Werk #15645: postgres: Fix Internal error: 'NoneType' object has no attribute 'value_to_json_safe'

In Werk 16016, an incompatible change to rule PostgreSQL database and sessions (Linux, Windows) was introduced. This Werk caused multiple regression bugs, particularly affecting users with existing rulesets.

If a user upgraded to 2.1.0p33 and had an existing rule PostgreSQL database and sessions (Linux, Windows), then the would see the following error during upgrade:

- ERROR: Failed to transform rule: (Ruleset: agent_config:mk_postgres, ...}}:

Moreover, if users tried to address the issue by editing the rule, then the following error was shown:

Internal error: 'NoneType' object has no attribute 'value_to_json_safe'

With this Werk, the configuration is automatically migrated to the new format and the errors should no longer occur. Users, whom upgraded to 2.2.0p8 were not affected by this problem.

If a user updated the agent plugin mk_postgres.py with means other than the bakery, then they would encounter the following error while executing mk_postgres.py:

ValueError: not enough values to unpack (expected 4, got 3)

This error could be addressed by adopting the postgres.cfg in the ways described by Werk 16016. However, if the environment file was called .env, then another error might occur:

ValueError: Instance name can not be inferred from .env file, instance name should be specified explicitly

With this Werk, these errors no longer occur. Both, old configuration files and configuration files where the instance name is empty, are considered to be valid. The absence of an instance name is handled in the same way it was handled before Werk 16016.

Note, that an empty instance is still a mistake. If you are affected by any of the two errors above, it is recommended to migrate to the configuration format and to specify a non-empty instance name explicitely. For example, let's assume your configuration file contains this line:

INSTANCE=/home/postgres/db1.env:USER_NAME:/PATH/TO/.pgpass

Then, you can find the instance name by taking the environment file path (/home/postgres/db1.env), removing the directory (db1.env), and removing everything after the . (db1). Thus, the new format is equivalent to:

INSTANCE=/home/postgres/db1.env:USER_NAME:/PATH/TO/.pgpass:db1

Sometimes, this may fail if your instance name is empty. For example,

INSTANCE=/home/postgres/.env:USER_NAME:/PATH/TO/.pgpass

would result in

INSTANCE=/home/postgres/.env:USER_NAME:/PATH/TO/.pgpass:

With this version of mk_postgres.py this configuration is allowed again, but it is not recommended. You view your instances, by creating a psql session and using the command

postgres-# \l

Additionally, Werk 15644 fixes the crash of the postgres_instances check.

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