orb_advertise_multi: failed to set queue size

[stmoon]

Hi,

I found that there is a error when booting.

[uorb] orb_advertise_multi: failed to set queue size

However, I don't understand what's the meaning.

Could you tell me the meaning?

Thanks

[bkueng]

It happens if you have multiple publishers of the same topic (and instance) and they try to set different queue sizes: once, set the queue size cannot be changed, as it would lead to race conditions.
Make sure all your advertisers use the same queue size.

[stmoon]

Thanks @bkueng

I heard that uORB can cover multiple publishers using instance even though I published same topic.

Should I use just one publisher for a topic?

To solve this problem, which function can I use?

Thanks in advance

[bkueng]

Yes, depending on the use-case you should use multiple instances to separate the data from different publishers - we do that for example for multiple gyro sensors.
There is documentation here: https://dev.px4.io/en/middleware/uorb.html#multi-instance

[stmoon]

Thanks... @bkueng

I understand it!!