User-defined tasks allow scheduled execution of SQL statements. Tasks run according to a specified execution configuration, using any combination of a set interval and/or a flexible schedule using a subset of familiar cron utility syntax. Tasks currently run in user-specified warehouses but will eventually run in a serverless environment using Snowflake-supplied compute resources. Currently, a task can execute a single SQL statement, including a call to a stored procedure. Tasks can be combined with table streams for continuous ELT workflows to process recently changed table rows. Streams ensure exactly once semantics for new or changed data in a table. Tasks can also be used independently to generate periodic reports by inserting or merging rows into a report table or perform other periodic work.
Task Scheduling
There is no event source that can trigger a task; instead, a task runs on a schedule, which can be defined when creating a task (using CREATE TASK) or later (using ALTER TASK). Snowflake ensures only one instance of a task with a schedule (i.e. a standalone task or the root task in a tree of tasks) is executed at a given time. If a task is still running when the next scheduled execution time occurs, then that scheduled time is skipped.
Task History
Query the TASK_HISTORY table function to verify the task did not run. It is possible that the task ran successfully but the SQL statement in the task definition failed. In particular, note the scheduled and completed times, as well as any error code and message. If the task has a parent task (in a tree of tasks), verify whether the parent task completed successfully.
There is a 60 minute default limit on a single run of a task. This limitation was implemented as a safeguard against non-terminating tasks.
Link: https://docs.snowflake.com/en/user-guide/tasks-intro.html
