Network Swiftlet

The Network Swiftlet is the interface for SwiftMQ Swiftlets to the network. It uses non-blocking I/O and is based on Netty.

Number Selector Tasks

Specifies the number of threads responsible for processing network events. Default value is 5. You might increase it if you have a large number of simultaneous connects or a high number of high throughput connections in general.

Limiting the incoming Message Size

Since 12.5.0

To enable administrators to limit the incoming size of messages for the whole router and thus avoid OutOfMemory errors, attribute max-chunk-size can be set. The value is in bytes. Default is -1 (unlimited).

For example, to allow a maximum size of 10 MB, set it to

    <swiftlet name="sys$net" max-chunk-size="10485760"/>

The connection will be closed if a client tries to send larger messages. This might turn into reconnect attempts until the client gives up:

2022-07-21 15:40:49.789/swiftlet=sys$jms, port=5001/INFORMATION/connection accepted: 127.0.0.1:54770
2022-07-21 15:40:49.843/127.0.0.1:54770/INFORMATION/Exception, EXITING: java.lang.Exception: Input message size (10485926) exceeds max-chunk-size (10485760)
2022-07-21 15:40:49.846/sys$jms/INFORMATION/JMSConnection v750/127.0.0.1:54770/connection closed
2022-07-21 15:40:49.846/sys$net/INFORMATION/127.0.0.1:54770/connection inactive, closing
2022-07-21 15:40:59.849/swiftlet=sys$jms, port=5001/INFORMATION/connection accepted: 127.0.0.1:54774
2022-07-21 15:40:59.883/127.0.0.1:54774/INFORMATION/Exception, EXITING: java.lang.Exception: Input message size (10485968) exceeds max-chunk-size (10485760)
2022-07-21 15:40:59.883/sys$jms/INFORMATION/JMSConnection v750/127.0.0.1:54774/connection closed

Detecting Zombi Connections

Zombi connections are those connections that are created but where no data is sent. Since the keepalive has not been started yet, these connections remain open.

Zombi connections can occur if, for example, SwiftMQ is monitored by opening telnet connections on a JMS listener port and also by DoS attacks.

To prevent those zombi connections brings the router down, attribute zombi-connection-timeout can be set to a millisecond value, e.g. 10000 (10 secs). The Network Swiftlet then starts a timer on each connection and disconnects the connection if the protocol has not been initiated when the timer fires.

Configuration

The configuration of the Network Swiftlet is defined within the element

      <swiftlet name="sys$net" .../>

of the router's configuration file.

Attributes of Element "swiftlet"

Definition

Values

Element List "usage", Parent Element: "swiftlet"

Active Connections. This element list contains zero or more "usage" elements with this template definition:

Definition

Values