What exactly happens when Azure worker role instance count is set to more than 1? Does this mean multiple VMs? I am using worker role do deploy a socket server. If I set instance count to 2 then will it mean that there will be 2 sockets listening for the requests?
Yes, you are right, basically one role instance is a separate VM.
2 instances also means two open sockets. But access to those sockets would be available via one single Endpoint (declared in role config) and would be automatically load balanced between 2 instances.
Based on what I heard in the FailSafe series on Channel9 by Mark Simms - web or worker role instance is another VM loaded in the virtualizing host.
Related
So, I'm using a hypnotoad server for my application and is trying to maintain state for connections. Turns out for every connection a different worker is spawned/selected. Can I somehow make this selection explicit? Also is there a way to know which worker was used for my last request and use it again for corresponding requests?
You can ran multiple masters (every with one worker or like morbo - single processes).
And add load balancer before 'em which will be responsible to selection of concrete process per connection.
Typically I used nginx with upstream module sticky setting.
I am implementing a service broker for my SaaS application on Cloud Foundry.
On create-service of my SaaS application, I create instance of another service (Say service-A) also ie. a new service instance of another service (service-A) is also created for every tenant which on-boards my application.
The details of the newly created service instance (service-A) is passed to my service-broker via environment variable.
To be able to process this newly injected environment variable, the service-broker need to be restaged/restarted.
This means a down-time for the service-broker for every new on-boarding customer.
I have following questions:
1) How these kind on use-cases are handled in Cloud Foundry?
2) Why Cloud Foundry chose to use environment variables to pass the info required to use a service? It seems limiting, as it requires application restart.
As a first guess, your service could be some kind of API provided to a customer. This API must store the data it is sent in some database (e.g. MongoDb or Mysql). So MongoDb or Mysql would be what you call Service-A.
Since you want the performance of the API endpoints for your customers to be independent of each other, you are provisioning dedicated databases for each of your customers, that is for each of the service instances of your service.
You are right in that you would need to restage your service broker if you were to get the credentials to these databases from the environment of your service broker. Or at least you would have to re-read the VCAP_SERVICES environment variable. Yet there is another solution:
Use the CC-API to create the services, and bind them to whatever app you like. Then use again the CC-API to query the bindings of this app. This will include the credentials. Here is the link to the API docs on this endpoint:
https://apidocs.cloudfoundry.org/247/apps/list_all_service_bindings_for_the_app.html
It sounds like you are not using services in the 'correct' manner. It's very hard to tell without more detail of your use case. For instance, why does your broker need to have this additional service attached?
To answer your questions:
1) Not like this. You're using service bindings to represent data, rather than using them as backing services. Many service brokers (I've written quite a few) need to dynamically provision things like Cassandra clusters, but they keep some state about which Cassandra clusters belong to which CF service in a data store of their own. The broker does not bind to each thing it is responsible for creating.
2) Because 12 Factor applications should treat backing services as attached, static resources. It is not normal to say add a new MySQL database to a running application.
I have an environment (Graphite) that looks like the following:
N worker servers
1 relay server that forwards work to these worker servers
1 web server that can query the relay server.
I would like to use Chef to setup and deploy this environment in EC2 without having to create each worker server individually, get their IPs and set them as attributes in the relay cookbook, create that relay, get the IP, set it as an attribute in the web server cookbook, etc.
Is there a way using chef in which I can make sure that the environment is properly deployed, configured and running without having to set the IPs manually? Particularly, I would like to be able to add a worker server and have the relay update its worker list, or swap the relay server for another one and have the web server update its reference accordingly.
Perhaps this is not what Chef is intended for and is more for per-server configuration and deployment, if that is the case, what would be a technology that facilitates this?
Things you will need are:
knife-ec2 - This is used to start/stop Amazon EC2 instances.
chef-server - To be able to use search in your recipes. It should be also accessible from your EC2 instances.
search - with this you will be able to find among the nodes provisioned by chef, exactly the one you need using different queries.
