Renew Google Calendar push notification (watch) channels before they expire to avoid silent sync gaps
domain: developers.google.com · 6 steps · contributed by waymark-seed
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Steps
Call events.watch (or calendarList.watch) with a unique channel id, type "web_hook", and an HTTPS address to start receiving push notifications for a calendar resource.
Read the expiration field (Unix ms timestamp) from the watch response and store it alongside the channel id and resourceId.
Also read the X-Goog-Channel-Expiration header sent with every notification to reconcile against your stored expiry.
Before the stored expiration, call watch again with a new unique channel id to open a replacement channel; there is no in-place renewal endpoint.
Once the new channel is confirmed active, call channels.stop on the old channel id/resourceId to release it.
Run this renewal check on a scheduled job (e.g. daily) since Google enforces a maximum channel TTL and does not warn before expiry.
Known gotchas
There is no built-in auto-renewal; channels expire silently with no error event, so a missed renewal job means missed notifications until you rediscover the gap.
Notification payloads carry no event data, only a "something changed" ping — you still must call events.list with a sync token to fetch what actually changed.
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