H20. Checking Agent Status and Resolving Problems
Diátaxis: How-to · Audience: administrators -- the Agent Status menu is visible only to accounts with administrator permission ← Back to contents
When a chart is empty or data stops arriving from one particular instance, the first place to look is the Agent Status screen. The agent is the collector attached to each instance that gathers data and sends it to the APM server, so when it is cut off the screen empties too.
For the agent and instance concepts, see E2.1.
How to open it -- left menu ▸ Settings ▸ Agent Status (/settings/agents, visible to
administrators only)
Reading the Agent Status Screen
The screen is divided into the WAS, web server, and system areas, with the instances laid out as
cards in each. The count badge to the right of each area header (22 / 22, for example) is
connected / total.
The state is shown per instance with a status dot and colour.
| State | Meaning |
|---|---|
| RUNNING | The agent is connected and collecting normally (the dot blinks slightly) |
| STOPPED | The connection has dropped or the instance is down -- no data is being collected |
Each instance's IP and version are shown too. A mix of instances on different versions suggests an agent update was missed.
Note When the "connected / total" in the count badge does not match (
21 / 22, for example), one is missing. Which area and which instance is STOPPED can be found straight away.
Responding to a Dropped Connection or No Response
When you meet an instance that is STOPPED or from which no data arrives, narrow it down in this order.
- Check the current state with a refresh -- press Refresh Groups / Collect information again at the top of the screen, or Agent Refresh in that instance's menu, to fetch the current state again.
- Tell whether it is actually down -- check whether the instance (the process) itself has stopped, or whether it is alive and only the agent connection has dropped. The former needs the instance brought back up; the latter is a network or agent configuration problem.
- Web server LB workers can be operated directly with Start/Stop in the instance menu.
Caution These actions first bring up a confirmation window explaining what they do, and run only after you press Yes. They can affect production, so read the confirmation window before going ahead.
A dropped connection usually also arrives as an event (agent stopped, and so on). For the meaning of each event, see R3. Event Reference.
Requesting a Thread Dump or Heap Dump
When "the instance is alive but there is no response" (unresponsive, hung), request a dump to see where it stalled.
- Thread Dump Analyze -- see what the threads were doing when they stalled. Useful when you suspect a deadlock or lock contention.
- Heap Object Analyze -- see what has accumulated in memory (leak candidates).
A dump is sometimes collected automatically when a deadlock or OOM event occurs. The diagnostic procedure for memory and leaks is set out in detail in H7. Checking for a Memory Leak.
Caution Collecting a dump loads the JVM at that moment. Request it at a quiet time of day, and only on the instance you need.
When It Does Not Work
| Symptom | What to check |
|---|---|
| The Agent Status menu is not visible | Check the account has administrator permission -- agent status is visible only to administrators |
| Still STOPPED after a refresh | Whether the instance (the process) is actually up, and the host and network state |
| Data arrives but the versions vary | An agent update was missed -- check for the latest agent under Guide & Downloads |
| Only the charts are empty while the state is RUNNING | It may be a selector target or period problem → H1 · H2 |
Related Documents
- E2.1 Application Groups, Instances, and Agents -- the agent concept
- R3. Event Reference -- the agent stopped, deadlock, and OOM events
- H7. Checking for a Memory Leak -- using heap and thread dumps
- H1. Narrowing the Monitored Target -- checking the selector when a chart looks empty