[question] Emit ping via WriteMessage() or WriteControl()?

[tomsun]

Are both idiomatic?

What are the trade-offs?

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Chat example emits ping using WriteMessage()

websocket/examples/chat/client.go

Line 116 in 58729a2

if err := c.conn.WriteMessage(websocket.PingMessage, nil); err != nil {

Command example emits ping using WriteControl()

websocket/examples/command/main.go

Line 87 in 5ed622c

if err := ws.WriteControl(websocket.PingMessage, []byte{}, time.Now().Add(writeWait)); err != nil {

[tomsun]

Assuming both are ok, is WriteControl() safer concurrency-wise: for example if you don't want to couple ping and the writer of regular messages? Or is that a bad idea?

Applications are responsible for ensuring that no more than one goroutine calls the write methods ( ... WriteMessage ... )

The Close and WriteControl methods can be called concurrently with all other methods.

https://pkg.go.dev/github.com/gorilla/websocket#hdr-Concurrency

[ghost]

WriteControl can be called concurrently with other write methods. WriteMessage cannot. Control messages (ping is a control message) can be written with both methods.

In the chat example, all application writes to the connection are from a single goroutine. Because concurrency is not an issue here, either method can be used.

The command example writes ping messages from a different goroutine than the goroutine that writes data messages. WriteControl or some form of synchronization is required in the example.

WriteControl can write a message concurrently with WriteMessage because control messages can be interleaved with a data message's frames in the websocket protocol.

There's no downside to calling WriteControl for all control messages.

[tomsun]

@TaylorRex ok, thanks for the confirmation!

So I should be able to use WriteControl() if I can't structure my app to ping from the same goroutine. But I give up the ability to use things like SetWriteDeadline() for the ping message itself, like in the chat example.

[ghost]

But I give up the ability to use things like SetWriteDeadline()

Use the WriteControl deadline argument to specify a deadline for writes using the method.

[tomsun]

Oh, perfect!

[kuchaguangjie]

WriteControl can be called concurrently with other write methods. WriteMessage cannot.

What exactly does this mean?