Getting started

Now it’s time to begin doing some work with Cloudant and Python. For working code samples of any of the API’s please go to our test suite.

Connections

In order to manage a connection you must first initialize the connection by constructing either a Cloudant or CouchDB client. Since connecting to the Cloudant managed service provides extra end points as compared to a CouchDB server, we provide the two different client implementations in order to connect to the desired database service. Once the client is constructed, you follow that up by connecting to the server, performing your tasks, and then disconnecting from the server.

Later in the Context managers section we will see how to simplify this process through the use of the Python with statement.

Note: If you require retrying requests after an HTTP 429 error, the Replay429Adapter can be added when constructing a Cloudant client and configured with an initial back off and retry count.

Note: Currently, the connect and read timeout will wait forever for a HTTP connection or a response on all requests. A timeout can be set using the timeout argument when constructing a client.

Connecting with a client

# Use CouchDB to create a CouchDB client
# from cloudant.client import CouchDB
# client = CouchDB(USERNAME, PASSWORD, url='http://127.0.0.1:5984', connect=True)

# Use Cloudant to create a Cloudant client using account
from cloudant.client import Cloudant
client = Cloudant(USERNAME, PASSWORD, account=ACCOUNT_NAME, connect=True)
# or using url
# client = Cloudant(USERNAME, PASSWORD, url='https://acct.cloudant.com')

# or with a 429 replay adapter that includes configured retries and initial backoff
# client = Cloudant(USERNAME, PASSWORD, account=ACCOUNT_NAME,
#                   adapter=Replay429Adapter(retries=10, initialBackoff=0.01))

# or with a connect and read timeout of 5 minutes
# client = Cloudant(USERNAME, PASSWORD, account=ACCOUNT_NAME,
#                   timeout=300)

# Perform client tasks...
session = client.session()
print('Username: {0}'.format(session['userCtx']['name']))
print('Databases: {0}'.format(client.all_dbs()))

# Disconnect from the server
client.disconnect()

Authentication

When constructing a Cloudant client, you can authenticate using the cookie authentication functionality. The server will always attempt to automatically renew the cookie shortly before its expiry. However, if the client does not send a request to the server during this renewal window and auto_renew=False then the cookie is not renewed.

Using auto_renew=True will attempt to renew the cookie at any point during the lifetime of the session when either of the following statements hold true:

  • The server returns a credentials_expired error message.
  • The server returns a 401 Unauthorized status code.
  • The server returns a 403 Forbidden status code.
# Create client using auto_renew to automatically renew expired cookie auth
client = Cloudant(USERNAME, PASSWORD, url='https://acct.cloudant.com',
                 connect=True,
                 auto_renew=True)

Identity and Access Management (IAM)

IBM Cloud Identity & Access Management enables you to securely authenticate users and control access to all cloud resources consistently in the IBM Bluemix Cloud Platform.

See IBM Cloud Identity and Access Management for more information.

The production IAM token service at https://iam.cloud.ibm.com/identity/token is used by default. You can set an IAM_TOKEN_URL environment variable to override this.

You can easily connect to your Cloudant account using an IAM API key:

# Authenticate using an IAM API key
client = Cloudant.iam(ACCOUNT_NAME, API_KEY, connect=True)

Resource sharing

The Cloudant or CouchDB client objects make HTTP calls using the requests library. requests uses the urllib3 library which features connection pooling and thread safety.

Connection pools can be managed by using the requests library’s HTTPAdapter when constructing a Cloudant or ClouchDB client instance. The default number set by the urllib3 library for cached connection pools is 10. Use the HTTPAdapter argument pool_connections to set the number of urllib3 connection pools to cache, and the pool_maxsize argument to set the maximum number of connections to save in the pool.

Although the client session is documented as thread safe and it’s possible for a static client to be accessible by multiple threads, there are still cases that do not guarantee thread safe execution. It’s recommended to use one client object per thread.

# Create client with 15 cached pool connections and a max pool size of 100
httpAdapter = HTTPAdapter(pool_connections=15, pool_maxsize=100)
client = Cloudant(USERNAME, PASSWORD, url='https://acct.cloudant.com'
                 connect=True,
                 adapter=httpAdapter)

Note: Idle connections within the pool may be terminated by the server, so will not remain open indefinitely meaning that this will not completely remove the overhead of creating new connections.

