An asynchronous python client for etcd
A python client for Etcd https://github.com/coreos/etcd
Official documentation: http://python-aio-etcd.readthedocs.org/
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 3.5. It will not work in older versions of python due to ist use of “async def” syntax.
Python 2 is not supported.
$ python setup.py install
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
import aio_etcd as 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='127.0.0.1', port=4003) client = etcd.Client(host=(('127.0.0.1', 4001), ('127.0.0.1', 4002), ('127.0.0.1', 4003))) client = etcd.Client(host='127.0.0.1', 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 _etcd._tcp.example.com pointing to the clients client = etcd.Client(srv_domain='example.com', protocol="https") # create a client against https://api.example.com:443/etcd client = etcd.Client(host='api.example.com', protocol='https', port=443, version_prefix='/etcd')
Write a key
await client.write('/nodes/n1', 1) # with ttl await client.set('/nodes/n1', 1) # Equivalent, for compatibility reasons. await client.write('/nodes/n2', 2, ttl=4) # sets the ttl to 4 seconds
Read a key
(await client.read('/nodes/n2')).value # read a value (await client.get('/nodes/n2')).value # Equivalent, for compatibility reasons. await client.read('/nodes', recursive = True) # get all the values of a directory, recursively. # raises etcd.EtcdKeyNotFound when key not found try: client.read('/invalid/path') except etcd.EtcdKeyNotFound: # do something print "error"
Delete a key
Atomic Compare and Swap
await client.write('/nodes/n2', 2, prevValue = 4) # will set /nodes/n2 's value to 2 only if its previous value was 4 await client.write('/nodes/n2', 2, prevExist = False) # will set /nodes/n2 's value to 2 only if the key did not exist before await 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 await client.test_and_set('/nodes/n2', 2, 4) #equivalent to client.write('/nodes/n2', 2, prevValue = 4)
You can also atomically update a result:
await client.write('/foo','bar') result = await client.read('/foo') print(result.value) # bar result.value += u'bar' updated = await client.update(result) # if any other client wrote to '/foo' in the meantime this will fail print(updated.value) # barbar
Watch a key
result = await client.read('/nodes/n1') # start from a known initial value result = await client.read('/nodes/n1', wait = True, waitIndex = result.modifiedIndex+1) # will wait till the key is changed, and return once it's changed result = await client.read('/nodes/n1', wait = True, waitIndex = 10) # get all changes on this key starting from index 10 result = await client.watch('/nodes/n1') # equivalent to client.read('/nodes/n1', wait = True) result = await client.watch('/nodes/n1', index = result.modifiedIndex+1)
If you want to time out the read() call, wrap it in asyncio.wait_for:
result = await asyncio.wait_for(client.read('/nodes/n1', wait=True), timeout=30)
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.
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
# Initialize the lock object: # NOTE: this does not acquire a lock from aio_etcd.lock import Lock 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: await 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 await lock.acquire(lock_ttl=60) # renew a lock await lock.release() # release an existing lock lock.is_acquired # False # The lock object may also be used as a context manager: async with Lock(client, 'customer1') as my_lock: do_stuff() my_lock.is_acquired # True await my_lock.acquire(lock_ttl=60) my_lock.is_acquired # False
Get machines in the cluster
machines = await client.machines()
Get leader of the cluster
leaderinfo = await client.leader()
Generate a sequential key in a directory
x = await client.write("/dir/name", "value", append=True) print("generated key: " + x.key) # actually the whole path print("stored value: " + x.value)
List contents of a directory
#stick a couple values in the directory await client.write("/dir/name", "value1", append=True) await client.write("/dir/name", "value2", append=True) directory = await client.get("/dir/name") # loop through a directory's children for result in directory.children: print(result.key + ": " + result.value) # or just get the first child value print(directory.next(children).value)
The usual setuptools commands are available.
$ python3 setup.py install
To test, you should have etcd available in your system path:
$ python3 setup.py test
to generate documentation,
$ cd docs $ make
To make a release
- Update release date/version in NEWS.txt and setup.py
- Run ‘python setup.py sdist’
- Test the generated source distribution in dist/
- Upload to PyPI: ‘python setup.py sdist register upload’
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