I am using Gmail push notifications for email processing. When I receive a message notification from Google, I use the history list API with the previously stored historyId and can see new messages using messagesAdded. Once I have retrieved the messages, I store the last historyId for the next request.

When testing, if I send two mail messages (about 30 seconds apart) to the watched mailbox, I see two messages notifications from Google and when I call the history API for each of the notifications I see the message ids. This is all good.

If I repeat the same test but send the two mail messages immediately after each other, I get the two notifications from Google but when I call the history API for the first message, I get the two message ids in that history API call. When I call the history API call for the second notification, I get a duplicate of the last message id.

How can I prevent seeing duplicate message ids in this scenario? Any help or pointers would be much appreciated.

Updated: Added request and response example for second test.

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1 Answers

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Swordfish On Best Solutions

I noticed in the response from the Google History API a historyId showing the latest messages that have been processed. If I store this value as the next start point instead of the historyId sent in the notification message, it works around the duplicate issue as on the second request there are no more messages. Not sure if this is the right way to do this as it means I don't store or use the historyId sent in the notification message.