<p dir="ltr">Hi Tatsuo, </p>
<p dir="ltr">Any additional feedback on the updated patches submitted by Usama? Usama is working on the last piece of this effort. It will be good to get this functionality integrated in the main branch in January.</p>
<p dir="ltr">-- Ahsan<br>
</p>
<div class="gmail_quot<blockquote class=" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi Tatsuo<div><br></div><div>Thanks a bundle for looking into the patch.<br><div class="gmail_extra">
<br><br><div class="gmail_quote">On Sat, Dec 14, 2013 at 2:35 PM, Tatsuo Ishii <span dir="ltr"><<a href="mailto:ishii@postgresql.org" target="_blank">ishii@postgresql.org</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">Usama,<br>
<br>
Thanks for the great work.<br>
I have take a look at your patches.<br>
<br>
Compiling the source code:<br>
<br>
I see some "//" comments. I believe they are temporary ones. We follow<br>
the PostgreSQL coding standard and it does not allow to use "//"<br>
comments. I also see some compiler warnings because of function<br>
prototypes are not declared.<br></blockquote><div><br></div><div>Yes I intend to follow the PostgreSQL coding style and standards, the "//" style comments were left</div><div>in the code unintentionally, and I had this thing in the mind and last TODO of this effort is to clean up</div>
<div>the code for these kind of mistakes. </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<br>
I noticed you commented out following line which causes lots of<br>
compiler warnings. Is that intended?<br>
<br>
extern size_t strlcpy(char *dst, const char *src, size_t siz);<br></blockquote><div><br></div><div>Actually I use Mac OS/X for development and since OS/X is BSD based which already</div><div>contains the native strlcpy function defined in string.h, So I was getting the compilation error.</div>
<div><br></div><div>Please find the attached patch (strlcpy_fix.patch) to properly fix this problem, The patch adds the check</div><div>in configure to test if strlcpy is provided by OS and in that case does not externs the function in pool.h.</div>
<div>Since this issue also exists in the master branch so If you feel the comfortable with the patch and the fix</div><div>,can you please also apply this on master branch. </div><div>Note: You will require to run the autoconf after this patch.</div>
<div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div><br>
> pgpool_main.c PgpoolMain()<br>
><br>
> The patch changes the flow of how health check failures are processed,<br>
> health_check() function which<br>
> previously used to return health check failing node number or success is<br>
> changed to do_health_check(),<br>
> which reports an error through ereport in case of failed health check on<br>
> backend node and than the failure is<br>
> processed by "process_backend_health_check_failure()" function.<br>
> This portion of the code requires the most review and suggestions, Since<br>
> there are many different<br>
> ways to implement this health checking.<br>
<br>
</div>I saw followings:<br>
<br>
LOG: starting health check<br>
LOCATION: pgpool_main.c:369<br>
LOG: after retry 0, All backends are returned to healthy state<br>
LOCATION: pgpool_main.c:411<br>
<br>
Before "starting health check" message was debug message and should<br>
remain debug IMO. Otherwise they flood the log file.<br>
<br>
I also see problem with "after retry 0, All backends are returned to<br>
healthy state" message since the message appears even there's no retry<br>
(again before we do not spit the message if we are not doing retry).<br></blockquote><div><br></div><div>Thanks for pointing these. The 2nd attached patch "exmgr_fix.patch" tries to fix these, which can be applied</div>
<div>on EXCEPTION_MGR development branch.</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<br>
Most importantly, the message style is pretty different from current<br>
one. no timestamp, no pid.<br></blockquote><div><br></div><div>Yes this one is known thing, I some how missed to point it out specifically. This is the part of the TODO item mentioned</div><div>upthread "changes and cleanup of elog.c and elog.h". I have intentionally left it as a last item because it deals mostly with</div>
<div>cosmetic issues. Apart from that this TODO item also have couple of more things which are needed to be done</div><div>by elog api. e.g. adding the configuration parameters similar to PostgreSQL's <br>log_min_error_statement, log_min_messages, client_min_messages to control the level of message generated and reported by pgpool.</div>
<div><br></div><div><br></div><div><br></div><div>Thanks</div><div>Muhammad Usama</div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div>
> Another way could be to use PG_TRY and PG_CATCH inside health_check<br>
> function and if<br>
> "make_persistent_db_connection()" throws an error, the PG_CATCH block<br>
> catches the error<br>
> and return the failing node number<br>
><br>
> something like<br>
><br>
> health_check()<br>
> {<br>
> ....<br>
> for(i =0; i< MAX_BACKEND; i++)<br>
> PG_TRY()<br>
> {<br>
> make_persistent_db_connection();<br>
> ...<br>
> }<br>
> PG_CATCH();<br>
> {<br>
> ....<br>
> return i;<br>
> }<br>
> PG_END_TRY();<br>
> return 0;<br>
> }<br>
><br>
><br>
> And than the main loop process the failure, the similar way it it<br>
> processing it now (with out the patch).<br>
> But the current approach followed by the patch seems to come more natural<br>
> with the exception manager<br>
> and yet on the negative side the current approach requires to add a state<br>
> machine to the main loop.<br>
<br>
</div>Agreed.<br>
<div><div><br>
> So suggestions and comments on this portion of code and implementation<br>
> approach would be very helpful.<br>
><br>
> pgpool child process loop<br>
> ==================<br>
> src/protocol/child.c do_child()<br>
><br>
> do_child() function is the work horse of pg_pool child process, and<br>
> basically contains two loops those<br>
> spans the life cycle of child process. First step is to wait for the client<br>
> connection, and once this part<br>
> is successful, the child is connected with the front end, the process goes<br>
> into the query process mode.<br>
> So I have used two memory contexts instead of one per loop memory context<br>
> for this process.<br>
> QueryProcessMemoryContext and ChildLoopMemoryContext, where later is used<br>
> for the pahse<br>
> where child is waiting for the front end connections and the former is for<br>
> the query process phase.<br>
><br>
> Secondly for the query processing function all my current code browsing<br>
> leads me to the believe that<br>
> although "pool_process_query()" caller has handled five possible return<br>
> values from the function<br>
> i.e POOL_END, POOL_ERROR, POOL_FATAL, POOL_IDLE and POOL_CONTINUE.<br>
> But in actual the function returns only POOL_END, POOL_ERROR and the<br>
> success which is<br>
> POOL_CONTINUE. and to squeeze in the managers in query processing function<br>
> I have moved forward<br>
> with the above mentioned assumptions. Also my current code understanding on<br>
> child process flow is when<br>
> ever some error occurs in query process phase of child process that error<br>
> actually terminates that particular client<br>
> So I have added the below code in elog.c file to treat the ERROR in child<br>
> process as FATAL in case the<br>
> front end clint is connected with the child process.<br>
><br>
> if(elevel == ERROR)<br>
> {<br>
> if(processType == PT_CHILD)<br>
> {<br>
> /*<br>
> * If the frontend connection exists, treat this error as FATAL<br>
> */<br>
> if(is_session_connected())<br>
> elevel = FATAL;<br>
> }<br>
> }<br>
><br>
> Reviews comments and suggestions are most welcome<br>
><br>
> Thanks<br>
><br>
> Muhammad Usama<br>
</div></div></blockquote></div><br></div></div></div>
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