Patroni

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Released 2016-07-05

This release introduces the global dynamic configuration that allows dynamic changes of the PostgreSQL and Patroni configuration parameters for the entire HA cluster. It also delivers numerous bugfixes.

**Upgrade notice**

When upgrading from v0.90 or below, always upgrade all replicas before the master. Since we don't store replication credentials in DCS anymore, an old replica won't be able to connect to the new master.

**Dynamic Configuration**

- Implement the dynamic global configuration (Alexander Kukushkin)

Introduce new REST API endpoint /config to provide PostgreSQL and Patroni configuration parameters that should be set globally for the entire HA cluster (master and all the replicas). Those parameters are set in DCS and in many cases can be applied without disrupting PostgreSQL or Patroni. Patroni sets a special flag called "pending restart" visible via the API when some of the values require the PostgreSQL restart. In that case, restart should be issued manually via the API.

Patroni SIGHUP or POST to /reload will make it re-read the configuration file.

See the :ref:`Patroni configuration <patroni_configuration>` for the details on which parameters can be changed and the order of processing difference configuration sources.

The configuration file format *has changed* since the v0.90. Patroni is still compatible with the old configuration files, but in order to take advantage of the bootstrap parameters one needs to change it. Users are encourage to update them by referring to the :ref:`dynamic configuration documentation page <dynamic_configuration>`.

**More flexible configuration***

- Make postgresql configuration and database name Patroni connects to configurable (Misja Hoebe)

Introduce `database` and `config_base_name` configuration parameters. Among others, it makes possible to run Patroni with PipelineDB and other PostgreSQL forks.

- Implement possibility to configure some Patroni configuration parameters via environment (Alexander Kukushkin)

Those include the scope, the node name and the namespace, as well as the secrets and makes it easier to run Patroni in a dynamic environment, i.e. Kubernetes Please, refer to the :ref:`supported environment variables <environment>` for further details.

- Update the built-in Patroni docker container to take advantage of environment-based configuration (Feike Steenbergen).

- Add Zookeeper support to Patroni docker image (Alexander Kukushkin)

- Split the Zookeeper and Exhibitor configuration options (Alexander Kukushkin)

- Make patronictl reuse the code from Patroni to read configuration (Alexander Kukushkin)

This allows patronictl to take advantage of environment-based configuration.

- Set application name to node name in primary_conninfo (Alexander Kukushkin)

This simplifies identification and configuration of synchronous replication for a given node.

**Stability, security and usability improvements**

- Reset sysid and do not call pg_controldata when restore of backup in progress (Alexander Kukushkin)

This change reduces the amount of noise generated by Patroni API health checks during the lengthy initialization of this node from the backup.

- Fix a bunch of pg_rewind corner-cases (Alexander Kukushkin)

Avoid running pg_rewind if the source cluster is not the master.

In addition, avoid removing the data directory on an unsuccessful rewind, unless the new parameter *remove_data_directory_on_rewind_failure* is set to true. By default it is false.

- Remove passwords from the replication connection string in DCS (Alexander Kukushkin)

Previously, Patroni always used the replication credentials from the Postgres URL in DCS. That is now changed to take the credentials from the patroni configuration. The secrets (replication username and password) and no longer exposed in DCS.

- Fix the asynchronous machinery around the demote call (Alexander Kukushkin)

Demote now runs totally asynchronously without blocking the DCS interactions.

- Make patronictl always send the authorization header if it is configured (Alexander Kukushkin)

This allows patronictl to issue "protected" requests, i.e. restart or reinitialize, when Patroni is configured to require authorization on those.

- Handle the SystemExit exception correctly (Alexander Kukushkin)

Avoids the issues of Patroni not stopping properly when receiving the SIGTERM

- Sample haproxy templates for confd (Alexander Kukushkin)

Generates and dynamically changes haproxy configuration from the patroni state in the DCS using confide

- Improve and restructure the documentation to make it more friendly to the new users (Lauri Apple)

- API must report role=master during pg_ctl stop (Alexander Kukushkin)

Makes the callback calls more reliable, particularly in the cluster stop case. In addition, introduce the `pg_ctl_timeout` option to set the timeout for the start, stop and restart calls via the `pg_ctl`.

- Fix the retry logic in etcd (Alexander Kukushkin)

Make retries more predictable and robust.

- Make Zookeeper code more resilient against short network hiccups (Alexander Kukushkin)

Reduce the connection timeouts to make Zookeeper connection attempts more frequent.

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Released 2016-04-27

This releases adds support for Consul, includes a new *noloadbalance* tag, changes the behavior of the *clonefrom* tag, improves *pg_rewind* handling and improves *patronictl* control program.

**Consul support**

- Implement Consul support (Alexander Kukushkin)

Patroni runs against Consul, in addition to Etcd and Zookeeper. the connection parameters can be configured in the YAML file.

