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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <memory>
#include <queue>
#include "mongo/executor/egress_tag_closer.h"
#include "mongo/executor/egress_tag_closer_manager.h"
#include "mongo/stdx/functional.h"
#include "mongo/stdx/mutex.h"
#include "mongo/stdx/unordered_map.h"
#include "mongo/transport/session.h"
#include "mongo/transport/transport_layer.h"
#include "mongo/util/duration.h"
#include "mongo/util/future.h"
#include "mongo/util/net/hostandport.h"
#include "mongo/util/out_of_line_executor.h"
#include "mongo/util/time_support.h"
namespace mongo {
class BSONObjBuilder;
namespace executor {
struct ConnectionPoolStats;
/**
* The actual user visible connection pool.
*
* This pool is constructed with a DependentTypeFactoryInterface which provides the tools it
* needs to generate connections and manage them over time.
*
* The overall workflow here is to manage separate pools for each unique
* HostAndPort. See comments on the various Options for how the pool operates.
*/
class ConnectionPool : public EgressTagCloser, public std::enable_shared_from_this<ConnectionPool> {
class SpecificPool;
public:
class ConnectionInterface;
class DependentTypeFactoryInterface;
class TimerInterface;
using ConnectionHandleDeleter = stdx::function<void(ConnectionInterface* connection)>;
using ConnectionHandle = std::unique_ptr<ConnectionInterface, ConnectionHandleDeleter>;
using GetConnectionCallback = unique_function<void(StatusWith<ConnectionHandle>)>;
static constexpr Milliseconds kDefaultHostTimeout = Minutes(5);
static constexpr size_t kDefaultMaxConns = std::numeric_limits<size_t>::max();
static constexpr size_t kDefaultMinConns = 1;
static constexpr size_t kDefaultMaxConnecting = 2;
static constexpr Milliseconds kDefaultRefreshRequirement = Minutes(1);
static constexpr Milliseconds kDefaultRefreshTimeout = Seconds(20);
static const Status kConnectionStateUnknown;
struct Options {
Options() {}
/**
* The minimum number of connections to keep alive while the pool is in
* operation
*/
size_t minConnections = kDefaultMinConns;
/**
* The maximum number of connections to spawn for a host. This includes
* pending connections in setup and connections checked out of the pool
* as well as the obvious live connections in the pool.
*/
size_t maxConnections = kDefaultMaxConns;
/**
* The maximum number of processing connections for a host. This includes pending
* connections in setup/refresh. It's designed to rate limit connection storms rather than
* steady state processing (as maxConnections does).
*/
size_t maxConnecting = kDefaultMaxConnecting;
/**
* Amount of time to wait before timing out a refresh attempt
*/
Milliseconds refreshTimeout = kDefaultRefreshTimeout;
/**
* Amount of time a connection may be idle before it cannot be returned
* for a user request and must instead be checked out and refreshed
* before handing to a user.
*/
Milliseconds refreshRequirement = kDefaultRefreshRequirement;
/**
* Amount of time to keep a specific pool around without any checked
* out connections or new requests
*/
Milliseconds hostTimeout = kDefaultHostTimeout;
/**
* An egress tag closer manager which will provide global access to this connection pool.
* The manager set's tags and potentially drops connections that don't match those tags.
*
* The manager will hold this pool for the lifetime of the pool.
*/
EgressTagCloserManager* egressTagCloserManager = nullptr;
/**
* Connections created through this connection pool will not attempt to authenticate.
*/
bool skipAuthentication = false;
};
explicit ConnectionPool(std::shared_ptr<DependentTypeFactoryInterface> impl,
std::string name,
Options options = Options{});
~ConnectionPool();
void shutdown();
void dropConnections(const HostAndPort& hostAndPort) override;
void dropConnections(transport::Session::TagMask tags) override;
void mutateTags(const HostAndPort& hostAndPort,
const stdx::function<transport::Session::TagMask(transport::Session::TagMask)>&
mutateFunc) override;
SemiFuture<ConnectionHandle> get(const HostAndPort& hostAndPort,
transport::ConnectSSLMode sslMode,
Milliseconds timeout);
void get_forTest(const HostAndPort& hostAndPort,
Milliseconds timeout,
GetConnectionCallback cb);
void appendConnectionStats(ConnectionPoolStats* stats) const;
size_t getNumConnectionsPerHost(const HostAndPort& hostAndPort) const;
private:
std::string _name;
// Options are set at startup and never changed at run time, so these are
// accessed outside the lock
const Options _options;
const std::shared_ptr<DependentTypeFactoryInterface> _factory;
// The global mutex for specific pool access and the generation counter
mutable stdx::mutex _mutex;
stdx::unordered_map<HostAndPort, std::shared_ptr<SpecificPool>> _pools;
EgressTagCloserManager* _manager;
};
/**
* Interface for a basic timer
*
* Minimal interface sets a timer with a callback and cancels the timer.
