Do once

19.0.0 released Nov 08, 2023

Do once

Purpose: Execute statements only once in a process.

do-once
    <any statements>
    ...
end-do-once

do-once will execute <any statements> only once in a single process regardless of how many requests that process serves. <any statements> end with end-do-once. The first time a process reaches do-once, <any statements> will execute; in all subsequent cases the program control will skip to immediately after end-do-once.

do-once cannot be nested, but otherwise can be used any number of times. <any statements> execute in the same scope as the code prior and after the do-once/end-do-once.

Typical use of do-once may be a one-time setup of variables or making calls that need to be performed only once per process.

Examples

In this example, a process-scoped hash (that is available to multiple requests of a single process) is created in the very first request a process serves and data is written to it; the subsequent requests do not create a new hash but rather just write to it.

...
do-once
new-hash define my_hash size 1024 process-scope
end-do-once
write-hash my_hash key my_key value my_data
...