123 lines
4.3 KiB
Text
123 lines
4.3 KiB
Text
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Just a small hint-file for me to see how cinit works:
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- cinit starts
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* cinit executes either init or a profile
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- the dependency-tree begins
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- now cinit begins to try to execute the dependencies
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* first the needs (if those fail, wants are never called)
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- fork() for every dependency?
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--------------------------------------------------------------------------------
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another idea:
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- cinit starts
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- cinit reads the full depedency tree
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* it builds n-depth trees
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* it begins at the set init service (profile or init!)
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* init is the first entry. always.
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* read full service information (like on/off/params/respawn)
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* design of each tree element: see below
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- add a tree for the needs
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- add a tree for the wants
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- the elements have links, one service is created only once
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- after the tree is created, execution begins
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* begin from the bottom
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* save a pointer to the last level somehow before?
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Pre calculation:
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- need to act on changes (some kind of file watcher)
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* need to keep status (?)
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* what with now missing needs / wants?
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- missing needs: shutdown now missing needs?
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- simply ignore them?
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- shut them down if not needed (no one has a link in needs?)
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*
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--------------------------------------------------------------------------------
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Sample dependency tree:
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init
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/ \
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needs wants
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/ | \ / | \
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a b c d e f
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/ | \ / | \
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needs needs needs END needs END
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/ | \ \ | | | |
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b c d c f a e a
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--------------------------------------------------------------------------------
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How this would be sorted::
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init:
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needs: a b c
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wants: d e f
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a:
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needs: b c d
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b:
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needs: c f
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c:
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needs: a e
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d:
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-
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e:
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needs: a
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f:
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-
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--------------------------------------------------------------------------------
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So in this case, cinit may start services the following way:
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d f
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-> Wouldn't be possible in pre-calculation, because of circular dependencies.
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--------------------------------------------------------------------------------
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Try a 'real' dependency tree:
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a needs b c d
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b needs c d
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c and d do not need other stuff
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--------------------------------------------------------------------------------
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Now cinit would it do the following way:
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start c, start d
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b will be started, as soon as c and d successfully finish
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as soon as b is finished, a will be started
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--------------------------------------------------------------------------------
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Now let's think about how this could look like in code...
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- when we built up the tree, we have some ends (n to say)
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- we can / must start starting (;-) at the end
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- we would have more than one line back (z may be needed by c, i, and a)
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* like in "c is needed by s, c, o"
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* maxdepth counter?
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* asynchronous rollback?
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--> to think more about it!
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--------------------------------------------------------------------------------
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tree elements:
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* name (= path)
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* on, off, +params
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* respawn_delay
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- -1 if not respawning
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- >= 0 time to wait between restart
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* status
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- NOT STARTED (status on initialisation)
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- RESPAWNING (running, respawning)
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- RESPAWN_DELAY (waiting to respawn it)
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- ONCE (started once)
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* errormsg
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- pointer to an error message in case of failure
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* needs
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- List of services we need
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* wants
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- List of services we want
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* used_by
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- List of services which use this service
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--------------------------------------------------------------------------------
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Conclusions
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------------
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cinit as the main executor
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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If cinit should start all services directly and manage dependencies
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only internally, it will need to have build a reverse dependency tree,
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so it begins starting at the end.
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cinit could execute all possible parallel running services in parallel
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and open pipes to the (dumb) service executors.
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