domotz-remote-pawn/src/discovery/snmp/snmp_overlay_device_db.js

Domotz Agent

/** This file is part of Domotz Agent.
 * Copyright (C) 2021  Domotz Ltd
 *
 * Domotz Agent 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 3 of the License, or
 * (at your option) any later version.
 *
 * Domotz Agent 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 Domotz Agent.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 * Created by Fausto Lelli <fausto@domotz.com>
 */

var path = require('path');
var os = require('os');

const OID_DB_REMOTE_ENDPOINT = '/overlay/device-catalog';
const OVERLAY_DB_SEMAPHORE = 'SNMP_OVERLAY_DEVICE_DB_SEMAPHORE';
const OID_DB_FILE = path.join(os.tmpdir(), 'overlay_device_db.json');

var snmpOverlayDeviceDBFactory = function (resourceLocator) {
    'use strict';

    var fileUtils = resourceLocator.utils.file;
    var crypto = resourceLocator.crypto;
    var mutex = resourceLocator.utils.mutex;
    var engineRequest = resourceLocator.engineRequest;
    var forceOverlayDiscovery = require('../../events/handler/snmpOverlayDiscovery').forceNextDiscovery;

    var myConsole = resourceLocator.log.decorateLogs();

    // the following variables must be invalidated
    var currentMD5 = null;
    var currentDB = null;

    var lockDiscovery = function () {
        return mutex.lock(OVERLAY_DB_SEMAPHORE, 1);
    };

    var unlockDiscovery = function () {
        mutex.safeUnlock(OVERLAY_DB_SEMAPHORE, 1);
    };

    function getOverlayDeviceDBFromFile() {
        var content = fileUtils.readFile(OID_DB_FILE);
        if (content) {
            try {
                return JSON.parse(content);
            } catch (e) {
                myConsole.info('Can not parse db file: %s', e);
            }
        }
        return null;
    }

    function getOverlayDeviceDB() {
        if (currentDB) {
            return currentDB;
        }

        var db = getOverlayDeviceDBFromFile();
        if (db && db.hasOwnProperty('devices')) {
            currentDB = db.devices;
            return db.devices;
        } else {
            return null;
        }
    }

    function saveOverlayDB(db) {
        fileUtils.writeFileSafe(OID_DB_FILE, db);
        currentMD5 = null;
        currentDB = null;
        getOverlayMD5();
    }

    function getOverlayMD5() {
        if (currentMD5) {
            return currentMD5;
        }

        var devices = getOverlayDeviceDB();
        if (devices) {
            var contentMD5 = '';
            if (devices.length > 0) {
                contentMD5 = devices[0].device_hw_address + '-' + devices[0].overlay_id;
            }

            for (var i = 1; i < devices.length; i++) {
                contentMD5 += ',' + devices[i].device_hw_address + '-' + devices[i].overlay_id;
            }

            currentMD5 = crypto.createHash('md5').update(contentMD5).digest('hex');
            myConsole.info('New MD5 computed: %s ', currentMD5);
            return currentMD5;
        } else {
            return null;
        }
    }

    function invalidate() {
        myConsole.info('Force check of Overlay Device DB cache');
        currentMD5 = null;
        checkOverlayDeviceDB(true);
    }

    function checkOverlayDeviceDB(forceDiscoveryOnChange) {
        if (!lockDiscovery()) {
            myConsole.warn('WARNING: SNMP Overlay DB Check already in progress, ignoring the call');
            return;
        }

        var currentMD5 = getOverlayMD5();

        var url = OID_DB_REMOTE_ENDPOINT;
        if (currentMD5 !== null) {
            url = OID_DB_REMOTE_ENDPOINT + '?md5=' + currentMD5;
        }
        myConsole.info('Check MIB Overlay DB, url: ' + url);

        engineRequest
            .sendWithPromise(url, 'GET', null, function (response) {
                myConsole.debug('Received response code : ' + response.statusCode);
                if (response.statusCode === 304) {
                    myConsole.info('MIB Overlay DB is unchanged, using cached info ');
                } else {
                    myConsole.info('Writing MIB Overlay DB to filesystem');
                    saveOverlayDB(response.body);
                    if (forceDiscoveryOnChange) {
                        forceOverlayDiscovery(resourceLocator);
                    }
                }
            })
            .catch(function (err) {
                myConsole.error('Can not retrieve MIB Overlay DB ' + err);
            })
            .finally(function () {
                unlockDiscovery();
            });
    }

    return {
        getOverlayMD5: getOverlayMD5,
        getOverlayDeviceDB: getOverlayDeviceDB,
        checkOverlayDeviceDB: checkOverlayDeviceDB,
        invalidate: invalidate,
    };
};

module.exports.factory = snmpOverlayDeviceDBFactory;