Improve documentation for all options

etc/emq.conf

@@ -29,9 +29,10 @@ cluster.discovery = manual
 ## Default: on
 cluster.autoheal = on
 
-## AutoClean down node after this duration.
+## Autoclean down node. A down node will be removed from the cluster
+## if this value > 0.
 ##
-## Value: time duration with units
+## Value: Duration
 ## -h: hour, e.g. '2h' for 2 hours
 ## -m: minute, e.g. '5m' for 5 minutes
 ## -s: second, e.g. '30s' for 30 seconds
@@ -70,8 +71,6 @@ cluster.autoclean = 5m
 ## Multicast Ttl.
 ##
 ## Value: 0-255
-##
-## Default: 255
 ## cluster.mcast.ttl = 255
 
 ## Multicast loop.
@@ -101,7 +100,7 @@ cluster.autoclean = 5m
 ## cluster.etcd.server = http://127.0.0.1:2379
 
 ## The prefix helps build nodes path in etcd. Each node in the cluster
-## will create a path in etcd: v2/keys/{prefix}/{cluster.name}/{node.name}
+## will create a path in etcd: v2/keys/<prefix>/<cluster.name>/<node.name>
 ##
 ## Value: String
 ## cluster.etcd.prefix = emqcl
@@ -121,7 +120,7 @@ cluster.autoclean = 5m
 ## Value: String
 ## cluster.k8s.apiserver = http://10.110.111.204:8080
 
-## The service name helps build node name: {service_name}@{ip}
+## The service name helps lookup EMQ nodes in the cluster.
 ##
 ## Value: String
 ## cluster.k8s.service_name = emq
@@ -142,7 +141,9 @@ cluster.autoclean = 5m
 
 ## Node name.
 ##
-## Value: {name}@{host}
+## See: http://erlang.org/doc/reference_manual/distributed.html
+##
+## Value: <name>@<host>
 ##
 ## Default: emq@127.0.0.1
 node.name = emq@127.0.0.1
@@ -159,14 +160,13 @@ node.smp = auto
 
 ## Heartbeat monitoring of an Erlang runtime system. Comment the line to disable
 ## heartbeat, or set the value as 'on'
-## or the line comment.
 ##
 ## Value: on
 ##
 ## vm.args: -heart
 ## node.heartbeat = on
 
-## Enable Kernel Poll.
+## Enable kernel poll.
 ##
 ## Value: on | off
 ##
@@ -174,7 +174,8 @@ node.smp = auto
 node.kernel_poll = on
 
 ## Sets the number of threads in async thread pool. Valid range is 0-1024.
-## More information at: http://erlang.org/doc/man/erl.html
+##
+## See: http://erlang.org/doc/man/erl.html
 ##
 ## Value: 0-1024
 ##
@@ -183,7 +184,8 @@ node.async_threads = 32
 
 ## Sets the maximum number of simultaneously existing processes for this
 ## system if a Number is passed as value.
-## More information at: http://erlang.org/doc/man/erl.html
+##
+## See: http://erlang.org/doc/man/erl.html
 ##
 ## Value: Number [1024-134217727]
 ##
@@ -192,7 +194,8 @@ node.process_limit = 256000
 
 ## Sets the maximum number of simultaneously existing ports for this system
 ## if a Number is passed as value.
-## More information at: http://erlang.org/doc/man/erl.html
+##
+## See: http://erlang.org/doc/man/erl.html
 ##
 ## Value: Number [1024-134217727]
 ##
@@ -200,15 +203,16 @@ node.process_limit = 256000
 node.max_ports = 65536
 
 ## Set the distribution buffer busy limit (dist_buf_busy_limit).
-## More information at: http://erlang.org/doc/man/erl.html
+##
+## See: http://erlang.org/doc/man/erl.html
 ##
 ## Value: Number [1KB-2GB]
 ##
 ## vm.args: +zdbbl size
-node.dist_buffer_size = 16MB
+node.dist_buffer_size = 8MB
 
-## Sets the maximum number of ETS tables. Note that mnesia and SSL
+## Sets the maximum number of ETS tables. Note that mnesia and SSL will
-## will create temporary ETS tables.
+## create temporary ETS tables.
 ##
 ## Value: Number
 ##
@@ -227,11 +231,11 @@ node.fullsweep_after = 1000
 ## Value: Log file
 node.crash_dump = {{ platform_log_dir }}/crash.dump
 
-## Specifies the net_kernel tick time. TickTime is specified in seconds.
+## Sets the net_kernel tick time. TickTime is specified in seconds.
 ## Notice that all communicating nodes are to have the same TickTime
 ## value specified.
 ##
-## More information at: http://www.erlang.org/doc/man/kernel_app.html#net_ticktime
+## See: http://www.erlang.org/doc/man/kernel_app.html#net_ticktime
 ##
 ## Value: Number
 ##
@@ -239,10 +243,10 @@ node.crash_dump = {{ platform_log_dir }}/crash.dump
 node.dist_net_ticktime = 60
 
