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Overview

The diagnostic Aggregator is a node that listens to DiagnosticArray's on /diagnostics, processes and categorizes the data, and republishes on /diagnostics_agg. The Aggregator loads Analyzer's to perform the diagnostics processing and categorization. The configuration and setup for each analyzer is specific to each robot.

The two analyzers in this package, GenericAnalyzer and ComponentAnalyzer, simply hold and categorize diagnostic messages. They're useful for categorizing components or systems. They warn when an item is stale, but other than that, do no analysis of the diagnostics.

Analyzers

The Aggregator will create analyzers to store and process the diagnostic data. Each analyzer inherits from the base class diagnostic_analyzer/Analyzer. Analyzers should be in packages that depend directly on "pluginlib" and "diagnostic_aggregator".

The base analyzer class is the Analyzer. All derived classes must implement these methods as specified by the Analyzer:

• init
• analyze
• getPrefix
• getName

Analyzers can choose the error state for any DiagnosticStatus message they analyzer. Generally, the "parent" of an analyzer has an error state of the maximum of its children, but it can follow any rule. The header ("/Robot" above) will have the diagnostic level of the greatest of its immediate children, so an error in "Motors" will give an error in "Robot".

GenericAnalyzer

generic_analyzer holds the GenericAnalyzer class, which is the most basic of the Analyzer's. It is used by the diagnostic_aggregator/Aggregator to store, process and republish diagnostics data. The GenericAnalyzer is loaded by the pluginlib as a Analyzer plugin. It is the most basic of all Analyzer's.

The following YAML parameters will create a GenericAnalyzer to motor a PR2 power system.

powersystem:
  type: GenericAnalyzer
  prefix: Power System
  expected: [ 
    'IBPS 0',
    'IBPS 1']
  startswith: [
    'Smart Battery']
  name: [
    'Power Node 1018']
  contains: [
    'Battery']

That would create an GenericAnalyzer that will process any DiagnosticStatus message that has a name that matches the given criteria ("startswith", "contains", "name", or "expected"). "expected" and "name" status names require an exact match. Any names in the "expected" list will give an error if not observed.

ComponentAnalyzer

The component analyzer is useful when a category of components have different sub categories.

The following YAML parameters will create a ComponentAnalyzer to monitor the sensors on a PR2.

sensors:
  type: ComponentAnalyzer
  prefix: Sensors
  timeout: 5.0
  base_hk:
    name: Base Hokuyo
    start_name: base_hokuyo_node
    fields: [
      'base_hokuyo_node: Connection Status',
      'base_hokuyo_node: Frequency Status']
  tilt_hk:
    name: Tilt Hokuyo
    start_name: tilt_hokuyo_node
    fields: [
      'tilt_hokuyo_node: Connection Status',
      'tilt_hokuyo_node: Frequency Status']
  imu:
    name: IMU
    start_name: imu_node
    fields: [
      'imu_node: Calibration Status',
      'imu_node: Frequency Status',
      'imu_node: IMU Status']

Each component is given a name, 'IMU', and given "fields" of messages to expect. Every message that matches those fields will be categorized under 'IMU'. The "start_name" parameter gives the user an option of removing a string from the start of the message name. This is for beautifying messages, ex: "imu_node: Frequency Status" to "Frequency Status".

Setup

To look for an example of an aggregator in use, look in the "demo" directory in the diagnostic_aggregator package. Users specify each Analyzer in the private parameter space of the aggregator, then start the node. If there are any failures in initialization, the aggregator program will exit.

<node pkg="diagnostic_aggregator" type="aggregator_node"
      name="diag_agg" args="Robot" >
  <rosparam command="load" 
            file="$(find diagnostic_aggregator)/demo/pr2_analyzers.yaml" />
</node>

The argument to the aggregator, "Robot" is the root name of all data from the aggregator.

See Stating the Diagnostic Aggregator for details.

Creating an Analyzer

See Creating a Diagnostic Analyzer for details.