I need to setup two-node Web cluster for Apache web site. I have Hyper-V infrastructure and only two nodes.
The points are load-balancing and high availability.
I installed and configured two VMs with CentOS 7, Pacemaker cluster, MariaDB 10. I configured Master/Slave ocf::percona:mysql resource in Pacemaker.
Next i need a shared storage for web site content.
I created DRBD disk in dual-primary mode and GFS2 in top of it. I tested it without adding to Pacemaker. All worked fine but, to make it automaticaly promoted, i need to manage these via Pacemaker.
The problem is that Pacemaker need fencing to create DRBD resource but there is no stonith agents for Hyper-V.
I read that in previous version for CentOS 6 it was possible to create SSH stonith agent. I tried to do this, but pcs not works with it.
Is it possible to use Pacemaker in top of Hyper-V for now? Or may be exist another way to use DRBD in dual primary?
I have tried many solutions but no one did not work well.
I have made two-way file replication using lsyncd instead.
Related
I have several Windows servers available and would like to setup a Kubernetes cluster on them.
Is there some tool or a step by step instruction how to do so?
What I tried so far is to install DockerDesktop and enable its Kubernetes feature.
That gives me a single node Cluster. However, adding additional nodes to that Docker-Kubernetes Cluster (from different Windows hosts) does not seem to be possible:
Docker desktop kubernetes add node
Should I first create a Docker Swarm and could then run Kubernetes on that Swarm? Or are there other strategies?
I guess that I need to open some ports in the Windows Firewall Settings of the hosts? And map those ports to some Docker containers in which Kubernetes is will be installed? What ports?
Is there some program that I could install on each Windows host and that would help me with setting up a network with multiple hosts and connecting the Kubernetes nodes running inside Docker containers? Like a "kubeadm for Windows"?
Would be great if you could give me some hint on the right direction.
Edit:
Related info about installing kubeadm inside Docker container:
https://github.com/kubernetes/kubernetes/issues/35712
https://github.com/kubernetes/kubeadm/issues/17
Related question about Minikube:
Adding nodes to a Windows Minikube Kubernetes Installation - How?
Info on kind (kubernetes in docker) multi-node cluster:
https://dotnetninja.net/2021/03/running-a-multi-node-kubernetes-cluster-on-windows-with-kind/
(Creates multi-node kubernetes cluster on single windows host)
Also see:
https://github.com/kubernetes-sigs/kind/issues/2652
https://hub.docker.com/r/kindest/node
You can always refer to the official kubernetes documentation which is the right source for the information.
This is the correct way to manage this question.
Based on Adding Windows nodes, you need to have two prerequisites:
Obtain a Windows Server 2019 license (or higher) in order to configure the Windows node that hosts Windows containers. If you are
using VXLAN/Overlay networking you must have also have KB4489899
installed.
A Linux-based Kubernetes kubeadm cluster in which you have access to the control plane (see Creating a single control-plane cluster with kubeadm).
Second point is especially important since all control plane components are supposed to be run on linux systems (I guess you can run a Linux VM on one of the servers to host a control plane components on it, but networking will be much more complicated).
And once you have a proper running control plane, there's a kubeadm for windows to proper join Windows nodes to the kubernetes cluster. As well as a documentation on how to upgrade windows nodes.
For firewall and which ports should be open check ports and protocols.
For worker node (which will be windows nodes):
Protocol Direction Port Range Purpose Used By
TCP Inbound 10250 Kubelet API Self, Control plane
TCP Inbound 30000-32767 NodePort Services All
Another option can be running windows nodes in cloud managed kuberneres, for example GKE with windows node pool (yes, I understand that it's not your use-case, but for further reference).
How can I ensure that a software installed on a cluster is always available.
I understand that I can install the software in a shared drive and if one node goes down, the other node will take care.
But what about the windows system dependencies like the registries, windows dir,
services etc?
Will these things as well get shared across the node?
Basically if I have a software written in C++/C# which has lots of windows O/S resource dependencies(registry, service etc), how can I ensure that it is highly available through a cluster? Is it possible?
Thanks & Regards
Sunil
For this scenario, let's assume:
There are two servers in the cluster. ServerA and ServerB.