 ## Sets the port range for the listener socket of a distributed Erlang node.
-## Note that if there is a firewall between clustered nodes, this port segment
+## Note that if there are firewalls between clustered nodes, this port segment
 ## for nodes’ communication should be allowed.
 ##
-## More information at: http://www.erlang.org/doc/man/kernel_app.html
+## See: http://www.erlang.org/doc/man/kernel_app.html
 ##
 ## Value: Port [1024-65535]
 node.dist_listen_min = 6369
@@ -273,7 +277,7 @@ log.console = console
 ## Default: error
 log.console.level = error
 
-## The file where console logs will be writed to, when 'log.console' is set to 'file'.
+## The file where console logs will be writed to, when 'log.console' is set as 'file'.
 ##
 ## Value: File Name 
 ## log.console.file = {{ platform_log_dir }}/console.log
@@ -328,12 +332,12 @@ log.crash = on
 ## Value: File Name
 log.crash.file = {{ platform_log_dir }}/crash.log
 
-## Enable Syslog.
+## Enable syslog.
 ##
 ## Values: on | off
 log.syslog = on
 
-## The severity level for syslog.
+## Sets the severity level for syslog.
 ##
 ## Value: debug | info | notice | warning | error | critical | alert | emergency
 log.syslog.level = error
@@ -343,7 +347,8 @@ log.syslog.level = error
 ##--------------------------------------------------------------------
 
 ## Allow Anonymous Authentication.
-## !!! Notice: Should disable the config for production deployment.
+##
+## Notice: Disable the option for production deployment.
 ##
 ## Value: true | false
 mqtt.allow_anonymous = true
@@ -358,7 +363,7 @@ mqtt.acl_nomatch = allow
 ## Value: File Name
 mqtt.acl_file = {{ platform_etc_dir }}/acl.conf
 
-## Cache ACL for PUBLISH Messages.
+## Whether to cache ACL for publish messages.
 ##
 ## Value: true | false
 mqtt.cache_acl = true
@@ -367,7 +372,7 @@ mqtt.cache_acl = true
 ## MQTT Protocol
 ##--------------------------------------------------------------------
 
-## Maximum MQTT clientId length allowed.
+## Maximum length of MQTT clientId allowed.
 ##
 ## Value: Number [23-65535]
 mqtt.max_clientid_len = 1024
@@ -380,13 +385,13 @@ mqtt.max_clientid_len = 1024
 mqtt.max_packet_size = 64KB
 
 ## Check if the websocket protocol header is valid.
-## Turn off the config when developing WeChat App.
+## Turn off the option when developing WeChat App.
 ##
 ## Value: on | off
 mqtt.websocket_protocol_header = on
 
 ## The backoff for MQTT keepalive timeout.
-## The broker will kick a MQTT connection out until 'Keepalive * backoff * 2' timeout.
+## EMQ will kick a MQTT connection out until 'Keepalive * backoff * 2' timeout.
 ##
 ## Value: Float > 0.5
 mqtt.keepalive_backoff = 0.75
@@ -395,7 +400,7 @@ mqtt.keepalive_backoff = 0.75
 ## MQTT Connection
 ##--------------------------------------------------------------------
 
-## Force GC the MQTT connection. Value 0 will disable the Force GC.
+## Force GC the MQTT connections. Value 0 will disable the Force GC.
 ##
 ## Value: Number >= 0 
 mqtt.conn.force_gc_count = 100
@@ -409,8 +414,7 @@ mqtt.conn.force_gc_count = 100
 ## Value: Duration
 mqtt.client.idle_timeout = 30s
 
-## Maximum publish rate of MQTT messages per second.
+## TODO: Maximum publish rate of MQTT messages per second.
-## TODO: R2.4 release
 ##
 ## Value: Number
 ## mqtt.client.max_publish_rate = 5
@@ -439,7 +443,7 @@ mqtt.session.upgrade_qos = off
 ## Value: Number
 mqtt.session.max_inflight = 32
 
-## Retry interval for QoS1/2 message redelivering.
+## Retry interval for QoS1/2 message delivering.
 ##
 ## Value: Duration
 mqtt.session.retry_interval = 20s
@@ -470,7 +474,7 @@ mqtt.session.enable_stats = on
 ## Default: 2h, 2 hours
 mqtt.session.expiry_interval = 2h
 
-## Ignore loop delivery of messages.
+## Whether to ignore loop delivery of messages.
 ##
 ## Value: true | false
 ##
@@ -481,12 +485,12 @@ mqtt.session.ignore_loop_deliver = false
 ## MQTT Message Queue
 ##--------------------------------------------------------------------
 
