Is it possible to send a broadcast message to all instances behind the ELB?

Question

I want to send update to all instances behind the ELB. I prefer to send update instead of polling from instance side. Is it possible to send a message to ELB that will be broadcasted to all instances ?

Answer 1

Not directly, no.

A programmatic workaround is to query the ELB API to discover the identities of the healthy instances then the EC2 API to discover the IP addresses of those instances, and then send the message to each instance, directly.