ConETS table consistency while entries are deleted from 2 processes

[Frank Muller]

Hi all


Lets assume a public ETS table of type ‘ordered_set’.

Every minute, a process A is deleting expired entries from it (see below).

In the same time, another process B can delete any entry (ex. randomly)
from this table.

I’ve implemented two strategies which can be used by process A:

_________________________________________
-spec purge1(pos_integer()) -> ok.
purge1(Now) ->
    Key = ets:first(?MODULE),
    purge1(Now, Key).

purge1(Now, Key) when Key =< Now ->
    true = ets:delete(?MODULE, Key), %% idempotent call
    purge1(Now);
purge1(_, _) -> %% '$end_of_table’ or Key > Now
    ok.

or:
_________________________________________
-spec purge2(pos_integer()) -> ok.
purge2(Now) ->
    Key = ets:first(?MODULE),
    purge2(Now, Key).

purge2(Now, Key) when Key =< Now ->
    Next = ets:next(?MODULE, Key),
    true = ets:delete(?MODULE, Key), %% idempotent call
    purge2(Now, Next);
purge2(_, _) -> %% '$end_of_table’ or Key > Now
    ok.
_________________________________________

Question: is it safe in general to have process B deleting entries while A
is running?

Which strategy is more consistent: purge1/1 or purge2/1?

Best
/Frank
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