Re: Measuring replay lag

On Thu, Dec 29, 2016 at 1:28 AM, Thomas Munro
<thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> On Thu, Dec 22, 2016 at 10:14 AM, Thomas Munro
> <thomas(dot)munro(at)enterprisedb(dot)com> wrote:
>> On Thu, Dec 22, 2016 at 2:14 AM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
>>> I agree that the capability to measure the remote_apply lag is very useful.
>>> Also I want to measure the remote_write and remote_flush lags, for example,
>>> in order to diagnose the cause of replication lag.
>>
>> Good idea. I will think about how to make that work.
>
> Here is an experimental version that reports the write, flush and
> apply lag separately as requested. This is done with three separate
> (lsn, timestamp) buffers on the standby side. The GUC is now called
> replication_lag_sample_interval. Not tested much yet.

Here is a new version that is slightly refactored and fixes a problem
with stale samples after periods of idleness.

--
Thomas Munro
http://www.enterprisedb.com