This chapter includes the following sections:
A virtual target represents a target for a resource group, both at the domain level and in a domain partition. It defines the access points to resources, such as one or more host names, a URI prefix, and the Managed Servers or cluster to which the virtual target is itself targeted.
Virtual targets are similar to virtual hosts in Oracle WebLogic Server. Like virtual hosts, virtual targets provide a separate HTTP server (web container) on each target.
A virtual target isolates a resource group from the physical attributes of where the container is running.
Each resource group requires one or more virtual targets. The virtual targets that you can select depend on whether the resource group is at the domain level, or associated with a domain partition:
For domain-level resource groups, you can select any existing virtual target that is not already assigned as an available target to a partition.
For resource groups in a domain partition, you must select only from the existing virtual targets available to the partition.
Consider the following guidelines for using virtual targets:
A virtual target can be used by only one partition at a time, or at the domain level. A virtual target is never shared by more than one partition, or by a partition and the domain level.
A virtual target can be used by many resource groups within a partition, or by many resource groups at the domain level.
A virtual target can be targeted to one cluster or one Managed Server.
Many virtual targets can be targeted to the same cluster or Managed Server.
If two virtual targets have the same host names, URI prefix, and port number, they must be targeted to different clusters or Managed Servers.
A virtual target contains the following:
Host names. The list of host names to which this virtual target will serve requests. The host names that you specify must have domain name system (DNS) entries that resolve to the correct servers, or to a load balancer:
If you are not using Oracle Traffic Director to balance the connection load for a partition, then specify the actual host name of the WebLogic Server cluster or Managed Server.
If you are using Oracle Traffic Director to load balance connections for a partition, then you access applications through Oracle Traffic Director. The host names that you specify for a virtual target must resolve to the location of the Oracle Traffic Director Administration Server.
If you do not specify a host name, then it is the equivalent of using a wild card for the host name to match all incoming requests.
The host name used by a client to access the resource group must exactly match one of the host names specified in the virtual target.
You can specify multiple host names for the virtual target. You might find it convenient to specify both the simple and the fully qualified host name to ensure a match.
Optional URI prefix to which this virtual target will serve requests. For example, if you enter www.example.com as the host name and MyApp as the URI prefix, then this virtual target serves requests to www.example.com/MyApp, but not to www.example.com or www.example.com/foo.
To extend this example, assume that your application root is /app. The resulting URL for the application would be www.example.com/MyApp/app.
Target cluster and Managed Server from the list of the targets in the current domain. Targets must be either a single server or a single cluster.
There are two general approaches when using virtual targets: route by the host name (http://partition1.com, http://partition2.com), or by URI prefix (http://server.com/partition1, http://server.com/partition2). You might find it easier to manage your environment if you consistently use one approach, but there is no requirement that you do so.
You must specify at least one of host name, URI prefix, or port number.
Virtual targets do not determine how a request gets to a particular server. DNS or a load balancer determines how requests get to a specific server instance. The host names used in the virtual target do not control the routing, but they must be consistent with it.
Virtual targets do determine what happens to a request after it enters a server. When a request enters a server, it is matched against all of the virtual targets targeted to that server. If an incoming request matches the information on any of the virtual targets, then it is assumed that the request is intended for that virtual target. If both host names and URI prefix are specified, then both must match. If two virtual targets match, then the one with the longest URI prefix match receives the request. If none matches, then the request is sent to the default HTTP server.
For example, assume that you have a virtual target with the host names www.example1.com, www.example2.com, and www.example3.com. The virtual target is targeted to cluster1. Requests sent to www.example1.com, www.example2.com, and www.example3.com all match that virtual target and are all sent to cluster1.
If you specify multiple virtual targets for a resource group, then the virtual target matching works the same. There is no implicit load balancing among virtual targets.
For example, assume that in PartitionA you have a virtual target with the host name www.example1.com targeted to cluster1, and a second virtual target with the host name www.example2.com targeted to cluster2. Requests sent to www.example1.com match only that virtual target and are sent only to cluster1. Requests sent to www.example2.com match only that virtual target and are sent only to cluster2.
Use Oracle Traffic Director if you require load balancing.
You can optionally specify existing channel and port (explicit or offset) information to use as a reference for a partition-specific channel for a virtual target.
A network channel is a configurable resource that defines the attributes of a network connection to WebLogic Server. A network channel in a WebLogic Server instance is a combination of the following four attributes: communication protocol, listen address, listen port, and channel name. See Understanding Network Channels in Administering Server Environments for Oracle WebLogic Server.
The channel must exist on the selected target and be configured using the same protocol. If you specify a value for Partition Channel, then you must specify either an explicit port or a port offset.
Allowable values for an explicit port are 1 to 65535, with 1 to 1023 (well-known or system ports) requiring system (or root) process privileges. The port must not already be bound by another process.
Consider the following example:
Create a virtual target with the host name myexample.com and the URI prefix /foo.
In the Partition Channel field, specify the existing channel Channel-1 to use as a reference for creating a partition-specific channel.
Channel-1 has a listen address and listen port of 127.0.0.1:7002 and an external address and listen port of 127.0.0.1:7002.