Each server has their own local drive. (C:)
Each server has access to a shared/common drive called F:\ (probably on an external SAN)
When installing or updating your application on the Failover Cluster, first ensure ServerA is the cluster owner/active node. Install your application as usual, insuring the install path is a folder on the shared drive F:.
Once the install is complete to ServerA, go into Failover Cluster manager and make ServerB the cluster owner/active node. Repeat the install on ServerB, using the same folder on F:\ for the installation path.
If your application is a Windows service (or set of services), make sure after the application installation that you configure the service as a Generic Service Resource in the Failover Cluster. Then, always stop/start the service via Failover Cluster Manager
Newbie w/ etcd/zookeeper type services ...
I'm not quite sure how to handle cluster installation for etcd. Should the service be installed on each client or a group of independent servers? I ask because if I'm on a client, how would I query the cluster? Every tutorial I've read shows a curl command running against localhost.
For etcd cluster installation, you can install the service on independent servers and form a cluster. The cluster information can be queried by logging onto one of the machines and running curl or remotely by specifying the IP address of one of the cluster member node.
For more information on how to set it up, follow this article
I spun up a Mesosphere cluster on Digital Ocean (development) and it's not allowing me to allow external (non vpn) connections to containers or apps. How can this be solved ?
To ensure that the world doesn't have access to your cluster normally, there have been iptables rules installed. By default, these allow full access inside the cluster and nothing externally.
If you're interested in running real applications, I'd recommend the following:
Put HAProxy on a single node.
Setup the haproxy-marathon-bridge script.
On the same box that you installed HAProxy on, setup iptables to allow access to the port that HAProxy is listening on.
By doing this, you'll have a single place to refer to when giving access to applications running on your Mesos cluster. No matter where the app or container is scheduled (with marathon), you'll always be able to reach it via. haproxy.
I am new to Spark and I am trying to run it on EC2. I follow the tutorial on spark webpage by using spark-ec2 to launch a Spark cluster. Then, I try to use spark-submit to submit the application to the cluster. The command looks like this:
./bin/spark-submit --class org.apache.spark.examples.SparkPi --master spark://ec2-54-88-9-74.compute-1.amazonaws.com:7077 --executor-memory 2G --total-executor-cores 1 ./examples/target/scala-2.10/spark-examples_2.10-1.0.0.jar 100
However, I got the following error:
ERROR SparkDeploySchedulerBackend: Application has been killed. Reason: All masters are unresponsive! Giving up.
Please let me know how to fix it. Thanks.
You're seeing this issue because the master node of your spark-standalone cluster cant open a TCP connection back to the drive (on your machine). The default mode of spark-submit is client which runs the driver on the machine that submitted it.
A new cluster mode was added to spark-deploy that submits the job to the master where it is then run on a client, removing the need for a direct connection. Unfortunately this mode is not supported in standalone mode.
You can vote for the JIRA issue here: https://issues.apache.org/jira/browse/SPARK-2260
Tunneling your connection via SSH is possible but latency would be a big issue since the driver would be running locally on your machine.
I'm curious if you still having this issue ... But in case anyone is asking here is a brief answer. As clarified by jhappoldt, the master node of your spark-standalone cluster cant open a TCP connection back to the drive (on your local machine). Two workarounds are possible, tested and succeeded.
(1) From EC2 Management Console, create a new security group and add rules to enable TCP back and forth from your PC (public IP). (what I did was adding TCP rules inbound and outbound) ... Then add this security group to your master instance. (right click --> Networking --> Change security groups). Note: add it and don't remove the already established security groups.
This solution work well, but in your specific scenario, deploying your application from local machine to EC2 cluster, you will face further problems (resource related) so the next option is the best one
(2) Having your .jar file (or .egg) copy it to the master node using scp. You can check this link http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/AccessingInstancesLinux.html for information about how to do that; and deploy your application from the master node. Note: spark is already pre-insalled so you will do nothing but write the same exact command you write on your local machine from ~/spark/bin. This shall work perfect.
Are you executing the command on your local machine, or on the created EC2 node? If you're doing it locally, make sure port 7077 is open in the security settings, as its closed to the outside by default.