-## Message Queue Type.
+## Message queue type.
 ##
 ## Value: simple | priority
 mqtt.mqueue.type = simple
 
-## Topic Priority. Default is 0.
+## Topic priority. Default is 0.
 ##
 ## Value: Number [0-255]
 ##
@@ -508,7 +512,7 @@ mqtt.mqueue.low_watermark = 20%
 ## Value: Percent
 mqtt.mqueue.high_watermark = 60%
 
-## Queue Qos0 messages?
+## Whether to enqueue Qos0 messages.
 ##
 ## Value: false | true
 mqtt.mqueue.store_qos0 = true
@@ -517,19 +521,19 @@ mqtt.mqueue.store_qos0 = true
 ## MQTT Broker and PubSub
 ##--------------------------------------------------------------------
 
-## System Interval of publishing $SYS Messages.
+## System interval of publishing $SYS messages.
 ##
 ## Value: Duration
 ##
 ## Default: 1m, 1 minute
 mqtt.broker.sys_interval = 1m
 
-## The PubSub pool size. Default value should be scheduler numbers.
+## The PubSub pool size. Default value should be same as scheduler numbers.
 ##
 ## Value: Number > 1
 mqtt.pubsub.pool_size = 8
 
-## TODO: Subscribe Asynchronously.
+## TODO: Subscribe asynchronously.
 ##
 ## Value: true | false
 mqtt.pubsub.async = true
@@ -609,15 +613,18 @@ listener.tcp.external.max_clients = 102400
 ## listener.tcp.external.rate_limit = 100,10
 
 ## The access control rules for the MQTT/TCP listener.
-## More information at: https://github.com/emqtt/esockd#allowdeny
+##
+## See: https://github.com/emqtt/esockd#allowdeny
 ##
 ## Value: ACL Rule
-## listener.tcp.external.access.1 = allow 192.168.0.0/24
+##
-listener.tcp.external.access.2 = allow all
+## Example: allow 192.168.0.0/24
+listener.tcp.external.access.1 = allow all
 
-## Enable the Proxy Protocol V1/2 if the EMQ cluster is deployed behind
+## Enable the Proxy Protocol V1/2 if the EMQ cluster is deployed
-## HAProxy or Nginx.
+## behind HAProxy or Nginx.
-## More information at: https://www.haproxy.com/blog/haproxy/proxy-protocol/
+##
+## See: https://www.haproxy.com/blog/haproxy/proxy-protocol/
 ##
 ## Value: on | off
 ## listener.tcp.external.proxy_protocol = on
@@ -635,8 +642,6 @@ listener.tcp.external.access.2 = allow all
 ## Value: cn
 ## listener.tcp.external.peer_cert_as_username = cn
 
-## TCP socket options for the MQTT listener.
-
 ## The TCP backlog defines the maximum length that the queue of pending
 ## connections can grow to.
 ##
@@ -654,13 +659,15 @@ listener.tcp.external.send_timeout = 15s
 listener.tcp.external.send_timeout_close = on
 
 ## The TCP receive buffer(os kernel) for MQTT connections.
-## More information at: http://erlang.org/doc/man/inet.html
+##
+## See: http://erlang.org/doc/man/inet.html
 ##
 ## Value: Bytes
 ## listener.tcp.external.recbuf = 4KB
 
 ## The TCP send buffer(os kernel) for MQTT connections.
-## More information at: http://erlang.org/doc/man/inet.html
+##
+## See: http://erlang.org/doc/man/inet.html
 ##
 ## Value: Bytes
 ## listener.tcp.external.sndbuf = 4KB
@@ -671,7 +678,8 @@ listener.tcp.external.send_timeout_close = on
 ## >= max(val(sndbuf),val(recbuf)) to avoid performance issues because
 ## of unnecessary copying. val(buffer) is automatically set to the above
 ## maximum when values sndbuf or recbuf are set.
-## More information at: http://erlang.org/doc/man/inet.html
+##
+## See: http://erlang.org/doc/man/inet.html
 ##
 ## Value: Bytes
 ## listener.tcp.external.buffer = 4KB
@@ -690,8 +698,8 @@ listener.tcp.external.nodelay = true
 ##--------------------------------------------------------------------
 ## Internal TCP Listener for MQTT Protocol
 
-## The IP address and port that the internal MQTT/TCP protocol listener will
+## The IP address and port that the internal MQTT/TCP protocol listener
-## bind.
+## will bind.
 ##
 ## Value: IP:Port, Port
 ##
@@ -713,61 +721,73 @@ listener.tcp.internal.max_clients = 102400
 ## Value: String
 ## listener.tcp.internal.zone = internal
 
