If the application invokes handler.nack() or allows handler to go out of scope, then the service will redeliver the message.
With exactly-once delivery subscriptions, the service will stop redelivering the message once the application invokes handler.ack() and the invocation succeeds. With best-efforts subscriptions, the service may redeliver the message, even after a successful handler.ack() invocation.
If handler is not an rvalue, you may need to use std::move(handler).ack() or std::move(handler).nack().
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 UTC."],[[["\u003cp\u003eThis webpage provides access to the C++ Pub/Sub library documentation for various versions, ranging from version 2.11.0 to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe documentation specifically references the \u003ccode\u003ePullResponse\u003c/code\u003e struct within the \u003ccode\u003egoogle::cloud::pubsub\u003c/code\u003e namespace, across each version.\u003c/p\u003e\n"],["\u003cp\u003eThe content details how the message will be redelivered if the application invokes \u003ccode\u003ehandler.nack()\u003c/code\u003e or allows \u003ccode\u003ehandler\u003c/code\u003e to go out of scope.\u003c/p\u003e\n"],["\u003cp\u003eWith exactly-once delivery subscriptions, the message stops being redelivered after a successful \u003ccode\u003ehandler.ack()\u003c/code\u003e, while best-effort subscriptions might still redeliver the message even after acknowledgment.\u003c/p\u003e\n"],["\u003cp\u003eThe content provides a link to the exact-once delivery subscription documentation for more information: \u003ca href=\"https://cloud.google.com/pubsub/docs/exactly-once-delivery\"\u003ehttps://cloud.google.com/pubsub/docs/exactly-once-delivery\u003c/a\u003e.\u003c/p\u003e\n"]]],[],null,[]]
