Google

Cloud storage

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Overview

REX-Ray ships with support for Google Compute Engine (GCE) as well.

GCE Persistent Disk

The Google Compute Engine Persistent Disk (GCEPD) driver registers a driver named gcepd with the libStorage service registry and is used to connect and mount Google Compute Engine (GCE) persistent disks with GCE machine instances.

Requirements

• GCE account
• The libStorage server must be running on a GCE instance created with a Service Account with appropriate permissions, or a Service Account credentials file in JSON format must be supplied. If not using the Compute Engine default Service Account with the Cloud Platform/"all cloud APIs" scope, create a new Service Account via the IAM Portal. This Service Account requires the Compute Engine/Instance Admin, Compute Engine/Storage Admin, and Project/Service Account Actor roles. Then create/download a new private key in JSON format. see creating a service account for details. The libStorage service must be restarted in order for permissions changes on a service account to take effect.

Configuration

The following is an example with all possible fields configured. For a running example see the Examples section.

gcepd:
  keyfile: /etc/gcekey.json
  zone: us-west1-b
  defaultDiskType: pd-ssd
  tag: rexray
  statusMaxAttempts:  10
  statusInitialDelay: 100ms
  statusTimeout:      2m
  convertUnderscores: false

Configuration Notes

• The keyfile parameter is optional. It specifies a path on disk to a file containing the JSON-encoded Service Account credentials. This file can be downloaded from the GCE web portal. If keyfile is specified, the GCE instance's service account is not considered, and is not necessary. If keyfile is not specified, the application will try to lookup application default credentials. This has the effect of looking for credentials in the priority described here.
• The zone parameter is optional, and configures the driver to only allow access to the given zone. Creating and listing disks from other zones will be denied. If a zone is not specified, the zone from the client Instance ID will be used when creating new disks.
• The defaultDiskType parameter is optional and specifies what type of disk to create, either pd-standard or pd-ssd. When not specified, the default is pd-ssd.
• The tag parameter is optional, and causes the driver to create or return disks that have a matching tag. The tag is implemented by using the GCE label functionality available in the beta API. The value of the tag parameter is used as the value for a label with the key libstoragetag. Use of this parameter is encouraged, as the driver will only return volumes that have been created by the driver, which is most useful to eliminate listing the boot disks of every GCE disk in your project/zone. If you wsih to "expose" previously created disks to the GCEPD driver, you can edit the labels on the existing disk to have a key of libstoragetag and a value matching that given in tag.
• statusMaxAttempts is the number of times the status of a volume will be queried before giving up when waiting on a status change
• statusInitialDelay specifies a time duration used to wait when polling volume status. This duration is used in exponential backoff, such that the first wait will be for this duration, the second for 2x, the third for 4x, etc. The units of the duration must be given (e.g. "100ms" or "1s").
• statusTimeout is a maximum length of time that polling for volume status can occur. This serves as a backstop against a stuck request of malfunctioning API that never returns.
• convertUnderscores is a boolean flag that controls whether the driver will automatically convert underscores to dashes during a volume create request. GCE does not allow underscores in the volume name, but some container orchestrators (e.g. Docker Swarm) automatically prefix volume names with a string containing a dash. This flag enables such requests to proceed, but with the volume name modified.

Runtime behavior

• The GCEPD driver enforces the GCE requirements for disk sizing and naming. Disks must be created with a minimum size of 10GB. Disk names must adhere to the regular expression of [a-z]([-a-z0-9]*[a-z0-9])?, which means the first character must be a lowercase letter, and all following characters must be a dash, lowercase letter, or digit, except the last character, which cannot be a dash.
• If the zone parameter is not specified in the driver configuration, and a request is received to list all volumes that does not specify a zone in the InstanceID header, volumes from all zones will be returned.
• By default, all disks will be created with type pd-ssd, which creates an SSD based disk. If you wish to create disks that are not SSD-based, change the default via the driver config, or the type can be changed at creation time by using the Type field of the create request.

Activating the Driver

To activate the GCEPD driver please follow the instructions for activating storage drivers, using gcepd as the driver name.

Troubleshooting

• Make sure that the JSON credentials file as specified in the keyfile configuration parameter is present and accessible, or that you are running in a GCE instance created with a Service Account attached. Whether using a keyfile or the Service Account associated with the GCE instance, the Service Account must have the appropriate permissions as described in Configuration Notes

Examples

Below is a full config.yml that works with GCE

libstorage:
  # The libstorage.service property directs a libStorage client to direct its
  # requests to the given service by default. It is not used by the server.
  service: gcepd
  server:
    services:
      gcepd:
        driver: gcepd
        gcepd:
          keyfile: /etc/gcekey.json
          tag: rexray

Caveats

• Snapshot and copy functionality is not yet implemented
• Most GCE instances can have up to 64 TB of total persistent disk space attached. Shared-core machine types or custom machine types with less than 3.75 GB of memory are limited to 3 TB of total persistent disk space. Total persistent disk space for an instance includes the size of the root persistent disk. You can attach up to 16 independent persistent disks to most instances, but instances with shared-core machine types or custom machine types with less than 3.75 GB of memory are limited to a maximum of 4 persistent disks, including the root persistent disk. See GCE Disks docs for more details.
• If running libStorage server in a mode where volume mounts will not be performed on the same host where libStorage server is running, it should be possible to use a Service Account without the Service Account Actor role, but this has not been tested. Note that if persistent disk mounts are to be performed on any GCE instances that have a Service Account associated with the, the Service Account Actor role is required.