2017-06-19 20:24 GMT+02:00 Daniel Gustafsson <dan...@yesql.se>:

> When terminating, or cancelling, a backend it’s currently not possible to
> let
> the signalled session know *why* it was dropped.  This has nagged me in the
> past and now it happened to come up again, so I took a stab at this.  The
> attached patch implements the ability to pass an optional text message to
> the
> signalled session which is included in the error message:
>   SELECT pg_terminate_backend(<pid> [, message]);
>   SELECT pg_cancel_backend(<pid> [, message]);
> Right now the message is simply appended on the error message, not sure if
> errdetail or errhint would be better? Calling:
>   select pg_terminate_backend(<pid>, 'server rebooting');
> ..leads to:
>   FATAL:  terminating connection due to administrator command: "server
> rebooting"
> Omitting the message invokes the command just like today.
> The message is stored in a new shmem area which is checked when the
> session is
> aborted.  To keep things simple a small buffer is kept per backend for the
> message.  If deemed too costly, keeping a central buffer from which slabs
> are
> allocated can be done (but seemed rather complicated for little gain
> compared
> to the quite moderate memory spend.)
> cheers ./daniel


very good idea


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