-## Mountpoint of the MQTT/TCP Listener. All the topics will
+## Mountpoint of the MQTT/TCP Listener.
-## be prefixed with the mount point if this option is enabled.
+##
+## See: listener.tcp.<name>.mountpoint
 ##
 ## Value: String
-## listener.tcp.external.mountpoint = internal/
+## listener.tcp.internal.mountpoint = internal/
 
 ## Rate limit for the internal MQTT/TCP connections.
-## Format is 'burst,rate'.
+##
+## See: listener.tcp.<name>.rate_limit
 ##
 ## Value: burst,rate
-## Unit: KB/sec
 ## listener.tcp.internal.rate_limit = 1000,100
 
-## The TCP backlog defines the maximum length that the queue of
+## The TCP backlog of internal MQTT/TCP Listener.
-## pending connections can grow to.
+##
+## See: listener.tcp.<name>.backlog
 ##
 ## Value: Number >= 0
 listener.tcp.internal.backlog = 512
 
 ## The TCP send timeout for internal MQTT connections.
 ##
+## See: listener.tcp.<name>.send_timeout
+##
 ## Value: Duration
 listener.tcp.internal.send_timeout = 5s
 
 ## Close the MQTT/TCP connection if send timeout.
 ##
+## See: listener.tcp.<name>.send_timeout_close
+##
 ## Value: on | off
 listener.tcp.external.send_timeout_close = on
 
-## The TCP receive buffer(os kernel) for MQTT connections.
+## The TCP receive buffer(os kernel) for internal MQTT connections.
-## More information at: http://erlang.org/doc/man/inet.html
+##
+## See: listener.tcp.<name>.recbuf
 ##
 ## Value: Bytes
 listener.tcp.internal.recbuf = 16KB
 
-## The TCP send buffer(os kernel) for MQTT connections.
+## The TCP send buffer(os kernel) for internal MQTT connections.
-## More information at: http://erlang.org/doc/man/inet.html
+##
+## See: http://erlang.org/doc/man/inet.html
 ##
 ## Value: Bytes
 listener.tcp.internal.sndbuf = 16KB
 
 ## The size of the user-level software buffer used by the driver.
-## See: listener.tcp.external.buffer
+##
+## See: listener.tcp.<name>.buffer
 ##
 ## Value: Bytes
 listener.tcp.internal.buffer = 16KB
 
 ## Sets the 'buffer = max(sndbuf, recbuf)' if this option is enabled.
 ##
+## See: listener.tcp.<name>.tune_buffer
+##
 ## Value: on | off
 listener.tcp.internal.tune_buffer = on
 
-## The TCP_NODELAY flag for MQTT connections.
+## The TCP_NODELAY flag for internal MQTT connections.
-## See: listener.tcp.external.nodelay
+##
-#
+## See: listener.tcp.<name>.nodelay
+##
 ## Value: true | false
 listener.tcp.internal.nodelay = false
 
@@ -797,43 +817,43 @@ listener.ssl.external.max_clients = 1024
 ## Value: String
 ## listener.ssl.external.zone = external
 
-## Mountpoint of the MQTT/SSL Listener. All the topics of this
+## Mountpoint of the MQTT/SSL Listener.
-## listener will be prefixed with the mount point if this option
-## is enabled.
 ##
 ## Value: String
 ## listener.ssl.external.mountpoint = inbound/
 
-## Rate limit for the external MQTT/SSL connections.
-## Format is 'burst,rate'.
-##
-## Value: burst,rate
-## Unit: KB/sec
-## listener.ssl.external.rate_limit = 100,10
-
-## Enable the Proxy Protocol V1/2 if the EMQ cluster is deployed behind
-## HAProxy or Nginx.
-## More information at: https://www.haproxy.com/blog/haproxy/proxy-protocol/
-##
-## Value: on | off
-## listener.ssl.external.proxy_protocol = on
-
-## Sets the timeout for proxy protocol. EMQ will close the TCP connection
-## if no proxy protocol packet recevied within the timeout.
-##
-## Value: Duration
-## listener.ssl.external.proxy_protocol_timeout = 3s
-
 ## The access control rules for the MQTT/SSL listener.
-## More information at: https://github.com/emqtt/esockd#allowdeny
+##
+## See: listener.tcp.<name>.access
 ##
 ## Value: ACL Rule
 listener.ssl.external.access.1 = allow all
 
