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f9be6f4a83
After obtaining the CQL response, check if its actual size exceeds the initially acquired memory permit. If so, acquire additional semaphore units and adopt them into the permit, ensuring accurate memory accounting for large responses.
Additionally, move the permit into a .then() continuation so that the semaphore units are kept alive until write_message finishes, preventing premature release of memory permit. This is especially important with slow networks and big responses when buffers can accumulate and deplete a node's memory.
Fixes: https://scylladb.atlassian.net/browse/SCYLLADB-1306
Related https://scylladb.atlassian.net/browse/SCYLLADB-740
Backport: all supported versions
Closes scylladb/scylladb#29288
* github.com:scylladb/scylladb:
transport: add per-service-level pending response memory metric
transport: hold memory permit until response write completes
transport: account for response size exceeding initial memory estimate
(cherry picked from commit 86417d49de)
Closes scylladb/scylladb#29410
37 lines
1.1 KiB
C++
37 lines
1.1 KiB
C++
/*
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* Copyright (C) 2019-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.0
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*/
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#pragma once
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#include <seastar/core/semaphore.hh>
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#include <seastar/core/shared_ptr.hh>
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class service_permit {
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seastar::lw_shared_ptr<seastar::semaphore_units<>> _permit;
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service_permit(seastar::semaphore_units<>&& u) : _permit(seastar::make_lw_shared<seastar::semaphore_units<>>(std::move(u))) {}
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friend service_permit make_service_permit(seastar::semaphore_units<>&& permit);
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friend service_permit empty_service_permit();
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public:
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size_t count() const { return _permit ? _permit->count() : 0; };
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// Merge additional semaphore units into this permit.
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// Used to grow the permit after the actual resource cost is known.
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void adopt(seastar::semaphore_units<>&& units) {
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if (_permit) {
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_permit->adopt(std::move(units));
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}
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}
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};
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inline service_permit make_service_permit(seastar::semaphore_units<>&& permit) {
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return service_permit(std::move(permit));
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}
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inline service_permit empty_service_permit() {
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return make_service_permit(seastar::semaphore_units<>());
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}
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