FAQ

Monitor

Published: May 19, 2020
Edited: May 21, 2020

Monitor Plugin

Version: 1.0

Status:

Monitor plugin for Thunder framework.

Table of Contents

Introduction

Scope

This document describes purpose and functionality of the Monitor plugin. It includes detailed specification of its configuration, methods and properties provided, as well as notifications sent.

Case Sensitivity

All identifiers on the interface described in this document are case-sensitive. Thus, unless stated otherwise, all keywords, entities, properties, relations and actions should be treated as such.

Acronyms, Abbreviations and Terms

The table below provides and overview of acronyms used in this document and their definitions.

Acronym Description
API Application Programming Interface
HTTP Hypertext Transfer Protocol
JSON JavaScript Object Notation; a data interchange format
JSON-RPC A remote procedure call protocol encoded in JSON

The table below provides and overview of terms and abbreviations used in this document and their definitions.

Term Description
callsign The name given to an instance of a plugin. One plugin can be instantiated multiple times, but each instance the instance name, callsign, must be unique.

References

Ref ID Description
HTTP HTTP specification
JSON-RPC JSON-RPC 2.0 specification
JSON JSON specification
Thunder Thunder API Reference

Description

The Monitor plugin provides a watchdog-like functionality for framework processes.

The plugin is designed to be loaded and executed within the Thunder framework. For more information about the framework refer to [Thunder].

Configuration

The table below lists configuration options of the plugin.

Name Type Description
callsign string Plugin instance name (default: Monitor)
classname string Class name: Monitor
locator string Library name: libWPEFrameworkMonitor.so
autostart boolean Determines if the plugin is to be started automatically along with the framework

Methods

The following methods are provided by the Monitor plugin:

Monitor interface methods:

Method Description
restartlimits Sets new restart limits for a service
resetstats Resets memory and process statistics for a single service watched by the Monitor

restartlimits method

Sets new restart limits for a service.

Parameters

Name Type Description
params object
params.callsign string The callsign of a service to reset measurements snapshot of
params.restart object
params.restart.limit number Maximum number or restarts to be attempted
params.restart.window number Time period (in seconds) within which failures must happen for the limit to be considered crossed

Result

Name Type Description
result null Always null

Example

Request

{
    "jsonrpc": "2.0",
    "id": 1234567890,
    "method": "Monitor.1.restartlimits",
    "params": {
        "callsign": "WebServer",
        "restart": {
            "limit": 3,
            "window": 60
        }
    }
}

Response

{
    "jsonrpc": "2.0",
    "id": 1234567890,
    "result": null
}

resetstats method

Resets memory and process statistics for a single service watched by the Monitor.

Parameters

Name Type Description
params object
params.callsign string The callsign of a service to reset statistics of

Result

Name Type Description
result object Measurements for the service before reset
result.measurements object Measurements for the service
result.measurements.resident object Resident memory measurement
result.measurements.resident.min number Minimal value measured
result.measurements.resident.max number Maximal value measured
result.measurements.resident.average number Average of all measurements
result.measurements.resident.last number Last measured value
result.measurements.allocated object Allocated memory measurement
result.measurements.allocated.min number Minimal value measured
result.measurements.allocated.max number Maximal value measured
result.measurements.allocated.average number Average of all measurements
result.measurements.allocated.last number Last measured value
result.measurements.shared object Shared memory measurement
result.measurements.shared.min number Minimal value measured
result.measurements.shared.max number Maximal value measured
result.measurements.shared.average number Average of all measurements
result.measurements.shared.last number Last measured value
result.measurements.process object Processes measurement
result.measurements.process.min number Minimal value measured
result.measurements.process.max number Maximal value measured
result.measurements.process.average number Average of all measurements
result.measurements.process.last number Last measured value
result.measurements.operational boolean Whether the service is up and running
result.measurements.count number Number of measurements
result.observable string A callsign of the watched service
result.restart object Restart limits for memory/operational failures applying to the service
result.restart.limit number Maximum number or restarts to be attempted
result.restart.window number Time period (in seconds) within which failures must happen for the limit to be considered crossed

Example

Request

{
    "jsonrpc": "2.0",
    "id": 1234567890,
    "method": "Monitor.1.resetstats",
    "params": {
        "callsign": "WebServer"
    }
}

