mod_s2s_cache_failures

Description

This module essentially rate limits the number of outgoing connection attempts to domains that Prosody hasn’t been able to connect to.

This can help with resource usage (no need to queue undelivered stanzas for unreachable domains), and also reduces noise in the log files.

The retry period is proportional to the amount of time since Prosody last had a connection to the domain. It also includes some randomness to prevent multiple servers unintentially flooding a domain with reconnection attempts at the same time. On average a failed domain will be tried around 15 times in the first hour of unavailability, decreasing in frequency to 1-2 attempts per hour after that.

Configuration

The only configuration option is:

s2s_cache_failures_domain_cache_size

The number of failed domains that will be remembered (overflows will simply cause failures to be forgotten, and Prosody will retry those domains sooner).

Compatibility

Not compatible with Prosody 13.0 or earlier. Compatible with Prosody trunk from 2026-10-29.

Commit 4067a95336dd also introduces a new s2s_block_immediate_retries option which you may want to enable, to catch some cases of retries which this module cannot otherwise prevent.

sudo prosodyctl install --server=https://modules.prosody.im/rocks/ mod_s2s_cache_failures