-## TLS versions only to protect from POODLE attack.
+## Rate limit for the external MQTT/SSL connections.
-## See http://erlang.org/doc/man/ssl.html
 ##
-## Value: String
+## Value: burst,rate
+## listener.ssl.external.rate_limit = 100,10
+
+## Enable the Proxy Protocol V1/2 if the EMQ cluster is deployed behind
+## HAProxy or Nginx.
+##
+## See: listener.tcp.<name>.proxy_protocol
+##
+## Value: on | off
+## listener.ssl.external.proxy_protocol = on
+
+## Sets the timeout for proxy protocol.
+##
+## See: listener.tcp.<name>.proxy_protocol_timeout
+##
+## Value: Duration
+## listener.ssl.external.proxy_protocol_timeout = 3s
+
+## TLS versions only to protect from POODLE attack.
+##
+## See: http://erlang.org/doc/man/ssl.html
+##
+## Value: String, seperated by ','
 ## listener.ssl.external.tls_versions = tlsv1.2,tlsv1.1,tlsv1
 
 ## TLS Handshake timeout.
@@ -842,17 +862,20 @@ listener.ssl.external.access.1 = allow all
 listener.ssl.external.handshake_timeout = 15s
 
 ## Path to the file containing the user's private PEM-encoded key.
-## More information at: http://erlang.org/doc/man/ssl.html
+##
+## See: http://erlang.org/doc/man/ssl.html
 ##
 ## Value: File
 listener.ssl.external.keyfile = {{ platform_etc_dir }}/certs/key.pem
 
 ## Path to a file containing the user certificate.
 ##
+## See: http://erlang.org/doc/man/ssl.html
+##
 ## Value: File
 listener.ssl.external.certfile = {{ platform_etc_dir }}/certs/cert.pem
 
-## Path to a file containing PEM-encoded CA certificates. The CA certificates
+## Path to the file containing PEM-encoded CA certificates. The CA certificates
 ## are used during server authentication and when building the client certificate chain.
 ##
 ## Value: File
@@ -891,14 +914,17 @@ listener.ssl.external.certfile = {{ platform_etc_dir }}/certs/cert.pem
 ## Value: true | false
 ## listener.ssl.external.fail_if_no_peer_cert = true
 
-## This is the single most important configuration option of an Erlang SSL application.
+## This is the single most important configuration option of an Erlang SSL
-## Ciphers (and their ordering) define the way the client and server encrypt information
+## application. Ciphers (and their ordering) define the way the client and
-## over the wire, from the initial Diffie-Helman key exchange, the session key encryption
+## server encrypt information over the wire, from the initial Diffie-Helman
-## algorithm and the message digest algorithm. Selecting a good cipher suite is critical
+## key exchange, the session key encryption ## algorithm and the message
-## for the application’s data security, confidentiality and performance.
+## digest algorithm. Selecting a good cipher suite is critical for the
+## application’s data security, confidentiality and performance.
+##
 ## The cipher list above offers:
 ##
-## A good balance between compatibility with older browsers. It can get stricter for Machine-To-Machine scenarios.
+## A good balance between compatibility with older browsers.
+## It can get stricter for Machine-To-Machine scenarios.
 ## Perfect Forward Secrecy.
 ## No old/insecure encryption and HMAC algorithms
 ##
@@ -907,8 +933,8 @@ listener.ssl.external.certfile = {{ platform_etc_dir }}/certs/cert.pem
 ## Value: Ciphers
 ## listener.ssl.external.ciphers = ECDHE-ECDSA-AES256-GCM-SHA384,ECDHE-RSA-AES256-GCM-SHA384,ECDHE-ECDSA-AES256-SHA384,ECDHE-RSA-AES256-SHA384,ECDHE-ECDSA-DES-CBC3-SHA,ECDH-ECDSA-AES256-GCM-SHA384,ECDH-RSA-AES256-GCM-SHA384,ECDH-ECDSA-AES256-SHA384,ECDH-RSA-AES256-SHA384,DHE-DSS-AES256-GCM-SHA384,DHE-DSS-AES256-SHA256,AES256-GCM-SHA384,AES256-SHA256,ECDHE-ECDSA-AES128-GCM-SHA256,ECDHE-RSA-AES128-GCM-SHA256,ECDHE-ECDSA-AES128-SHA256,ECDHE-RSA-AES128-SHA256,ECDH-ECDSA-AES128-GCM-SHA256,ECDH-RSA-AES128-GCM-SHA256,ECDH-ECDSA-AES128-SHA256,ECDH-RSA-AES128-SHA256,DHE-DSS-AES128-GCM-SHA256,DHE-DSS-AES128-SHA256,AES128-GCM-SHA256,AES128-SHA256,ECDHE-ECDSA-AES256-SHA,ECDHE-RSA-AES256-SHA,DHE-DSS-AES256-SHA,ECDH-ECDSA-AES256-SHA,ECDH-RSA-AES256-SHA,AES256-SHA,ECDHE-ECDSA-AES128-SHA,ECDHE-RSA-AES128-SHA,DHE-DSS-AES128-SHA,ECDH-ECDSA-AES128-SHA,ECDH-RSA-AES128-SHA,AES128-SHA
 
