Many TIME_WAIT errors for connecting to mongodb4

[jhhe66]

配置了emqx_auth_mongo，但是报了很多time_wait.

配置文件如下：

##--------------------------------------------------------------------
## MongoDB Auth/ACL Plugin
##--------------------------------------------------------------------

## MongoDB Topology Type.
##
## Value: single | unknown | sharded | rs
auth.mongo.type = rs

## The set name if type is rs.
##
## Value: String
auth.mongo.rs_set_name = devauth_mongo_set

## MongoDB server list.
##
## Value: String
##
## Examples: 127.0.0.1:27017,127.0.0.2:27017...
auth.mongo.server = ip01:15306,ip01:15307

## MongoDB pool size
##
## Value: Number
auth.mongo.pool = 8

## MongoDB login user.
##
## Value: String
auth.mongo.login = devauth_mongo

## MongoDB password.
##
## Value: String
auth.mongo.password = ***

## MongoDB AuthSource
##
## Value: String
## Default: mqtt
auth.mongo.auth_source = admin

## MongoDB database
##
## Value: String
auth.mongo.database = DeviceAuth_db

## MongoDB query timeout
##
## Value: Duration
## auth.mongo.query_timeout = 5s

## Whether to enable SSL connection.
##
## Value: true | false
## auth.mongo.ssl = false

## SSL keyfile.
##
## Value: File
## auth.mongo.ssl_opts.keyfile =

## SSL certfile.
##
## Value: File
## auth.mongo.ssl_opts.certfile =

## SSL cacertfile.
##
## Value: File
## auth.mongo.ssl_opts.cacertfile =

## MongoDB write mode.
##
## Value: unsafe | safe
## auth.mongo.w_mode =

## Mongo read mode.
##
## Value: master | slave_ok
## auth.mongo.r_mode =

## MongoDB topology options.
auth.mongo.topology.pool_size = 1
auth.mongo.topology.max_overflow = 0
## auth.mongo.topology.overflow_ttl = 1000
## auth.mongo.topology.overflow_check_period = 1000
## auth.mongo.topology.local_threshold_ms = 1000
## auth.mongo.topology.connect_timeout_ms = 20000
## auth.mongo.topology.socket_timeout_ms = 100
## auth.mongo.topology.server_selection_timeout_ms = 30000
## auth.mongo.topology.wait_queue_timeout_ms = 1000
## auth.mongo.topology.heartbeat_frequency_ms = 10000
## auth.mongo.topology.min_heartbeat_frequency_ms = 1000

## Authentication query.
auth.mongo.auth_query.collection = device_auth_col

## Password mainly fields
##
## Value:  password | password,salt
auth.mongo.auth_query.password_field = password

## Password hash.
##
## Value: plain | md5 | sha | sha256 | bcrypt
auth.mongo.auth_query.password_hash = plain

## sha256 with salt suffix
## auth.mongo.auth_query.password_hash = sha256,salt

## sha256 with salt prefix
## auth.mongo.auth_query.password_hash = salt,sha256

## bcrypt with salt prefix
## auth.mongo.auth_query.password_hash = salt,bcrypt

## pbkdf2 with macfun iterations dklen
## macfun: md4, md5, ripemd160, sha, sha224, sha256, sha384, sha512
## auth.mongo.auth_query.password_hash = pbkdf2,sha256,1000,20


## Authentication Selector.
##
## Variables:
##  - %u: username
##  - %c: clientid
##  - %C: common name of client TLS cert
##  - %d: subject of client TLS cert
##
## auth.mongo.auth_query.selector = {Field}={Placeholder}
auth.mongo.auth_query.selector = username=%u

## Enable superuser query.
auth.mongo.super_query = on

auth.mongo.super_query.collection = device_auth_col

auth.mongo.super_query.super_field = is_superuser

#auth.mongo.super_query.selector = username=%u, clientid=%c
auth.mongo.super_query.selector = username=%u

## Enable ACL query.
auth.mongo.acl_query = on

auth.mongo.acl_query.collection = device_auth_col

## ACL Selector.
##
## Multiple selectors could be combined with '$or'
##   when query acl from mongo.
##
## e.g.
##
## With following 2 selectors configured:
##
## auth.mongo.acl_query.selector.1 = username=%u
## auth.mongo.acl_query.selector.2 = username=$all
##
## And if a client connected using username 'ilyas',
##   then the following mongo command will be used to
##   retrieve acl entries:
##
## db.mqtt_acl.find({$or: [{username: "ilyas"},  {username: "$all"}]});
##
## Variables:
##  - %u: username
##  - %c: clientid
##
## Examples:
##
## auth.mongo.acl_query.selector.1 = username=%u,clientid=%c
## auth.mongo.acl_query.selector.2 = username=$all
## auth.mongo.acl_query.selector.3 = clientid=$all

auth.mongo.acl_query.selector = username=%u