<div dir="ltr">Hello Avi.<div><br></div><div>I check standby node is up, with postgresql service running, and configured as slave server. I check "select * from pg_stat_replication".</div><div><br></div><div>Regards.</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Jun 24, 2016 at 6:33 AM, 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:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Assuming that you are attaching standby node.<br>
<br>
> When is it safe to attach a detached node? What do I need to check before attaching a node (I have one master one slave setup)?<br>
<br>
In summary, the detaching PostgreSQL standby should be running<br>
normally.<br>
<br>
First of all, you need to make sure that the detaching PostgreSQL<br>
standby node is up and running.<br>
<br>
Next you need to make sure that the standby node properly connects to<br>
the primary PostgreSQL server. You can check it by looking at<br>
pg_stat_replication view for example.<br>
<br>
> * Do I need to make sure replication lag is 0? If I attach a slave when replication lag is not 0 what problems can arise (if any)<br>
<br>
If the standby proper connects to the primary, even if replication lag<br>
is not 0, it is expected that it wil eventually become 0.<br>
<br>
The risk with replication lag is that SELECT might return outdated<br>
data but you could mitigate the problem by using delay_threshold<br>
parameter.<br>
<br>
> * Before I attach a node do I need to check the state of the other node?<br>
<br>
No.<br>
<br>
> * What other checks to I need to do before attaching a node?<br>
<br>
Best regards,<br>
--<br>
Tatsuo Ishii<br>
SRA OSS, Inc. Japan<br>
English: <a href="http://www.sraoss.co.jp/index_en.php" rel="noreferrer" target="_blank">http://www.sraoss.co.jp/index_en.php</a><br>
Japanese:<a href="http://www.sraoss.co.jp" rel="noreferrer" target="_blank">http://www.sraoss.co.jp</a><br>
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</blockquote></div><br></div>