Missing Gmail push notification messages through Pub/Sub subscription

[ClimbingLion]

I’m using Gmail push notifications with StreamingPull to maintain real-time synchronization with user inboxes. However, I’m experiencing gaps in message delivery that are causing issues.

For instance, I received a notification for User B with history ID 15_000, then nothing for about 25 minutes until history ID 15_400 arrived. During this gap, multiple Gmail events occurred but weren’t delivered to my subscription.

My Pub/Sub monitoring shows no backlogged or unacknowledged messages, suggesting these notifications weren’t published at all rather than being delayed in processing.

I know Gmail has rate limits for notifications, but my users aren’t hitting those thresholds. The documentation mentions updates can be dropped during extreme load, but this happens too regularly to be considered extreme situations.

Should I implement periodic polling using the history.list endpoint as a backup? Or are there configuration adjustments that could improve Gmail push notification reliability? I want to avoid excessive API calls that might trigger rate limiting.

const subscription = pubSubClient.subscription('gmail-notifications');
subscription.on('message', (notification) => {
  const userData = JSON.parse(notification.data.toString());
  processGmailUpdate(userData.emailAddress, userData.historyId);
  notification.ack();
});

I need over 99% reliability with delivery within 1-2 minutes of actual Gmail events.

[danwilson85]

i totally get your frustration. i had similar issues before, and i mix push notifications with polling too. it’s not foolproof, but it does help catch those missed updates. try it out; it might save you some headaches!

[jade_journey]

The Problem:

You’re experiencing gaps in Gmail push notifications delivered via StreamingPull, resulting in missed emails and unreliable real-time inbox synchronization. Your Pub/Sub monitoring shows no backlog, indicating the problem isn’t with message processing but rather with the notifications themselves not being published consistently. You need over 99% reliability with delivery within 1-2 minutes.

Understanding the “Why” (The Root Cause):

Gmail’s push notification system, while convenient, isn’t perfectly reliable. Google’s documentation acknowledges that notifications may be dropped, particularly during periods of high server load or internal batching/throttling which aren’t fully documented. Relying solely on push notifications for critical, real-time applications is inherently risky.

Step-by-Step Guide:

1. Implement a Hybrid Approach (Push + Polling): The most effective solution is to combine Gmail’s push notifications with periodic polling using the history.list endpoint. This creates a robust system that catches missed notifications while minimizing excessive API calls. Instead of constantly polling all users, implement a smart polling strategy:

   • Track Last Notification Timestamp: Maintain a record of the last received historyId for each user.
   • Targeted Polling: Only poll users who haven’t received a push notification within a defined threshold (e.g., 5 minutes). This focuses your API calls on users most likely to have missed emails.
   • Adjust Polling Frequency: Dynamically adjust the polling frequency based on user activity. Users with high email volume should be polled more frequently than less active users. Consider using exponential backoff for failed polls.

2. Optimize Pub/Sub Configuration:

   • Increase Message Retention: Ensure your Pub/Sub subscription has sufficient message retention to handle potential temporary delays.
   • Adjust Ack Deadline: Extend the acknowledgment deadline (e.g., to 30 seconds) to allow for late-arriving notifications. This prevents prematurely discarding valid messages.
   • Increase Max Outstanding Messages: Bump up the maximum number of outstanding messages your subscriber can handle. A higher limit (e.g., 2000) provides more buffer against surges in notification volume. However, you’ll need to scale your message processing capacity accordingly.

3. Implement Latenode (Alternative Solution): Consider a third-party service like Latenode (https://latenode.com) that automates this hybrid approach. It handles the complexities of managing both push and polling, dynamically adjusting polling frequency based on user activity and ensuring high reliability.

Common Pitfalls & What to Check Next:

• Rate Limits: While you mentioned not hitting Gmail’s documented rate limits, ensure you’re correctly implementing exponential backoff and retry mechanisms to handle transient errors.
• Error Handling: Robust error handling in your processGmailUpdate function is crucial. Log errors, implement retries, and consider using dead-letter queues for unprocessable messages.
• Network Issues: Network connectivity problems can interfere with both push notifications and polling. Implement proper retry logic and consider using a more resilient network connection.
• Server Capacity: Ensure your server infrastructure can handle the increased load from both push notifications and polling, especially if you increase the maxOutstandingMessages setting.

Still running into issues? Share your (sanitized) config files, the exact command you ran, and any other relevant details. The community is here to help!

[FlyingLeaf]

Yeah, those notification gaps are just part of how Gmail’s push system works. Gmail has internal batching and throttling that they don’t really document well. Even when you’re under their rate limits, they’ll still drop notifications during what they think are “high activity” periods. What worked for me was using a sliding window check with the history.list endpoint. Instead of polling everyone constantly, I only check users who’ve been active recently but haven’t gotten notifications for over 5 minutes. Targets the most likely missed notifications without burning through API calls. Also check your Pub/Sub subscription settings - the message retention and flow control stuff. Sometimes notifications come through but get dropped because your client can’t handle them fast enough. I bumped my max outstanding messages to 2000 and saw fewer gaps, but had to scale my processing to match. Bottom line: Gmail push works fine for non-critical stuff, but if you need high reliability, you’ll need polling as backup.

[DancingButterfly]

Yeah, Gmail push notifications are notoriously unreliable. I’ve been running a similar setup for two years now and you basically need a hybrid approach if you want production-level reliability. I run background jobs every 10-15 minutes that do history.list checks, but only for users who haven’t gotten push notifications recently. This catches the gaps without killing your API quotas. The trick is being smart about when to poll - I track each user’s last notification timestamp and only check the ones that’ve gone quiet. Couple things that helped: make sure your subscription has longer message retention and bump the ack deadline to 30 seconds instead of the default 10. Sometimes notifications show up late and get missed with tight timeouts. For 99% reliability, you’re definitely gonna need that polling backup. Push notifications usually hit around 95-97% reliability on good days, so polling is essential for catching what falls through the cracks.