Isolate incoming application requests with virtual hosts
A virtual host is a configuration entity that enables a single server to host multiple domain name and port configurations. You can configure virtual hosts on your Open Liberty server to isolate incoming application requests from each other and from administrative traffic, such as metrics and JMX communications.
For example, your company might maintain two applications on the same server, one for customers and another for employees. By using virtual hosts, you can specify different hostname and port number configurations for each application. You can also specify aliases for each host so that the customer application is accessed from the
customer.example.com URL and the employee application is accessed from the
employee.example.com URL. Although the two applications run on the same server and share many of the same configuration resources, incoming requests for each application are isolated from the other. Inbound requests that are associated with one virtual host cannot access applications that are associated with any other virtual host, even if those other virtual hosts share a physical machine.
You can also configure a dedicated virtual host for your application to keep incoming application requests isolated from administrative traffic, such as metrics and JMX communications, which are handled by the default virtual host.
Each virtual host has an ID value and a list of one or more host aliases by which it is known. A host alias is the TCP/IP hostname and port number combination that is used to request a resource, for example,
yourHostName:80. When no port number is specified, the default is port number is
The virtual host configuration accepts a wildcard value (
*) for the hostname in virtual host alias configurations. You can use wildcard entries for aliases by port to specify that all valid hostname and address combinations on a particular port map to a particular virtual host. However, wildcard hostname values are not recommended for security-hardened production environments. For more information, see Virtual hosts and application security in production environments.
The default alias for a virtual host is
*:80, which uses an external port that is not secure. This default is used for any virtual hosts that do not specify an alias configuration, including the
default_host default virtual host.
The configuration of a virtual host alias determines whether a virtual host uses secure ports, and whether the ports are internal or external:
Aliases of the form
*:9080use the internal port that is not secure.
Aliases of the form
*:9443use the secure internal port.
Aliases of the form
*:443use the secure external port.
If a request specifies a resource by using an alias that cannot be mapped to an alias of a defined virtual host, the result is a 404 error.
Open Liberty provides one default virtual host that is called
default_host, which is automatically configured the first time that you start your server. Unless you specifically want to isolate resources on the same server from one another, you probably do not need any virtual hosts other than the default virtual host. However, the default virtual host is also used for JMX communications and other metrics processes. To separate this traffic from incoming requests to an application, you can configure another virtual host for the application.
The host aliases for the default virtual host are configured as
*:9080, where port
80 is the HTTP server port and port
9080 is the port for HTTP transport. The default virtual host includes common aliases, such as the machine IP address, short hostname, and fully qualified hostname. One of these aliases comprises the first part of the path for accessing a resource, such as a servlet. For example, the
localhost:80 alias is used in the
As part of hardening your network security configuration, you can use virtual hosts to restrict incoming requests to your applications. To keep Open Liberty administrative traffic separate from application requests, configure applications to run on a virtual host other than the default host for the server. Furthermore, the best practice for security-hardened production environments is to avoid wildcard values (
*) in alias hostnames. Rather than using wildcards, alias hostname values must match only the specific hosts that administrators expect a server to handle. For more information, see Network security hardening: Virtual hosts.
In Open Liberty, you can define virtual hosts or adjust the configuration of the default virtual host by specifying attributes for the virtualHost configuration element in your
The following example illustrates a common use case for virtual hosting: configuring two applications to run on different ports on the same server. The configuration defines two HTTP endpoints and two virtual hosts. The alias configurations associate the
application-1 virtual host with the
defaultHttpEndpoint endpoint and the
application-2 virtual host with the
<httpEndpoint id="defaultHttpEndpoint" host="*" httpPort="9080" />
<httpEndpoint id="alternateEndpoint" host="*" httpPort="9081" />
<enterpriseApplication location="myApp.ear" name="App1"/>
<webApplication location="myApp2.war" name="App2" />
Furthermore, the virtual host configuration for the
application-2 virtual host specifies that an application on this host is available only on the
localhost interface. This configuration is useful if you want an application to accept traffic only from the computer where it is running, for development or testing purposes.
defaultHttpEndpoint HTTP endpoint is configured to expose all interfaces on port
alternateEndpoint HTTP endpoint is configured to expose all interfaces on port 9081. If the
App1 application has a WAR file with an
ibm-web-bnd.xml file that specifies
virtual-host name="application-1", then this application can be accessed only at the
your_host_name:9080/app1_context_root endpoint. If the
App2 application that is configured in the
webApplication element has an
ibm-web-bnd.xml file that specifies
virtual-host name="application-2", then this application can be accessed only at the
If a third application that doesn’t specify a virtual host is deployed on the same server, it is accessible by a proxied request that maps to the default virtual host. For example, port
80 is not defined by any of the
hostAlias attributes. If a request is made to a proxy on that port, it is routed to the
default_host virtual host.
The default virtual host in Open Liberty,
default_host, is used for administrative traffic, such as JMX communications. To isolate incoming application requests from administrative traffic, you can configure a separate virtual host for your application.
The following example illustrates a
virtualHost element and
hostAlias attribute configuration in the
If requests are coming from a proxy, this configuration routes any request that is made to the proxy host and port to the "proxiedRequests" virtual host.
To associate your application with this virtual host, you must add a reference to it in the application code. Add a
virtual-host element to the
ibm-web-bnd.xmi file of the application
WAR file, as shown in the following example:
<?xml version="1.0" encoding="UTF-8"?>
<virtual-host name="proxiedRequests" />
To restrict access to system applications that are using the
defaultHttpEndpoint HTTP endpoint, you can define a new endpoint and specify the
allowFromEndpointRef attribute in your virtual host configuration. When this attribute is specified, a virtual host accepts requests only from the specified endpoint. While virtual host aliases can filter requests based on the
Host HTTP header, the
allowFromEndpointRef attribute can specify a constraint at the system network interface layer.
In the following example, the
localHostOnly HTTP endpoint specifies that ports
9444 are exposed only on the
localhost interface. The
default_host is restricted to this endpoint by the
<httpEndpoint id="localHostOnly" host="localhost" httpPort="9081" httpsPort="9444"/>
<virtualHost id="default_host" allowFromEndpointRef="localHostOnly">
With this configuration, the
default_host virtual host now accepts requests that are directed only at
localhost:9444 that also originate from the
localHostOnly endpoint. Any other request to ports
9444 are refused. For example, a request from the
Host headers that reference
localhost:9081 is refused.
proxiedRequests virtual host accepts any request to port
9443, which are the ports that are used by the
defaultHttpEndpoint HTTP endpoint. It also accepts requests that have a host header that references the external hostname from the proxy and port