79 lines
2.7 KiB
C++
79 lines
2.7 KiB
C++
/*
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* This file is open source software, licensed to you under the terms
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* of the Apache License, Version 2.0 (the "License"). See the NOTICE file
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* distributed with this work for additional information regarding copyright
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* ownership. You may not use this file except in compliance with the License.
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*
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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/*
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* Copyright 2020 ScyllaDB
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*/
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// Demonstration of seastar::sharded_parameter
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#include <seastar/core/sharded.hh>
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#include <seastar/core/app-template.hh>
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#include <seastar/core/thread.hh>
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#include <seastar/util/closeable.hh>
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#include <cassert>
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// This is some service that we wish to run on all shards.
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class service_one {
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int _capacity = 7;
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public:
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// Pretend that this int is some important resource.
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int get_capacity() const { return _capacity; }
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};
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// Another service that we run on all shards, that depends on service_one.
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class service_two {
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int _resource_allocation;
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public:
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service_two(service_one& s1, int resource_allocation) : _resource_allocation(resource_allocation) {}
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int get_resource_allocation() const { return _resource_allocation; }
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};
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int main(int ac, char** av) {
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seastar::app_template app;
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return app.run(ac, av, [&] {
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// sharded<> setup code is typically run in a seastar::thread
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return seastar::async([&] {
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// Launch service_one
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seastar::sharded<service_one> s1;
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s1.start().get();
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auto stop_s1 = seastar::deferred_stop(s1);
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auto calculate_half_capacity = [] (service_one& s1) {
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return s1.get_capacity() / 2;
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};
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// Launch service_two, passing it per-shard dependencies from s1
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seastar::sharded<service_two> s2;
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// Start s2, passing two parameters to service_two's constructor
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s2.start(
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// Each service_two instance will get a reference to a service_one instance on the same shard
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std::ref(s1),
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// This calculation will be performed on each shard
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seastar::sharded_parameter(calculate_half_capacity, std::ref(s1))
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).get();
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auto stop_s2 = seastar::deferred_stop(s2);
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s2.invoke_on_all([] (service_two& s2) {
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assert(s2.get_resource_allocation() == 3);
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}).get();
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});
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});
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}
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