libmysqlclient 连接池

#include <stdio.h>
#include <stdlib.h>
#include <mysql.h>

#define POOL_SIZE 10

typedef struct {
    MYSQL *connections[POOL_SIZE];
    int count;
} ConnectionPool;

ConnectionPool pool;

void init_pool() {
    for (int i = 0; i < POOL_SIZE; i++) {
        pool.connections[i] = mysql_init(NULL);
        if (!mysql_real_connect(pool.connections[i], "localhost", "user", "password", "database", 0, NULL, 0)) {
            fprintf(stderr, "%s\n", mysql_error(pool.connections[i]));
            exit(1);
        }
    }
    pool.count = POOL_SIZE;
}

MYSQL* get_connection() {
    if (pool.count > 0) {
        return pool.connections[--pool.count];
    } else {
        fprintf(stderr, "No available connections in the pool.\n");
        return NULL;
    }
}

void release_connection(MYSQL *conn) {
    pool.connections[pool.count++] = conn;
}

void finish_pool() {
    for (int i = 0; i < POOL_SIZE; i++) {
        mysql_close(pool.connections[i]);
    }
}

int main() {
    init_pool();

    MYSQL *conn = get_connection();
    if (conn) {
        mysql_query(conn, "SELECT * FROM table");
        MYSQL_RES *result = mysql_store_result(conn);
        // Process result
        mysql_free_result(result);
        release_connection(conn);
    }

    finish_pool();
    return 0;
}