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 2025-04-17 UTC."],[[["The webpage documents the `MaxOutstandingBytesOption` for the Cloud Pub/Sub C++ client library, detailing its role in managing the maximum number of unacknowledged bytes received via streaming pull requests."],["Version 2.37.0-rc is the latest release candidate, with a full list of versions available from 2.11.0 up to this most current one, all referencing the `MaxOutstandingBytesOption` struct."],["The library stops requesting new messages if the total size of unacknowledged or unrejected messages reaches the configured `MaxOutstandingBytesOption` limit, then resumes when the number of outstanding bytes falls below the low watermark, which defaults to 0."],["The value for outstanding bytes, if set to negative or 0, will allow for unlimited bytes."],["This option is configured using the `Options` class with `.set\u003cpubsub::MaxOutstandingBytesOption\u003e()` , as demonstrated in the provided code example."]]],[]]