From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
---|---|
To: | Hannu Krosing <hannu(at)2ndquadrant(dot)com> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Sync Rep Design |
Date: | 2010-12-31 10:06:12 |
Message-ID: | 4D1DAB14.5000800@enterprisedb.com |
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Lists: | pgsql-hackers |
On 31.12.2010 09:50, Hannu Krosing wrote:
> On 30.12.2010 22:27, Robert Haas wrote:
>> On Thu, Dec 30, 2010 at 2:04 PM, Simon Riggs<simon(at)2ndquadrant(dot)com>
>> wrote:
>>> synchronous_replication (boolean)
>>> Specifies whether transaction commit will wait for WAL records
>>> to be replicated before the command returns a "success"
>>> indication to the client.
>> The word "replicated" here could be taken to mean different things,
>> most obviously:
>>
>> - slave has received the WAL
>> - slave has fsync'd the WAL
>> - slave has applied the WAL
> Perhaps the level of "replication guarantee" should be decided on the
> slave side, by
> having a configuration parameter there
>
> report_as_replicated = received|written_to_disk|fsynced|applied
>
> for different types of hosts may have wildly different guarantees and
> performance
> parameters for these. One could envision a WAL-archive type "standby"
> which is
> there for data persistence only will and never "apply" WAL.
Agreed, it feels natural to specify when a piece of WAL is acknowledged
in the standby.
Regarding the rest of the proposal, I would still prefer the UI
discussed here:
http://archives.postgresql.org/message-id/4CAE030A.2060701@enterprisedb.com
It ought to be the same amount of work to implement, and provides the
same feature set, but makes administration a bit easier by being able to
name the standbys. Also, I dislike the idea of having the standby
specify that it's a synchronous standby that the master has to wait for.
Behavior on the master should be configured on the master.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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