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How does agentless monitoring work?

From what I understood (or not), it seems this is accomplished by logging into the node-being-monitored from a central server and uploading-then-running scripts on it?

What are the major differences between agent-based and agentless monitoring? What kinds of advantages and disadvantages can I expect when agentless monitoring solutions?

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What would you like to monitor? –  ewwhite Jun 13 at 15:16
    
You should look into SNMP. There's advantages and disadvantages to agentless monitoring. Advantages: no extra load on the the clients, easier to manage; disadvantages: single point of failure, loads of network traffic. –  Flo Jun 13 at 15:16
    
This question is somewhat out of scope because it mainly asks for personal opinions. –  Felix Frank Jun 13 at 16:16

1 Answer 1

The role of the Agent

Monitoring is umbrella term for many functions. The function of an "agent" is essentially to make data available to the rest of the system. To put it in context, you might try to fit it into the model proposed by Dickson from his "Working theory of Monitoring" talk.

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So agents generally fit into "Sensing/Measurement" and maybe the "Collection" pieces of this model.

What is an agent anyways?

Agent-less monitoring is a bit of a misnomer. So what do people mean when they say "agent-less " monitoring? It essentially means that you are using functionality built-in to the thing being monitored, instead of installing a third-party utility to accomplish your data collecting goals. So to be more accurate, lets reform this as "using third-party collection tools vs standard OS functionality (or package that "ship" with the thing) to monitor.

Mosby's Pros and Cons

There are no absolute rules, and no holy grail, but generally I think the pros and cons are as follows:

Built-in Data collection Functionality:

  • Pro: Generally assumed to be more reliable. Less likely to have an impact on the system being monitored. SNMP for example is "tried and true".
  • Con: Can be less flexible, they may not provide the things you want to monitor
  • Pro/Con (Depending on how you look at it): Many third party collection agents are designed with a specific monitoring system in mind, so they fit nicely together.

Third-Party:

  • Pro: Integrate tightly with the other pieces of your monitoring system
  • Con: Since they are not as common as things that ship with the system, they don't get tested as much, and might be less reliable (have impact on their host system)
  • Pro: Since these agents run on the machine, they they can make local library and system calls and get information that might not be possible to get from standard built-in monitoring functionality.

Remember, these are generalizations. You can certainlly extend SNMP (but that almost becomes "third party"). And builtin tools could still use a lot of memory and crash. Your best bet is not to worry about one vs the other, but set out the requirements of what it is you need to monitor, and see what delivers that.

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ah, Kyle's back in the house! Does that mean we can look forward to a new blog post? –  the-wabbit Jun 13 at 17:25
    
@syneticon-dj: Eventually :-P –  Kyle Brandt Jun 13 at 17:28

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