How to set a write deadline for GoLang bufio.Writer?

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I am using buffio.Writer in GoLang as follows.

conn, err := net.Dial("tcp", address) // address is of form ip:port
w := bufio.NewWriter(conn)
w.WriteByte(code) // code is a byte
w.Write(data) // data is a byte buffer
w.Flush()

I am trying to modify the above code so that the write() events have a deadline: when the deadline is passed, the write() event will return irrespective of the fact that it was successful or not.

In GoLang its possible to have a deadline, if the conn (connection object) is directly used for writing using conn.SetWriteDeadline(time.Now().Add(n * time.Second)). However, when I use bufifo.writer object, which is essentially a wrapper around conn for buffered IO, there is no API to set a deadline.

While its possible to use conn.SetWriteDeadline(time.Now().Add(n * time.Second)) and use conn.Write(b), its very inefficient since it doesn't buffer the write events (thus a lot of context switches)

Is there a way in GoLang where I can use buffered IO with a writeDeadline()?

Thanks

go tcp io networking network-programming
1 Answers

There are two cases to note here.

If you want to have per write() deadline, then its not possible to use buffering. When you use buffering, then the actual write() is triggered when the buffer is full. So technically its not possible to know when your write() is completed. In this case, you are essentially using conn.write() and you can use conn.SetWriteDeadline(time.Now().Add(n * time.Second)).

In the second case, as @icza has mentioned in the comment, you can set the deadline in the underlying conn object, and the buffio.writer() wrapper will adhere to this rule. While this is semantically correct, it doesn't provide the networking abstraction you want.

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