Connection won't raise error with bad host - ruby

Question

The application I'm working on allows users to add additional connections to other databases through a UI. I'm simply trying to create a validation that ensures that a connection can be made.
I created a separate class to test the DB connections:
class StoredProcConnection < ActiveRecord::Base
def self.abstract_class?
true # So it gets its own connection
end
end
I then create the connection:
def connect
adapter = sql_server? ? 'mssql' : 'mysql2'
default_port = sql_server? ? '1443' : '3306'
#connection_pool = StoredProcConnection.establish_connection(
adapter: adapter,
username: username,
password: password,
host: host,
database: database_name,
port: port || default_port,
timeout: 300)
end
def connection_pool
connect unless #connection_pool
#connection_pool
end
Then I validate it with this method:
def connection_test
if connection_pool.connection
#remove the connection from the StoredProcConnection pool
connection_pool.remove(connection_pool.connection)
return true
else
return false
end
rescue Exception => error
logger.info "unable to create connection with connection.id = #{id} - #{error}"
return false
end
Unfortunately, when it gets to this line with a bad host address like 127.0.0.abcdefg or 666.666.666.666
if connection_pool.connect
The app gets stuck, no errors raised or anything. It just freezes and I have to shut down the server manually.
I have a workaround but it feels quite sloppy. I am just inserting my own timeout in there, but I feel like Active Record should be throwing some kind of error.
def connection_test
Timeout::timeout(3) {
if connection_pool.connection
#remove the connection from the StoredProcConnection pool
connection_pool.remove(connection_pool.connection)
return true
else
return false
end
}
rescue Exception => error
logger.info "unable to create connection with connection.id = #{id} - #{error}"
return false
end
Does anyone see anything that might be causing the freeze? It seems pretty straight forward to me. I'm not sure why the connection pool is even created in the first place with a bad host passed in.

Answer 1

It just freezes...
Odds are good it's not frozen, it's just waiting to see if that connection can be made. TCP/IP has a long timeout value, which fools people into thinking things are frozen, when actually it's being patient.
Few people really understand how the internet works, and how it's really a house built of straw that we try to keep running no matter what. Long IP timeouts are one of the ways that we try to make it self-healing. Software doesn't care about how long something takes, only people care.
Since it appears you're concerned about malformed IP addresses, why aren't you pre-testing them to make sure they're at least in a valid format?
Use Ruby's built-in IPAddr class and try to parse them:
require 'ipaddr'
%w[
127.0.0.abcdefg
666.666.666.666
127.0.0.1
192.168.0.1
255.255.255.255
].each do |ip|
begin
IPAddr.new ip
puts "Good: #{ ip }"
rescue IPAddr::InvalidAddressError => e
puts "#{ e }: #{ ip }"
end
end
# >> invalid address: 127.0.0.abcdefg
# >> invalid address: 666.666.666.666
# >> Good: 127.0.0.1
# >> Good: 192.168.0.1
# >> Good: 255.255.255.255
For "fun reading" there's "TCP Timeout and Retransmission" and "TCP Socket no connection timeout".