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110 lines
3.5 KiB
C++
110 lines
3.5 KiB
C++
#pragma once
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#include "Pool.h"
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#define MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_START_CONNECTIONS 1
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#define MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_MAX_CONNECTIONS 16
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#define MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_MAX_TRIES 3
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namespace mysqlxx
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{
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/** MySQL connection pool with support of failover.
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* Have information about replicas and their priorities.
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* Tries to connect to replica in an order of priority. When equal priority, choose replica with maximum time without connections.
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*
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* It could be configured without replicas, exactly as ordinary Pool:
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*
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* <mysql_metrica>
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* <host>mtstat01c*</host>
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* <port>3306</port>
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* <user>metrica</user>
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* <password></password>
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* <db>Metrica</db>
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* </mysql_metrica>
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*
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* Or like this:
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*
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* <mysql_metrica>
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* <replica>
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* <host>mtstat01c</host>
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* <port>3306</port>
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* <user>metrica</user>
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* <password></password>
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* <db>Metrica</db>
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* <priority>0</priority>
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* </replica>
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* <replica>
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* <host>mtstat01d</host>
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* <port>3306</port>
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* <user>metrica</user>
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* <password></password>
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* <db>Metrica</db>
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* <priority>1</priority>
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* </replica>
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* </mysql_metrica>
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*
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* Or like this:
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*
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* <mysql_metrica>
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* <port>3306</port>
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* <user>metrica</user>
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* <password></password>
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* <db>Metrica</db>
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* <replica>
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* <host>mtstat01c</host>
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* <priority>0</priority>
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* </replica>
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* <replica>
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* <host>mtstat01d</host>
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* <priority>1</priority>
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* </replica>
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* </mysql_metrica>
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*/
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class PoolWithFailover final
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{
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private:
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using PoolPtr = std::shared_ptr<Pool>;
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using Replicas = std::vector<PoolPtr>;
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/// [priority][index] -> replica.
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using ReplicasByPriority = std::map<int, Replicas>;
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ReplicasByPriority replicas_by_priority;
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/// Number of connection tries.
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size_t max_tries;
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/// Mutex for set of replicas.
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std::mutex mutex;
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/// Can the Pool be shared
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bool shareable;
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public:
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using Entry = Pool::Entry;
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/**
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* config_name Name of parameter in configuration file.
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* default_connections Number of connection in pool to each replica at start.
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* max_connections Maximum number of connections in pool to each replica.
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* max_tries_ Max number of connection tries.
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*/
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PoolWithFailover(const std::string & config_name_,
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unsigned default_connections_ = MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_START_CONNECTIONS,
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unsigned max_connections_ = MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_MAX_CONNECTIONS,
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size_t max_tries_ = MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_MAX_TRIES);
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PoolWithFailover(const Poco::Util::AbstractConfiguration & config_,
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const std::string & config_name_,
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unsigned default_connections_ = MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_START_CONNECTIONS,
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unsigned max_connections_ = MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_MAX_CONNECTIONS,
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size_t max_tries_ = MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_MAX_TRIES);
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PoolWithFailover(const PoolWithFailover & other);
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/** Allocates a connection to use. */
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Entry get();
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};
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}
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