作者
digoal
日期
2021-04-08
标签
PostgreSQL , pg_wait_for_backend_termination
背景
pg_wait_for_backend_termination(pid, ms), 发送terminate信号给进程, 并等待若干ms, 如果PID未被kill, 则返回false和warning.
之前的版本terminate pid时, 不等待, 只发信号, 也不知道pid是否真实被kill.
+ * Wait until there is no backend process with the given PID and return true.
+ * On timeout, a warning is emitted and false is returned.
+ */
+static bool
+pg_wait_until_termination(int pid, int64 timeout)
+{
+ /*
+ * Wait in steps of waittime milliseconds until this function exits or
+ * timeout.
+ */
+ int64 waittime = 100;
+ /*
+ * Initially remaining time is the entire timeout specified by the user.
+ */
+ int64 remainingtime = timeout;
+
+ /*
+ * Check existence of the backend. If the backend still exists, then wait
+ * for waittime milliseconds, again check for the existence. Repeat this
+ * until timeout or an error occurs or a pending interrupt such as query
+ * cancel gets processed.
+ */
+ do
+ {
+ if (remainingtime < waittime)
+ waittime = remainingtime;
+
+ if (kill(pid, 0) == -1)
+ {
+ if (errno == ESRCH)
+ return true;
+ else
+ ereport(ERROR,
+ (errcode(ERRCODE_INTERNAL_ERROR),
+ errmsg("could not check the existence of the backend with PID %d: %m",
+ pid)));
+ }
+
+ /* Process interrupts, if any, before waiting */
+ CHECK_FOR_INTERRUPTS();
+
+ (void) WaitLatch(MyLatch,
+ WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+ waittime,
+ WAIT_EVENT_BACKEND_TERMINATION);
+
+ ResetLatch(MyLatch);
+
+ remainingtime -= waittime;
+ } while (remainingtime > 0);
+
+ ereport(WARNING,
+ (errmsg("backend with PID %d did not terminate within %lld milliseconds",
+ pid, (long long int) timeout)));
+
+ return false;
+}
+ </para>
+ <para>
+ If <parameter>timeout</parameter> is not specified or zero, this
+ function returns <literal>true</literal> whether the process actually
+ terminates or not, indicating only that the sending of the signal was
+ successful. If the <parameter>timeout</parameter> is specified (in
+ milliseconds) and greater than zero, the function waits until the
+ process is actually terminated or until the given time has passed. If
+ the process is terminated, the function
+ returns <literal>true</literal>. On timeout a warning is emitted and
+ <literal>false</literal> is returned.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_wait_for_backend_termination</primary>
+ </indexterm>
+ <function>pg_wait_for_backend_termination</function> ( <parameter>pid</parameter> <type>integer</type>, <parameter>timeout</parameter> <type>bigint</type> <literal>DEFAULT</literal> <literal>5000</literal> )
+ <returnvalue>boolean</returnvalue>
+ </para>
+ <para>
+ Waits for the backend process with the specified Process ID to
+ terminate. If the process terminates before
+ the <parameter>timeout</parameter> (in milliseconds)
+ expires, <literal>true</literal> is returned. On timeout, a warning
+ is emitted and <literal>false</literal> is returned.
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=aaf043257205ec523f1ba09a3856464d17cf2281
```
Add functions to wait for backend termination
author Magnus Hagander magnus@hagander.net
Thu, 8 Apr 2021 09:32:14 +0000 (11:32 +0200)
committer Magnus Hagander magnus@hagander.net
Thu, 8 Apr 2021 09:40:54 +0000 (11:40 +0200)
commit aaf043257205ec523f1ba09a3856464d17cf2281
tree 61ed249bb2622454f53511d051dc1508980ab8e3 tree
parent fb310f17812e7321599845a29af2f36c7f1191c3 commit | diff
Add functions to wait for backend termination
This adds a function, pg_wait_for_backend_termination(), and a new
timeout argument to pg_terminate_backend(), which will wait for the
backend to actually terminate (with or without signaling it to do so
depending on which function is called). The default behaviour of
pg_terminate_backend() remains being timeout=0 which does not waiting.
For pg_wait_for_backend_termination() the default wait is 5 seconds.
Author: Bharath Rupireddy
Reviewed-By: Fujii Masao, David Johnston, Muhammad Usama,
Hou Zhijie, Magnus Hagander
Discussion: https://postgr.es/m/CALj2ACUBpunmyhYZw-kXCYs5NM+h6oG_7Df_Tn4mLmmUQifkqA@mail.gmail.com
```
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