Thread: [HACKERS] Determine if an error is transient by its error code.
Hello folks,
I'm trying to define a transient fault detection strategy for a client application when calling a postgres database.
Essentially I want to determine by the error code if it is worth retrying the call (transient) or if the error was due to a bad query or programmer error, in which case don't retry.
Going through the codes as posted here https://www.postgresql.org/docs/9.6/static/errcodes-appendix.html I had a go at making a list of error codes which may be transient:
53000: insufficient_resources
53100: disk_full
53200: out_of_memory
53300: too_many_connections
53400: configuration_limit_exceeded
57000: operator_intervention
57014: query_canceled
57P01: admin_shutdown
57P02: crash_shutdown
57P03: cannot_connect_now
57P04: database_dropped
58000: system_error
58030: io_error
These next few I am not sure whether they should be treated as transient or not, but I am guessing so
55P03: lock_not_available
55006: object_in_use
55000: object_not_in_prerequisite_state
08000: connection_exception
08003: connection_does_not_exist
08006: connection_failure
08001: sqlclient_unable_to_establish_sqlconnection
08004: sqlserver_rejected_establishment_of_sqlconnection
08007: transaction_resolution_unknown
Are there any codes listed above where retrying would actually not be helpful?
Are there any codes that I did not include that I should have?
Thanks,
-Dominick
On 20 March 2017 at 10:26, Dominick O'Dierno <odiernod@gmail.com> wrote: > Hello folks, > > I'm trying to define a transient fault detection strategy for a client > application when calling a postgres database. > > Essentially I want to determine by the error code if it is worth retrying > the call (transient) or if the error was due to a bad query or programmer > error, in which case don't retry. > > Going through the codes as posted here > https://www.postgresql.org/docs/9.6/static/errcodes-appendix.html I had a go > at making a list of error codes which may be transient: > > 53000: insufficient_resources > 53100: disk_full > 53200: out_of_memory > 53300: too_many_connections > 53400: configuration_limit_exceeded > 57000: operator_intervention > 57014: query_canceled > 57P01: admin_shutdown > 57P02: crash_shutdown > 57P03: cannot_connect_now > 57P04: database_dropped > 58000: system_error > 58030: io_error Depends on how transient you mean, really. I/O error, disk full, cannot_connect_now, etc may or may not require admin intervention. I would argue that database_dropped isn't transient. But I guess you might be re-creating it? > These next few I am not sure whether they should be treated as transient or > not, but I am guessing so > > 55P03: lock_not_available Yeah, I'd say that's transient. > 55006: object_in_use Same. > 55000: object_not_in_prerequisite_state Varies. This can be a bit of a catchall error, encompassing things that need configuration changes, things that need system state changes (won't work in recover or whatever), and things that will change in a short span of time. In general you'll need classes of retry: * just reissue the query (deadlock retry, etc) * reconnect and retry etc. -- Craig Ringer http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services
Craig Ringer <craig@2ndquadrant.com> writes: > On 20 March 2017 at 10:26, Dominick O'Dierno <odiernod@gmail.com> wrote: >> Essentially I want to determine by the error code if it is worth retrying >> the call (transient) or if the error was due to a bad query or programmer >> error, in which case don't retry. > In general you'll need classes of retry: > * just reissue the query (deadlock retry, etc) > * reconnect and retry Yeah. There's a pretty significant fraction of these where just blindly repeating the failing query isn't likely to help; the error code is meant to suggest that the DBA has to fix something, eg adjust configuration limits. I'm also pretty dubious about the value of a blind retry for, eg, disk_full. One you missed that I think *is* supposed to imply "just retry" is 40001 serialization_failure. You have to retry the whole transaction though, not just one query. regards, tom lane