-## SSL parameter renegotiation is a feature that allows a client and
+## SSL parameter renegotiation is a feature that allows a client and a server
-## a server to renegotiate the parameters of the SSL connection on the fly.
+## to renegotiate the parameters of the SSL connection on the fly.
 ## RFC 5746 defines a more secure way of doing this. By enabling secure renegotiation,
 ## you drop support for the insecure renegotiation, prone to MitM attacks.
 ##
@@ -918,7 +944,8 @@ listener.ssl.external.certfile = {{ platform_etc_dir }}/certs/cert.pem
 ## A performance optimization setting, it allows clients to reuse
 ## pre-existing sessions, instead of initializing new ones.
 ## Read more about it here.
-## More information at: http://erlang.org/doc/man/ssl.html
+##
+## See: http://erlang.org/doc/man/ssl.html
 ##
 ## Value: on | off
 ## listener.ssl.external.reuse_sessions = on
@@ -938,38 +965,57 @@ listener.ssl.external.certfile = {{ platform_etc_dir }}/certs/cert.pem
 ## listener.ssl.external.peer_cert_as_username = cn
 
 ## TCP backlog for the SSL connection.
-## See 'listener.tcp.external.backlog'
+##
+## See listener.tcp.<name>.backlog
 ##
 ## Value: Number >= 0
 ## listener.ssl.external.backlog = 1024
 
 ## The TCP send timeout for the SSL connection.
-## See 'listener.tcp.external.send_timeout'
+##
+## See listener.tcp.<name>.send_timeout
 ##
 ## Value: Duration
 ## listener.ssl.external.send_timeout = 15s
 
-## See 'listener.tcp.external.send_timeout_close'
+## Close the SSL connection if send timeout.
+##
+## See: listener.tcp.<name>.send_timeout_close
 ##
 ## Value: on | off
 ## listener.ssl.external.send_timeout_close = on
 
-## See 'listener.tcp.external.recbuf'
+## The TCP receive buffer(os kernel) for the SSL connections.
+##
+## See: listener.tcp.<name>.recbuf
 ##
 ## Value: Bytes
 ## listener.ssl.external.recbuf = 4KB
 
-## See 'listener.tcp.external.sndbuf'
+## The TCP send buffer(os kernel) for internal MQTT connections.
+##
+## See: listener.tcp.<name>.sndbuf
 ##
 ## Value: Bytes
 ## listener.ssl.external.sndbuf = 4KB
 
-## See 'listener.tcp.external.buffer'
+## The size of the user-level software buffer used by the driver.
+##
+## See: listener.tcp.<name>.buffer
 ##
 ## Value: Bytes
 ## listener.ssl.external.buffer = 4KB
 
-## See 'listener.tcp.external.nodelay'
+## Sets the 'buffer = max(sndbuf, recbuf)' if this option is enabled.
+##
+## See: listener.tcp.<name>.tune_buffer
+##
+## Value: on | off
+## listener.ssl.external.tune_buffer = on
+
+## The TCP_NODELAY flag for SSL connections.
+##
+## See: listener.tcp.<name>.nodelay
 ##
 ## Value: true | false
 ## listener.ssl.external.nodelay = true
@@ -993,21 +1039,23 @@ listener.ws.external.acceptors = 4
 ## Maximum number of concurrent MQTT/Websocket connections.
 ##
 ## Value: Number
-listener.ws.external.max_clients = 64
+listener.ws.external.max_clients = 102400
 
 ## TODO: Zone of the external MQTT/Websocket listener belonged to.
 ##
 ## Value: String
 ## listener.ws.external.zone = external
 
-## Mountpoint of the MQTT/Websocket Listener. All the topics of
+## Mountpoint of the MQTT/Websocket Listener.
-## this listener will be prefixed with the mount point if this
+##
-## option is enabled.
+## See: listener.tcp.<name>.mountpoint
 ##
 ## Value: String
 ## listener.ws.external.mountpoint = external/
 
-## The access control rules for the MQTT/Websocket listener.
+## The access control for the MQTT/Websocket listener.
+##
+## See: listener.tcp.<name>.access
 ##
 ## Value: ACL Rule
 listener.ws.external.access.1 = allow all
@@ -1015,43 +1063,70 @@ listener.ws.external.access.1 = allow all
 ## Enable the Proxy Protocol V1/2 if the EMQ cluster is deployed behind
 ## HAProxy or Nginx.
 ##
+## See: listener.tcp.<name>.proxy_protocol
+##
 ## Value: on | off
 ## listener.ws.external.proxy_protocol = on
 
