Re: [HACKERS] Proposal : For Auto-Prewarm.

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От Neha Sharma
Тема Re: [HACKERS] Proposal : For Auto-Prewarm.
Дата
Msg-id CANiYTQsraV04hOZk=eXRZt6SWiWvqzH+KweaZEcJcsF52y0E3A@mail.gmail.com
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Ответы Re: [HACKERS] Proposal : For Auto-Prewarm.  (Mithun Cy <mithun.cy@enterprisedb.com>)
Список pgsql-hackers
Hi,

I have been testing this feature for a while and below are the observations for few scenarios.

Observation:
scenario 1: If we set pg_prewarm.dump_interval = -1.0,we get an additional warning message in logfile and instead of ending the task of auto-dump it executes successfully.
[centos@test-machine bin]$ more logfile 
2017-06-06 08:39:53.127 GMT [21905] WARNING:  invalid value for parameter "pg_prewarm.dump_interval": "-1.0"
2017-06-06 08:39:53.127 GMT [21905] HINT:  Valid units for this parameter are "ms", "s", "min", "h", and "d".
2017-06-06 08:39:53.127 GMT [21905] LOG:  listening on IPv6 address "::1", port 5432
2017-06-06 08:39:53.127 GMT [21905] LOG:  listening on IPv4 address "127.0.0.1", port 5432
2017-06-06 08:39:53.130 GMT [21905] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"
2017-06-06 08:39:53.143 GMT [21906] LOG:  database system was shut down at 2017-06-06 08:38:20 GMT
2017-06-06 08:39:53.155 GMT [21905] LOG:  database system is ready to accept connections
2017-06-06 08:39:53.155 GMT [21912] LOG:  autoprewarm has started
[centos@test-machine bin]$ ps -ef | grep prewarm
centos   21912 21905  0 08:39 ?        00:00:00 postgres: bgworker: autoprewarm                            
[centos@test-machine bin]$ ./psql postgres 
psql (10beta1)
Type "help" for help.

postgres=# show pg_prewarm.dump_interval;
 pg_prewarm.dump_interval 
--------------------------
 5min
(1 row)

scenario 2: If we set pg_prewarm.dump_interval = 0.0,we get an additional warning message in logfile and the message states that the task was started and the worker thread it is also active,but the dump_interval duration is set to default 5 min (300 sec) instead of 0.

[centos@test-machine bin]$ ps -ef | grep prewarm
centos   21980 21973  0 08:54 ?        00:00:00 postgres: bgworker: autoprewarm                            

[centos@test-machine bin]$ more logfile 
2017-06-06 09:20:52.436 GMT [22223] WARNING:  invalid value for parameter "pg_prewarm.dump_interval": "0.0"
2017-06-06 09:20:52.436 GMT [22223] HINT:  Valid units for this parameter are "ms", "s", "min", "h", and "d".
2017-06-06 09:20:52.436 GMT [22223] LOG:  listening on IPv6 address "::1", port 5432
2017-06-06 09:20:52.437 GMT [22223] LOG:  listening on IPv4 address "127.0.0.1", port 5432
2017-06-06 09:20:52.439 GMT [22223] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"
2017-06-06 09:20:52.452 GMT [22224] LOG:  database system was shut down at 2017-06-06 09:19:49 GMT
2017-06-06 09:20:52.455 GMT [22223] LOG:  database system is ready to accept connections
2017-06-06 09:20:52.455 GMT [22230] LOG:  autoprewarm has started

[centos@test-machine bin]$ ./psql postgres 
psql (10beta1)
Type "help" for help.

postgres=# show pg_prewarm.dump_interval;
 pg_prewarm.dump_interval 
--------------------------
 5min
(1 row)


On Mon, Jun 5, 2017 at 8:06 PM, Robert Haas <robertmhaas@gmail.com> wrote:
On Mon, Jun 5, 2017 at 7:58 AM, Rafia Sabih
<rafia.sabih@enterprisedb.com> wrote:
> I had a look at the patch from stylistic/formatting point of view,
> please find the attached patch for the suggested modifications.

Many of these seem worse, like these ones:

-         * Quit if we've reached records for another database. Unless the
+         * Quit if we've reached records of another database. Unless the

-         * When we reach a new relation, close the old one.  Note, however,
-         * that the previous try_relation_open may have failed, in which case
-         * rel will be NULL.
+         * On reaching a new relation, close the old one.  Note, that the
+         * previous try_relation_open may have failed, in which case rel will
+         * be NULL.

-         * Try to open each new relation, but only once, when we first
-         * encounter it.  If it's been dropped, skip the associated blocks.
+         * Each relation is open only once at it's first encounter. If it's
+         * been dropped, skip the associated blocks.

Others are better, like these:

-                (errmsg("could not continue autoprewarm worker is
already running under PID %d",
+                (errmsg("autoprewarm worker is already running under PID %d",

- * Start of prewarm per-database worker. This will try to load blocks of one
+ * Start prewarm per-database worker, which will load blocks of one

Others don't really seem better or worse, like:

-         * Register a per-database worker to load new database's block. And
-         * wait until they finish their job to launch next one.
+         * Register a per-database worker to load new database's block. Wait
+         * until they finish their job to launch next one.

IMHO, there's still a good bit of work needed here to make this sound
like American English.  For example:

- *        It is a bgworker which automatically records information about blocks
- *        which were present in buffer pool before server shutdown and then
- *        prewarm the buffer pool upon server restart with those blocks.
+ *        It is a bgworker process that automatically records information about
+ *        blocks which were present in buffer pool before server
shutdown and then
+ *        prewarms the buffer pool upon server restart with those blocks.

This construction "It is a..." without a clear referent seems to be
standard in Indian English, but it looks wrong to English speakers
from other parts of the world, or at least to me.

+     * Since there could be at max one worker who could do a prewarm, hence,
+     * acquiring locks is not required before setting skip_prewarm_on_restart.

To me, adding a comma before hence looks like a significant
improvement, but the word hence itself seems out-of-place.  Also, I'd
change "at max" to "at most" and maybe reword the sentence a little.
There's a lot of little things like this which I have tended be quite
strict about changing before commit; I occasionally wonder whether
it's really worth the effort.  It's not really wrong, it just sounds
weird to me as an American.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


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Regards,

Neha Sharma

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