Specify a port offset of 5. That results in 7002 +5 for the listen port.
myexample.com must resolve to 127.0.0.1.
To access this virtual target, use myexample.com:7007/foo.
If you create another virtual target that also uses Channel-1, then you must use another port offset (or explicit port) or there will be a port conflict.
In all cases, specify either an explicit port value to use as-is, or a port offset. Otherwise, there is no port assigned and the channel is not created and used.
You use the Oracle WebLogic Server Administration Console to create a channel. See Configure custom network channels in the WebLogic Server Administration Console online help.
Note:
The partition channel is ignored if you use Oracle Traffic Director to load balance the domain partition.
A partition administrative virtual target is a virtual target that is created automatically for every partition when the partition is created and has the domain's Administration Server as its physical target.
A partition administrative virtual target contains the following settings:
Hostname: empty (wildcard)
uriPrefix: /partitions/<partition-name>
Note:
You can change the uriPrefix, /partitions, to something else. This setting is used for the entire domain. To change it, use:
DomainMBean.setPartitionUriSpace(String uriPrefix);
However, Oracle recommends leaving this the default setting if possible.
Target: the Administration Server
It inherits its other settings from the Administration Server's default HTTP server
You can retrieve the partition administrative virtual target settings from the partition's configuration MBean.
Using WebLogic Scripting Tool (WLST):
serverConfig() partition = cmo.lookupPartition(partitionName) adminVT = partition.getAdminVirtualTarget()
The administrative virtual target is not automatically added to the list of available targets for a partition. The system administrator must explicitly add it to the partition's available targets if partition administrators are to be allowed to use it for resource group targeting.
You can use the administrative virtual target for targeting a partition the same as you would any other virtual target; however, the administrative virtual target is read-only and cannot be changed or deleted.
Creating virtual targets includes certain required steps, such as providing a name, specifying host names, and selecting available targets.
Note:
Do not configure a virtual target as host name: "", URI prefix: /, explicit port: 0, port offset: 0. This configuration makes the virtual target intercept all requests intended for the default HTTP server. This configuration is not allowed.
The main steps for creating a virtual target are as follows:
Enter a name for this virtual target.
Optionally, enter a URI prefix for this virtual target.
Add one or more host names for the virtual target. The host names that you specify must resolve to the target cluster and Managed Servers that you specify, or resolve to the Oracle Traffic Director Administration Server if you are using Oracle Traffic Director for load balancing.
Optionally, specify partition channel and port (explicit or offset) information to use for this virtual target, as described in Using Partition Channels with Virtual Targets. The channel must exist on the selected target and be configured using the same protocol. If you specify a value for Partition Channel, then you must specify either an explicit port or a port offset.
Note:
These options are ignored if you use Oracle Traffic Director to load balance the domain partition.
Select one target from the available targets. You can select a single Managed Server or a single cluster.
If you are using the WebLogic Server Administration Console, WebLogic Scripting Tool (WLST), or Representational State Transfer (REST) to create the virtual target, additional HTTP configuration options are available for configuring the virtual web server. See Configure HTTP for a virtual target in Oracle WebLogic Server Administration Console Online Help.
To create a virtual target using Fusion Middleware Control, see Create virtual targets in the online help.
The example does the following:
Creates a domain partition.
Creates a virtual target.
Sets the host name and URI prefix for the virtual target.
Targets the virtual target to the Administration Server. (You would typically not select the WebLogic Administration Server.)
Adds the virtual target as an available target in the partition.
Creates the resource group.
Adds the virtual target to the resource group.
Activates the changes.
Starts the partition.
Note:
If this is the first partition created in production mode, then you must restart the Administration Server before you can start the partition.
# Create virtual target
edit()
startEdit()
wls:/base_domain/edit/ !> domain=getMBean('/')
wls:/base_domain/edit/ !> peppart=domain.createPartition('Pep')
wls:/base_domain/edit/ !> vt=domain.createVirtualTarget('TestVT')
wls:/base_domain/edit/ !> vt.setHostNames(jarray.array([String('localhost')],String))
wls:/base_domain/edit/ !> vt.setUriPrefix('/foo')
wls:/base_domain/edit/ !> tgt=getMBean('/Servers/AdminServer')
wls:/base_domain/edit/ !> vt.addTarget(tgt)
wls:/base_domain/edit/ !> peppart.addAvailableTarget(vt)
wls:/base_domain/edit/ !> peprg=peppart.createResourceGroup('TestRG')
wls:/base_domain/edit/ !> peprg.addTarget(vt)
wls:/base_domain/edit/ !> activate()
wls:/base_domain/edit/ !> startPartitionWait(peppart) For an example of creating virtual targets using REST, see Creating Partitions in Administering Oracle WebLogic Server with RESTful Management Services.
In particular, see the section "Create a virtual target for the new partition."
To manage virtual targets, you can modify the URI prefix, host names for the virtual target, and its target servers or cluster.
If you make a change to a virtual target that is in use by a running resource group in a running partition, then you may need to restart the partition to have the change take effect.
