delay DNS lookup for connect option
This option is useful for dynamic DNS, or when DNS is not available during stunnel startup (road warrior VPN, dial-up configurations).
Delayed resolver mode is automatically engaged when stunnel fails to resolve on startup any of the connect targets for a service.
Delayed resolver inflicts failover = prio.
default: no
This is odd, but we're seeing failures again with this config. We're seeing that with delay=yes, and 6 total connection targets (5 servers, 1 ELB), stunnel picks up the first connection (the ELB) and never uses any of the other targets. Ever. If we use tcpkill to block access to the ELB, we end up completely screwed.
Anyone else seeing this as a problem still?
On Jan 7, 2013, at 12:39 PM, Matt Wise <matt@nextdoor.com> wrote:
Ah. Thats it! I also see a fix in 4.54, am I right?
- "delay = yes" fixed to work even if specified *after* "connect" option.
- Multiple "connect" targets fixed to also work with delayed resolver.
--Matt
On Jan 7, 2013, at 11:39 AM, Michal Trojnara <Michal.Trojnara@mirt.net> wrote:
Hi Matt,
Load balancing is incompatible with delayed resolver. Remove "delay =
yes" from your configuration file.
Mike
On 2013-01-07 18:38, Matt Wise wrote:
I've got dozens of clients connecting with Stunnel to a group of 5 servers. Each system has a config that looks like this:
cert = /etc/stunnel/zookeeper.pem
key = /etc/stunnel/zookeeper.key
CAfile = /etc/stunnel/zookeeper_ca.pem
verify = 2
delay = yes
sslVersion = TLSv1
client = yes
setuid = stunnel4
setgid = stunnel4
pid = /var/lib/stunnel4/zookeeper.stunnel4.pid
socket = l:TCP_NODELAY=1
socket = r:TCP_NODELAY=1
TIMEOUTconnect = 2
session = 86400
debug = 5
[zookeeper]
accept = 127.0.0.1:2182
failover = rr
connect = prod-zookeeper:2182
connect = prod-zookeeper-1:2182
connect = prod-zookeeper-2:2182
connect = prod-zookeeper-3:2182
connect = prod-zookeeper-4:2182
connect = prod-zookeeper-5:2182
Essentially the first host is a load balancer, and the next 5 are the actual zookeeper hosts so that we can bypass the ELB if its giving us fits. Now what we're seeing is that almost every connection ends up on prod-zookeeper-5. Over and over and over again, our hosts pick the same system each time. We're running Stunnel 4.52:
Clients allowed=8000
stunnel 4.52 on i486-pc-linux-gnu platform
Compiled/running with OpenSSL 0.9.8k 25 Mar 2009
Threading:PTHREAD SSL:ENGINE Auth:LIBWRAP Sockets:POLL,IPv6
Any ideas what might be wrong here? Obviously we want the connections to be *roughly* random across the list of hosts... and if one of the hosts goes down, and the connection fails, we want the stunnel service to try again, and randomly pick a new host. It doesn't really seem to be doing that though.
--Matt
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