apminsight/lib/instrument/index.js

monitor nodejs applications

var mod = require("module");
var coreModules = require("./core-modules");
var logger = require("./../util/logger");
var supportedModulesInfo = require("./npm-modules");
var wrapper = require("./wrapper");

var actLoad = mod._load;

var modulesCacheInfo = {};
var supportedModules = Object.keys(supportedModulesInfo);

function start() {
    instrumentCoreModules();
    patchModuleLoad();
    checkaddAsyncHooks();
}

function instrumentCoreModules() {
    var modulesInfo = coreModules.MODULES_INFO;
    Object.keys(modulesInfo).forEach(function (moduleName) {
        logger.info("Instrumenting module::", moduleName);
        try {
            var actualModule =
                moduleName === "global" ? global : require(moduleName);
        } catch (err) {
            logger.info("module ::" + moduleName + " is not available");
            return;
        }
        modulesInfo[moduleName].forEach(function (eachFunction) {
            wrapper.checkAndWrapFunction(
                actualModule,
                eachFunction,
                moduleName,
                eachFunction.functionName
            );
        });
    });
}

/* eslint-disable no-unused-vars */
function patchModuleLoad() {
    mod._load = function (request, parent, Main) {
        var actualContent = actLoad.apply(this, arguments);
        if (supportedModules.indexOf(request) < 0) {
            return actualContent;
        }
        return checkAndInstrument(request, actualContent);
    };
}
/* eslint-enable no-unused-vars */

function instrumentCustomModules(moduleName, moduleInfo) {
    supportedModulesInfo[moduleName] = moduleInfo;
    supportedModules.push(moduleName);
}

function checkAndInstrument(request, actualContent, moduleName) {
    if (modulesCacheInfo[request] && modulesCacheInfo[request].wrapped) {
        return modulesCacheInfo[request].wrapped;
    }
    logger.info("Instrumenting module::" + request);
    var functionInfo;
    if (moduleName) {
        var modInfo = supportedModulesInfo[moduleName];
        functionInfo = modInfo[request];
    } else {
        moduleName = request;
        functionInfo = supportedModulesInfo[moduleName];
    }

    functionInfo.functions.forEach(function (eachFunction) {
        wrapper.checkAndWrapFunction(
            actualContent,
            eachFunction,
            moduleName,
            eachFunction.functionName
        );
    });
    modulesCacheInfo[request] = {};
    modulesCacheInfo[request].wrapped = actualContent;
    return actualContent;
}

/* eslint-disable no-unused-vars */
function checkaddAsyncHooks() {
    try {
        var asyncHooks = require("async_hooks");
        var contextMapping = {};
        asyncHooks
            .createHook({
                init: function initHook(id, type, triggerId, promiseWrap) {
                    var curTxn = apmInsightAgentInstance.getCurTxn();
                    if (!curTxn || type !== "PROMISE") {
                        return;
                    }
                    contextMapping[id] = {
                        txn: curTxn,
                        tracker: apmInsightAgentInstance.getCurTracker()
                    };
                },
                before: function (id) {
                    if (contextMapping[id]) {
                        var context = contextMapping[id];
                        apmInsightAgentInstance.setCurContext(
                            context.txn,
                            context.tracker
                        );
                    }
                },
                after: function (id) {
                    if (contextMapping[id]) {
                        apmInsightAgentInstance.clearCurContext();
                    }
                },
                destroy: function (id) {
                    if (contextMapping[id]) {
                        delete contextMapping[id];
                    }
                }
            })
            .enable();
    } catch (error) {
        logger.info("Async hook module is not available");
    }
}
/* eslint-enable no-unused-vars */

module.exports = {
    start: start,
    instrumentCustomModules: instrumentCustomModules
};