function createApmClient()

in lib/apm-client/apm-client.js [31:129]
88 lines of code
22 McCabe index (conditional complexity)

function createApmClient(config, agent) {
  if (config.disableSend || config.contextPropagationOnly) {
    return new NoopApmClient();
  } else if (typeof config.transport === 'function') {
    return config.transport(config, agent);
  }

  const client = new HttpApmClient(getHttpClientConfig(config, agent));

  client.on('config', (remoteConf) => {
    agent.logger.debug({ remoteConf }, 'central config received');
    try {
      const conf = {};
      const unknown = [];

      for (const [key, value] of Object.entries(remoteConf)) {
        const newKey = CENTRAL_CONFIG_OPTS[key];
        if (newKey) {
          conf[newKey] = value;
        } else {
          unknown.push(key);
        }
      }
      if (unknown.length > 0) {
        agent.logger.warn(
          `Central config warning: unsupported config names: ${unknown.join(
            ', ',
          )}`,
        );
      }

      if (Object.keys(conf).length > 0) {
        normalize(conf, agent.logger);
        for (const [key, value] of Object.entries(conf)) {
          const oldValue = agent._conf[key];
          agent._conf[key] = value;
          if (
            key === 'logLevel' &&
            value !== oldValue &&
            !logging.isLoggerCustom(agent.logger)
          ) {
            logging.setLogLevel(agent.logger, value);
            // Hackily also set the HttpApmClient._log level.
            logging.setLogLevel(client._log, value);
            agent.logger.info(
              `Central config success: updated logger with new logLevel: ${value}`,
            );
          }
          agent.logger.info(`Central config success: updated ${key}: ${value}`);
        }
      }
    } catch (err) {
      agent.logger.error(
        { remoteConf, err },
        'Central config error: exception while applying changes',
      );
    }
  });

  client.on('error', (err) => {
    agent.logger.error('APM Server transport error: %s', err.stack);
  });

  client.on('request-error', (err) => {
    const haveAccepted = Number.isFinite(err.accepted);
    const haveErrors = Array.isArray(err.errors);
    let msg;

    if (err.code === 404) {
      msg =
        'APM Server responded with "404 Not Found". ' +
        "This might be because you're running an incompatible version of the APM Server. " +
        'This agent only supports APM Server v6.5 and above. ' +
        "If you're using an older version of the APM Server, " +
        'please downgrade this agent to version 1.x or upgrade the APM Server';
    } else if (err.code) {
      msg = `APM Server transport error (${err.code}): ${err.message}`;
    } else {
      msg = `APM Server transport error: ${err.message}`;
    }

    if (haveAccepted || haveErrors) {
      if (haveAccepted)
        msg += `\nAPM Server accepted ${err.accepted} events in the last request`;
      if (haveErrors) {
        for (const error of err.errors) {
          msg += `\nError: ${error.message}`;
          if (error.document) msg += `\n  Document: ${error.document}`;
        }
      }
    } else if (err.response) {
      msg += `\n${err.response}`;
    }

    agent.logger.error(msg);
  });

  return client;
}