a custom context implementation). There are similar nuances at play around #28728 and the performance implications of propagating cancellation across context types: in that case it's not strictly about what an implementer can do, but rather the degree to which the stdlib plays nicely with others. I also renamed things so the test is easier to follow. sorry for my bad English at all. I'd also consider adding a version of the Done() method that returns the error. Here is one image illustrate the connection and stream of HTTP2 from web dev If you cancel the context in one gRPC call before the response comes back. The error goes away if I remove the timeout context and use one without any limit. // If the request context is canceled by the user just before a transactions commit is, // attempted, then the following error will occur. Based on the feedback from several of you, I'll prototype an alternative I seek a SF short story where the husband created a time machine which could only go back to one place & time but the wife was delighted. Then, you'll add a main function that creates a context and calls doSomething using that context. Leveraging Observables to solve unique performance challenges in FullStorys session replay app. "revision": "314dd2c0bf3ebd592ec0d20847d27e79d0dbe8dd", => "revision": "1e0a3fa8ba9a5c9eb35c271780101fdaf1b205d7", program terminated with error message : context canceled. Thanks a lot for the explanation and guidance. I can add this to the spec in the CL. Thanks! i run this code thousand of times and in line err := chromedp.Run(ctx,tasks(usrcrd)) error will be set to context canceled. I'm quite certain it's within the httpclient.Do function somewhere, or at least that's the stdlib function that's being called from my own code. completes or an RPC comes in to explicitly cancel it. It still reads above like this is user error and you got lucky in the past, so I'd like to keep this bug about thinking about ways to make this debugging easier for other users making similar errors. We read every piece of feedback, and take your input very seriously. In the particular case of a stdlib ctx, I think we should guarantee that, if Err() is nil, Cause() is also nil. OverflowAI: Where Community & AI Come Together, Behind the scenes with the folks building OverflowAI (Ep. . If the parentContext(say, an http request context) is canceled, the groupContext. The text was updated successfully, but these errors were encountered: Sorry, but there isn't enough information here to say anything useful. go. Writing into a full channel blocks forever until some reader makes space, and reading from an empty channel blocks forever until the writer adds a new value or closes the channel. September 2022 | No Comments Takeaways Errors as uint64 for better performance By convention, 0 is "OK" or "no error" Use the exhaustive linter with switch Use enums to define error cases Implement Stringer on enums for human readable error messages Use generic T ~uint64 to type custom structs to errors i expect to see fine message instead of this. In Running mode : Unexpected end of JSON input. What versions are you running? 594), Stack Overflow at WeAreDevelopers World Congress in Berlin, Temporary policy: Generative AI (e.g., ChatGPT) is banned, Preview of Search and Question-Asking Powered by GenAI. @adam-p Are you able to review / test the CL https://go-review.googlesource.com/c/go/+/145204 ? 235 // 236 // Canceling this context releases resources associated with it, so code should 237 // call cancel as soon as the operations running in this Context . To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Connect and share knowledge within a single location that is structured and easy to search. We always receive a calendarClient back, so calendar.New is being called correctly. The answer lies in Gosselectstatement. This is when a ctx on the chain from ctx1 to ctx2 overrode the Done() channel. So thats fine. That'd be support for bad practice on dubious practice, no? Since client is waiting on stream.Recv() (since its a blocking call) then server has to call SendAndClose() after it has received data in its own Recv() call right ? - Peter Jun 15, 2020 at 8:20 Add a comment 1 Answer Sorted by: 19 I personally find the second version a lot more clear about what is going on as I no longer have to make the logic leap that when a context is "cancelled" that results in the channel that is returned via the to a function call of Done(). This seems surprising. You switched accounts on another tab or window. I am new to Go and still learning it every signle day. I don't think so. Have you ever written a Go server handler that could be parallelized, but you left it as a linear sequence of operations? when debugging is disabled. Since stream.Send() buffers the data in internal buffer as explained in the link above I have no indication at client side about this failure. Golang version : 1.11.5 What did you do? For long-lived streams, you could build ACKs into your protocol, but this is not something