Using library in app server environment

This library can be used in an app server, and the example below shows how to use client in a flask app server.

from flask import Flask
import atexit

app = Flask(__name__)

@app.route('/')
def hello_world():
   # Cookie authentication can be renewed automatically using ``auto_renew=True``
   # which is typically what you would require when running in an application
   # server where the connection may stay open for a long period of time

   # Note: Each time you instantiate an instance of the Cloudant client, an
   # authentication request will be made to Cloudant to retrieve the session cookie.
   # If the performance overhead of this call is a concern for you, consider
   # using vanilla python requests with a custom subclass of HTTPAdapter that
   # performs the authentication call to Cloudant when it establishes the http
   # connection during the creation of the connection pool.
   client = Cloudant(USERNAME, PASSWORD, url='https://acct.cloudant.com',
                     connect=True,
                     auto_renew=True)

   # do something with client
   return 'Hello World!'

# When shutting down the app server, use ``client.disconnect()`` to properly
# logout and end the ``client`` session
@atexit.register
def shutdown():
   client.disconnect()

Databases

Once a connection is established you can then create a database, open an existing database, or delete a database. The following examples assume a client connection has already been established.

Creating a database

# Create a database using an initialized client
# The result is a new CloudantDatabase or CouchDatabase based on the client
my_database = client.create_database('my_database')

# You can check that the database exists
if my_database.exists():
    print('SUCCESS!!')

Opening a database

Opening an existing database is done by supplying the name of an existing database to the client. Since the Cloudant and CouchDB classes are sub-classes of dict, this can be accomplished through standard Python dict notation.

# Open an existing database
my_database = client['my_database']

Deleting a database

# Delete a database using an initialized client
client.delete_database('my_database')

Documents

Working with documents using this library is handled through the use of Document objects and Database API methods. A document context manager is also provided to simplify the process. This is discussed later in the Context managers section. The examples that follow demonstrate how to create, read, update, and delete a document. These examples assume that either a CloudantDatabase or a CouchDatabase object already exists.

Creating a document

# Create document content data
data = {
    '_id': 'julia30', # Setting _id is optional
    'name': 'Julia',
    'age': 30,
    'pets': ['cat', 'dog', 'frog']
    }

# Create a document using the Database API
my_document = my_database.create_document(data)

# Check that the document exists in the database
if my_document.exists():
    print('SUCCESS!!')

Retrieving a document

Accessing a document from a database is done by supplying the document identifier of an existing document to either a CloudantDatabase or a CouchDatabase object. Since the CloudantDatabase and CouchDatabase classes are sub-classes of dict, this is accomplished through standard dict notation.

my_document = my_database['julia30']

# Display the document
print(my_document)

Checking if a document exists

You can check if a document exists in a database the same way you would check if a dict has a key-value pair by key.

doc_exists = 'julia30' in my_database

if doc_exists:
    print('document with _id julia30 exists')

Retrieve all documents

You can also iterate over a CloudantDatabase or a CouchDatabase object to retrieve all documents in a database.

# Get all of the documents from my_database
for document in my_database:
    print(document)

Update a document

# First retrieve the document
my_document = my_database['julia30']

# Update the document content
# This can be done as you would any other dictionary
my_document['name'] = 'Jules'
my_document['age'] = 6

# You must save the document in order to update it on the database
my_document.save()

Delete a document

# First retrieve the document
my_document = my_database['julia30']

# Delete the document
my_document.delete()

Dealing with results

If you want to get Pythonic with your returned data content, we’ve added a Result class that provides a key accessible, sliceable, and iterable interface to result collections. To use it, construct a Result object passing in a reference to a raw data callable such as the all_docs method from a database object or a view object itself, which happens to be defined as callable and then access the data as you would using standard Python key access, slicing, and iteration techniques. The following set of examples illustrate Result key access, slicing and iteration over a result collection in action. It assumes that either a CloudantDatabase or a CouchDatabase object already exists.

from cloudant.result import Result, ResultByKey

# Retrieve Result wrapped document content.
# Note: The include_docs parameter is optional and is used to illustrate that view query
# parameters can be used to customize the result collection.
result_collection = Result(my_database.all_docs, include_docs=True)

# Get the result at a given location in the result collection
# Note: Valid result collection indexing starts at 0
result = result_collection[0]                   # result is the 1st in the collection
result = result_collection[9]                   # result is the 10th in the collection

