2011-09-07 22:37:27 +00:00
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[[!meta title="Cdist: The scripts vs. functions and local variables problem"]]
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Today I've found a very nasty problem during development of
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2011-09-07 22:51:10 +00:00
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[[cdist|software/cdist]] 1.8.0,
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2011-09-07 22:37:27 +00:00
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related to shell functions and the non-local variables.
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## Background
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cdist, up to version 1.7.x, is implemented in shell scripts. As it turned out,
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most of the time during a cdist call is spent within the kernel, which seems
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to be related to some thousands of forks we do for each run (you can use
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oprofile to verify this yourself). To speedup cdist, the idea was to rewrite
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cdist to use functions for internal functionality, instead of the shell
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scripts.
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## The implementation
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So the idea was very simple:
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* Take all existing shell scripts
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* Add a function header
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* Move shell script from bin/ to core/
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* Source all functions from core/
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But the first problem that came up is that the **local** keyword had been removed
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from the POSIX standard. Thus I began to eliminate global variables by
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either prefixing them with the function name or by removing them completly.
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## The problem
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After a some time I realised that the __cdist_object_run() function calls itself
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recursively. This leads to subsequent overwritten variables, which in turn leads
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to unwanted behaviour.
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## The question
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I'm aware that the **local** keyword is still supported by some shells, but I am
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wondering, whether you have a good idea, on how to speedup cdist (having fast
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fork()s would be great!) without violating the POSIX standard?
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[[!tag config eth unix]]
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