Summary

When Confluence rate-limiting is enabled it could limit the requests coming from Team Calendar synchronization which might cause not having the meetings/events in third-party calendars since the synchronization requests might be rejected as well.

Environment

Confluence server and Data Center version 7.13.5

Diagnosis

In the application logs:

WARN [http-nio-8090-exec-4] [ratelimiting.internal.filter.RateLimitFilter] lambda$userHasBeenRateLimited$0 User [rate_limiting_anonymous_user] has been rate limited
 -- url: /rest/calendar-services/1.0/calendar/export/subcalendar/private/calendar.ics | traceId: 355081bc9cce042a | userName: anonymous
WARN [http-nio-8090-exec-11] [ratelimiting.internal.filter.RateLimitFilter] lambda$userHasBeenRateLimited$0 User [rate_limiting_anonymous_user] has been rate limited
 -- url: /rest/calendar-services/1.0/calendar/export/subcalendar/private/calendar.ics | traceId: 4c68b59b0314d2f6 | userName: anonymous

When ICAL URL is tested on a browser Confluence returns below:

Cause

When a third-party calendar is subscribed to Confluence Team Calendar, it sends synchronization requests to Confluence by using an anonymous user. If the Rate Limiting feature is enabled it rejects the request coming from the third-party calendar and might cause not having the meetings in third-party calendars.

Solution

Adding exemptions

Exemptions are, well, special limits for users who really need to make more requests than others. Any exemptions you choose will take precedence over global settings.

To add an exemption:

1. Go to the Exemptions tab.
2. Click Add exemption.
3. Find the Anonymous user and choose their new settings.
4. The options available here are just the same as in global settings: Allow unlimited requests, or Assign a custom limit.
5. Save your changes.

If you want to edit an exemption later, just click Edit next to a user’s name in the Exemptions tab.

Allow listing URLs and resources

For Rate Limiting there is a way to allow whole URLs and resources on your Confluence instance using a system property. This should be used as a quick fix for something that gets rate limited but shouldn’t.

To allow specific URLs to be excluded from rate limiting:

1. Stop Confluence.

2. Add the com.atlassian.ratelimiting.whitelisted-url-patterns system property, and set the value to a comma-separated list of URLs, for example:

   CATALINA_OPTS="-Dcom.atlassian.ratelimiting.whitelisted-url-patterns=/**/rest/applinks/**,/**/rest/capabilities,/**/rest/calendar-services/** ${CATALINA_OPTS}"

   
   The way you add system properties depends on how you run Confluence. See Configuring System Properties for more information.

3. Restart Confluence.

Disabling Rate Limiting

If the rate limit is controlled by an intermediate layer like reverse proxy, load balancer, or firewall, you may also disable the rate-limiting feature by following the below steps:

1. Navigate to > General Configuration > Rate Limiting,
2. Select Disabled,
3. Then Save your changes.

The page should look like the below: