Zabbix

/*

** Zabbix

** Copyright (C) 2001-2023 Zabbix SIA

**

** This program is free software; you can redistribute it and/or modify

** it under the terms of the GNU General Public License as published by

** the Free Software Foundation; either version 2 of the License, or

** (at your option) any later version.

**

** This program is distributed in the hope that it will be useful,

** but WITHOUT ANY WARRANTY; without even the implied warranty of

** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

** GNU General Public License for more details.

**

** You should have received a copy of the GNU General Public License

** along with this program; if not, write to the Free Software

** Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

**/

​

// watch package provides utility functionality for easier Watcher plugin implementation.

// Watcher plugin listens for events specified by the item requests and comnverts those

// events to item values. This package handles event source initialization/deinitialization,

// event filtering and conversion to item values/errors.

package watch

​

import (

    "sync"

    "time"

​

    "git.zabbix.com/ap/plugin-support/plugin"

)

​

// EventSource generates events by calling Manager.Notify() method and passing arbitrary

// data. The data is converted to string values by event filter that was created by the

// event source during Manager update.

type EventSource interface {

    // initialize event source and start generating events

    Initialize() error

    // stop generating events and release internal resources allocated by event source

    Release()

    // create new event filter based on item key

    NewFilter(key string) (filter EventFilter, err error)

}

​

// EventProvider interface provides methods to get event source by item key. An new or existing

// event source can be returned. EventProvider is required to create Manager instance.

type EventProvider interface {

    EventSourceByKey(key string) (EventSource, error)

}

​

// EventFilter has two responsibilities. The first is to convert data to a string value.

// The second is optional - based on internal filter parameters (item key for example)

// it can make the data to be ignored by returning nil value.

type EventFilter interface {

    // Process processes data from event source and returns:

    //   value - data is valid and matches filter

    //   error - invalid data

    //   nothing - data is valid, but does not match the filter

    Process(data interface{}) (value *string, err error)

}

​

// eventWriter links event filter to output sink where the filtered results must be written

type eventWriter struct {