-## See 'listener.tcp.external.proxy_protocol_timeout'
+## Sets the timeout for proxy protocol.
+##
+## See: listener.tcp.<name>.proxy_protocol_timeout
 ##
 ## Value: Duration
 ## listener.ws.external.proxy_protocol_timeout = 3s
 
-## TCP Options
+## The TCP backlog of external MQTT/Websocket Listener.
+##
+## See: listener.tcp.<name>.backlog
+##
+## Value: Number >= 0
 listener.ws.external.backlog = 1024
 
-## See 'listener.tcp.external.send_timeout'
+## The TCP send timeout for external MQTT/Websocket connections.
+##
+## See: listener.tcp.<name>.send_timeout
 ##
 ## Value: Duration
 listener.ws.external.send_timeout = 15s
 
-## See 'listener.tcp.external.send_timeout_close'
+## Close the MQTT/Websocket connection if send timeout.
+##
+## See: listener.tcp.<name>.send_timeout_close
 ##
 ## Value: on | off
 listener.ws.external.send_timeout_close = on
 
-## See 'listener.tcp.external.recbuf'
+## The TCP receive buffer(os kernel) for external MQTT/Websocket connections.
+##
+## See: listener.tcp.<name>.recbuf
 ##
 ## Value: Bytes
 ## listener.ws.external.recbuf = 4KB
 
-## See 'listener.tcp.external.sndbuf'
+## The TCP send buffer(os kernel) for external MQTT/Websocket connections.
+##
+## See 'listener.tcp.<name>.sndbuf'
 ##
 ## Value: Bytes
 ## listener.ws.external.sndbuf = 4KB
 
-## See 'listener.tcp.external.buffer'
+## The size of the user-level software buffer used by the driver.
+##
+## See: listener.tcp.<name>.buffer
 ##
 ## Value: Bytes
 ## listener.ws.external.buffer = 4KB
 
-## See 'listener.tcp.external.nodelay'
+## Sets the 'buffer = max(sndbuf, recbuf)' if this option is enabled.
+##
+## See: listener.tcp.<name>.tune_buffer
+##
+## Value: on | off
+listener.ws.external.tune_buffer = on
+
+## The TCP_NODELAY flag for external MQTT/Websocket connections.
+##
+## See: listener.tcp.<name>.nodelay
 ##
 ## Value: true | false
 listener.ws.external.nodelay = true
@@ -1082,64 +1157,149 @@ listener.wss.external.max_clients = 64
 ## Value: String
 ## listener.wss.external.zone = external
 
-## See 'listener.ssl.external.mountpoint'
+## Mountpoint of the MQTT/Websocket/SSL Listener.
+##
+## See 'listener.tcp.<name>.mountpoint'
 ##
 ## Value: String
 ## listener.wss.external.mountpoint = inbound/
 
-## See 'listener.ssl.external.acess.1'
+## The access control rules for the MQTT/Websocket/SSL listener.
+##
+## See: listener.tcp.<name>.access.<no>
 ##
 ## Value: ACL Rule
 listener.wss.external.access.1 = allow all
 
-## See 'listener.ssl.external.proxy_protocol'
+## Enable the Proxy Protocol V1/2 support.
+##
+## See: listener.tcp.<name>.proxy_protocol
 ##
 ## Value: on | off
 ## listener.wss.external.proxy_protocol = on
 
-## See 'listener.ssl.external.proxy_protocol_timeout'
+## Sets the timeout for proxy protocol.
+##
+## See: listener.tcp.<name>.proxy_protocol_timeout
 ##
 ## Value: Duration
 ## listener.wss.external.proxy_protocol_timeout = 3s
 
-## SSL Options. Same to 'listener.ssl.*'
+## TLS Handshake timeout.
+##
+## See: listener.ssl.<name>.handshake_timeout
+##
+## Value: Duration
 listener.wss.external.handshake_timeout = 15s
 
+## Path to the file containing the user's private PEM-encoded key.
+##
+## See: listener.ssl.<name>.keyfile
+##
+## Value: File
 listener.wss.external.keyfile = {{ platform_etc_dir }}/certs/key.pem
 
+## Path to a file containing the user certificate.
+##
+## See: listener.ssl.<name>.certfile
+##
+## Value: File
 listener.wss.external.certfile = {{ platform_etc_dir }}/certs/cert.pem
 
+## Path to the file containing PEM-encoded CA certificates.
+##
+## See: listener.ssl.<name>.cacert
+##
+## Value: File
 ## listener.wss.external.cacertfile = {{ platform_etc_dir }}/certs/cacert.pem
 
+## See: listener.ssl.<name>.dhfile
+##
+## Value: File
 ## listener.ssl.external.dhfile = {{ platform_etc_dir }}/certs/dh-params.pem
 
+## See: listener.ssl.<name>.vefify
+##
+## Value: vefify_peer | verify_none
 ## listener.wss.external.verify = verify_peer
 
