Introduction to the WebLogic SNMP Agent

WebLogic Server can use Simple Network Management Protocol (SNMP) to communicate with enterprise-wide management systems. The WebLogic Server subsystem that gathers WebLogic management data, converts it to SNMP communication modules (trap notifications), and forwards the trap notifications to third-party SNMP management systems is called the WebLogic SNMP agent. The WebLogic SNMP agent supports the SNMPv1 and SNMPv2 protocols.

Typically, you use SNMP to provide a single location from which to manage a heterogeneous software and hardware environment.

The following sections describe the SNMP management model and how WebLogic Server implements this model:

For more information, refer to the following:

 

The SNMP Agent/Manager Model

SNMP management is based on the agent/manager model described in the network management standards defined by the International Organization for Standardization (ISO). In this model, a network/systems manager exchanges monitoring and control information about system and network resources with distributed software processes called agents.

Any system or network resource that is manageable through the exchange of information is a managed resource. This could be a software resource, such as a Java Database Connectivity connection pool, or a hardware resource, such as a router.

Agents function as "collection devices" that gather and send data about the managed resource in response to a request from a manager. In addition, agents often have the ability to issue unsolicited reports to managers when they detect certain predefined thresholds or conditions on a managed resource. In SNMP terminology, these unsolicited event reports are called trap notifications.

A manager relies upon a database of definitions and information about the properties of managed resources and the services the agents support - this makes up the Management Information Base (MIB). When new agents are added to extend the management reach of a manager, the manager must be provided with a new MIB component that defines the manageable features of the resources managed through that agent. The manageable attributes of resources, as defined in an SNMP-compliant MIB, are called managed objects. Defining the heterogeneous components of an enterprise's distributed systems within a common MIB on the management station provides a unified perspective and single access point for managing system and network resources.

 

The Role of the SNMP Agent in a WebLogic Server Domain

The WebLogic SNMP agent runs on a domain's Administration Server. (See Figure 1-1.)

A WebLogic Server administration domain is a logically related group of WebLogic Server resources. Domains include a special WebLogic Server instance called the Administration Server, which is the central point from which you configure and manage all resources in the domain. Typically, you configure a domain to include additional WebLogic Server instances called Managed Servers. You deploy applications, EJBs, and other resources on the Managed Servers and use the Administration Server for configuration and management purposes only.

Using multiple Managed Servers lets you balance loads and provide failover protection for critical applications, while using a single Administration Server simplifies the management of the Managed Server instances. For more information about domains, refer to "Overview of WebLogic Server Domains in Configuring and Managing WebLogic Server.

Figure 1-1 SNMP Management of a WebLogic Domain


You can use the WebLogic SNMP agent to do the following:

  • Respond to simple GET requests from an SNMP manager for the current value of WebLogic attributes.
  • Send trap notifications to SNMP managers when the Administration Server starts and when any Managed Server starts or shuts down.
  • Send trap notifications to SNMP managers when messages are logged in a Managed Server that satisfy criteria that you specify.
  • Send trap notifications to SNMP managers when a WebLogic configuration attribute that you specify has changed value.
  • Offload polling of WebLogic attributes to the WebLogic Administration Server using standard JMX monitors, based on thresholds and polling intervals that you define. A trap notification is sent to the SNMP manager when the criteria you specify are satisfied.
  • Act as a proxy agent that passes requests from an SNMP manager to other SNMP agents (such as an Oracle database agent) on the same machine.

For information on enabling and configuring the WebLogic SNMP agent, refer to "Enabling and Configuring the WebLogic SNMP Agent in the Administration Console Online Help.

 

WebLogic Server Managed Resources and MBeans

Resources on WebLogic Server instances use Java Management Extensions (JMX) Managed Beans (MBeans) to expose their management functions. An MBean is a concrete Java class that is developed in accordance with JMX specifications. It can provide getter and setter operations for each management attribute within a managed resource along with additional management operations that the resource makes available.

WebLogic Server MBeans that expose the configuration data of a managed resource are called Configuration MBeans while MBeans that provide performance metrics and other information about the runtime state of a managed resource are called Runtime MBeans. For example, a ServerMBean Configuration MBean indicates the listen port for a server instance while the ServerRuntimeMBean Runtime MBean indicates the current lifecycle state of a server instance.

While you can create MBeans (custom MBeans) to manage the applications or services that you deploy on WebLogic Server, the WebLogic SNMP agent does not recognize these custom MBeans as SNMP managed resources. You cannot configure the WebLogic SNMP agent to monitor or generate traps for custom MBeans.

For more information about MBeans on WebLogic Server, refer to the following:

 

Documentation for Configuration MBean APIs

To view the documentation for Configuration MBeans, do the following:

  1. Open the WebLogic Server Javadoc.
  2. In the top left pane of the Web browser, click weblogic.management.configuration.

    The lower left pane displays links for the package.

  3. In the lower left pane, click weblogic.management.configuration again.

    The right pane displays the package summary. (See Figure 1-2.)

    Figure 1-2 Javadoc for the configuration Package

    Javadoc for the configuration Package

  4. Click on an interface name to view its API documentation.

 

Documentation for Runtime MBean APIs

To view the documentation for Runtime MBeans, do the following:

  1. Open the WebLogic Server Javadoc.
  2. In the top left pane of the Web browser, click weblogic.management.runtime.

    The lower left pane displays links for the package.

