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@ -76,3 +76,66 @@ TBD |
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Most tools should check the =CHARM_STORE= bash environment variable |
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that should be the path to reach the root of this repository. If not |
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defined, most tools will look in =/srv/charm-store= by default. |
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* Specs |
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** charm type |
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Not all charm are intended to bring up services as having a container |
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always running and listening. |
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In ~metadata.yml~, the root level ~type~ can be one of: |
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- ~service~ (default) |
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If not specified, this is the default. A charm brings up a service. |
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It is meant to be *always running*. For instance, ~apache~, ~mysql~, |
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~postgres~ are services. |
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They usually open ports and are listening to provide their service, |
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or carry background listening of other ressources (like checking |
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time and sending scheduling command for the ~cron~ services), and or |
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use files to trigger or report on their activity. |
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It will have an entry in the final ~docker-compose.yml~, and thus, a |
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container will run and stay in memory and have a ~restart: |
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unless-stopped~ policy. They use CPU and memory ressources. |
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- ~run-once~ |
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The entry is meant to describe *a command that run once*, |
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it will be called by a service and *will exit after execution*. |
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For instance, ~logrotate~, ~rsync-backup~, or ~letsencrypt~ are |
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of type ~run-once~. |
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They are meant to be run by service for specific events. They |
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usually will use relations to ensure they are called at specific |
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moment by service... |
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A command does not have an automatic ~restart~ policy as services |
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have. |
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They use CPU and memory ressources only when run and gives them back |
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once finished. |
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- ~stub~ |
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The entry describes an entity that will *not be run at all*. It is |
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used to hold information in the ~compose.yml~ and often to *stand |
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for* a real service managed outside of ~compose.yml~ (on an other |
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host or on a different managing system, like a local installation or |
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LXC, virtualbox, ...). |
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For instance, ~stmp-stub~ can be used to stand for an external ~smtp~. |
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It is through their relation that they shine as they can provide |
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similar interface than actual services would have |
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provided. ~smtp-stub~ is a ~smtp-server~ provider and other charm |
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can connect to it. |
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They usually implement relation hooks, and are providers. |
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No entry will be created in the final ~docker-compose.yml~. |
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They use no CPU or memory ressources at all. |