[pgpool-hackers: 1558] Re: [pgpool-committers: 3203] pgpool: Adding new SHOW command for pgpool-II configuration parameters.
Muhammad Usama
m.usama at gmail.com
Wed May 11 18:01:56 JST 2016
On Wed, May 11, 2016 at 7:31 AM, Tatsuo Ishii <ishii at postgresql.org> wrote:
> Usama,
>
> It seems doc changes are not in your commit.
>
Yes, I will cover the documentation part after finishing the coding changes
as a separate commit.
Best regards
Muhammad Usama
> Best regards,
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese:http://www.sraoss.co.jp
>
> > Adding new SHOW command for pgpool-II configuration parameters.
> >
> > This is the next in series patch to add the SHOW and SET commands for
> pgpool-II
> > configuration parameters, similar to the PostgreSQL's SET and SHOW
> commands for
> > GUC variables. This patch adds the show variable functionality and for
> that it
> > adds a new syntax in pgpool which is similar to PostgreSQL's show
> variable
> > syntax with an addition of pgpool keyword at the start to distinguish the
> > pgpool's show command from PG's. Another reason for using the changed
> syntax
> > from the PG's show command is that there are some configuration
> parameter names
> > that are same in PostgreSQL and pgpool-II like "port",
> "log_min_messages"...
> > And if we use the same syntax without any difference, we would have no
> way of
> > telling if the command is referring to the pgpool-II or PG's config
> parameter.
> >
> > Although on most parts the PGPOOL SHOW command works similar to the
> > PG's SHOW command but below are some differences.
> >
> > -- syntax:
> > PGPOOL SHOW config_var_name;
> > PGPOOL SHOW all;
> >
> > -- config parameter with index:
> > Since unlike PostgreSQL pgpool-II also have config parameters that can be
> > assigned with multiple values using the index number at the end of a
> parameter
> > name (e.g. backend_port12). For all these type of variables if the index
> number
> > is supplied in PGPOOL SHOW command than the single value corresponding
> to that
> > index will be printed otherwise if index is not present at the end of
> variable
> > name the pgpool show command will print the values at all indexes for
> that
> > config parameter.
> >
> > -- group parameters.
> > There are some configuration parameters in pgpool-II that can be
> considered as
> > part of a logical group. For example the parameters to configure the
> backend
> > servers and parameters to configure the watchdog nodes. Providing the
> logical
> > group name in pgpool show command will print the values of all config
> parameters
> > belonging to that particular group.
> >
> > For example:
> > postgres=# pgpool show backend;
> > item | value |
> description
> >
> -------------------------+-------------------------------+-----------------------------------------------
> > backend_hostname0 | 127.0.0.1 | hostname or IP
> address of PostgreSQL backend.
> > backend_port0 | 5434 | port number of
> PostgreSQL backend.
> > backend_weight0 | 0 | load balance
> weight of backend.
> > backend_data_directory0 | /var/lib/pgsql/data | data directory
> of the backend.
> > backend_flag0 | ALLOW_TO_FAILOVER | Controls
> various backend behavior.
> > backend_hostname1 | 192.168.0.1 | hostname or IP
> address of PostgreSQL backend.
> > backend_port1 | 5432 | port number of
> PostgreSQL backend.
> > backend_weight1 | 1 | load balance
> weight of backend.
> > backend_data_directory1 | /home/usama/work/installed/pg | data directory
> of the backend.
> > backend_flag1 | ALLOW_TO_FAILOVER | Controls
> various backend behavior.
> > (10 rows)
> >
> > Here in the above example the "backend" is the group name and 'pgpool
> show backend'
> > command lists the values of all parameters belonging to the backend
> group.
> >
> > This patch creates three logical config parameter groups.
> > 1- "backend": This group combines all the parameters related to the
> backend
> > server configurations
> > 2- "other_pgpool": This group contains the parameters for remote
> watchdog
> > node configurations.
> > 3- "heartbeat": Config parameters related to watchdog lifecheck node
> > configurations are part of this logical group.
> >
> > Apart from adding the new show variable command there are few other
> under the
> > hood changes and design decision made by this patch that requires a
> mentioning.
> >
> > -- The patch adds the new log level (FRONTEND_ONLY_ERROR) to elog API,
> that acts
> > as a non error type, message internally for pgpool-II (the code is
> returned to
> > the caller unlike the ERROR message where elog API performs a long jump)
> but is
> > forwarded to the front-end client as an ERROR message followed by the
> > ReadyForQuery message.
> > This new ereport(FRONTEND_ONLY_ERROR,...) can be used to terminate the
> current
> > query from a client with an error while keeping the client session
> intact.
> >
> > -- for the new syntax the patch uses the same parse node structure
> VariableShowStmt
> > used by PG's SHOW command but with the different node tag.
> > i.e. T_PgpoolVariableShowStmt instead of T_VariableShowStmt. This is
> specifically
> > done to make sure we make a minimum amount of changes in parser imported
> from the
> > PostgreSQL. Otherwise, keeping the parser of pgpool in-sync with
> PostgreSQL would
> > require more merging efforts.
> >
> > Branch
> > ------
> > master
> >
> > Details
> > -------
> >
> http://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=25dc79e478c24aa884a7be3eb5bc2af51dc6f396
> >
> > Modified Files
> > --------------
> > src/config/pool_config_variables.c | 1119 +-
> > src/include/parser/kwlist.h | 1 +
> > src/include/parser/nodes.h | 6 +-
> > src/include/pool_config_variables.h | 74 +-
> > src/include/utils/elog.h | 15 +-
> > src/include/utils/pool_process_reporting.h | 2 +
> > src/parser/gram.c | 49612
> +++++++++++++--------------
> > src/parser/gram.h | 716 +-
> > src/parser/gram.y | 17 +-
> > src/protocol/pool_proto_modules.c | 13 +
> > src/utils/error/elog.c | 44 +-
> > src/utils/pool_process_reporting.c | 103 +
> > 12 files changed, 25514 insertions(+), 26208 deletions(-)
> >
> > _______________________________________________
> > pgpool-committers mailing list
> > pgpool-committers at pgpool.net
> > http://www.pgpool.net/mailman/listinfo/pgpool-committers
>
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