MemoryMonitor API

Version: 1.0.0

Status:

MemoryMonitor interface for Thunder framework.

(Defined with IMemoryMonitor in IMemoryMonitor.h)

Table of Contents

• Introduction
• Description
• Methods
• Properties
• Notifications

Introduction

Scope

This document describes purpose and functionality of the MemoryMonitor interface (version 1.0.0). It includes detailed specification about its methods and properties as well as sent notifications.

Case Sensitivity

All identifiers of the interfaces 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

MemoryMonitor JSON-RPC interface.

This interface uses legacy lowercase naming convention. With the next major release the naming convention will change to camelCase.

Methods

The following methods are provided by the MemoryMonitor interface:

Built-in methods:

Method	Description
exists	Checks if a JSON-RPC method or property exists
register	Registers for an asynchronous JSON-RPC notification
unregister	Unregisters from an asynchronous JSON-RPC notification

MemoryMonitor interface methods:

Method	Description
resetstatistics	Resets memory statistics for a given service

exists ^method

Checks if a JSON-RPC method or property exists.

Description

This method will return True for the following methods/properties: restartinglimits, observables, measurementdata, exists, register, unregister, resetstatistics.

Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.method	string	mandatory	Name of the method or property to look up

Result

Name	Type	M/O	Description
result	boolean	mandatory	Denotes if the method exists or not

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.exists",
  "params": {
    "method": "methodName"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": false
}

register ^method

Registers for an asynchronous JSON-RPC notification.

Description

This method supports the following event names: statuschanged.

Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.event	string	mandatory	Name of the notification to register for
params.id	string	mandatory	Client identifier

Result

Name	Type	M/O	Description
result	null	mandatory	Always null

Errors

Message	Description
ERROR_FAILED_REGISTERED	Failed to register for the notification (e.g. already registered)

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.register",
  "params": {
    "event": "eventName",
    "id": "myapp"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": null
}

unregister ^method

Unregisters from an asynchronous JSON-RPC notification.

Description

This method supports the following event names: statuschanged.

Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.event	string	mandatory	Name of the notification to register for
params.id	string	mandatory	Client identifier

Result

Name	Type	M/O	Description
result	null	mandatory	Always null

Errors

Message	Description
ERROR_FAILED_UNREGISTERED	Failed to unregister from the notification (e.g. not yet registered)

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.unregister",
  "params": {
    "event": "eventName",
    "id": "myapp"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": null
}

resetstatistics ^method

Resets memory statistics for a given service.

Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.callsign	string	mandatory	Callsign of the service

Result

Name	Type	M/O	Description
result	null	mandatory	Always null

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.resetstatistics",
  "params": {
    "callsign": "WebServer"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": null
}

Properties

The following properties are provided by the MemoryMonitor interface:

MemoryMonitor interface properties:

Property	R/W	Description
restartinglimits	read/write	Limits of restarting of a service
observables	read-only	List of services watched by the Monitor
measurementdata	read-only	Memory statistics for a given service

restartinglimits ^property

Provides access to the limits of restarting of a service.

The callsign parameter shall be passed as the index to the property, i.e. restartinglimits@<callsign>.

Index

Name	Type	M/O	Description
callsign	string	mandatory	Callsign of the service

Value

Name	Type	M/O	Description
(property)	object	mandatory	Limits of restarting of a service
(property).value	object	mandatory	Limits of restarts applying to a given service
(property).value.limit	integer	mandatory	Maximum number or restarts to be attempted
(property).value.window	integer	mandatory	Time period (in seconds) within which failures must happen for the limit to be considered crossed

Name	Type	M/O	Description
(property)	object	mandatory	Limits of restarting of a service
(property).limit	integer	mandatory	Maximum number or restarts to be attempted
(property).window	integer	mandatory	Time period (in seconds) within which failures must happen for the limit to be considered crossed

Example

Get Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.restartinglimits@WebServer"
}

Get Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": {
    "limit": 3,
    "window": 60
  }
}

Set Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.restartinglimits@WebServer",
  "params": {
    "value": {
      "limit": 3,
      "window": 60
    }
  }
}

Set Response

{
    "jsonrpc": "2.0",
    "id": 42,
    "result": "null"
}

observables ^property

Provides access to the list of services watched by the Monitor.

This property is read-only.

Value

Name	Type	M/O	Description
(property)	array	mandatory	List of monitored services
(property)[#]	string	mandatory	...

Example

Get Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.observables"
}

Get Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": [
    "..."
  ]
}

measurementdata ^property

Provides access to the memory statistics for a given service.

This property is read-only.

The callsign parameter shall be passed as the index to the property, i.e. measurementdata@<callsign>.

Index

Name	Type	M/O	Description
callsign	string	mandatory	Callsign of the service

Value

Name	Type	M/O	Description
(property)	object	mandatory	Statistics for the requested callsign
(property).resident	object	mandatory	Resident memory measurement
(property).resident.min	integer	mandatory	Minimal value measured
(property).resident.max	integer	mandatory	Maximal value measured
(property).resident.average	integer	mandatory	Average of all measurements
(property).resident.last	integer	mandatory	Last measured value
(property).allocated	object	mandatory	Allocated memory measurement
(property).allocated.min	integer	mandatory	Minimal value measured
(property).allocated.max	integer	mandatory	Maximal value measured
(property).allocated.average	integer	mandatory	Average of all measurements
(property).allocated.last	integer	mandatory	Last measured value
(property).shared	object	mandatory	Shared memory measurement
(property).shared.min	integer	mandatory	Minimal value measured
(property).shared.max	integer	mandatory	Maximal value measured
(property).shared.average	integer	mandatory	Average of all measurements
(property).shared.last	integer	mandatory	Last measured value
(property).process	object	mandatory	Processes measurement
(property).process.min	integer	mandatory	Minimal value measured
(property).process.max	integer	mandatory	Maximal value measured
(property).process.average	integer	mandatory	Average of all measurements
(property).process.last	integer	mandatory	Last measured value
(property).operational	boolean	mandatory	Whether the service is up and running
(property).count	integer	mandatory	Number of measurements

Example

Get Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.measurementdata@WebServer"
}

Get Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": {
    "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
  }
}

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 MemoryMonitor interface:

MemoryMonitor interface events:

Notification	Description
statuschanged	Signals an action taken by the Monitor

statuschanged ^notification

Signals an action taken by the Monitor.

Notification Parameters

Name	Type	M/O	Description
params	object	mandatory	...
params.callsign	string	mandatory	Callsign of the service the Monitor acted upon
params.action	string	mandatory	Ation executed by the Monitor on a service (must be one of the following: Activated, Deactivated, RestartingStopped)
params?.reason	string	optional	Mssage describing the reason the action was taken (must be one of the following: ExceededMemory, NotOperational)

Example

Registration

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "<callsign>.1.register",
  "params": {
    "event": "statuschanged",
    "id": "myid"
  }
}

Notification

{
  "jsonrpc": "2.0",
  "method": "myid.statuschanged",
  "params": {
    "callsign": "WebServer",
    "action": "Deactivate",
    "reason": "EXCEEDED_MEMORY"
  }
}

The client ID parameter is passed within the notification designator, i.e. <client-id>.statuschanged.