**New and improved tags**

- Implement *noloadbalance* tag (Alexander Kukushkin)

This tag makes Patroni always return that the replica is not available to the load balancer.

- Change the implementation of the *clonefrom* tag (Alexander Kukushkin)

Previously, a node name had to be supplied to the *clonefrom*, forcing a tagged replica to clone from the specific node. The new implementation makes *clonefrom* a boolean tag: if it is set to true, the replica becomes a candidate for other replicas to clone from it. When multiple candidates are present, the replicas picks one randomly.

**Stability and security improvements**

- Numerous reliability improvements (Alexander Kukushkin)

Removes some spurious error messages, improves the stability of the failover, addresses some corner cases with reading data from DCS, shutdown, demote and reattaching of the former leader.

- Improve systems script to avoid killing Patroni children on stop (Jan Keirse, Alexander Kukushkin)

Previously, when stopping Patroni, *systemd* also sent a signal to PostgreSQL. Since Patroni also tried to stop PostgreSQL by itself, it resulted in sending to different shutdown requests (the smart shutdown, followed by the fast shutdown). That resulted in replicas disconnecting too early and a former master not being able to rejoin after demote. Fix by Jan with prior research by Alexander.

- Eliminate some cases where the former master was unable to call pg_rewind before rejoining as a replica (Oleksii Kliukin)

Previously, we only called *pg_rewind* if the former master had crashed. Change this to always run pg_rewind for the former master as long as pg_rewind is present in the system. This fixes the case when the master is shut down before the replicas managed to get the latest changes (i.e. during the "smart" shutdown).

- Numerous improvements to unit- and acceptance- tests, in particular, enable support for Zookeeper and Consul (Alexander Kukushkin).

- Make Travis CI faster and implement support for running tests against Zookeeper (Exhibitor) and Consul (Alexander Kukushkin)

Both unit and acceptance tests run automatically against Etcd, Zookeeper and Consul on each commit or pull-request.

- Clear environment variables before calling PostgreSQL commands from Patroni (Feike Steenbergen)

This prevents a possibility of reading system environment variables by connecting to the PostgreSQL cluster managed by Patroni.

**Configuration and control changes**

- Unify patronictl and Patroni configuration (Feike Steenbergen)

patronictl can use the same configuration file as Patroni itself.

- Enable Patroni to read the configuration from the environment variables (Oleksii Kliukin)

This simplifies generating configuration for Patroni automatically, or merging a single configuration from different sources.

- Include database system identifier in the information returned by the API (Feike Steenbergen)

- Implement *delete_cluster* for all available DCSs (Alexander Kukushkin)

Enables support for DCSs other than Etcd in patronictl.

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Released 2016-03-14

This release adds support for *cascading replication* and simplifies Patroni management by providing *scheduled failovers*. One may use older versions of Patroni (in particular, 0.78) combined with this one in order to migrate to the new release. Note that the scheduled failover and cascading replication related features will only work with Patroni 0.80 and above.

**Cascading replication**

- Add support for the *replicatefrom* and *clonefrom* tags for the patroni node (Oleksii Kliukin).

The tag *replicatefrom* allows a replica to use an arbitrary node a source, not necessary the master. The *clonefrom* does the same for the initial backup. Together, they enable Patroni to fully support cascading replication.

- Add support for running replication methods to initialize the replica even without a running replication connection (Oleksii Kliukin).

This is useful in order to create replicas from the snapshots stored on S3 or FTP. A replication method that does not require a running replication connection should supply *no_master: true* in the yaml configuration. Those scripts will still be called in order if the replication connection is present.

**Patronictl, API and DCS improvements**

- Implement scheduled failovers (Feike Steenbergen).

Failovers can be scheduled to happen at a certain time in the future, using either patronictl, or API calls.

- Add support for *dbuser* and *password* parameters in patronictl (Feike Steenbergen).

- Add PostgreSQL version to the health check output (Feike Steenbergen).

- Improve Zookeeper support in patronictl (Oleksandr Shulgin)

- Migrate to python-etcd 0.43 (Alexander Kukushkin)

**Configuration**

- Add a sample systems configuration script for Patroni (Jan Keirse).

- Fix the problem of Patroni ignoring the superuser name specified in the configuration file for DB connections (Alexander Kukushkin).

- Fix the handling of CTRL-C by creating a separate session ID and process group for the postmaster launched by Patroni (Alexander Kukushkin).

**Tests**

- Add acceptance tests with *behave* in order to check real-world scenarios of running Patroni (Alexander Kukushkin, Oleksii Kliukin).

The tests can be launched manually using the *behave* command. They are also launched automatically for pull requests and after commits.

Release notes for some older versions can be found on `project's github page <https://github.com/patroni/patroni/releases>`__.