Sahara Cluster Statuses Overview¶

1. Validating¶

Before performing any operations with OpenStack environment, Sahara validates user input.

There are two types of validations, that are done:

• Check that a request contains all necessary fields and that the request does not violate any constraints like unique naming, etc.
• Plugin check (optional). The provisioning Plugin may also perform any specific checks like a Cluster topology validation check.

If any of the validations fails during creating, the Cluster object will still be kept in the database with an Error status. If any validations fails during scaling the Active Cluster, it will be kept with an Active status. In both cases status description will contain error messages about the reasons of failure.

2. InfraUpdating¶

This status means that the Provisioning plugin is performing some infrastructure updates.

3. Spawning¶

Sahara sends requests to OpenStack for all resources to be created:

• VMs
• Volumes
• Floating IPs (if Sahara is configured to use Floating IPs)

It takes some time for OpenStack to schedule all the required VMs and Volumes, so sahara will wait until all of the VMs are in an Active state.

4. Waiting¶

Sahara waits while VMs’ operating systems boot up and all internal infrastructure components like networks and volumes are attached and ready to use.

5. Preparing¶

Sahara prepares a Cluster for starting. This step includes generating the /etc/hosts file or changing /etc/resolv.conf file (if you use Designate service), so that all instances can access each other by a hostname. Also Sahara updates the authorized_keys file on each VM, so that VMs can communicate without passwords.

6. Configuring¶

Sahara pushes service configurations to VMs. Both XML and JSON based configurations and environmental variables are set on this step.

7. Starting¶

Sahara is starting Hadoop services on Cluster’s VMs.

8. Active¶

Active status means that a Cluster has started successfully and is ready to run EDP Jobs.

1. Validating¶

Sahara checks the scale/shrink request for validity. The Plugin method called for performing Plugin specific checks is different from the validation method in creation.

2. Scaling¶

Sahara performs database operations updating all affected existing Node Groups and creating new ones to join the existing Node Groups.

3. Adding Instances¶

Status is similar to Spawning in Cluster creation. Sahara adds required amount of VMs to the existing Node Groups and creates new Node Groups.

4. Configuring¶

Status is similar to Configuring in Cluster creation. New instances are being configured in the same manner as already existing ones. The VMs in the existing Cluster are also updated with a new /etc/hosts file or /etc/resolv.conf file.

5. Decommissioning¶

Sahara stops Hadoop services on VMs that will be deleted from a Cluster. Decommissioning a Data Node may take some time because Hadoop rearranges data replicas around the Cluster, so that no data will be lost after that Data Node is deleted.

6. Deleting Instances¶

Sahara sends requests to OpenStack to release unneeded resources:

• VMs
• Volumes
• Floating IPs (if they are used)

7. Active¶

The same Active status as after Cluster creation.

1. Deleting¶

The only step, that releases all Cluster’s resources and removes it from the database.

2. Force Deleting¶

In extreme cases the regular “Deleting” step may hang. Sahara APIv2 introduces the ability to force delete a Cluster. This prevents deleting from hanging but comes with the risk of orphaned resources.