According to https://github.com/zalando/patroni/issues/48 'clonefrom'
tag should be boolean and it should be used to mark node as a suitable
for creation of a new replica from. If there are more then one such node
in the cluster (with tag clonefrom=true), one of them will be chosed
randomly.
Instead of starting it up in "read-only", it wil wait 2 seconds, to give
a time to somebody to prompte and after it will execute normal `recover`
procedure.
Such situation is causing patroni crash. Usually it was happening during
manual failover, after former master has demoted and `reset_cluster`
method has been called. In this case `fetch_cluster` was `False` and
`_load_cluster` method was returning value from `self._cluster`, which
was `None`.
In addition to that rename confusing `Etcd.client` and
`ZooKeeper.client` into `_client`. This attribute is available from
AbstractDCS and people had wrong impression that it provides the same
interface for different DCS implementations, which is obviously not the
case. For Etcd it has type etcd.Client and for ZooKeeper - KazooClient.
Despite this release was very buggy it has really nice features:
* EtcdWatchTimedOut exception is raised when `watch` call timed out
* it supports SRV autodiscovery
Since we already implemented our own SRV discovery this feature is not
really interesting for us, but it solves the problem of having two
requirements files for different python versions, because python-etcd
will install dnspython or dnspython3 as a dependency.
In order to fix https://github.com/jplana/python-etcd/issues/152 and
https://github.com/jplana/python-etcd/pull/154 I had to override
`api_execute` method.
Previously, "without_leader" suffix was used in the name of methods
and functions that initialize a replica without an active replication
connection, and leader was part of the name for parameters and messages
that require an active replication conneciton. Since we support init
from the members other than the leader, those conventions have to be
changed.
At the moment we just replace the master with the
node at the 'clonefrom' tag if it's present. Master
should be available anyway, otherwise, it will not
even try to do cloning.
Acceptance tests:
https://github.com/zalando/patroni/pull/144/commits
Alexander Kukushkin