The main steps for managing a virtual target are as follows:
Select the virtual target that you want to manage.
Enter a URI prefix for this virtual target or modify the existing URI prefix.
Add one or more host names for the virtual target. The host names that you specify must resolve to the target cluster and Managed Servers that you specify, or resolve to the Oracle Traffic Director Administration Server if you are using Oracle Traffic Director for load balancing.
If needed, delete one or more host names for the virtual target.
Optionally, specify partition channel and port (explicit or offset) information to use for this virtual target, as described in Using Partition Channels with Virtual Targets. The channel must exist on the selected target and be configured using the same protocol. If you specify a value for Partition Channel, then you must specify either an explicit port or a port offset.
Note:
These options are ignored if you use Oracle Traffic Director to load balance the domain partition.
Select one target from the available targets. You can select a single Managed Server or a single cluster. (You would typically not select the WebLogic Server Administration Server unless you have a special reason to do so.)
Deselect any target that you do not want to use.
If you are using the WebLogic Server Administration Console, WLST, or REST to manage the virtual target, then additional HTTP configuration options are available for configuring the virtual web server. See Configure HTTP for a virtual target in Oracle WebLogic Server Administration Console Online Help for more information.
If you made a change to a virtual target that is in use by a running resource group in a running partition, then restart the partition to have the change take effect.
To manage a virtual target using Fusion Middleware Control, see Configure virtual targets in the Fusion Middleware Control online help.
You cannot delete a virtual target that is in use by a resource group in a partition. You must first remove it from the resource group.
To delete a virtual target that is in use by a partition:
To delete a virtual target using Fusion Middleware Control, see Delete virtual targets in use by a partition in the Fusion Middleware Control online help.
You cannot delete a virtual target that is in use by a resource group at the domain level. You must first remove it from the resource group.
To delete a virtual target that is in use by a resource group at the domain level:
To delete a virtual target, see Delete virtual targets in use by a resource group at the domain level in the Fusion Middleware Control online help.
The following example modifies the existing virtual target TestVT with the URI prefix /app and sets the host name to be myhost.example.com.
myVT is an instance of VirtualTargetMBean.
cd('/')
edit()
startEdit()
cd('VirtualTargets')
cd ('TestVT')
cmo.setUriPrefix('/app')
cmo.setHostNames(jarray.array([String("myhost.example.com")],String))
activate()
You can also use the DomainMBean to look up a virtual target by name and return the VirtualTargetMBean.
domain=getMBean('/')
vt=domain.lookupVirtualTarget('TestVT')
vt.setUriPrefix('/app')
Delete a Virtual Target
The following example deletes the virtual target TestVT. It first removes the virtual target as an available target for the partition Pep.
cd('/')
edit()
startEdit()
domain=getMBean('/')
vt=domain.lookupVirtualTarget('TestVT')
part=domain.lookupPartition('Pep')
part.removeAvailableTarget(vt)
domain.destroyVirtualTarget(vt)
activate()Retarget a Virtual Target
The example does the following:
Creates a domain partition.
Creates a virtual target.
Sets the host name and URI prefix for the virtual target.
Targets the virtual target to the Administration Server. (You would typically not select the WebLogic Server Administration Server unless you have a special reason to do so.)
Adds the virtual target as an available target in the partition.
Creates the resource group.
Adds the virtual target to the resource group.
Activates the changes.
Starts the partition.
Note:
If this is the first partition created in production mode, then you must restart the Administration Server before you can start the partition.
Removes the Administration Server as a target.
Retargets the virtual target to Cluster-0.
# Create Pep partition and ResourceGroup
edit()
startEdit()
wls:/base_domain/edit/ !> domain=getMBean('/')
wls:/base_domain/edit/ !> peppart=domain.createPartition('Pep')
wls:/base_domain/edit/ !> vt=domain.createVirtualTarget('TestVT')
wls:/base_domain/edit/ !> vt.setHostNames(jarray.array([String('localhost')],String))
wls:/base_domain/edit/ !> vt.setUriPrefix('/foo')
wls:/base_domain/edit/ !> tgt=getMBean('/Servers/AdminServer')
wls:/base_domain/edit/ !> vt.addTarget(tgt)
wls:/base_domain/edit/ !> peppart.addAvailableTarget(vt)
wls:/base_domain/edit/ !> peprg=peppart.createResourceGroup('TestRG')
wls:/base_domain/edit/ !> peprg.addTarget(vt)
wls:/base_domain/edit/ !> activate()
wls:/base_domain/edit/ !> startPartitionWait(peppart)
startEdit()
wls:/base_domain/edit/ !> vt.removeTarget(tgt)
wls:/base_domain/edit/ !> tgt=getMBean('/Clusters/Cluster-0')
wls:/base_domain/edit/ !> vt.addTarget(tgt)
wls:/base_domain/edit/ !> activate()For an example of creating virtual targets using REST, see Creating Partitions in Administering Oracle WebLogic Server with RESTful Management Services.
In particular, see the section "View the default values for a new virtual target."
Understanding Network Channels in Administering Server Environments for Oracle WebLogic Server