+## See: listener.ssl.<name>.fail_if_no_peer_cert
+##
+## Value: false | true
 ## listener.wss.external.fail_if_no_peer_cert = true
 
+## See: listener.ssl.<name>.ciphers
+##
+## Value: Ciphers
 ## listener.wss.external.ciphers =
 
+## See: listener.ssl.<name>.secure_renegotiate
+##
+## Value: on | off
 ## listener.wss.external.secure_renegotiate = off
 
+## See: listener.ssl.<name>.reuse_sessions
+##
+## Value: on | off
 ## listener.wss.external.reuse_sessions = on
 
+## See: listener.ssl.<name>.honor_cipher_order
+##
+## Value: on | off
 ## listener.wss.external.honor_cipher_order = on
 
+## See: listener.ssl.<name>.peer_cert_as_username
+##
+## Value: cn | dn
 ## listener.wss.external.peer_cert_as_username = cn
 
-## TCP Options. Same to 'listener.tcp.*'
+## TCP backlog for the Websocket/SSL connection.
+##
+## See 'listener.tcp.<name>.backlog'
+##
+## Value: Number >= 0
 listener.wss.external.backlog = 1024
 
+## The TCP send timeout for the Websocket/SSL connection.
+##
+## See 'listener.tcp.<name>.send_timeout'
+##
+## Value: Duration
 listener.wss.external.send_timeout = 15s
 
+## Close the Websocket/SSL connection if send timeout.
+##
+## See: listener.tcp.<name>.send_timeout_close
+##
+## Value: on | off
 listener.wss.external.send_timeout_close = on
 
+## The TCP receive buffer(os kernel) for the Websocket/SSL connections.
+##
+## See: listener.tcp.<name>.recbuf
+##
+## Value: Bytes
 ## listener.wss.external.recbuf = 4KB
 
+## The TCP send buffer(os kernel) for the Websocket/SSL connections.
+##
+## See: listener.tcp.<name>.sndbuf
+##
+## Value: Bytes
 ## listener.wss.external.sndbuf = 4KB
 
+## The size of the user-level software buffer used by the driver.
+##
+## See: listener.tcp.<name>.buffer
+##
+## Value: Bytes
 ## listener.wss.external.buffer = 4KB
 
+## The TCP_NODELAY flag for Websocket/SSL connections.
+##
+## See: listener.tcp.<name>.nodelay
+##
+## Value: true | false
 ## listener.wss.external.nodelay = true
 
 ##--------------------------------------------------------------------
@@ -1163,18 +1323,18 @@ listener.api.mgmt.acceptors = 4
 listener.api.mgmt.max_clients = 64
 
 ## The access control rules for the listener.
-## More information at: https://github.com/emqtt/esockd#allowdeny
+##
+## See: https://github.com/emqtt/esockd#allowdeny
 ##
 ## Value: ACL Rule
 listener.api.mgmt.access.1 = allow all
 
-## The TCP backlog defines the maximum length that the queue of pending
+## The TCP backlog for HTTP API.
-## connections can grow to.
 ##
 ## Value: Number >= 0
 listener.api.mgmt.backlog = 512
 
-## The TCP send timeout.
+## The TCP send timeout for HTTP API.
 ##
 ## Value: Duration
 listener.api.mgmt.send_timeout = 15s
@@ -1196,13 +1356,15 @@ listener.api.mgmt.send_timeout_close = on
 sysmon.long_gc = false
 
 ## Enable Long Schedule(ms) monitoring.
-## More information at: http://erlang.org/doc/man/erlang.html#system_monitor-2
+##
+## See: http://erlang.org/doc/man/erlang.html#system_monitor-2
 ##
 ## Value: Number
 sysmon.long_schedule = 240
 
 ## Enable Large Heap monitoring.
-## More information at: http://erlang.org/doc/man/erlang.html#system_monitor-2
+##
+## See: http://erlang.org/doc/man/erlang.html#system_monitor-2
 ##
 ## Value: bytes
 ##
@@ -1210,13 +1372,15 @@ sysmon.long_schedule = 240
 sysmon.large_heap = 8MB
 
 ## Enable Busy Port monitoring.
-## More information at: http://erlang.org/doc/man/erlang.html#system_monitor-2
+##
+## See: http://erlang.org/doc/man/erlang.html#system_monitor-2
 ##
 ## Value: true | false
 sysmon.busy_port = false
 
 ## Enable Busy Dist Port monitoring.
-## More information at: http://erlang.org/doc/man/erlang.html#system_monitor-2
+##
+## See: http://erlang.org/doc/man/erlang.html#system_monitor-2
 ##
 ## Value: true | false
 sysmon.busy_dist_port = true