Troubleshooting

Find below some possible problem scenarios and corresponding diagnostic steps.

Checking Node Application Metrics has started

By default, a message similar to the following will be written to console output when Node Application Metrics starts:

[Fri Aug 21 09:36:58 2015] com.ibm.diagnostics.healthcenter.loader INFO: Node Application Metrics 1.0.1-201508210934 (Agent Core 3.0.5.201508210934)

Error "Conflicting appmetrics module was already loaded by node-hc. Try running with node instead." when using node-hc

This error indicates you are using node-hc to run an application that uses the Node Application Metrics monitoring API (see Modifying your application to use the local installation). Resolve this by using node to run the application instead. Alternatively, you could remove (or disable temporarily) the use of the Node Application Metrics monitoring API in your application.

This error was added to prevent the scenario where 2 instances of the agent can be accidentally created and started in parallel -- the globally installed one created by node-hc and the locally installed one created by the require('appmetrics'); call in an application modified to use the Node Application Metrics monitoring API.

Error "The specified module could not be found ... appmetrics.node"

This error indicates there was a problem while loading the native part of the module or one of its dependent libraries. On Windows, appmetrics.node depends on a particular version of the C runtime library and if it cannot be found this error is the likely result.

Check:

• Does the appmetrics.node file exist in the indicated location? If not, try reinstalling the module.
• For version 1.0.0 on Windows: are msvcr100.dll and msvcp100.dll installed on your Windows system, and do they match the bitness (32-bit or 64-bit) of your Node.js runtime environment? If not, you may be able to install them with the Visual C++ Redistributable Packages for Visual Studio 2010 package from the Microsoft website.
• For version 1.0.1 on Windows: does msvcr120.dll and msvcp120.dll exist in the module installation directory (see Installation) and does it match the bitness of your Node.js runtime environment? If not, try reinstalling the module.

Note: On Windows, the global module installation directory might be shared between multiple Node.js runtime environments. This can cause problems with globally installed modules with native components, particularly if some of the Node.js runtime environments are 32-bit and others are 64-bit because the native components will only work with those with matching bitness.

No profiling data present for Node.js applications

Method profiling data is not collected by default, check Configuring Node Application Metrics for information on how to enable it.

If collection is enabled, an absence of method profiling data from a Node.js application could be caused by the type of tasks that are being run by your application -- it may be running long, synchronous tasks that prevent collection events from being scheduled on the event loop.

If a task uses the Node.js thread exclusively then shuts down the Node.js runtime environment, the Health Center agent may not get the opportunity to obtain any profiling data. An example of such an application is the Octane JavaScript benchmark suite, which loads the CPU continuously rather than dividing the load across multiple units of work.

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Applies to: appmetrics-1.0.1