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 page documents the `MaxOutstandingBytesOption` for the Google Cloud Pub/Sub C++ client library, which controls the maximum number of outstanding bytes allowed for streaming pull requests."],["The `MaxOutstandingBytesOption` is used to manage flow control, as the service stops delivering messages if the total size of unacknowledged or unrejected messages reaches this limit."],["The latest version documented is 2.37.0-rc with many other versions listed such as 2.36.0, 2.35.0, and all the way down to 2.11.0, allowing users to view the documentation of the specific version they need."],["Supplying a negative or zero value for `MaxOutstandingBytesOption` results in an unlimited number of outstanding bytes."],["The `MaxOutstandingBytesOption` is used in conjunction with `MaxOutstandingMessagesOption`, and both high and low watermarks must be met before the client library stops or resumes requests for messages."]]],[]]
