[IMP] odoo_sh: recurring questions about crons

opw-2058254

odoo_sh/advanced/frequent_technical_questions.rst

@@ -6,6 +6,31 @@
 Frequent Technical Questions
 ==================================
 
+"Automated actions do not run at the exact time they were expected"
+-------------------------------------------------------------------
+
+On the Odoo.sh platform, we cannot guarantee an exact running time for automated actions.
+
+This is due to the fact that there might be multiple customers on the same server, and we must guarantee a fair share of the server for every customer. Automated actions are therefore implemented slightly differently than on a regular Odoo server, and are run on a *best effort* policy.
+
+.. warning::
+    Do not expect any automated action to be run more often than every 5 min.
+
+Are there "best practices" regarding automated actions?
+-------------------------------------------------------
+
+**Odoo.sh always limits the execution time of automated actions (*aka* crons).**
+Therefore, you must keep this fact in mind when developing your own crons.
+
+We advise that:
+
+- Your automated actions should work on small batches of records.
+- Your automated actions should commit their work after processing each batch;
+  this way, if they get interrupted by the time-limit, there is no need to start over.
+- Your automated actions should be
+  `idempotent <https://stackoverflow.com/a/1077421/3332416>`_: they must not
+  cause side-effects if they are started more often than expected.
+
 
 Can you install pycups or some similar library linked to `CUPS <https://www.cups.org/>`_ ?
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