# Get the result for matching a key
result = result_collection['julia30']           # result is all that match key 'julia30'

# If your key is an integer then use the ResultByKey class to differentiate your integer
# key from an indexed location within the result collection which is also an integer.
result = result_collection[ResultByKey(9)]      # result is all that match key 9

# Slice by key values
result = result_collection['julia30': 'ruby99'] # result is between and including keys
result = result_collection['julia30': ]         # result is after and including key
result = result_collection[: 'ruby99']          # result is up to and including key

# Slice by index values
result = result_collection[100: 200]            # result is between 100 to 200, including 200th
result = result_collection[: 200]               # result is up to and including the 200th
result = result_collection[100: ]               # result is after the 100th

# Iterate over the result collection
for result in result_collection:
    print(result)

Context managers

Now that we’ve gone through the basics, let’s take a look at how to simplify the process of connection, database acquisition, and document management through the use of Python with blocks and this library’s context managers.

Handling your business using with blocks saves you from having to connect and disconnect your client as well as saves you from having to perform a lot of fetch and save operations as the context managers handle these operations for you.

This example uses the cloudant context helper to illustrate the process but identical functionality exists for CouchDB through the couchdb and couchdb_admin_party context helpers.

from cloudant import cloudant

# ...or use CouchDB variant
# from cloudant import couchdb

# Perform a connect upon entry and a disconnect upon exit of the block
with cloudant(USERNAME, PASSWORD, account=ACCOUNT_NAME) as client:

# ...or use CouchDB variant
# with couchdb(USERNAME, PASSWORD, url=COUCHDB_URL) as client:

    # Perform client tasks...
    session = client.session()
    print('Username: {0}'.format(session['userCtx']['name']))
    print('Databases: {0}'.format(client.all_dbs()))

    # Create a database
    my_database = client.create_database('my_database')
    if my_database.exists():
        print('SUCCESS!!')

    # You can open an existing database
    del my_database
    my_database = client['my_database']

The following example uses the Document context manager. Here we make multiple updates to a single document. Note that we don’t save to the server after each update. We only save once to the server upon exiting the Document context manager.

from cloudant import cloudant
from cloudant.document import Document

with cloudant(USERNAME, PASSWORD, account=ACCOUNT_NAME) as client:

    my_database = client.create_database('my_database')

    # Upon entry into the document context, fetches the document from the
    # remote database, if it exists. Upon exit from the context, saves the
    # document to the remote database with changes made within the context
    # or creates a new document.
    with Document(database, 'julia006') as document:
        # If document exists, it's fetched from the remote database
        # Changes are made locally
        document['name'] = 'Julia'
        document['age'] = 6
        # The document is saved to the remote database

    # Display a Document
    print(my_database['julia30'])

    # Delete the database
    client.delete_database('my_database')

    print('Databases: {0}'.format(client.all_dbs()))

Always use the _deleted document property to delete a document from within a Document context manager. For example:

with Document(my_database, 'julia30') as doc:
    doc['_deleted'] = True

You can also delete non underscore prefixed document keys to reduce the size of the request.

Warning

Don’t use the doc.delete() method inside your Document context manager. This method immediately deletes the document on the server and clears the local document dictionary. A new, empty document is still saved to the server upon exiting the context manager.

Endpoint access

If for some reason you need to call a Cloudant/CouchDB endpoint directly rather using the API you can still benefit from the Cloudant/CouchDB client’s authentication and session usage by directly accessing its underlying Requests session object.

Access the session object using the r_session attribute on your client object. From there, use the session to make requests as the user the client is set up with. The following example shows a GET to the _all_docs endpoint, but obviously you can use this for any HTTP request to the Cloudant/CouchDB server. This example assumes that either a Cloudant or a CouchDB client object already exists.

# Define the end point and parameters
end_point = '{0}/{1}'.format(client.server_url, 'my_database/_all_docs')
params = {'include_docs': 'true'}

# Issue the request
response = client.r_session.get(end_point, params=params)

# Display the response content
print(response.json())

TLS 1.2 Support

The TLS protocol is used to encrypt communications across a network to ensure that transmitted data remains private. There are three released versions of TLS: 1.0, 1.1, and 1.2. All HTTPS connections use TLS.

If your server enforces the use of TLS 1.2 then the python-cloudant client will continue to work as expected (assuming you’re running a version of Python/OpenSSL that supports TLS 1.2).