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wraps Google cloud client to facilitate deployment.

Project description

gcloudwrap

gcloudwrap provides a wrapper around the Google API client to help you manage your Google cloud (i.e. its ‘compute’ component). The original client provides all the needed functionality and gcloudwrap adds little in terms of extras. However, we found it easier to have a thin wrapper around the cloud management to give us a domain language closer to the tasks we had to repeatedly execute.

We initially found it hard to develop using original Google API client since it lacked type annotations and its dynamic approach to object creation allowed no code inspection in an IDE such as PyCharm. Since scripts involving cloud management usually take longer to execute, we found our development iterations to be fairly long and often broke due to minor errors related to incorrect types. Therefore, we added type annotations so that the static analyzer (such as mypy) would panic and catch the type errors early. This substantially facilitated the development of the deployment scripts.

Mind that we have not wrapped all of Google Compute API. We focused only on the parts necessary for the deployment. Please create an issue if you would like more functionality to be wrapped.

Scenarios

Batch Jobs

Writing a deployment script for large batch jobs is straight-forward with gcloudwrap:

  • You spin up a couple of machines.
  • Use google-cloud-storage module to copy the necessary data from the storage.
  • Use an SSH Python module (such as spurplus) to install the dependencies, copy the released executables and initiate the processes within tmux (so that they stay alive after you exit the shell).

With this setup, no extra virtualization layer (such as Docker) is necessary, and you do not need to understand how to set up and maintain an extra cluster management tool. It worked very well for us for different scales (from trivial one-off batch jobs to large-scale deployments). Additionally, we found it much simpler to debug (and resume afterwards) directly on a machine than going through an extra virtualization layer.

Deployment

Apart from batch jobs, we intensively use gcloudwrap for the deployment in the cloud. Our workflow includes:

  • Reserving an external address,
  • Creating the instance,
  • Tagging the instance (usually in order to modify the firewall rules),
  • Authorizing the SSH keys,
  • Creating and attaching persistent disks,
  • Formatting the disks (if necessary) and mounting them and
  • Running an initialization & installation script (based on an SSH module like spurplus).

gcloudwrap is intended to substantially simplify the process compared to the original Google Python API client.

(In case you need to deploy on other premises, we would suggest you to explicitly separate the initialization script from the deployment script. The initialization scripts should accept user name and host name as arguments and execute the commands remotely via SSH.

When you deploy on Google Cloud, create the instance and authorize your SSH key with it. Once the instance is up, run the initialization script against its external IP address as host name and whatever user you authorized your SSH key with.

If you need to deploy on other premises, ask them to authorize you your SSH key. Now you can simply run the same initialization script with a different pair of user and host name.)

Usage

We tried to follow the naming of the API as much as possible. The definition and description of the API can be found here: Google Compute API. However, we complied to Python naming convention, and renamed all camelCase arguments into snake_case.

The following code snippet shows a common deployment which creates an instance with a persistent disk and a reserved external IP address. The instance is tagged with ‘default-allow-http’ to open a HTTP port in its firewall. Finally, we authorize a public SSH key with the instance.

import pathlib

import gcloudwrap

instance = 'some-instance'
address = 'some-address'
disk = 'some-persistent-disk'
device_name = 'persistency'

service_account = 'some-service-account@some-project-221984.iam.gserviceaccount.com

public_ssh_key = pathlib.Path(
    '/some/path/to/ssh/id_rsa.pub').read_text()

gce = gcloudwrap.Gce()

gce.addresses.insert(name=address)
static_ip = gce.addresses.static_ip(
    address=address)

gce.disks.insert(
    name=disk,
    disk_type='pd-standard',
    size_gb=5)

gce.instances.insert(
    name=instance,
    machine_type='f1-micro',
    address=static_ip,
    service_account=service_account)

gce.instances.attach_disk(
    instance=instance,
    disk=disk,
    device_name=device_name)

# open up HTTP port
tags = gce.instances.tags(instance=instance)
tags.items.add('default-allow-http')
gce.instances.set_tags(
    instance=instance, tags=tags)

# authorize the SSH key
keys = gcloudwrap.SSHKey(
    user='some-user',
    public_key=public_key)

metadata = gce.instances.metadata(instance=instance)
metadata.set_ssh_keys(keys=[key])

gce.instances.set_metadata(
    instance=instance,
    metadata=metadata)

# format the persistent disk and mount it
ssh = gce.instances.ssh(
    instance=instance,
    user="some-devop-user")

operator = gcloudwrap.Operator(call_fn=ssh.call)

operator.format_disk(
    device_name=device_name)

operator.mount_disk(
    device_name=device_name,
    path=pathlib.Path('/mnt/disks/persistency'))

Sometimes it is convenient to store the list of authorized SSH keys in a file and re-use this list when deploying the instance. We provide a shortcut function gcloudwrap.ssh_keys_from_file to achieve that:

import gcloudwrap

instance = 'some-instance'
keys_path = '/path/to/some/keys.txt'

keys = gcloudwrap.ssh_keys_from_file(
    path=keys_path,
    default_user='some-default-user')

metadata = gce.instances.metadata(instance=instance)
metadata.set_ssh_keys(keys=keys)

gce.instances.set_metadata(
    instance=instance,
    metadata=metadata)

Installation

  • Create a virtual environment:
python3 -m venv venv3
  • Activate it:
source venv3/bin/activate
  • Install gcloudwrap with pip:
pip3 install gcloudwrap
  • Set up the application-default credentials
gcloud auth application-default login

Development

  • Check out the repository.
  • In the repository root, create the virtual environment:
python3 -m venv venv3
  • Activate the virtual environment:
source venv3/bin/activate
  • Install the development dependencies:
pip3 install -e .[dev]
  • We provide a set of live tests. You need to set up your environment such that the credentials can be directly inferred by the tests. Apart from the credentials, you can also use the following environment variables:

    • TEST_GCLOUDWRAP_SERVICE_ACCOUNT to specify the service account attached to the instances created during the test. If unspecified, default service account of the GCE project is used.
    • TEST_GCLOUDWRAP_PREFIX to specify the prefix of all the created Google cloud resources; if not specified, equals “test-gcloudwrap”
    • TEST_GCLOUDWRAP_SSH_PUBLIC_KEY_PATH to specify the path to the SSH public key; if not specified, equals ~/.ssh/id_rsa.pub (where “~” is expanded to the user home directory)

    Mind that the live tests will use Google Cloud resources for which you will be billed. Always check that no resources are used after the tests finished so that you don’t incur an unnecessary cost!

  • We use tox for testing and packaging the distribution. Assuming that the virtual environment has been activated and the development dependencies have been installed, run:

tox
  • We also provide a set of pre-commit checks that lint and check code for formatting. Run them locally from an activated virtual environment with development dependencies:
./precommit.py
  • The pre-commit script can also automatically format the code:
./precommit.py  --overwrite

Versioning

We follow Semantic Versioning. The version X.Y.Z indicates:

  • X is the major version (backward-incompatible),
  • Y is the minor version (backward-compatible), and
  • Z is the patch version (backward-compatible bug fix).

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