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From: Cyrill Gorcunov via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: Serge Petrenko <sergepetrenko@tarantool.org>
Cc: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>,
	TML <tarantool-patches@dev.tarantool.org>
Subject: Re: [Tarantool-patches] [RFC] on downstream.lag design
Date: Wed, 2 Jun 2021 11:41:11 +0300	[thread overview]
Message-ID: <YLdEJ5xfwiupWxsF@grain> (raw)
In-Reply-To: <43b6b0d8-b5e9-e8e5-1b6d-ed550c674c11@tarantool.org>

On Wed, Jun 02, 2021 at 09:55:38AM +0300, Serge Petrenko wrote:
> What's wal_st? Is it a list of all sent out xrow.tms?

It is a new structure, where I will remember the last xrow.tms.
In previous version I kept there first synchro row timestamp.

> > 
> > Once ACK is obtained the lag set to some positive value [ev_now - xrow.tm].
> > This value remains immutable until new sync transaction is sent. On new
> > sync transaction we do the same -- asign value from row.tm and count
> > time until ACK is received.
> I'm not sure I understood it all correstly. Correct me if I'm wrong,
> here's how I unerstand it:
> You save xrow.tm in a list or something in relay, once sending the
> corresponding row out.
> When applier sends out an acks for the row, the ack contains the same
> xrow.tm received earlier.
> Relay, upon receiving an ack, finds the corresponding xrow.tm in list and
> removes it.
> Every time downstream.lag is read it is equal ev_now() - oldest xrow.tm in
> list.
> Is this right?

Kind of. I hasn't considered a list here but rather a single timestamp value
per relay. As we've discussed verbally instead I should think over moving
this tracking into txn_limbo instead. Gimme some time to propose a new design,
I'll post it here.

  reply	other threads:[~2021-06-02  8:41 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-01 22:02 Cyrill Gorcunov via Tarantool-patches
2021-06-02  6:55 ` Serge Petrenko via Tarantool-patches
2021-06-02  8:41   ` Cyrill Gorcunov via Tarantool-patches [this message]
2021-06-03 22:20   ` Cyrill Gorcunov via Tarantool-patches

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