ef1de114f0
This commit adds admission control in the form of passing service permits to the Thrift server. The support is partial, because Thrift also supports running CQL queries, and for that purpose a query_state object is kept in the Thrift handler. However, the handler is generally created once per connection, not once per query, and the query_state object is supposed to keep the state of a single query only. In order to keep this series simpler, the CQL-on-top-of-Thrift layer is not touched and is left as TODO. Moreover, the Thrift layer does not make it easy to pass custom per-query context (like service_permit), so the implementation uses a trick: the service permit is created on the server and then passed as reference to its connections and their respective Thrift handlers. Then, each time a query is read from the socket, this service permit is overwritten and then read back from the Thrift handler. This mechanism heavily relies on the fact that there are zero preemption points between overwriting the service permit and reading it back by the handler. Otherwise, races may occur. This assumption was verified by code inspection + empirical tests, but if somebody is aware that it may not always hold, please speak up.
56 lines
1.7 KiB
C++
56 lines
1.7 KiB
C++
/*
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* Copyright (C) 2020 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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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/distributed.hh>
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#include <seastar/core/future.hh>
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#include "service/memory_limiter.hh"
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using namespace seastar;
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class thrift_server;
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class database;
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namespace auth { class service; }
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namespace cql3 { class query_processor; }
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class thrift_controller {
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std::unique_ptr<distributed<thrift_server>> _server;
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semaphore _ops_sem; /* protects start/stop operations on _server */
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bool _stopped = false;
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distributed<database>& _db;
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sharded<auth::service>& _auth_service;
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sharded<cql3::query_processor>& _qp;
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sharded<service::memory_limiter>& _mem_limiter;
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future<> do_start_server();
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future<> do_stop_server();
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public:
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thrift_controller(distributed<database>&, sharded<auth::service>&, sharded<cql3::query_processor>&, sharded<service::memory_limiter>&);
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future<> start_server();
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future<> stop_server();
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future<> stop();
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future<bool> is_server_running();
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};
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