Not all configs returned from CONFIG GET * are settable by config set. (Error in documentation?)

[AlexanderB]

The docs for config set (https://redis.io/commands/config-set) state:

"The list of configuration parameters supported by CONFIG SET can be obtained issuing a CONFIG GET * command, that is the symmetrical command used to obtain information about the configuration of a running Redis instance."

However after a bit of trial and error, it appears that for redis 3.2 at least, the following options are returned from CONFIG GET * but are not settable via CONFIG SET. 

The following options return ERR Unsupported CONFIG parameter
port 

tcp-backlog

databases

daemonize

rdbchecksum

supervised

syslog-facility 

unixsocketperm

bind

These configs could just be removed from the return value of conget get * if it can be classified as a straight up bug and hopefully no one is explictly relying on it. 

[Itamar Haber]

I think that the doc should be changed. These config directive are (most at least) good to have via get. The fact that they can't be changed in runtime is less important imo.

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[Jan-Erik Rediger]

I'm with Itamar here, it is still useful to have them. We should change
the documentation (also: removing them would be a breaking change)

On Tue, Aug 01, 2017 at 11:50:43PM +0300, Itamar Haber wrote:
> I think that the doc should be changed. These config directive are (most at
> least) good to have via get. The fact that they can't be changed in runtime
> is less important imo.
>
> On Aug 1, 2017 11:38 PM, "AlexanderB" <alb...@demonware.net> wrote:
>
> > The docs for config set (https://redis.io/commands/config-set) state:
> >
> > "The list of configuration parameters supported by CONFIG SET

> > <https://redis.io/commands/config-set> can be obtained issuing a CONFIG

> > GET * command, that is the symmetrical command used to obtain information
> > about the configuration of a running Redis instance."
> >
> > However after a bit of trial and error, it appears that for redis 3.2 at
> > least, the following options are returned from CONFIG GET * but are not
> > settable via CONFIG SET.
> >
> > The following options return ERR Unsupported CONFIG parameter
> > port
> > tcp-backlog
> > databases
> > daemonize
> > rdbchecksum
> > supervised
> > syslog-facility
> > unixsocketperm
> > bind
> >
> > These configs could just be removed from the return value of conget get *
> > if it can be classified as a straight up bug and hopefully no one is
> > explictly relying on it.
> >
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[Itamar Haber]

I think the honor of making this PR to redis-doc should be Mr. Boyd's, unless he is gracious/laptopless and assigns it to the void and then I'd be happy to help ;)

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[AlexanderB]

The problem with just changing the documentation is that CONFIG GET * does already hide some config variables but not all. 

For instance while CONFIG GET * will return the value of "syslog-facility"  (https://github.com/antirez/redis/blob/unstable/src/config.c#L1324) none of the other syslog option such as "syslog-enabled" or "syslog-ident" are returned.

I think that leaves us in a situation where we would need to make a change to source to either return all values unfiltered for what can be set dynamically, or fix the filter. Leaving the filter inconsistently applied is the worst of both worlds.

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[Jan-Erik Rediger]

then we should change the code to return _all_ options.

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[hva...@gmail.com]

I suggest that CONFIG GET * returns all options, but a second argument (perhaps CONFIG GET * settable) will filter the output to have only those options that can be changed by CONFIG SET.

[AlexanderB]

Having CONFIG GET * return all options, and another flag to filter out only the ones that are settable dynamically seems the best option to me as well. I'll dig a bit more into the source and see what it would take for me to add a new test and this functionality.