Previously we were running pg_rewind only in limited amount of cases:
* when we knew postgres was a master (no recovery.conf in data dir)
* when we were doing a manual switchover to a specific node (no
guaranty that this node is the most up-to-date)
* when a given node has nofailover tag (it could be ahead of new master)
This approach was kind of working in most of the cases, but sometimes we
were executing pg_rewind when it was not necessary and in some other
cases we were not executing it although it was needed.
The main idea of this PR is first try to figure out that we really need
to run pg_rewind by analyzing timelineid, LSN and history file on master
and replica and run it only if it's needed.
* Reassemble postgresql parameters when major version became known
Otherwise we were writing some "unknown" parameters into postgresql.conf
and postgres was refusing to start. Only 9.3 was affected.
In addition to that move rename of wal_level from hot_standby to replica
into get_server_parameters method. Now this rename is handled in a
single place.
* Bump etcd and consul versions
starting from 9.6 we need wal_level = 'replica' which is alias for 'hot_standby'. It was working before without problems, but if somebody change wal_level to replica, Patroni will expose pending_restart flag, although restart in this case is not necessary.
* bump versions of consul and etcd to the latest for travis integration-tests
Without sudo travis is executing build tasks using docker and waiting
time in this case is really small, usually not longer then 10 seconds.
postgresql-9.5 is installed via addons.apt.packages (without sudo)
But ports 5432 and 5433 are busy. So I had to ajust environment.py to
assign port from higher diapason.
And a few words about build tasks:
First task is used for executing unit tests for all different python versions
The second one is used for executing acceptance tests against etcd
The third one is used for executing acceptance tests against zookeeper
acceptance tests are executed with python2.7 and python3.5
In addition that I've introduced caching of python virtual environment.
It really helps to reduce time needed to install python modules.
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.
In case if one member of a cluster is not available it will retry with
another one and fetch the new cluster configuration. Default timeout for
all requests to etcd is 5 seconds.
Initial cluster configuration can be resolved through:
1) /v2/members call on one of the cluster members on a client port
2) when it is possible to resolve hostname into multiple ip's it will
iterate through list and try to perform action from 1)
3) If there is discovery_srv defined in etcd section of config file it
will resolve peer addresses of all cluster members and will fetch
cluster configuration with using peer protocol by doing /members call on
a peer port
