transport: Fix handling of closed connections in ReadyReader (#9031) ## Problem The `ReadyReader` interface was added to support non-blocking reads using the `syscall` package in #8964. While working on [follow-up changes](https://github.com/grpc/grpc-go/compare/master...arjan-bal:h2-read-buffer-pool?expand=1) to support pooling read buffers in the http2 layer, I noticed test failures where servers were closing the TCP connection, but the client channel remained in the READY state. ## Root Cause The [unix.Read](https://pkg.go.dev/golang.org/x/sys/unix#Read) function doesn't consider the graceful closure of a connection to be an error and instead returns `(0, nil)`. Since consumers of the `io.Reader` interface expect an `io.EOF` error in such cases, the translation from `(0, nil)` to `(0, io.EOF)` needs to be handled by the reader implementation. RELEASE NOTES: N/A
The Go implementation of gRPC: A high performance, open source, general RPC framework that puts mobile and HTTP/2 first. For more information see the Go gRPC docs, or jump directly into the quick start.
Simply add the following import to your code, and then go [build|run|test] will automatically fetch the necessary dependencies:
import "google.golang.org/grpc"
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The golang.org domain may be blocked from some countries. go get usually produces an error like the following when this happens:
$ go get -u google.golang.org/grpc package google.golang.org/grpc: unrecognized import path "google.golang.org/grpc" (https fetch: Get https://google.golang.org/grpc?go-get=1: dial tcp 216.239.37.1:443: i/o timeout)
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go mod edit -replace=google.golang.org/grpc=github.com/grpc/grpc-go@latest go mod tidy go mod vendor go build -mod=vendor
Again, this will need to be done for all transitive dependencies hosted on golang.org as well. For details, refer to golang/go issue #28652.
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The default logger is controlled by environment variables. Turn everything on like this:
$ export GRPC_GO_LOG_VERBOSITY_LEVEL=99 $ export GRPC_GO_LOG_SEVERITY_LEVEL=info
"code = Unavailable desc = transport is closing"This error means the connection the RPC is using was closed, and there are many possible reasons, including:
It can be tricky to debug this because the error happens on the client side but the root cause of the connection being closed is on the server side. Turn on logging on both client and server, and see if there are any transport errors.