Changing the Default Transport

On the back end, APIs are Apache Synapse configurations that WSO2 API Manager accesses through a transport. The default API Manager transport is the PassThrough transport, but you can configure a different default transport in your axis2.xml file. For example, to use the HTTP-NIO transport as the default, go to the <APIM_HOME>/repository/conf/axis2 folder, open the axis2.xml file, and then in the "Transport Ins" and "Transport Outs" sections, comment out the PassThrough configurations and uncomment the configurations for the HTTP-NIO transport.

WSO2 products do not use the HTTP/S servlet transport configurations that are in axis2.xml file. Instead, they use Tomcat-level servlet transports, which are used by the management console in <PRODUCT_HOME>/repository/conf/tomcat/catalina-server.xml file.

The following topics provide more information on these transports:

HTTP PassThrough transport

HTTP PassThrough Transport is the default, non-blocking HTTP transport implementation based on HTTP Core NIO and is specially designed for streaming messages. It is similar to the old message relay transport, but it does not care about the content type and simply streams all received messages through. It also has a simpler and cleaner model for forwarding messages back and forth. The two classes that implement the receiver and sender APIs are org.apache.synapse.transport.passthru.PassThroughHttpListener and org.apache.synapse.transport.passthru.PassThroughHttpSender, respectively. The PassThrough Transport does not require the binary relay builder and expanding formatter.

HTTP-NIO transport

The HTTP-NIO transport is a module of the Apache Synapse project. Apache Synapse ships the HTTP-NIO transport as the default, non-blocking HTTP transport implementation. The two classes that implement the receiver and sender APIs are org.apache.synapse.transport.nhttp.HttpCoreNIOListener and org.apache.synapse.transport.nhttp.HttpCoreNIOSender, respectively. These classes are available in the JAR file named synapse-nhttp-transport.jar. The transport implementation is based on Apache HTTP Core - NIO and uses a configurable pool of non-blocking worker threads to grab incoming HTTP messages off the wire. The PassThrough transport is the preferred default transport for WSO2 API Manager, but HTTP-NIO is supported for backward compatibility.

Transport receiver parameters

Parameter Name	Description	Required	Possible Values	Default Value
port	The port on which this transport receiver should listen for incoming messages.	No	A positive integer less than 65535	8280
non-blocking	Setting this parameter to true is vital for reliable messaging and a number of other scenarios to work properly.	Yes	`true` or `false`	`true`
bind-address	The address of the interface to which the transport listener should bind.	No	A host name or an IP address	127.0.0.1
WSDLEPRPrefix	A URL prefix which will be added to all service EPRs and EPRs in WSDLs etc.	No	A URL of the form <protocol>://<hostname>:<port>/
httpGetProcessor	An extension point used to execute a special interceptor for HTTP GET requests.	Yes	An extension point	`org.wso2.carbon.mediation.transport.handlers .PassThroughNHttpGetProcessor`
priorityConfigFile	The location of the file containing the configuration for priority based dispatching.	No	A file location

Transport sender parameters

Parameter Name	Description	Required	Possible Values	Default Value
non-blocking	Setting this parameter to true is vital for reliable messaging and a number of other scenarios to work properly.	Yes	`true` or `false`	`true`
warnOnHTTP500	Logs warnings for HTTP 500 responses only for the specified content-types. For example, `<parameter name="warnOnHTTP500 locked="false">x-application/hessian\|none</parameter>` would log warnings for HTTP 500 responses of content-type 'x-application/hessian' or messages missing a content-type.	No	A list of content types separated by "\|"
http.proxyHost	If the outgoing messages should be sent through an HTTP proxy server, use this parameter to specify the target proxy.	No	A host name or an IP address
http.proxyPort	The port through which the target proxy accepts HTTP traffic.	No	A positive integer less than 65535
http.nonProxyHosts	The list of hosts to which the HTTP traffic should be sent directly without going through the proxy. When trying to add multiple hostnames along with an asterisk in order to define a set of sub-domains for non-proxy hosts, you need to add a period before the asterisk when configuring proxy server. `".*.abc.my.com\|localhost"`	No	A list of host names or IP addresses separated by '\|'

Connection throttling

With the HTTP PassThrough and HTTP NIO transports, you can enable connection throttling to restrict the number of simultaneous open connections. To enable connection throttling, edit the <PRODUCT_HOME>/repository/conf/nhttp.properties (for the HTTP NIO transport) or <PRODUCT_HOME>/repository/conf/passthru.properties (for the PassThrough transport) and add the following line: max_open_connections = 2

This will restrict simultaneous open incoming connections to 2. To disable throttling, delete the max_open_connections setting or set it to -1.

Connection throttling is never exact. For example, setting this property to 2 will result in roughly two simultaneous open connections at any given time.