编译安装pgbouncer-checking for OpenSSL... configure: error: not found

花了一上午时间将pgbouncer的参数通读了一遍，对他有个大致的了解：
1.配置分为连接池和pgbouncer两个部分[database]\[pgbouncer　　]。
2.一条记录对应创建一个连接池，连接池的大小可以在这条配置中设置，如果不设置，则使用pgbouncer部分中配置的默认值20，当然也可以修改。
3.验证模式使用md5，则需要配置user.txt文件，即密码文件；如果使用hba，则需要指定对应的pg_hba.conf文件（即可以使用PostgreSQL的验证模式）。
4.admin_user是允许哪些用户可以在控制台连接pgbouncer这个管理数据库，并进行修改。
5.在database配置连接池中，又分为配置user/password和auth_user，这里还有点迷糊，后面实验了再来说，下面是解释：

user, password
If user= is set, all connections to the destination database will be done with the specified user, meaning that there will be only one pool for this database.
 
Otherwise PgBouncer tries to log into the destination database with client username, meaning that there will be one pool per user.
 
auth_user
If auth_user is set, any user not specified in auth_file will be queried from pg_shadow in the database using auth_user. Auth_user’s password will be taken from auth_file.
 
Direct access to pg_shadow requires admin rights. It’s preferable to use non-admin user that calls SECURITY DEFINER function instead.

6.超时时间中server_lifetime和server_idle_timeout表示不是很明白，超时后第一个直接close掉，第二个直接drop掉，是何意思？

server_lifetime
The pooler will try to close server connections that have been connected longer than this. Setting it to  means the connection is to be used only once, then closed. [seconds]
 
Default: 3600.0
 
server_idle_timeout
If a server connection has been idle more than this many seconds it will be dropped. If  then timeout is disabled. [seconds]
 
Default: 600.0

进入正题，安装过程中遇到了一个比较蛋疼的问题，openssl安装了，但是configure时提示没有找到。查了一些资料都是胡扯，最后发现是少了对应的库：

checking for OpenSSL... configure: error: not found
 
原因：

　　　　The OpenSSL library is usually already installed, but you have to install the header files. Depending on your Linux distribution, you'll need these packages:

• Red Hat, Fedora, CentOS - openssl-devel
• Debian, Ubuntu - libssl-dev
• Arch - openssl

yum install openssl-devel -y

下面是具体安装步骤了，官网的：

$ ./configure --prefix=/usr/local --with-libevent=libevent-prefix
$ make
$ make install

配置文件：

-bash-4.1$ cat pgbouncer.ini
[databases]
mydb = host=127.0.0.1 port= dbname=mydb user=postgres password=postgres
postgres = host=127.0.0.1 port= dbname=postgres user=postgres password=postgres
 
[pgbouncer]
listen_port =
listen_addr = *
auth_type = md5
auth_file = /var/lib/pgsql/pgbouncer/config/user.txt
logfile = /var/lib/pgsql/pgbouncer/config/pgbouncer.log
pidfile = /var/lib/pgsql/pgbouncer/config/pgbouncer.pid
admin_users = postgres
pool_mode = session

由于配置的是md5，因此这里要用user.txt文件：

-bash-4.1$ cat user.txt
"postgres" "postgres"

启动：

$pgbouncer -d pgbouncer.ini

-bash-4.1$ ps -ef|grep pgbouncer
  postgres 29377 1 0 16:19 ? 00:00:00 pgbouncer -d pgbouncer.ini
  postgres 31574 29031 0 16:28 pts/0 00:00:00 grep pgbouncer

使用：

-bash-4.1$ psql -p
psql: could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
-bash-4.1$ psql -p  -h localhost
Password:
psql (9.5.)
Type "help" for help.
 
postgres=#
postgres=# \d
No relations found.
postgres=# \l
                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
 postgres  | postgres | UTF8     | en_US.UTF- | en_US.UTF- |
 template0 | postgres | UTF8     | en_US.UTF- | en_US.UTF- | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF- | en_US.UTF- | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
( rows)

进入后台，查看连接和重载参数：

-bash-4.1$ psql -p  -h localhost pgbouncer
Password:
psql (9.5., server 1.7./bouncer)
Type "help" for help.
 
pgbouncer=#
pgbouncer=# show help;
NOTICE:  Console usage
DETAIL:
        SHOW HELP|CONFIG|DATABASES|POOLS|CLIENTS|SERVERS|VERSION
        SHOW STATS|FDS|SOCKETS|ACTIVE_SOCKETS|LISTS|MEM
        SHOW DNS_HOSTS|DNS_ZONES
        SET key = arg
        RELOAD
        PAUSE [<db>]
        RESUME [<db>]
        DISABLE <db>
        ENABLE <db>
        KILL <db>
        SUSPEND
        SHUTDOWN
SHOW
pgbouncer=# reload;
RELOAD
pgbouncer=# show clients;
 type |   user   | database  | state  | addr | port  | local_addr | local_port |    connect_time     |    request_time     |   ptr    | link | remote_pid | tls
------+----------+-----------+--------+------+-------+------------+------------+---------------------+---------------------+----------+------+------------+-----
 C    | postgres | pgbouncer | active | ::  |  | ::        |        | -- :: | -- :: | 0xebe780 |      |           |
( row)
 
pgbouncer=# show fds;
 fd |  task  |   user   | database |   addr    | port |    cancel     | link | client_encoding | std_strings | datestyle | timezone | password
----+--------+----------+----------+-----------+------+---------------+------+-----------------+-------------+-----------+----------+----------
   | pooler |          |          | 0.0.0.0   |  |              |     |                 |             |           |          |
   | pooler |          |          | ::        |  |              |     |                 |             |           |          |
  | pooler |          |          | unix      |  |              |     |                 |             |           |          |
  | server | postgres | postgres | 127.0.0.1 |  |  |     | UTF8            | on          | ISO, MDY  | PRC      |
( rows)

其他说明：
在[database]中，可以指定其他服务器的数据库，而且如果数据库名字重复，会以后一条的数据库生效：

[databases]
kdb = host=127.0.0.1 port=5433 dbname=mydb user=postgres password=postgres
postgres = host=127.0.0.1 port=5433 dbname=postgres user=postgres password=postgres
;;postgres = host=10.9.5.20 port=5433 dbname=postgres user=postgres password=postgres