Support "options" in ignore_startup_parameters again

[JelteF]

By supporting parsing the options startup parameter, we accidentally
stopped supporting using it in ignore_startup_parameters.

Users have put options in ignore_startup_parameters and so upgrading
to 1.20.0 might break their existing connection strings, if the actual
options that are contained in the options startup parameter are
unsupported.

This changes the parsing of options to allow any unsupported parameter
if options itself is in ignore_startup_parameters.

NOTE: There's other failure paths in the options startup parameter
parsing that could still trigger now even though options is in
ignore_startup_parameters:

• too long parameter
• non -c parameter
• options would have been unparsable by PostgreSQL too

But honestly those seem unlikely enough that I think it's better to
error for them than to ignore those errors.

Fixes #907

[emelsimsek]

Changes look good in restoring the compatibility with previous versions.

As a separate note, ignore_startup_parameters documentation is confusing to me. What does it mean that ignored parameters are handled by admin? I expect them not being cached but passed to postgres as they are.

ignore_startup_parameters
By default, PgBouncer allows only parameters it can keep track of in startup packets: client_encoding, datestyle, timezone and standard_conforming_strings. All others parameters will raise an error. To allow others parameters, they can be specified here, so that PgBouncer knows that they are handled by the admin and it can ignore them.

If you need to specify multiple values, use a comma-separated list (e.g. options,extra_float_digits)

[eulerto]

@JelteF The patch looks good to me. However, I have 2 suggestions:

• add a comment in the set_startup_options function describing the behavior of options value in ignore_startup_parameters.
• we should better document the options parameter. The commit dff974f does not add any documentation. I'm not sure exactly where to add it. Maybe in the ignore_startup_parameters as a new paragraph.

[JelteF]

Added the docs. Merging this now.

[torstenfohrer]

Hi, i trying to get pgbouncer work with some software that send following

And nothing set in ignore_startup_parameters=options,client_encoding,standard_conforming_strings will get around it.

Looking at code you try to find first -c option=value and then look if options is set in ignore_startup_parameters