How to setup IP connectivity for clients to access Vertica Cluster nodes

Connect via adminTools.

>> If only 1 node's IP can be used what happens if that node is down ?
adminTools will carry about it, adminTools will try sort of round robin algorithm for connectivity, i.e. if node is down adminTools will connect you to other node, which is up.

>> Is it mandatory to deploy Load Balancer VIP configurations ?
No.
FYI: actually Load Balancer is single point failure, so you need do carry about it too.


>> does that mean Load Balancers are not required in Vertica 6.x
No, but btw docs for version 6 has documentation about Load Balancing : https://my.vertica.com/docs/6.1.x/HTML/index.htm#15242.htm
By your logic you need it (if it in documentation).

Thanks  Daniel

Thanks Daniel for the replies!

Often, people need to connect via vsql or JDBC/ODBC/etc, rather than through adminTools.  Vertica 6.x doesn't automatically round-robin those tools.

That said, we know that people would like load-balancing technology.  Please do read the documentation for new versions of Vertica as they come out, including Vertica 7.0 (which we are in the process of publishing as we speak).

Vertica allows you to connect to the IP address of any node.  You mention only being able to connect to one node?  Is this because of a firewall that you have configured in front of the Vertica cluster?  If you have some sort of firewall that restricts access to one IP address, that address will typically be a single point of failure -- it's a single address; if it stops working for any reason (the Vertica node, the firewall, etc), you lose access to your cluster.

Some load balancing solutions have instant-failover functionality that avoids having a single IP become a single point of failure.  Our bundled load-balancing solution doesn't have that feature out of the box; proper instant failover is complex, and making a few IP addresses public instead of  one is typically something that people are comfortable with doing in the name of high availability.  However, if you get in contact with any of our sales reps, I'm confident that they'd be glad to sell you other load-balancing products that can do this :-)

Adam

Thanks Adam, 

   There are no firewalls, however i am not sure how to configure/setup the client machines to use multiple IP addresses.

  For example can i provide multiple IP addresses for the Servername parameter in the ODBC/JDBC client configurations ? If not, how should one configure the client libraries when using ODBC/JDBC ?


Thanks,
Guhen

>> If not, how should one configure the client libraries when using ODBC/JDBC ?
Programmatically only. Provide all IPs of cluster nodes to client app.
If you have access to one node (even if it down), so you can read adminTools or spread configuration file to get other IPs of cluster.

daniel@synapse ~ $ grep -m1 hosts /opt/vertica/config/admintools.conf 

hosts = 192.168.16.100, 192.168.16.101, 192.168.16.102, 192.168.16.103

Actually, we recommend avoiding using admintools.conf for this purpose, as it may change or go away in future releases.  Also it's typically not available unless you're already logged into one of the servers.  (At which point, if that server goes down, you're toast anyway :-) )

You can get the list of IP's by running the query:

SELECT * FROM nodes;

In current versions of Vertica, Daniel is correct that you'd have to implement this sort of load-balancing yourself.  The simplest/naive way is to just expose the server as a config option in your application, and manually switch IP's if a node fails.  A less-painful solution is to query the above table up front, and store the list of server IP's; then just have a retry loop that tries to connect to each IP until it finds one that works.

Again, please do read Vertica 7's documentation on this functionality as soon as it's available, as it works somewhat differently than in previous versions.

Hmm.. right, I read one more time a question

If only 1 node's IP can be used what happens if that node is down ?

my fail.

1) As solution you can configure a proxy/mediator on the "known" node, that will redirect a connection to other node in case if "known" is down (not physically of cause, just server application).

2) Also proxy, but another strategy: same IP but different ports - port per node and with ssh tunneling or port forwarding to redirect a connection.  

- So other nodes IP are not compromised.
- only one IP used for connection
but its still single point failure

Thanks Adam and Daniel You answers cleared my confusion.

Hi, may be this is already resolved issue. In Oracle, we use DNS resolving 3 ip addresses. With round robin setup - DNS each time gives next one in a circle. If you include all the IP addresses in Vertica cluster and publish the name say "myvcluster" then it should round robin. It is still victim of tcp/ip timeouts if one the node is unresponsive - but for that you need true vip which floats for each node managed by products such as F5 (unless there is public domain software for linux)

Thank you

I would suggest looking into DNS SRV technology for client side failover solution. I guess it could be a nice feature to avoid single point of failure such as a host name, node name, ip address of something like that. 

Tonight we've tried to construct DNS CNAME round robin keeping off ip bound. RFC 2181 does not recommend CNAME round robin, so we're only half way for bullet-proof architecture. If HP Vertica could provide DNS SRV handling for clients it would make us last half way complete.

Hi!

Thanks for info. But after some reading I understand that round-robin DNS provides rudimentary load balancing, but it's not failure-aware. Can you share how do you resolves it?


Thanks.

I meant it be nice if vertica supported DNS SRV technology. For now it does not. And if it is - DNS SRV could provide a simple failure aware strategy. When a node does not have a port open then client should try next in dns.