1PMDAJSON(1) General Commands Manual PMDAJSON(1)
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6 pmdajson - JSON PMDA
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9 pmdajson is a Performance Metrics Domain Agent (PMDA) which exports
10 metrics from arbitrary sources generating JavaScript Object Notation
11 (JSON) syntax.
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13 At least one pair of JSON inputs are required for pmdajson to provide
14 metrics for PCP clients; one describing metric metadata and one con‐
15 taining metric values data. Metadata is read once from a file at PMDA
16 startup while the data is read every time a request for metric values
17 is made by a PCP client. The data is read either from a JSON file or
18 an external command generating JSON output. More than one pair of JSON
19 inputs can be used to support arbitrary number of metric sources in
20 different configured directories.
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22 The overall JSON format description is at http://www.json.org/.
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25 pmdajson reads a mandatory JSON configuration file
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27 · $PCP_PMDAS_DIR/json/config.json
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29 This file can contain the following PMDA options using the JSON syntax:
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31 · directory_list
32 · trusted_directory_list
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34 pmdajson searches the directories listed for these options looking for
35 files named metadata.json and (by default) data.json. The JSON meta‐
36 data files describe the metric names, types, and other details of the
37 associated JSON metric data. The JSON data file name is configurable,
38 and can also be an external command instead of a periodically updated
39 (by external tools) data file.
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41 Each of these found JSON file/command pairs form a JSON data source.
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43 For example, let us assume the following simple JSON data file that
44 contains values for two metrics, one of type string and one numeric:
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46 {
47 "string_value": "testing, 1, 2, 3",
48 "read_count": 0
49 }
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51 For these metrics the metadata file needed by pmdajson would be:
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53 {
54 "metrics": [
55 {
56 "name": "string_value",
57 "pointer": "/string_value",
58 "type": "string"
59 },
60 {
61 "name": "read_count",
62 "pointer": "/read_count",
63 "type": "integer",
64 "description": "Times values read"
65 }
66 ]
67 }
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69 For further details on the JSON metadata format and options, see the
70 README file included as part of pmdajson installation.
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73 JSON data sources listed for the directory_list option are not trusted,
74 meaning that if external commands to generate the needed JSON data are
75 used, these commands are run as user nobody.
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77 JSON data sources listed for the trusted_directory_list option are
78 trusted, meaning that if external commands to generate the needed JSON
79 data are used, these commands are run as user root.
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81 For further details on security and description on running external
82 commands, see the README file included as part of pmdajson installa‐
83 tion.
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86 Install the JSON PMDA by using the Install script as root:
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88 # cd $PCP_PMDAS_DIR/json
89 # ./Install
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91 To uninstall, do the following as root:
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93 # cd $PCP_PMDAS_DIR/json
94 # ./Remove
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96 pmdajson is launched by pmcd(1) and should never be executed directly.
97 The Install and Remove scripts notify pmcd(1) when the agent is
98 installed or removed.
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101 $PCP_PMDAS_DIR/json/README
102 additional documentation for pmdajson used JSON files
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104 $PCP_PMDAS_DIR/json/config.json
105 configuration file for the pmdajson agent
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107 $PCP_PMDAS_DIR/json/Install
108 installation script for the pmdajson agent
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110 $PCP_PMDAS_DIR/json/Remove
111 undo installation script for the pmdajson agent
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113 $PCP_LOG_DIR/pmcd/json.log
114 default log file for messages from the pmdajson agent
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117 Environment variables with the prefix PCP_ are used to parameterize the
118 file and directory names used by PCP. On each installation, the file
119 /etc/pcp.conf contains the local values for these variables. The
120 $PCP_CONF variable may be used to specify an alternative configuration
121 file, as described in pcp.conf(5).
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124 PCPIntro(1), pmcd(1) and pminfo(1).
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128Performance Co-Pilot PCP PMDAJSON(1)