Response

{
    "jsonrpc": "2.0",
    "id": 1234567890,
    "result": {
        "measurements": {
            "resident": {
                "min": 0,
                "max": 100,
                "average": 50,
                "last": 100
            },
            "allocated": {
                "min": 0,
                "max": 100,
                "average": 50,
                "last": 100
            },
            "shared": {
                "min": 0,
                "max": 100,
                "average": 50,
                "last": 100
            },
            "process": {
                "min": 0,
                "max": 100,
                "average": 50,
                "last": 100
            },
            "operational": true,
            "count": 100
        },
        "observable": "callsign",
        "restart": {
            "limit": 3,
            "window": 60
        }
    }
}

Properties

The following properties are provided by the Monitor plugin:

Monitor interface properties:

Property Description
status RO Service statistics

status property

Provides access to the service statistics.

This property is read-only.

Value

Name Type Description
(property) array Service statistics
(property)[#] object
(property)[#].measurements object Measurements for the service
(property)[#].measurements.resident object Resident memory measurement
(property)[#].measurements.resident.min number Minimal value measured
(property)[#].measurements.resident.max number Maximal value measured
(property)[#].measurements.resident.average number Average of all measurements
(property)[#].measurements.resident.last number Last measured value
(property)[#].measurements.allocated object Allocated memory measurement
(property)[#].measurements.allocated.min number Minimal value measured
(property)[#].measurements.allocated.max number Maximal value measured
(property)[#].measurements.allocated.average number Average of all measurements
(property)[#].measurements.allocated.last number Last measured value
(property)[#].measurements.shared object Shared memory measurement
(property)[#].measurements.shared.min number Minimal value measured
(property)[#].measurements.shared.max number Maximal value measured
(property)[#].measurements.shared.average number Average of all measurements
(property)[#].measurements.shared.last number Last measured value
(property)[#].measurements.process object Processes measurement
(property)[#].measurements.process.min number Minimal value measured
(property)[#].measurements.process.max number Maximal value measured
(property)[#].measurements.process.average number Average of all measurements
(property)[#].measurements.process.last number Last measured value
(property)[#].measurements.operational boolean Whether the service is up and running
(property)[#].measurements.count number Number of measurements
(property)[#].observable string A callsign of the watched service
(property)[#].restart object Restart limits for memory/operational failures applying to the service
(property)[#].restart.limit number Maximum number or restarts to be attempted
(property)[#].restart.window number Time period (in seconds) within which failures must happen for the limit to be considered crossed

The callsign shall be passed as the index to the property, e.g. Monitor.1.status@WebServer. If omitted then all observed objects will be returned on read.

Example

Get Request

{
    "jsonrpc": "2.0",
    "id": 1234567890,
    "method": "Monitor.1.status@WebServer"
}

Get Response

{
    "jsonrpc": "2.0",
    "id": 1234567890,
    "result": [
        {
            "measurements": {
                "resident": {
                    "min": 0,
                    "max": 100,
                    "average": 50,
                    "last": 100
                },
                "allocated": {
                    "min": 0,
                    "max": 100,
                    "average": 50,
                    "last": 100
                },
                "shared": {
                    "min": 0,
                    "max": 100,
                    "average": 50,
                    "last": 100
                },
                "process": {
                    "min": 0,
                    "max": 100,
                    "average": 50,
                    "last": 100
                },
                "operational": true,
                "count": 100
            },
            "observable": "callsign",
            "restart": {
                "limit": 3,
                "window": 60
            }
        }
    ]
}

Notifications

Notifications are autonomous events, triggered by the internals of the implementation, and broadcasted via JSON-RPC to all registered observers.Refer to [Thunder] for information on how to register for a notification.

The following events are provided by the Monitor plugin:

Monitor interface events:

Event Description
action Signals an action taken by the Monitor

action event

Signals an action taken by the Monitor.

Parameters

Name Type Description
params object
params.callsign string Callsign of the service the Monitor acted upon
params.action string The action executed by the Monitor on a service. One of: "Activate", "Deactivate", "StoppedRestarting"
params.reason string A message describing the reason the action was taken

Example

{
    "jsonrpc": "2.0",
    "method": "client.events.1.action",
    "params": {
        "callsign": "WebServer",
        "action": "Deactivate",
        "reason": "EXCEEDED_MEMORY"
    }
}
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