Thread: Confused about stream replication protocol documentation

On 2020/12/22 18:07, Li Japin wrote:
> Hi, all
> 
> In Stream Replication Protocol [1], the documentation of `START_REPLICATION` message is
> 
> XLogData (B)
>    …
> Primary keepalive message (B)
>    …
> Standby status update (F)
>    …
> Hot Standby feedback message (F)
>    ...
> 
> I’m confused about the means of ‘B’ and ‘F’? If it doesn't make sense, why we document here?
> However, if it makes sense, should we explain it?
> Can someone help me out?

‘B’ means a backend and ‘F’ means a frontend. Maybe as [1] does, we should
add the note like "Each is marked to indicate that it can be sent by
  a frontend (F) and a backend (B)" into the description about each message
  format for START_REPLICATION.

[1]
https://www.postgresql.org/docs/devel/protocol-message-formats.html

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION

On 2020/12/23 11:08, Li Japin wrote:
> 
>> On Dec 22, 2020, at 11:13 PM, Fujii Masao <masao.fujii@oss.nttdata.com <mailto:masao.fujii@oss.nttdata.com>> wrote:
>>
>> ‘B’ means a backend and ‘F’ means a frontend. Maybe as [1] does, we should
>> add the note like "Each is marked to indicate that it can be sent by
>> a frontend (F) and a backend (B)" into the description about each message
>> format for START_REPLICATION.
>>
>> [1]
>> https://www.postgresql.org/docs/devel/protocol-message-formats.html
<https://www.postgresql.org/docs/devel/protocol-message-formats.html>
> 
> Thanks for your clarify.  Maybe we should move the "protocol message formats”
> before “stream replication protocol” or referenced it in "stream replication protocol”.

I like the latter. And maybe it's better to reference to also
"53.6. Message Data Types" there because the messages for
START_REPLICATION use the message data types.

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION

Patch applied to master, thanks.

---------------------------------------------------------------------------

On Thu, Dec 24, 2020 at 02:28:53AM +0000, Li Japin wrote:
> 
>     On Dec 23, 2020, at 8:11 PM, Fujii Masao <masao.fujii@oss.nttdata.com>
>     wrote:
> 
> 
>     On 2020/12/23 11:08, Li Japin wrote:
> 
>             On Dec 22, 2020, at 11:13 PM, Fujii Masao <
>             masao.fujii@oss.nttdata.com <mailto:masao.fujii@oss.nttdata.com>>
>             wrote:
> 
>             ‘B’ means a backend and ‘F’ means a frontend. Maybe as [1] does, we
>             should
>             add the note like "Each is marked to indicate that it can be sent
>             by
>             a frontend (F) and a backend (B)" into the description about each
>             message
>             format for START_REPLICATION.
> 
>             [1]
>             https://www.postgresql.org/docs/devel/protocol-message-formats.html
>              <https://www.postgresql.org/docs/devel/
>             protocol-message-formats.html>
> 
>         Thanks for your clarify.  Maybe we should move the "protocol message
>         formats”
>         before “stream replication protocol” or referenced it in "stream
>         replication protocol”.
> 
> 
>     I like the latter. And maybe it's better to reference to also
>     "53.6. Message Data Types" there because the messages for
>     START_REPLICATION use the message data types.
> 
> 
> Add reference about “protocol message types” and “protocol message formats”.
> 
> index 4899bacda7..5793936b42 100644
> --- a/doc/src/sgml/protocol.sgml
> +++ b/doc/src/sgml/protocol.sgml
> @@ -2069,8 +2069,9 @@ The commands accepted in replication mode are:
>       </para>
> 
>       <para>
> -      WAL data is sent as a series of CopyData messages.  (This allows
> -      other information to be intermixed; in particular the server can send
> +      WAL data is sent as a series of CopyData messages
> +      (See <xref linkend="protocol-message-types"/> and <xref linkend=
> "protocol-message-formats"/>).
> +      (This allows other information to be intermixed; in particular the
> server can send
>        an ErrorResponse message if it encounters a failure after beginning
>        to stream.)  The payload of each CopyData message from server to the
>        client contains a message of one of the following formats:
> 
> --
> Best regards
> Japin Li
> 

> diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
> index 4899bacda7..5793936b42 100644
> --- a/doc/src/sgml/protocol.sgml
> +++ b/doc/src/sgml/protocol.sgml
> @@ -2069,8 +2069,9 @@ The commands accepted in replication mode are:
>       </para>
>  
>       <para>
> -      WAL data is sent as a series of CopyData messages.  (This allows
> -      other information to be intermixed; in particular the server can send
> +      WAL data is sent as a series of CopyData messages
> +      (See <xref linkend="protocol-message-types"/> and <xref linkend="protocol-message-formats"/>).
> +      (This allows other information to be intermixed; in particular the server can send
>        an ErrorResponse message if it encounters a failure after beginning
>        to stream.)  The payload of each CopyData message from server to the
>        client contains a message of one of the following formats:


-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Only you can decide what is important to you.