A python client for etcd





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python-etcd documentation

A python client for Etcd

Official documentation:

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This version of python-etcd will only work correctly with the etcd server version 2.0.x or later. If you are running an older version of etcd, please use python-etcd 0.3.3 or earlier.

This client is known to work with python 2.7 and with python 3.3 or above. It is not tested or expected to work in more outdated versions of python.

From source

.. code:: bash

    $ python install
From Pypi

.. code:: bash

   $ python3.5 -m pip install python-etcd


The basic methods of the client have changed compared to previous versions, to reflect the new API structure; however a compatibility layer has been maintained so that you don't necessarily need to rewrite all your existing code.

Create a client object

.. code:: python

import etcd

client = etcd.Client() # this will create a client against etcd server running on localhost on port 4001
client = etcd.Client(port=4002)
client = etcd.Client(host='', port=4003)
client = etcd.Client(host=(('', 4001), ('', 4002), ('', 4003)))
client = etcd.Client(host='', port=4003, allow_redirect=False) # wont let you run sensitive commands on non-leader machines, default is true
# If you have defined a SRV record for pointing to the clients
client = etcd.Client(srv_domain='', protocol="https")
# create a client against
client = etcd.Client(host='', protocol='https', port=443, version_prefix='/etcd')

Write a key

.. code:: python

    client.write('/nodes/n1', 1)
    # with ttl
    client.write('/nodes/n2', 2, ttl=4)  # sets the ttl to 4 seconds
    client.set('/nodes/n2', 1) # Equivalent, for compatibility reasons.

Read a key

.. code:: python'/nodes/n2').value'/nodes', recursive = True) #get all the values of a directory, recursively.

    # raises etcd.EtcdKeyNotFound when key not found
    except etcd.EtcdKeyNotFound:
        # do something
        print "error"

Delete a key

.. code:: python


Atomic Compare and Swap

.. code:: python

    client.write('/nodes/n2', 2, prevValue = 4) # will set /nodes/n2 's value to 2 only if its previous value was 4 and
    client.write('/nodes/n2', 2, prevExist = False) # will set /nodes/n2 's value to 2 only if the key did not exist before
    client.write('/nodes/n2', 2, prevIndex = 30) # will set /nodes/n2 's value to 2 only if the key was last modified at index 30
    client.test_and_set('/nodes/n2', 2, 4) #equivalent to client.write('/nodes/n2', 2, prevValue = 4)

You can also atomically update a result:

.. code:: python

    result ='/foo')
    print(result.value) # bar
    result.value += u'bar'
    updated = client.update(result) # if any other client wrote '/foo' in the meantime this will fail
    print(updated.value) # barbar

Watch a key

.. code:: python'/nodes/n1', wait = True) # will wait till the key is changed, and return once its changed'/nodes/n1', wait = True, timeout=30) # will wait till the key is changed, and return once its changed, or exit with an exception after 30 seconds.'/nodes/n1', wait = True, waitIndex = 10) # get all changes on this key starting from index 10'/nodes/n1') #equivalent to'/nodes/n1', wait = True)'/nodes/n1', index = 10)

Refreshing key TTL

(Since etcd 2.3.0) Keys in etcd can be refreshed without notifying current watchers.

This can be achieved by setting the refresh to true when updating a TTL.

You cannot update the value of a key when refreshing it.

.. code:: python

    client.write('/nodes/n1', 'value', ttl=30)  # sets the ttl to 30 seconds
    client.refresh('/nodes/n1', ttl=600)  # refresh ttl to 600 seconds, without notifying current watchers

Locking module

.. code:: python

    # Initialize the lock object:
    # NOTE: this does not acquire a lock yet
    client = etcd.Client()
    # Or you can custom lock prefix, default is '/_locks/' if you are using HEAD
    client = etcd.Client(lock_prefix='/my_etcd_root/_locks')
    lock = etcd.Lock(client, 'my_lock_name')

    # Use the lock object:
    lock.acquire(blocking=True, # will block until the lock is acquired
          lock_ttl=None) # lock will live until we release it
    lock.is_acquired  # True
    lock.acquire(lock_ttl=60) # renew a lock
    lock.release() # release an existing lock
    lock.is_acquired  # False

    # The lock object may also be used as a context manager:
    client = etcd.Client()
    with etcd.Lock(client, 'customer1') as my_lock:
        my_lock.is_acquired  # True
    my_lock.is_acquired  # False

Get machines in the cluster

.. code:: python


Get leader of the cluster

.. code:: python


Generate a sequential key in a directory

.. code:: python

x = client.write("/dir/name", "value", append=True)
print("generated key: " + x.key)
print("stored value: " + x.value)

List contents of a directory

.. code:: python

    #stick a couple values in the directory
    client.write("/dir/name", "value1", append=True)
    client.write("/dir/name", "value2", append=True)

    directory = client.get("/dir/name")

    # loop through directory children
    for result in directory.children:
      print(result.key + ": " + result.value)

    # or just get the first child value

Development setup

To create a buildout,

.. code:: bash

    $ python
    $ bin/buildout

to test you should have etcd available in your system path:

.. code:: bash

    $ bin/test

to generate documentation,

.. code:: bash

    $ cd docs
    $ make

Release HOWTO

To make a release

    1) Update release date/version in NEWS.txt and
    2) Run 'python sdist'
    3) Test the generated source distribution in dist/
    4) Upload to PyPI: 'python sdist register upload'

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