Hi,
Thank you for the patch!
On 2021-10-30 12:50, kuroda.hay...@fujitsu.com wrote:
## Background
Currently there is no way to check the status of an foreign server in
PostgreSQL.
If an foreign server's postmaster goes down, or if the network between
servers is lost,
the backend process will only detect these when it uses the connection
corresponding to that foreign server.
Consider a workload that updates data on an foreign server only at the
beginning of a transaction,
and runs a lot of local SQLs. Even if the network is disconnected
immediately after accessing the foreign server,
the backend process will continue to execute local SQLs without
realizing it.
The process will eventually finish to execute SQLs and try to commit.
Only then will it realize that the foreign server cannot be connect
and will abort the transaction.
This situation should be detected as soon as possible
because it is impossible to commit a transaction when the foreign
server goes down.
This can be more of a problem if you have system-wide downtime
requirements.
That's why I want to implement the health-check feature to postgres.
It's a good idea. I also think such a situation should be avoided.
## Further work
As the next step I have a plan to implement the callback function to
postgres_fdw.
I already made a PoC, but it deeply depends on the following thread:
https://commitfest.postgresql.org/35/3098/
I also want you to review the postgres_fdw part,
but I think it should not be attached because cfbot cannot understand
such a dependency
and will throw build error. Do you know how to deal with them in this
case?
I don't know how to deal with them, but I hope you will attach the PoC,
as it may be easier to review.
--
Regards,
--
Shinya Kato
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION
