This wiki describes the specifications for designing the Binary Provisioning Agent required for the Integrated Cloud Native Akraino project.
Overview of BPA
The BPA is part of the infra local controller which runs as a bootstrap k8s cluster in the ICN project. As described in Integrated Cloud Native Akraino project, the purpose of the BPA is to install packages that cannot be installed using kubectl. It will be called once the operating system (Linux) has been installed in the compute nodes by the baremetal operator. The Binary Provisioning Agent will carry out the following functions;
- Get site specific information containing information about compute nodes and their resource capabilities.
- Assign roles to compute hosts and create the hosts.ini file required to install kubernetes on compute nodes in order to create a cluster using kubespray
- Instantiate the binary package installation and get the status of the installation
- Get application-k8s kubeconfig file
- BPA is also expected to store any private key and secret information in CSM
- Install the packages on newly added compute nodes
- Update package versions in compute nodes that require the update
- Store private keys
For more information on the BPA functions, check out the ICN Akraino project link above
We do not intend to make any changes to the existing kubernetes API in order to implement the specifications described in this document. We will simply be extending the Kubernetes API using Custom Resource Definition as described here and then creating a custom controller that will handle the requirements of our provisioning Agent custom resource.
Overview of Proposed Workflow for provisioning CRD
Prerequisites: This workflow assumes that the baremetal CR and baremetal operator have been created and has successfully installed the compute nodes with Linux OS. It also assumes that the BPA controller is running.
Fig 1: Illustration of the proposed workflow
- Create BPA CRD (Created only once and just creates the BPA resource kind)
Create the BPA Custom Resource
The BPA Operator continues to watch the k8s API server and once it sees that a new BPA CR object has been created, it queries the k8s API server for the Baremetal hosts lists. The baremetal hosts lists contains information about the compute nodes provisioned including the IP address, CPU, memory..etc of each host.
The BPA operator looks into the baremetal hosts list and knows which hosts should be master and which should be workers. As the master and worker fields have various parameters, it can do this in various ways;
- If the MAC address is provided in the BPA CR object, it compares that value with the value in the hosts list and assigns the roles. For example if a mac address of 00:c5:16:05:61:b2 is specified for master in the BPA CR spec, it checks the baremetal list for a host that has that MAC address and gives it the role of master.
- If there is no MAC address specified but just resources, it checks the baremetal list for hosts that meet the resource requirements
- If both MAC address and resource requirements are provided, it finds the host with the specified MAC address and confirms that the host meets the resource requirement provided in the BPA CR and then assigns the role.
- Using the MAC address of the host, the BPA operator looks in the DHCP file of the DHCP server running on the same host it is running and determines the IP address that corresponds to that MAC address
- The BPA operator reads a file containing the default username and password for the various hosts, copies its public key to those hosts in order to use kubespray later.
The BPA operator then creates the hosts.ini file using the assigned roles and their corresponding IP addresses.
The BPA operator then installs kubernetes using kubespray on the compute nodes thus creating an active kubernetes cluster. During installation, it would continue to check the status of the installation
On successful completion of the k8s cluster installation, the BPA operator would save the application-k8s kubeconfig file in order to access the k8s cluster and make changes such as software updates or add a worker node for future purposes.
The BPA CRD tells the Kubernetes API how to expose the provisioning custom resource object. The CRD yaml file is applied using
“kubectl create -f bpa_v1alpha1_provisioning_crd.yaml” See below for the CRD definition.
BPA CRD Yaml File (*_crd.yaml)
Provisioning Agent Object Definition( *_types,go)
The provisioning_types.go file is the API for the provisioning agent custom resource.
The variables in the ProvisioningSpec struct are used to create the data structures in the yaml spec for the custom resource. Three variables are added to the ProvisioningSpec struct;
- Masters: This variable will contain an array of Master objects. The master struct as defined in the *-types.go file above contains CPU and memory information, this information would be used by the BPA operator to determine which compute nodes to assign the role of Master to when it gets the baremetal list from the API server.
- Workers: This variable will contain an array of Worker objects. Similar to the case of the Masters variables, the Worker struct will contain resource requirements for the Worker nodes and the BPA operator will use this information to determine which hosts to assign the role of worker.
- Replicas: An integer that defines the number of pods that should run when the CR is deployed.
Sample Provisioning CR YAML files
The YAML file above can be used to create a provisioning custom resource which is an instance of the provisioning CRD describes above. The spec.master field corresponds to the Masters variable in the ProvisioningSpec struct of the *-types.go file, while the spec.worker field corresponds to the Workers variable in the ProvisioningSpec struct of the *-types.go file and the spec.replica field corresponds to the Replicas variable in the same struct.
Based on the values above, when the BPA operator gets the baremetal hosts object (Step 5in figure 1), it would assign hosts with 10 CPUs and 4Gi memory the role of master and it would assign hosts with 20CPUs and 8Gi memory the role of worker.
Sample Baremetal Lists from Query
In addition, we would also have two other CRDs that the BPA would use to perform its functions;
- Software CRD
- Cluster CRD
The software CRD will install the required software, drivers and perform software updates
Draft Software CRD
Sample Software CR YAML files
The cluster CRD will have the Cluster name and contain the provisioning CR and/or the software CR for the specified cluster
Draft Cluster CRD
Sample Cluster CR YAML files
- How does the BPA operator get the SSH information of the compute hosts ?
This proposal would make it possible to assign roles to nodes based on the features discovered. Currently, the proposal makes use of CPU, memory, SRIOV and QAT. However the baremetal operator list returns much more information about the nodes, we would be able to extend this feature to allow the operator assign roles based on more complex requirements such as CPU model. This would feed into Hardware Platform Awareness (HPA)