I am currently evaluating CrateDB and came up this question. I know that CrateDB proudly claims itself to be a no-config database. So, is there automatic load balancing? Or is it possible to add a load balancer before the dabase?
After browsing the web for a bit I found this howto indicating there is no automatic load balancing in CrateDB. Is that correct?
yes, load balancing happens automatically:
the client libraries can be configured with multiple nodes and then do round-robin scheduling
if you pass a query to a node - the execution of the query will happen distributed in the cluster anyhow.
Related
We have two apache servers for load balancing. Whenever I upload a file on one server. Using load balancing concepts, will it get copied into other server.
Do these two server maintain replica of each other?
If not, how to do that? How to maintain the replica of one another servers?
If Yes, what configuration is required.
Thanks for help.
Load balancing balances the requests that are sent to a load balancer to the server that actually answers them.
Handling files that are uploaded to one server is on the application level - it must be handled by your application - e.g. through storing it in a location that all nodes can access (filesystem, database).
There's nothing that tomcat or an appserver can do for you - because they don't know what needs to be replicated and what doesn't. They don't know if something that you uploaded will be processed and can be forgotten, or if it will be stored for later download.
The load balancing process indicated in this link :
https://httpd.apache.org/docs/2.4/mod/mod_proxy_balancer.html
Is requiring two servers to work.
How can I adapt the described process to make it work with only one server ?
The entire point of load balancing is to equally split traffic over a number of servers. Implementing load balancing with one server would be completely missing the point and entirely useless.
We have WCF service X: deployed on server A and Server B, host address:
http://127.0.0.1:8777/ServiceX/
And we load balance the two servers. We accesss the service via http://myappserver/ServiceX
We need to use per-session mode, and we set [reliable sessions] as true:
We don't find any issue till now based on testing. But the below linked MSDN article says that Do not use reliable sessions for Load Balancing with the WSHttp Binding? Please can someone give more details? Thanks a lot.
WCF Load Balancing http://msdn.microsoft.com/en-us/library/ms730128.aspx
Reliable Messaging means all your messages from your established client reach the same endpoint behind any intermediaries like routers and load balancers.
Load balancing means your calls will be distributed across all nodes as the load balancer sees fit.
Those two goals are mutually exclusive. You can have one or the other, not both.
I have not had time to try this myself yet, but I found this old blog entry (https://blogs.msdn.microsoft.com/drnick/2007/07/13/sticky-sessions/):
This division according to groups would allow a feature like reliable messaging to work because the same server would be used to process all of the messages in the reliable session. The feature that this division method represents is typically called “sticky sessions” or some other phrase for affinitization in the load balancer.
Given that you mention that your firewall supports sticky sessions, I suspect/hope you will be fine.
HI, just now i download the Elastic Load Balance 2.1.0 from WSO2 ,It
is running on terminal side of Linux ubuntu, but it is not showing the
Management console url. If it is not showing url where can i get UI
of Elastic Load Balance.
i have a multiple esb server with same configuration.if my a1 server
go down that time data load will shift to my a2 server .Is this use of
Elasticloadbalance will you explain me about this what is the exactly
use of this .
No, there is no UI component for ELB. Everything has to be done through configuring physical files.
Elastic LoadBalancer 2.1.0 is based on Hazlecast dependent clustering. This has two parts, one is load balancing and the other is elasticity. Load Balancing is simply distributing workload among a number of endpoints configured in a static or dynamic manner. Elasticity is simply scaling, ie monitoring load on worker nodes and starts or terminates nodes based on need on an IaaS environment.
Not only manages when a node goes down but also depending on load it can spawn new nodes to handle and if the load is low it can kill unwanted instances in an IaaS environment.
Currently I have the following setup:
Hardware load balancer directing traffic to two physical servers each with 2 instances of weblogic running.
Works ok. I'd like to be able to shutdown one of the servers without dropping active sessions. Right now if I shutdown one of the physical servers any traffic that was going there gets bounced back to a login screen.
I'm looking for the simplest way of accomplishing this with the smallest performance hit.
Things I've considered so far:
1. See if I can somehow store the session information on the Load Balancer and through some Load Balancer magic have it notice a server is dead and try another one with the same session information (not sure this is possible)
2. Configure weblogic clustering. Not sure what the performance hit would be. Im guessing this is what I'll end up with, but still fishing for alternatives.
3. ?
What I currently have is an overly designed DR solution (which was the requirement), but I'd like to move it more in the direction of HA (for the flexibility)
edit Also is it worthwhile to create 2 clusters and replicate the sessions between them (I was thinking one cluster per site, sites are close enough). This would cover the event of one cluster failing.
You could try setting up a JDBC Session Storage pointing (of course) both instances to the same datasource without setting up a cluster, but I think the right approach would be setting up a Weblogic Cluster.
A nice thing about clustering Weblogic Servers is that - (from the link above, emphasis mine):
Sessions can be shared across clustered WebLogic Servers. Note that session persistence is no longer a requirement in a WebLogic Cluster. Instead, you can use in-memory replication of state. For more information, see Using WebLogic Server Clusters.
We've got a write up of this on our blog http://blog.c2b2.co.uk/2012/10/basic-clustering-with-weblogic-12c-and.html which provides step by step instructions on setting up web session failover in a cluster.
Clusters are not heavyweight assuming you don't store huge amounts of data in the cluster as it will be replicated.