The maximum number of outstanding bytes per streaming pull.
The Cloud Pub/Sub C++ client library uses streaming pull requests to receive messages from the service. The service will stop delivering messages if this many bytes or more worth of messages have not been acknowledged nor rejected.
If a negative or 0 value is supplied, the number of bytes will be unlimited.
Example
namespace pubsub = ::google::cloud::pubsub;
using ::google::cloud::future;
using ::google::cloud::Options;
using ::google::cloud::StatusOr;
auto sample = [](std::string project_id, std::string subscription_id) {
// Change the flow control watermarks, by default the client library uses
// 0 and 1,000 for the message count watermarks, and 0 and 10MiB for the
// size watermarks. Recall that the library stops requesting messages if
// any of the high watermarks are reached, and the library resumes
// requesting messages when *both* low watermarks are reached.
auto constexpr kMiB = 1024 * 1024L;
auto subscriber = pubsub::Subscriber(pubsub::MakeSubscriberConnection(
pubsub::Subscription(std::move(project_id), std::move(subscription_id)),
Options{}
.set<pubsub::MaxOutstandingMessagesOption>(1000)
.set<pubsub::MaxOutstandingBytesOption>(8 * kMiB)));
auto session = subscriber.Subscribe(
[](pubsub::Message const& m, pubsub::AckHandler h) {
std::move(h).ack();
std::cout << "Received message " << m << "\n";
PleaseIgnoreThisSimplifiesTestingTheSamples();
});
return std::make_pair(subscriber, std::move(session));
};
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-03-14 UTC."],[[["This webpage details the `MaxOutstandingBytesOption` within the Google Cloud Pub/Sub C++ client library, which controls the maximum number of unacknowledged or unrejected bytes during streaming pull operations."],["The latest version of the documentation is for version 2.37.0-rc, with a range of other previous version options available for reference, starting from version 2.11.0 all the way up to 2.36.0, and including minor releases."],["Setting a negative or zero value for `MaxOutstandingBytesOption` effectively disables the limit, allowing an unlimited number of outstanding bytes, which is why the default is 0."],["The library will stop receiving new messages once this number of bytes is unacknowledged, and will start receiving again once the number of bytes acknowledged is below the low watermark."],["The struct for this option is `google::cloud::pubsub::MaxOutstandingBytesOption`, and is an alias for `std::int64_t`."]]],[]]