concurrent map iteration and map write

[maolinHu]

Expected behavior

Actual behavior

Tell us what happens instead

Steps to reproduce

How can we reproduce the issue

System configuration

Pulsar version: 0.8.1

[labuladong]

Can you describe the steps to reproduce this bug?

[zzzming]

There is a new feature in Go 1.8 to detect concurrent edit and access to a map. It's described at https://tip.golang.org/doc/go1.8#mapiter
The problem was reported (or panicked) by go map.
This should have been reported by a race detector.
I will do a PR to fix it, probably use mutex to protect the map access.

[maolinHu]

properties := make(map[string]string)
for _, data := range Arr {
msg := &pulsar.ProducerMessage{
Payload: data,
Properties: properties,
}
p.sendAsync(ctx, msg, fn)
}

I guess it is caused by multiplexing map(pulsar.ProducerMessage.Properties) when send asyn, This is an occasional bug.

[zzzming]

In Go, a map is a reference type. Properties is a map. A producer application can still update the map while it's passed to the go client. This might be where the problem is. The original stack trace is from internalSend that is a Send(). I guess the problem should exist in both Send and SendAsync. The producer application should not concurrently update the properties.

[thomas-bousquet]

Has this issue been fixed? I'm currently experiencing the problem with the version v0.14.0. I'm able to reproduce it with a end-to-end test and the issue is consistent.

Actual behavior

fatal error: concurrent map iteration and map write

Steps to reproduce

• Create a list of messages (I've tried with 500)
• Iterate over the list and each time use the producer to SendAsync() to send the individual message.
• Each message has some properties, like an internal id. I believe the properties list (map[string]string) is causing this issue, as pointed out above.

The fatal error usually occurs after just 40/50 iterations.

[nodece]

Have you changed the Properties during sending? Do you share the properties for each message?

[thomas-bousquet]

I had the map used as the source actually shared, when creating the messages individually. Thank you for your help, much appreciated.

[nodece]

When the map is shared, you will trigger this bug. Please avoid this usage.