/node_modules/newrelic/lib/error.js

'use strict';

var path    = require('path')
  , urltils = require(path.join(__dirname, 'util', 'urltils'))
  , logger  = require(path.join(__dirname, 'logger')).child({component : 'error_tracer'})
  , NAMES   = require(path.join(__dirname, 'metrics', 'names'))
  ;

/*
 *
 * CONSTANTS
 *
 */
var MAX_ERRORS = 20;

/**
 * Given either or both of a transaction and an exception, generate an error
 * trace in the JSON format expected by the collector. Since this will be
 * used by both the HTTP instrumentation, which uses HTTP status codes to
 * determine whether a transaction is in error, and the domain-based error
 * handler, which traps actual instances of Error, try to set sensible
 * defaults for everything.
 *
 * @param {Transaction} transaction      The agent transaction, presumably
 *                                       coming out of the instrumentation.
 * @param {Error}       exception        Something trapped by an error listener.
 * @param {object}      customParameters Any custom parameters associated with
 *                                       the request (optional).
 */
function createError(transaction, exception, customParameters) {
  // the collector throws this out, so don't bother setting it
  var timestamp = 0
    , name      = 'WebTransaction/Uri/*'
    , message   = ''
    , type      = 'Error'
    , params    = {}
    ;

  if (transaction && transaction.name) name = transaction.name;

  // NB: anything throwing / emitting strings is buggy, but it happens
  if (typeof exception === 'string') {
    message = exception;
  }
  else if (exception && exception.message) {
    message = exception.message;
    // only care about extracting the type if it's Error-like.
    if (exception && exception.constructor && exception.constructor.name) {
      type = exception.constructor.name;
    }
  }
  else if (transaction &&
           transaction.statusCode &&
           urltils.isError(transaction.agent.config, transaction.statusCode)) {
    message = 'HttpError ' + transaction.statusCode;
  }

  if (customParameters) {
    var ignored = [];
    if (transaction) ignored = transaction.agent.config.ignored_params;
    Object.keys(customParameters).forEach(function cb_forEach(param) {
      if (ignored.indexOf(param) === -1) params[param] = customParameters[param];
    });
  }

  if (transaction && transaction.url) {
    var url        = transaction.url
      , statusCode = transaction.statusCode || 500
      ;

    /* We need a name for this transaction, but since error-tracing can happen
     * in the middle of the request, and it's possible that the user will
     * recover from the error, name the transaction now, preserving the
     * necessary state to maintain any user-provided naming information.
     */
    if (!transaction.name) {
      var partialName = transaction.partialName;
      transaction.setName(url, statusCode);
      transaction.partialName = partialName;
    }

    name = transaction.name;
    params.request_uri = url;
    if (transaction.agent.config.capture_params) {
      var requestParams = urltils.parseParameters(url);

      // clear out ignored params
      transaction.agent.config.ignored_params.forEach(function cb_forEach(k) {
        // polymorphic hidden classes aren't an issue with data bags
        delete requestParams[k];
      });

      if (Object.keys(requestParams).length > 0) params.request_params = requestParams;
    }
  }

  var stack = exception && exception.stack;
  // FIXME: doing this work should not be the agent's responsibility
  if (stack) params.stack_trace = ('' + stack).split(/[\n\r]/g);

  return [timestamp, name, message, type, params];
}

/**
 * This is a fairly simple-minded tracer that converts errored-out HTTP
 * transactions and JS Errors into the error traces expected by the collector.
 *
 * It also acts as a collector for the traced errors.
 */
function ErrorTracer(config) {
  this.config     = config;
  this.errorCount = 0;
  this.errors     = [];
  this.seen       = [];
}

/**
 * Every finished transaction goes through this handler, so do as
 * little as possible.
 */
ErrorTracer.prototype.onTransactionFinished = function onTransactionFinished(transaction, metrics) {
  if (!transaction) throw new Error("Error collector got a blank transaction.");
  if (!metrics) throw new Error("Error collector requires metrics to count errors.");

  if (urltils.isError(this.config, transaction.statusCode) ||
      (transaction.statusCode < 1 && transaction.exceptions.length > 0)) {
    if (transaction.exceptions.length > 0) {
      transaction.exceptions.forEach(function cb_forEach(exception) {
        this.add(transaction, exception);
      }, this);
    }
    else {
      this.add(transaction);
    }

    var count = metrics.getOrCreateMetric(NAMES.ERRORS.PREFIX + transaction.name);
    count.incrementCallCount(1);
  }
};

/**
 * This function uses an array of seen exceptions to ensure errors don't get
 * double-counted. It can also be used as an unofficial means of marking that
 * user errors shouldn't be traced.
 *
 * For an error to be traced, at least one of the transaction or the error
 * must be present.
 *
 * NOTE: this interface is unofficial and may change in future.
 *
 * @param {Transaction} transaction      Transaction associated with the error
 *                                       (optional).
 * @param {Error}       exception        The error to be traced (optional).
 * @param {object}      customParameters Any custom parameters associated with
 *                                       the request (optional).
 */
ErrorTracer.prototype.add = function add(transaction, exception, customParameters) {
  if (!exception) {
    if (!transaction) return;
    if (!transaction.statusCode) return;
    if (transaction.error) return;
  }
  else {
    if (this.seen.indexOf(exception) !== -1) return;
    if (typeof exception !== 'string' && !exception.message && !exception.stack) {
      return;
    }
  }

  this.errorCount++;

  // allow enabling & disabling the error tracer at runtime
  if (!this.config.collect_errors ||
      !this.config.error_collector || !this.config.error_collector.enabled) return;

  if (exception) {
    logger.trace(exception, "Got exception to trace:");
    // put the error on the transaction to show we've already traced it
    if (transaction) transaction.error = exception;
    this.seen.push(exception);
  }

  if (this.errors.length < MAX_ERRORS) {
    var error = createError(transaction, exception, customParameters);
    logger.debug({error : error}, "Error to be sent to collector:");
    this.errors.push(error);
  }
  else {
    logger.debug("Already have %d errors to send to collector, not keeping.",
                 MAX_ERRORS);
  }
};

/**
 * If the connection to the collector fails, retain as many as will fit without
 * overflowing the current error list.
 *
 * @param array errors Previously harvested errors.
 */
ErrorTracer.prototype.merge = function merge(errors) {
  if (!errors) return;

  var len = Math.min(errors.length, MAX_ERRORS - this.errors.length);
  logger.warn("Merging %s (of %s) errors for next delivery.", len, errors.length);
  for (var i = 0; i < len; i++) this.errors.push(errors[i]);
};

module.exports = ErrorTracer;