Error not handled when client tries to connect and MapD server is down.

[pratik-dimebox]

🐞

• MacOS Sierra 10.12.6
• Node version - 10.4.1
• Steps to recreate:
  1. Turn down the MapD Server
  2. Try to connect to the server with the connect() function
• Description of issue:
  When the MapD server is down and we try to connect to the server then the error is not
  propagated forward to the callback. There is an error thrown to the console which is something
  like this:
  
  { Error: getaddrinfo ENOTFOUND mapd mapd:9090
  at errnoException (dns.js:50:10)
  at GetAddrInfoReqWrap.onlookup [as oncomplete] (dns.js:92:26)
  code: 'ENOTFOUND',
  errno: 'ENOTFOUND',
  syscall: 'getaddrinfo',
  hostname: 'mapd',
  host: 'mapd',
  port: '9090' }
  
  This error should be sent to the callback of the function connect(). But it is not sent and the
  process stops.
  A similar kind of issue occurs in the functions getFIelds() or query(). To recreate it you have to turn
  up the MapD server and establish a connection and keep this connection cached. Now turn down
  the server again and trying calling the query() or getFields() function. There will be an error thrown
  but this error will not be propagated to the callback function of these functions.

[clhenrick]

Relates to #80

[nermaljcat]

Look at: https://github.com/omnisci/mapd-connector/blob/master/thrift/browser/thrift.js#L336-L346

Seems the Thrift.Transport assumes success...