*/
class ConnectionPool::TimerInterface {
TimerInterface(const TimerInterface&) = delete;
TimerInterface& operator=(const TimerInterface&) = delete;
public:
TimerInterface() = default;
using TimeoutCallback = stdx::function<void()>;
virtual ~TimerInterface() = default;
/**
* Sets the timeout for the timer. Setting an already set timer should
* override the previous timer.
*/
virtual void setTimeout(Milliseconds timeout, TimeoutCallback cb) = 0;
/**
* It should be safe to cancel a previously canceled, or never set, timer.
*/
virtual void cancelTimeout() = 0;
/**
* Returns the current time for the clock used by the timer
*/
virtual Date_t now() = 0;
};
/**
* Interface for connection pool connections
*
* Provides a minimal interface to manipulate connections within the pool,
* specifically callbacks to set them up (connect + auth + whatever else),
* refresh them (issue some kind of ping) and manage a timer.
*/
class ConnectionPool::ConnectionInterface : public TimerInterface {
ConnectionInterface(const ConnectionInterface&) = delete;
ConnectionInterface& operator=(const ConnectionInterface&) = delete;
friend class ConnectionPool;
public:
explicit ConnectionInterface(size_t generation) : _generation(generation) {}
virtual ~ConnectionInterface() = default;
/**
* Indicates that the user is now done with this connection. Users MUST call either
* this method or indicateFailure() before returning the connection to its pool.
*/
void indicateSuccess();
/**
* Indicates that a connection has failed. This will prevent the connection
* from re-entering the connection pool. Users MUST call either this method or
* indicateSuccess() before returning connections to the pool.
*/
void indicateFailure(Status status);
/**
* This method updates a 'liveness' timestamp to avoid unnecessarily refreshing
* the connection.
*
* This method should be invoked whenever we perform an operation on the connection that must
* have done work. I.e. actual networking was performed. If a connection was checked out, then
* back in without use, one would expect an indicateSuccess without an indicateUsed. Only if we
* checked it out and did work would we call indicateUsed.
*/
void indicateUsed();
/**
* The HostAndPort for the connection. This should be the same as the
* HostAndPort passed to DependentTypeFactoryInterface::makeConnection.
*/
virtual const HostAndPort& getHostAndPort() const = 0;
virtual transport::ConnectSSLMode getSslMode() const = 0;
/**
* Check if the connection is healthy using some implementation defined condition.
*/
virtual bool isHealthy() = 0;
/**
* Returns the last used time point for the connection
*/
Date_t getLastUsed() const;
/**
* Returns the status associated with the connection. If the status is not
* OK, the connection will not be returned to the pool.
*/
const Status& getStatus() const;
/**
* Get the generation of the connection. This is used to track whether to
* continue using a connection after a call to dropConnections() by noting
* if the generation on the specific pool is the same as the generation on
* a connection (if not the connection is from a previous era and should
* not be re-used).
*/
size_t getGeneration() const;
protected:
/**
* Making these protected makes the definitions available to override in
* children.
*/
using SetupCallback = unique_function<void(ConnectionInterface*, Status)>;
using RefreshCallback = unique_function<void(ConnectionInterface*, Status)>;
/**
* Sets up the connection. This should include connection + auth + any
* other associated hooks.
*/
virtual void setup(Milliseconds timeout, SetupCallback cb) = 0;
/**
* Resets the connection's state to kConnectionStateUnknown for the next user.
*/
void resetToUnknown();
/**
* Refreshes the connection. This should involve a network round trip and
* should strongly imply an active connection
*/
virtual void refresh(Milliseconds timeout, RefreshCallback cb) = 0;
private:
size_t _generation;
Date_t _lastUsed;
Status _status = ConnectionPool::kConnectionStateUnknown;
};
/**
* Implementation interface for the connection pool
*
* This factory provides generators for connections, timers and a clock for the
* connection pool.
*/
class ConnectionPool::DependentTypeFactoryInterface {
DependentTypeFactoryInterface(const DependentTypeFactoryInterface&) = delete;
DependentTypeFactoryInterface& operator=(const DependentTypeFactoryInterface&) = delete;
public:
DependentTypeFactoryInterface() = default;
virtual ~DependentTypeFactoryInterface() = default;
/**
* Makes a new connection given a host and port
*/
virtual std::shared_ptr<ConnectionInterface> makeConnection(const HostAndPort& hostAndPort,
transport::ConnectSSLMode sslMode,
size_t generation) = 0;
/**
* Return the executor for use with this factory
*/
virtual const std::shared_ptr<OutOfLineExecutor>& getExecutor() = 0;
/**
* Makes a new timer
*/
virtual std::shared_ptr<TimerInterface> makeTimer() = 0;
/**
* Returns the current time point
*/
virtual Date_t now() = 0;
/**
* shutdown
*/
virtual void shutdown() = 0;
};
} // namespace executor
} // namespace mongo
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