Google Pub/Sub stops pushing events

Google Cloud Data Analytics
1

Hi Team,

We use the Gmail API watch() method to route inbound email notifications to our backend via a Cloud Pub/Sub push subscription.

Issue Description: On 2026-07-27, we experienced a ~40-minute total blackout in notifications. From ~22:08 to ~22:47 UTC, our Pub/Sub subscription received zero push deliveries across all watched inboxes. Then, at ~22:48 UTC, delivery abruptly resumed, and the entire 40-minute backlog was flushed in a single ~40-second burst.

Our Troubleshooting & Verification:

  1. Emails did arrive: We checked the actual inboxes and confirmed that new emails were actively arriving during the gap (22:08–22:47 UTC).

  2. Subscriptions were healthy: Our Gmail watch() subscriptions were fully active and had not expired.

  3. No downstream blockage: Our GCP Pub/Sub metrics show 0 push requests and 0 unacked messages (backlog) during the gap. This indicates the issue wasn’t our webhook rejecting the push, but rather Gmail API delaying the publishing of events to the Pub/Sub topic until 22:48 UTC.

Could please look into this issue? Thanks!

2

PubSub’s SLA(Service Level Agreement) guarantees 99.95% uptime per month. 40 minutes of downtime within 30 days falls well within the margin of error allowed by that SLA.

Google’s support team will probably look into your issue as a matter of courtesy, but I doubt it will get escalated.

The problem may not lie with Pub/Sub. Sometimes I’ll see messages in my inbox with timestamps that show they were delivered several minutes before they actually arrived. So it could be a mail server issue.

3

I’d be interested to know if anyone else saw this on July 27. A 40-minute gap followed by the entire backlog arriving within about 40 seconds does sound like the delay happened upstream of the Pub/Sub push delivery.

Since the watches were still active, emails were arriving normally, and Pub/Sub showed no backlog or failed push requests during the affected period, it seems unlikely that the issue was on the subscriber side.

Has anyone experienced similar delays with Gmail watch() notifications recently? It would be useful to know whether there was a temporary Gmail-to-Pub/Sub delivery issue around that time.