Re: waiting for client write

From: Ayub Khan <ayub(dot)hp(at)gmail(dot)com>
To: Pgsql Performance <pgsql-performance(at)lists(dot)postgresql(dot)org>
Subject: Re: waiting for client write
Date: 2021-06-11 18:19:19
Message-ID: CAHdeyEL6iJebkHmNEX=0QYLKcXJjosaDsCRqx7NZxRbpcQHDmw@mail.gmail.com
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Ranier,

I verified the link you gave and also checked AWS documentation and found
the exact output as shown in AWS:

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/network_mtu.html

[ec2-user ~]$ tracepath amazon.com
1?: [LOCALHOST] pmtu 9001
1: ip-xxx-xx-xx-1.us-west-1.compute.internal (xxx.xx.xx.x) 0.187ms pmtu 1500

Should the LOCALHOST pmtu needs to be updated to 1500 ?

On Wed, Jun 9, 2021 at 5:47 PM Ayub Khan <ayub(dot)hp(at)gmail(dot)com> wrote:

> attached is the screenshot of RDS performance insights for AWS and it
> shows high waiting client writes. The api performance is slow. I read that
> this might be due to IOPS on RDS. However we have 80k IOPS on this test
> RDS.
>
> Below is the query which is being load tested
>
> SELECT
>
> a.menu_item_id,
> a.menu_item_name,
> a.menu_item_category_id,
> b.menu_item_category_desc,
> c.menu_item_variant_id,
> c.menu_item_variant_type_id,
> c.price,
> c.size_id,
> c.parent_menu_item_variant_id,
> d.menu_item_variant_type_desc,
> e.size_desc,
> f.currency_code,
> a.image,
> a.mark_id,
> m.mark_name
>
> FROM .menu_item_category AS b, .menu_item_variant AS
> c,
> .menu_item_variant_type AS d, .item_size AS e,
> .restaurant AS f,
> .menu_item AS a
>
> LEFT OUTER JOIN .mark AS m
> ON (a.mark_id = m.mark_id)
>
> WHERE a.menu_item_category_id =
> b.menu_item_category_id AND a.menu_item_id = c.menu_item_id AND
> c.menu_item_variant_type_id =
> d.menu_item_variant_type_id AND d.is_hidden = 'false' AND
> c.size_id = e.size_id AND a.restaurant_id =
> f.restaurant_id AND f.restaurant_id = 1528 AND
> (a.menu_item_category_id = NULL OR NULL IS NULL)
>
> AND c.menu_item_variant_id = (SELECT
> min(menu_item_variant_id)
> FROM
> .menu_item_variant
> WHERE
> menu_item_id = a.menu_item_id AND deleted = 'N'
> LIMIT 1) AND
> a.active = 'Y'
> AND (CONCAT_WS('', ',', a.hidden_branch_ids,
> ',') NOT LIKE CONCAT_WS('', '%,4191,%') OR
> NULL IS NULL)
> AND .is_menu_item_available(a.menu_item_id, 'Y') = 'Y'
>
> ORDER BY a.row_order, menu_item_id;
>
> --Ayub
>

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