  3. In the lower left pane, click weblogic.management.runtime again.

    The right pane displays the package summary. (See Figure 1-3.)

    Figure 1-3 Javadoc for the runtime Package

    Javadoc for the runtime Package

  4. Click on an interface name to view its API documentation.

 

SNMP MIB for WebLogic Server

All WebLogic Server attributes that can be accessed by SNMP management software are defined in an SNMP-compliant Management Information Base (MIB).

Note: Not all objects in the WebLogic Server MIB represent MBean attributes. For example, the WebLogic Server MIB includes objects that define trap variables.

The BEA WebLogic SNMP MIB conforms to a coding standard called Abstract Syntax Notation.1 (ASN.1). An ASN.1 file is a standard SNMP file that defines the objects that make up an SNMP-compliant MIB. Each object in the file is defined in compliance with the SNMP standard. The BEA WebLogic Server software includes the ASN.1 file BEA- WEBLOGIC-MIB.asn1 for defining the BEA WebLogic Server MIB for SNMP. The BEA WebLogic SNMP MIB is written in compliance with RFC 1212, as required by the SNMP standard.

 

Browsing the MIB

You can use any of the following methods to browse the contents of the WebLogic Server MIB:

  • Use a MIB browser. WebLogic Server does not provide a MIB browser, but most vendors of SNMP utilities do. The MIB is located in a file named $WL_HOME/server/lib\BEA-WEBLOGIC-MIB.asn1.
  • Use a Web browser to view the WebLogic Server SNMP MIB Reference on the BEA e-docs Web site.

    Because the MIB Reference uses Javascript and DHTML to provide browsing capabilities that are similar to a MIB browser, use one of the following Web browsers:

    • Internet Explorer, version 5 or higher
    • Netscape Navigator, version 6 or higher
    • Opera 7 or higher
    • Mozilla
    • Phoenix

 

Object Identifiers

The WebLogic Server MIB assigns a unique number called an object identifier (OID) to its MBean attributes. Each MBean attribute in the MIB is an SNMP managed object and is manageable by an SNMP management system.

The MIB creates a hierarchical relationship between managed objects and expresses the hierarchy in a tree structure, called the MIB tree or registration tree. Each OID in the MIB consists of a left-to-right sequence of integers. This sequence defines the location of the object in the MIB tree and specifies a unique path through the tree to the object. Each node in the path have both a number and a name associated with it. The path .1.3.6.1.4.1 defines the private.enterprises OID and each number beneath that node on the tree represents the branches in the tree reserved for a particular vendor.

The BEA MIBs are registered at the location .1.3.6.1.4.1.140 in the tree. And the WebLogic Server MIB consists of all OIDs below .1.3.6.1.4.140.625.

 

OIDs for Types and Instances

All OIDs that represent WebLogic Server MBean attributes in the WebLogic Server MIB are identifiers for the MBean attribute type. For example, .1.3.6.1.4.1.140.625.360.1.60 is the OID for the serverRuntimeState attribute type.

To identify a specific instance of an attribute type, the WebLogic SNMP agent generates and appends an additional set of numbers to the OID of an attribute type. For example, the OID that specifies the value of the serverRuntimeState attribute for an active instance of the sample MedRecServer is .1.3.6.1.4.1.140.625.360.1.60.32.102.100.48.98.101.102.100.99.102.52.98.97.48.48.49.102.57.53.51.50.100.102.53.55.97.101.52.56.99.99.97.99

The OID is persistent across instantiations of the object type.

The WebLogic Server MIB Reference appends (.*) to the OIDs that represent attribute types. This convention indicates that specific instances of the type are identified by additional numbers. For example, the WebLogic Server MIB Reference indicates that the OID for the serverRuntimeState attribute type is .1.3.6.1.4.1.140.625.360.1.60(.*).

You can use the snmpwalk or snmpgetnext commands to see the object-instance OID for any WebLogic Server attribute. For more information, refer to "WebLogic SNMP Agent Command-Line Reference in the WebLogic Server Command Reference.

 

SNMP Community Names

To ensure that the entity requesting data from the WebLogic SNMP agent has permission to obtain the data, and to verify that the agent has permission to send trap notifications to a target manager, SNMP uses textual passwords called community names.

When you set up the SNMP agent capability of the Administration Server (described in "Enabling and Configuring the WebLogic SNMP Agent in the Administration Console Online Help), one of the things specify is the community name that the agent expects from the SNMP manager. If the agent receives an SNMP request with an incorrect community name, it generates an authenticationFailure trap and sends it to the source of the request.

 

Using Community Names to Specify Target Servers in Management Requests

You can use some SNMP managers to send requests to the WebLogic SNMP agent for the value of attributes. Because a WebLogic Server domain can have multiple server instances concurrently active, a request that specifies only an attribute name is potentially ambiguous. For example, the attribute serverUptime exists for each WebLogic Server instance in a domain.

To request the value of an attribute on a specific Managed Server, when you send a request from an SNMP manager, append the name of the server instance to the SNMP password (community) that it sends with the request as follows:
community_prefix@server_name

where community_prefix is the SNMP community name and server_name is the name of the targeted Managed Server. The community_prefix value sent by the manager must match the value that you set in the Community Prefix field when you configure the SNMP agent.

To request the value of an attribute on the Administration Server, send a community string to the WebLogic SNMP agent with the following form:
community_prefix

To request the value of an attribute for all server instances in a domain, send a community string with the following form:
community_prefix@domain_name

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