TableError: Internal database error: ERROR: canceling statement due to user request

Anvil Q&A
1

Hi,
I have built a simulator with multi-user. Until a few days all worked well.
But no there seems to be a change in the database:
I get several times the error:
TableError: Internal database error: ERROR: canceling statement due to user request
Seems to be a bug in there - Anvil can you check please.
Thanks Aaron

2

Hi Aaron,

Can you confirm that this error is still occurring? Can you share the code that is causing the error?

3

Hi Brooke,

unfortunately I cannot share the code. I will test it again and tell you the results.
Have you found something on your side?

4

so far it is running fine

5

I’ve also been getting this (and another similar error) quite a bit lately. It happens sporadically. I do think it’s an Anvil bug.

My workaround has been to write a wrapper function that catches anvil.tables.TableError exceptions and retries them.

6

Interesting, can you show us your solution.
I have tested yesterday and never got the error again. We are soon to launch and it would be very bad, if it shows again with customers.

7 
def retry_db(function, *args, db_retries=3, db_sleep_for=5, **kwargs):
  """
  Calls a function that requires at least one database call, with specified arguments.
  Retries up to `db_retries` times, waiting `db_sleep_for` seconds between each attempt,
  otherwise raising the final error encountered.
  """
  for _ in range(db_retries):
    try:
      with anvil.tables.Transaction() as txn:
        return function(*args, **kwargs)
    except (tables.TableError, tables.TransactionConflict) as e:
      time.sleep(db_sleep_for)
  raise e

Its function argument can be any function that reads/writes the DB, and will be executed in a transaction. For this reason function should be a fairly atomic operation, like a row update.

I’ve been using it in the following ways:

  • row['property'] = value becomes retry_db(row.update, property=value)
  • row.update(prop1=val1, prop2=val2) becomes retry_db(row.update, prop1=val1, prop2=val2)

Using this wrapper has completely eliminated the error you mentioned as well as the one I linked to in my other post. These errors have been sporadic and transient, and therefore difficult to debug due to not being able to reproduce on command.

2 Likes
8

Thank you very much - that helps a lot!!!

9

Today it happend again (just in a customer-presentation).