sap-instance-manager 0.4.2

SAP Python instance manager client

sap_instance_manager

Python package for creating and deleting service instances per tenant within an application at runtime.

Overview

This package provides a client for the Instance Manager - a component that creates and deletes service instances (via REST API) for a specified key. Instance Manager can be used in the context of multitenant applications where the tenant id is the key an instance is associated with.

Multitenancy is a concept for sharing resources between several different and unrelated to each other groups of users called tenants. Example: subscriptions to a commercial cloud application can be sold to two different companies each of which should use the application in isolation from the other one. Customizations are also applied (e.g. different branding, identity providers, database schemas etc.).

A typical application has access to external resources (e.g. a database or messaging) via services. If an application is used by different tenants, then using a separate service instance for each one will improve isolation since service binding provides access to a particular resource.

With this package a Python application can dynamically create and delete service instances per tenant at runtime. An instance of a managed service of the desired type is created first and is then bound to the application. For a HANA database the managed service is called ‘managed-hana’. This service binding only provides parameters (HTTP endpoints and credentials) which can later be used by the application for creating and deleting service instances of the desired type for each tenant.

API

.. code:: python

from sap import instance_manager

# create instance manager client
client = instance_manager.create(options)

# create instance
instance = client.create('my-tenant')
print(instance)
# ...

# get already created instance
instance = client.get('my-tenant')
print(instance)
# ...

# delete instance
client.delete('my-tenant')

Options

The *managed service* bound to the application (for example
*managed-hana*) provides credentials as well as REST endpoints of the
*Instance Manager* - the component that handles creation and deletion of
services. These credentials and endpoints are mandatory.

The create and delete operations are executed asynchronously on server
side. To provide an easier interface, this library also implements
polling until an operation is finished. Developers can tune polling via
some optional properties.

Since operations involve network activity (thus, can be considered
relatively slower) the package also caches the created instances. Cache
options can also be provided by developers.

+-------------------------------+-----------+---------+-------------------------------------------------------------------------------------------------------------------------------+
| Property                      | Mandatory | Type    | Details                                                                                                                       |
+===============================+===========+=========+===============================================================================================================================+
| user                          | x         | string  | User for authentication.                                                                                                      |
+-------------------------------+-----------+---------+-------------------------------------------------------------------------------------------------------------------------------+
| password                      | x         | string  | Password for the user.                                                                                                        |
+-------------------------------+-----------+---------+-------------------------------------------------------------------------------------------------------------------------------+
| post_managed_instance_url     | x         | string  | REST endpoint used for creating a new service instance for a tenant.                                                          |
+-------------------------------+-----------+---------+-------------------------------------------------------------------------------------------------------------------------------+
| get_managed_instance_url      | x         | string  | REST endpoint                                                                                                                 |
+-------------------------------+-----------+---------+-------------------------------------------------------------------------------------------------------------------------------+
| get_all_managed_instances_url | x         | string  | REST endpoint used for getting details about all instances (for all tenants).                                                 |
+-------------------------------+-----------+---------+-------------------------------------------------------------------------------------------------------------------------------+
| delete_managed_instance_url   | x         | string  | REST endpoint used for deletion of a service instance.                                                                        |
+-------------------------------+-----------+---------+-------------------------------------------------------------------------------------------------------------------------------+
| polling_interval_millis       |           | integer | States how many milliseconds to wait between requests in the polling phase. Defaults to 300 milliseconds. Minimum value is 0. |
+-------------------------------+-----------+---------+-------------------------------------------------------------------------------------------------------------------------------+
| polling_timeout_seconds       |           | integer | Sets a limit for the amount of time (in seconds) that can be spent in polling. Defaults to 120 seconds. Minimum value is 1.   |
+-------------------------------+-----------+---------+-------------------------------------------------------------------------------------------------------------------------------+
| cache_max_items               |           | integer | States the capacity of the cache. Default value is 500. Minimum value is 1.                                                   |
+-------------------------------+-----------+---------+-------------------------------------------------------------------------------------------------------------------------------+
| cache_item_expire_seconds     |           | integer | Number of seconds after which a cache entry expires. Defaults to 600 seconds. Minimum value is 1.                             |
+-------------------------------+-----------+---------+-------------------------------------------------------------------------------------------------------------------------------+


**Note**:

- A *managed service* binding contains all of the mandatory properties mentioned above.

- It is recommended to have a single instance manager client Python object per *managed service* bound to the application.


Methods

• create(tenant, optional_parameters) - creates a service instance for the provided tenant. The method polls until the instance is successfully created. Reports error if an instance for this tenant already exists. The second argument is optional. It is a dict with parameters for provisioning or binding, as would be done with the -c options of the CLI commands create-service and bind-service for unmanaged services. E.g.

  .. code:: python

  {
    "provisioning_parameters": { "database_id" : "<HANA Tenant DB Guid or Name>" },
    "binding_parameters": {"<key>" : "<value>"}
  }
  

• get(tenant) - gets the corresponding instance for the provided tenant either from cache or from server. Value of None means that a service instance for this tenant does not exist. Note: this method only polls if the instance is in status CREATION_IN_PROGRESS. In all other cases it returns the service instance as it is on server. Thus, having the credentials property on the instance object is not guaranteed.

• get_all() - gets the instances for all tenants as array of objects. Filtering of the instances according to their status (e.g. CREATION_SUCCEEDED, CREATION_IN_PROGRESS) does not take place. Thus, having the credentials property on each of the instances provided is not guaranteed. This method updates the cache.

• delete(tenant) - deletes service instance for the provided tenant. The method polls until the instance is successfully deleted. Reports error if an instance for this tenant does not exists.

When a method raises an error and this error is caused by an unexpected HTTP response code received from the server, then this error object will have a statusCode property with the status code of the received HTTP response.

SSL Certificates

When the Instance Manager is running on a host with a self-signed certificate, you can use the REQUESTS_CA_BUNDLE environment variable to specify the path to the certificate.