supported by grpc itself. Sign in So this statement blocks until either we can writeidinto thefriendIdschannel or thectx.Done()channel becomes readable. Does Recv() have a timeout of sort ? In our system, each user has a list of friend ids which refer to another user, and we can get a friend id iterator from the Friend service. When people implement custom contexts, I think they primarily do so for efficiency reasons. It looks like both packages (x/net and x/oauth2) were updated and that the previous version was decently old such that it may be very difficult to narrow anything down, but here are a couple of samples from the revisions: "checksumSHA1": "dr5+PfIRzXeN+l1VG+s0lea9qz8=", => "checksumSHA1": "GtamqiJoL7PGHsN454AoffBFMa8=", The text was updated successfully, but these errors were encountered: Note that a context can also be "Done" if it times out, if it was created using context.WithTimeout or context.WithDeadline. Not quite, I was suggesting to implement interface{ Is(error) bool } on the existing error so that errors.Is(err, context.SomeError) works. Why Do We Need Cancellation? Getting Started with Go Context. In short, we need cancellation to prevent our system from doing unnecessary work. Not the answer you're looking for? @andreimatei I added some tests: I am using curl because you previously told me to. Yes it does @bcmills. The defer cancel() causes the context to be cancelled before the client even gets to calendar.New. It seems like a sort of race condition as to where the canceled state is first detected. It looks like your vendor update uncovered a latent bug within your code. If I am not wrong, in "simple" terms, context cancelled means that the given request (via grpc using gokit) has been time out. We know that people do string matching on error strings, and in the past we've decided to not change error strings because doing so broke too much existing code. Systems engineer at FullStory since 2015. By clicking Sign up for GitHub, you agree to our terms of service and Your code is . Any of these individual network calls might fail, time out, or otherwise produce an error. Already on GitHub? How do you deal the "context canceled" in HTTP servers? I am trying to silence it, as my logs are all polluted with this error. NewClient (called by oauthConfig.Client): The returned client is not valid beyond the lifetime of the context. You switched accounts on another tab or window. GOHOSTARCH="amd64" GOTMPDIR="" Code with example: -. My guess would be that the Go code can't properly execute Chrome from within the IDE. Timeouts produce context.DeadlineExceeded. I think the behavior you're seeing is expected. To see all available qualifiers, see our documentation. Go has issues with exposing errors, i.e. i can't understand what's really happen? i just test my code with Goland IDE debugger. if you insist to use EvaluateAsDevTools please use []byte instead of interface. I guess I personally would be inclined towards maximal changes :). I think the conversation about what to do with errors when they are returned is less relevant here. For instance, if I wrote a function like this: Now if g or h fail because the context was canceled, the error returned from f won't be context.Canceled. Reddit, Inc. 2023. nanjingfm This replaces the ReverseProxy#defaultErrorHandler implementation with one that conditionally logs. @fraenkel I'm fine with whichever, but doesn't putting it on the client prevent me from needing to duplicate this context code across all calls? :=. I have chain of 3 proxy servers, and middle server was returning "context canceled". Would a change request help (to see what the change implies)? How can we avoid this pitfall? Regarding implementing Cause for custom contexts, users can do this easily by wrapping a context created using WithCancelCause. https://github.com/notifications/unsubscribe-auth/AJSK3TSfBWY21reU6GLskizNeC3fM3mEks5uHkBugaJpZM4VNsJ2, https://cs.opensource.google/go/go/+/refs/tags/go1.17.6:src/context/context.go;l=264, https://github.com/notifications/unsubscribe-auth/ACKIVXOCQENNWK5TYHTYNDTUU45W7ANCNFSM4FJWYJ3A, https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675, https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub, https://go-review.googlesource.com/c/go/+/375977/3/src/context/context.go, https://go-review.googlesource.com/c/go/+/375977/4/src/context/context_test.go#798, context: add APIs for writing and reading cancelation cause. you can use chromedp.SetValue or even chromedp.SendKey to set this input value. Associating that debug value with an Have a question about this project? A Context.Value call with an exported (but opaque) key to retrieve the reason code should be fine. So, as a matter of principle, FWIW, my opinion is that the performance and ergonomics of 3rd party impls should be a concern whenever mucking with the context library. Do these exercise the case you were describing? All rights reserved. @GoLover which version of chromedp and chrome did you use?
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