Troubleshoot Agent - Enterprise Manager Network Topology

How Enterprise Manager Handles Denied Agents
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How Enterprise Manager Handles Denied Agents
The MOM sends the data from loadbalancing.xml to all Collectors in the cluster every 10 minutes. The loadbalancing.xml and the introscope.apm.agentcontrol.agent.allowed property tell Enterprise Managers which agents are allowed and disallowed to connect to it. Based on the allow and disallow configurations, Enterprise Managers can accept or deny agent connection requests.
Here is what happens when an Enterprise Manager denies an agent connection.
Valid for pre-9.1 agents
If the agents are connected, the Enterprise Manager disconnects pre-9.1 agents. The agents use their Allowed Enterprise Managers list to try to connect to another allowed available Enterprise Manager. If the agents are denied connection to all Enterprise Managers, they continue trying to connect to the last Enterprise Manager that is:
  • Available.
  • Allowed to connect to the agent.
Valid for 9.1 and later agents
The Enterprise Manager disconnects 9.1 and later agents, which then try to connect to another allowed available Enterprise Manager. If the agents are denied connection to all Enterprise Managers, the agents connect to the last Enterprise Manager to which they had been connected. The agents remain connected to the Enterprise Manager, but do not send any data.
When Collector Uses introscope.apm.agentcontrol.agent.allowed Property
When the MOM connects to a Collector, the MOM provides the introscope.apm.agentcontrol.agent.allowed property and loadbalancing.xml to the Collector. If the MOM goes down, the Collector uses the following information provided by the MOM to know which agent connections to allow and disallow:
  • Current introscope.apm.agentcontrol.agent.allowed property setting in the IntroscopeEnterpriseManager.properties file.
  • loadbalancing.xml.
If the MOM has never connected to the Collector, the MOM has not transferred its introscope.apm.agentcontrol.agent.allowed property and loadbalancing.xml file to the Collector. Therefore, the Collector uses its own introscope.apm.agentcontrol.agent.allowed property to decide whether to allow or disallow specific agent connections.
Agent Does Not Match loadbalancing.xml Regular Expression as Allowed or Disallowed
The value of introscope.apm.agentcontrol.agent.allowed property in the IntroscopeEnterpriseManager.properties file determines whether agents not matched by regular expressions in loadbalancing.xml can connect to a Collector.
If the property value is true, then agents that do not match any regular expression in loadbalancing.xml are allowed to connect to Collectors.
If the property value is false, then agents that do not match any regular expression in loadbalancing.xml are denied from connecting to Collectors.
All Collectors Assigned to an Agent are Unavailable and Other Collectors are Available
Pre-9.1 agents
The Collector disconnects the agents, which then try to connect to the MOM. With no Collectors available to which the agents are allowed to connect, the MOM denies every agent connection attempt. The agent keeps trying to connect to the MOM until an allowed Collector for the agent is available. The MOM redirects the agents to an allowed Collector when the Collector becomes available.
9.1 and later agents
The Collector disconnects the agents, which then connect to the MOM but, do not send any data. The MOM redirects the agents to an allowed Collector when the Collector becomes available.
How Collector Handles a Disallowed Agent with a Direct Connection
The MOM periodically sends loadbalancing.xml to all Collectors in the cluster. The loadbalancing.xml file makes each Collector aware of the agents that are allowed to connect to it. If these actions take place:
  • The loadbalancing.xml file is updated so that an agent is disallowed on a particular Collector.
  • The agent tries to connect to that Collector.
Then the following actions result.
Pre-9.1 agents
The Collector denies the agent connection and the agent continues the connection attempt.
9.1 and later agents
The Collector gives the latest Allowed Enterprise Manager list to the agent. The agent is not allowed on the Collector based on the disallowed configuration setting. If the MOM available, it redirects the agent to an available allowed Collector. If the MOM is not available, then the agent uses its Allowed Enterprise Manager list to cycle through its allowed available Collectors.
Default Agent Connection Value When the introscope.apm.agentcontrol.agent.allowed Property is Missing
The default value for the introscope.apm.agentcontrol.agent.allowed property is
allowed
.
How Introscope Determines Where Agents Connect When No MOM Available
The Collector to which the agent is trying to connect decides whether the connection is allowed or denied. The Collector decides based on the current allowed and disallowed configurations in its loadbalancing.xml file.