DESCRIPTION

pmdajson is a Performance Metrics Domain Agent (PMDA) which exports metrics from arbitrary sources generating Javascript Object Notation (JSON) syntax, describing metric metadata and values.

Further details on the JSON format can be found at http://www.json.org

JSON DATA SOURCES

pmdajson searches the directories listed in the "directory_list" and "trusted_directory_list" config file options, looking for files called "metadata.json". These JSON metadata files describe the names, types, etc. of their associated JSON data. For example, let's assume the following simple JSON data file:

  {
    "string_value": "testing, 1, 2, 3",
    "read_count": 0
  }

The associated metadata file would look like the following:

  {
    "metrics": [
      {
        "name": "string_value",
        "pointer": "/string_value",
        "type": "string",
      },
      {
        "name": "read_count",
        "pointer": "/read_count",
        "type": "integer",
        "description": "Times values read"
      }
    ]
  }

For more details on the JSON metadata format, see the README file included with pmdajson.

SECURITY MODEL

JSON sources that come from "directory_list" config file option aren't "trusted", and any command that needs to be run to get JSON data is run as user "nobody".

JSON sources that come from "trusted_directory_list" config file option are trusted, and any command that needs to be run to get JSON data is run as user "root".

For more details on security, see the README file included with pmdajson.

INSTALLATION

Install the json PMDA by using the Install script as root:

      # cd $PCP_PMDAS_DIR/json

      # ./Install

To uninstall, do the following as root:

      # cd $PCP_PMDAS_DIR/json

      # ./Remove

pmdajson is launched by pmcd(1) and should never be executed directly. The Install and Remove scripts notify pmcd(1) when the agent is installed or removed.

FILES

$PCP_PMDAS_DIR/json/Install

installation script for the pmdajson agent

$PCP_PMDAS_DIR/json/Remove

undo installation script for the pmdajson agent

$PCP_PMDAS_DIR/json/config.json

configuration file for the pmdajson agent

$PCP_LOG_DIR/pmcd/json.log

default log file for error messages from pmdajson

PCP ENVIRONMENT

Environment variables with the prefix PCP_ are used to parameterize the file and directory names used by PCP. On each installation, the file /etc/pcp.conf contains the local values for these variables. The $PCP_CONF variable may be used to specify an alternative configuration file, as described in pcp.conf(5).