The beef production calendar is a management tool for producers to help them in scheduling practices pertaining to the cow herd over a twelve-month period. The calendar is based on a late March calving beef herd. The calendar addresses three categories:
Scheduling a Cow
This core scheduling logic is built into Rancher, but Rancher also supports additional scheduling abilities that are located in our external scheduler, which is part of our infrastructure services. Additional scheduling abilities include:
By selecting this option, you have the flexibility to choose your scheduling rules. Any host that follows all the rules is a host that could have the container started on. You can add rules by clicking on the + button.
For load balancers, only option 2 is available due to port conflicts. You are only given the choice to add scheduling rules. Click on the Scheduling tab. You can add as many scheduling rules as you want by clicking on the Add Scheduling Rule button.
When we write our scheduling rules, we have conditions for each rule, which dictates how Rancher uses the rule. An affinity condition is when we are trying to find a field that matches our value. An anti-affinity condition is when we are trying to find a field that does not match our value.
Currently, we only support global services with host labels fields that are using the hard condition. This means that only labels that are related to host_labels will be adhered to when scheduling and it must or must not equal the values. Any other label types will be ignored.
Note: Rancher does not support the concept of scheduling containers on a host that has >= a specific version. You can create specific whitelists and blacklists by using the host scheduling rules to determine if a specific version of Docker Engine is required for your services.
An important and complex aspect of container orchestration is scheduling the application containers. Appropriate placement of containers onto the shared infrastructure resources that are available is the key to achieve maximum performance at optimum compute resource usage.
Here is how to specify a host label affinity rule in the Rancher 2.0 UI. A hard affinity rule means that the host chosen must satisfy all the scheduling rules. If no such host can be found, the workload will fail to deploy.
If you are using these options in your Rancher 1.6 setups, it is possible to replicate them in Rancher 2.0 using native Kubernetes scheduling options. As of v2.0.8, there is no UI support for these options while deploying workloads, but you can always use them by importing the Kubernetes YAML specs on a Rancher cluster.
One of the most-used scheduling features in 1.6 was anti-affinity to the service itself using labels on containers. To replicate this behavior in Rancher 2.0, we can use pod anti-affinity constructs in Kubernetes YAML specs. For example, consider a Nginx web workload. To ensure that pods in this workload do not land on the same host, you can use the podAntiAffinity construct as shown below. By specifying podAntiAffinity using labels, we ensure that each Nginx replica does not co-locate on a single node.
In this article, we reviewed how the various scheduling functionalities of Rancher 1.6 can be migrated to Rancher 2.0. Most of the scheduling techniques have equivalent options available in Rancher 2.0, or they can be achieved via native Kubernetes constructs.
With all this change, why should we care about a topic like container orchestration and scheduling? We should care for the same reason that the successful farmers from the post-agricultural revolution cared about where they let their cattle graze.
The aim of this article is to provide input on choosing a container platform and, based on your requirements, the associated orchestration and scheduling mechanisms. However, this is based primarily on two example client case studies. There are numerous other product combinations and resulting stacks, everything from Docker Swarm mixed with Mesos to focuses on PaaS-based cloud orchestration builds with IBM.
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