Connect to Windows SQL Server 2008 R2 from Rails app

Question

My Rails 4.2.1 app has to connect to a Microsoft SQL 2008 R2 database. I am using the tiny_tds gem version 1.0.4. FreeTDS v1.00.15 is installed on the production server running Ubuntu 14.04.

I run queries inside an each loop and I can't get the loop to complete, the process crashes before completion. I tried playing with tiny_tds options without success.

Here's the code I am using to get the tiny_tds client (check tds_version and timeout options):

client = TinyTds::Client.new(username: db_conf['username'], password: db_conf['password'], host: db_conf['host'], port: db_conf['port'], database: db_conf['database'], tds_version: '7.3', timeout: 15000, appname: 'ERP')

Here's the FreeTDS log after such an error happens.

packet.c:741:Sending packet 0000 12 01 00 ce 00 00 00 00-16 03 01 00 86 10 00 00 |........ ........| 0010 82 00 80 6e d9 e2 dc 97-9d 77 59 9a 5b da e3 e2 |...n.... .wY.[...| 0020 8b aa 66 ed ec 5e e2 02-e5 6c fd db e1 ef 47 1a |..f..^.. .l....G.| 0030 9d 63 03 ed 6d 3e 28 3b-b9 64 fd 92 71 34 ff ba |.c..m>(; .d..q4..| 0040 7d 3c 8d ee 7b 34 75 e9-d5 b7 c6 83 a9 7d e6 7f |}<..{4u. .....}..| 0050 71 7e 25 11 82 b8 76 b1-c6 ba 86 b4 c3 0a 47 f0 |q~%...v. ......G.| 0060 51 96 c7 e2 5f ca 07 b2-95 53 b9 9e bb 2c e7 cb |Q..._... .S...,..| 0070 be 0a b5 eb b0 f3 41 1d-cd 86 fc a6 53 08 5e 56 |......A. ....S.^V| 0080 29 85 79 14 dc 2b 74 7b-b2 43 2c e8 0e 87 60 e4 |).y..+t{ .C,....| 0090 10 ef f8 14 03 01 00 01-01 16 03 01 00 30 c7 f0 |........ .....0..| 00a0 35 f5 2c 6e 79 8d 85 b9-bd 60 b7 09 8c 7e 29 18 |5.,ny... ....~).| 00b0 4a 56 ea c3 4e 13 bf e3-c5 8d f6 68 31 31 54 ee |JV..N... ...h11T.| 00c0 bf 2f 75 8d e9 9e c0 a9-d0 d2 9e 5b c9 92 |./u..... ...[..|

tls.c:105:in tds_pull_func_login query.c:3796:tds_disconnect() util.c:165:Changed query state from IDLE to DEAD util.c:322:tdserror(0x80b75e0, 0xa04ca80, 20017, 0) dblib.c:7947:dbperror(0xae62780, 20017, 0) dblib.c:8015:dbperror: Calling dblib_err_handler with msgno = 20017; msg->msgtext = "Unexpected EOF from the server (192.168.32.105:1433)" dblib.c:5777:dbgetuserdata(0xae62780) dblib.c:8037:dbperror: dblib_err_handler for msgno = 20017; msg->msgtext = "Unexpected EOF from the server (192.168.32.105:1433)" -- returns 2 (INT_CANCEL) util.c:352:tdserror: client library returned TDS_INT_CANCEL(2) util.c:375:tdserror: returning TDS_INT_CANCEL(2) util.c:375:tdserror: returning TDS_INT_CANCEL(2) tls.c:942:handshake failed login.c:530:login packet rejected util.c:322:tdserror(0x80b75e0, 0xa04ca80, 20002, 0) dblib.c:7947:dbperror(0xae62780, 20002, 0) dblib.c:8015:dbperror: Calling dblib_err_handler with msgno = 20002; msg->msgtext = "Adaptive Server connection failed"

And here's the output of tsql -C:

~$ tsql -C
Compile-time settings (established with the "configure" script)
                            Version: freetds v1.00.15
             freetds.conf directory: /usr/local/etc
     MS db-lib source compatibility: no
        Sybase binary compatibility: no
                      Thread safety: yes
                      iconv library: yes
                        TDS version: auto
                              iODBC: no
                           unixodbc: no
              SSPI "trusted" logins: no
                           Kerberos: no
                            OpenSSL: yes
                             GnuTLS: no
                               MARS: no

Any idea what I should do to fix those Unexpected EOF from the server errors?

Answer 1

Looking at the SQL Profiler, I found out the Rails application was opening way too many connections on the MSSQL server. Upon reaching its max number of open connection, the MSSQL server refused opening any new connection, resulting in the Unexpected EOF from the server error.

To solve the issue, I had to reuse my open connection when sending queries instead of opening a new connection for each query. I guess this is the correct way to use the tiny_tds connector anyway.

Translated to code:

def self.get_pmi_client
  if @@pmi_client.nil? or !@@pmi_client.active?
    db_conf = Rails.configuration.database_configuration["pmi_#{Rails.env}"]
    @@pmi_client = TinyTds::Client.new(username: db_conf['username'], password: db_conf['password'], host: db_conf['host'], port: db_conf['port'], database: db_conf['database'])
    raise MSSQLConnectionError, t('erp.errors.pmi_connection_error') unless @@pmi_client.active?
  end
  return @@pmi_client
end