Connection Overload Protection

Owned by Florian Raschbichler
Last updated: May 27, 2020 by Finn Zirngibl
1 min read

Question

How exactly do the values connect-rate and connect-burst-size from the Connect Overload Protection work?
How long will HiveMQ accept messages at the rate of the burst size?

Answer

HiveMQ internally uses a token system. The burst-size sets the initial amount of available tokens, each CONNECT uses up a token and tokens are refreshed at the connect-rate (per second).
If the tokens are used up and there are still incoming CONNECT messages above the rate HiveMQ will temporary stop reading from new sockets and finally disconnect newly connecting clients.
A constant stream of CONNECTS higher than the connect-rate will be throttled to the configured rate, after a swing-in phase.