I have lately written an article How to Run Dynamic Cloud Tests with 800 Tomcats, Amazon EC2, Jenkins and LiveRebel. It involves loadbalancer installation and loadbalancer must know all IP adresses of the servers it balances. You can check out the recipe of balanced node, how it looks for loadbalancer:
search(:node, "roles:lr-loadbalancer").first
And check out the loadbalancer recipe, how it looks for all the balanced nodes and updates the apache config file:
lr_nodes = search(:node, "role:lr-node")
template ::File.join( node[:apache2][:home], 'conf.d', 'httpd-proxy-balancer.conf' ) do
mode 0644
variables(:lr_nodes => lr_nodes)
notifies :restart, 'service[apache2]'
end
Perhaps you are looking for this?
http://www.infochimps.com/platform/ironfan
I'm interested in using Celery for an app I'm working on. It all seems pretty straight forward, but I'm a little confused about what I need to do if I have multiple load balanced application servers. All of the documentation assumes that the broker will be on the same server as the application. Currently, all of my application servers sit behind an Amazon ELB and tasks need to be able to come from any one of them.
This is what I assume I need to do:
Run a broker server on a separate instance
Configure each application instance to connect to that broker server
Each application instance will also be be a celery working (running
celeryd)?
My only beef with that is: What happens if my broker instance dies? Can I run 2 broker instances some how so I'm safe if one goes under?
Any tips or information on what to do in a setup like mine would be greatly appreciated. I'm sure I'm missing something or not understanding something.
For future reference, for those who do prefer to stick with RabbitMQ...
You can create a RabbitMQ cluster from 2 or more instances. Add those instances to your ELB and point your celeryd workers at the ELB. Just make sure you connect the right ports and you should be all set. Don't forget to allow your RabbitMQ machines to talk among themselves to run the cluster. This works very well for me in production.
One exception here: if you need to schedule tasks, you need a celerybeat process. For some reason, I wasn't able to connect the celerybeat to the ELB and had to connect it to one of the instances directly. I opened an issue about it and it is supposed to be resolved (didn't test it yet). Keep in mind that celerybeat by itself can only exist once, so that's already a single point of failure.
You are correct in all points.
How to make reliable broker: make clustered rabbitmq installation, as described here:
http://www.rabbitmq.com/clustering.html
Celery beat also doesn't have to be a single point of failure if you run it on every worker node with:
https://github.com/ybrs/single-beat
In a installation of WebSphere Application Server with Network Deployment, a node is:
a physical machine
an instance of operative system
a logical set of WAS instances that is independent of physical machine or OS instance
Basically,
A server is a runtime environment, a process of execution.
A node is a grouping of servers that share common configuration. It is a physical machine.
A cell is a grouping of nodes into a sigle administrative domain. For websphere, it mean that if you group several servers within a cell, then you can administer them with one Websphere admin console
Hope this helps!
#ggasp Here is what I got off IBM's Information Center
A node is a logical grouping of managed servers.
A node usually corresponds to a logical or physical computer system with a distinct IP host address. Nodes cannot span multiple computers.
http://publib.boulder.ibm.com/infocenter/wasinfo/v6r1/index.jsp?topic=/com.ibm.websphere.nd.multiplatform.doc/info/ae/ae/cagt_node.html
Keep in mind that usually <> always.
Since WAS 6.0 and up you usually want to setup more than one node in each physical computer, given the usual power of the server you use the node to separate logical business entities.
Like for example have 6 nodes, 3 in each of 2 machines and have 1 pair of nodes you could define 3 different clusters one for each stage (dev, qa, staging) and making each cluster be invisible to the other.
A Cell is a virtual unit that is built of a Deployment Manager and one or more Nodes. A Node is another virtual unit that is built of a Node Agent and one or more Server instances.
Here you can find more details including a diagram.