Thoughts on vttablet required credentials and configuration

[sjmudd]

When setting up vttablet for the first time a new user is quite overwhelmed with the number of startup options. One of them is simply about which credentials are needed and how to provide them. Also how the connection to mysqld is expected to take place.

Probably a section in the docs should say:

• the list of user types that are required, and their required grants (you have this in one of the init files but it's easy to not find it)
• the configuration parameters required to talk with these users to mysql in vtgate:

e.g.

...
        -db-config-allprivs-charset $CHARSET \
        -db-config-allprivs-dbname $KEYSPACE \
        -db-config-allprivs-uname $ALLPRIVS_USER \
        -db-config-allprivs-unixsocket $SOCKET \
        -db-config-app-charset $CHARSET \
        -db-config-app-dbname $KEYSPACE \
        -db-config-app-uname  $APP_USER \
        -db-config-app-unixsocket $SOCKET \
        -db-config-dba-charset $CHARSET \
        -db-config-dba-dbname $KEYSPACE \
        -db-config-dba-uname $DBA_USER \
        -db-config-dba-unixsocket $SOCKET \
        -db-config-filtered-charset $CHARSET \
        -db-config-filtered-dbname $KEYSPACE \
        -db-config-filtered-uname $FILTERED_USER \
        -db-config-filtered-unixsocket $SOCKET \
        -db-config-repl-charset $CHARSET \
        -db-config-repl-dbname $KEYSPACE \
        -db-config-repl-uname $LEGACY_REPL_USER \
        -db-config-repl-flags $REPL_FLAGS \
        -db-credentials-file $CREDENTIALS_FILE \
        -db-credentials-server file \
...

include in the same place an example of the credentials file.

I noticed that -enable_replication_reporter is needed to make the tablet "serve" and if this information is not available then the tablet will not be usable for serving traffic (or that's what it seems to me).

This option is good to temporarily get some log output to watch

       -alsologtostderr \

-tablet_path was not clear. There seems to be a need to reference a tablet by keyspace and UID, the latter being a unique identifier and this needs to be in a specific format, something like <keyspace>-<uid> with UID being that numeric value. This doesn't seem well explained but once seen or described it's easy to set this value to something that works.

For someone setting this up for the first time I think help putting this information in one place would be very good.

[alainjobart]

I agree the number of parameters is overwhelming and not intuitive.

Some documentation exists there:
http://vitess.io/user-guide/server-configuration.html
But it's not complete. We need to make this simpler.

[michael-berlin]

I didn't know about that page :) That answers already a lot of questions.

Regarding flags: I suggest that we enable more flags by default e.g. -enable_replication_reporter is an obvious candidate.

[sougou]

For db configs, we should require only one set of connection parameters. The rest should be just user credentials.

[michael-berlin]

Other thoughts:

• We should get rid of the VTDATAROOT environment variable. Our configuration should not depend on any environment variable.
• tablet_path should not just refer to the subdirectory below $VTDATAROOT, but the full path instead. Everything else is confusing IMO. The old behavior only makes sense for tests IMO or am I overlooking something here?

[alainjobart]

@michael-berlin See the cl with the doc changes I just sent, I think VTDATAROOT is useful to have the symlinks to different partitions for different data types (bin-logs on spindle, ...). I am not sure of an easy way to do something similar with just tablet_dir.

Maybe changing it to a command line though?