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60 lines
2.8 KiB
Markdown
60 lines
2.8 KiB
Markdown
## File Server
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**File Server** stores data, that should be kept outside of **WebApp's**
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database (both because storing files in a database is inefficient and because
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the workers need to access the files in the simplest possible way). It should
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meet following requirements:
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- store files without duplicates
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- keep consistent state with main database
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- serve files to workers on demand
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- allow versioning of tasks with revert back feature
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To meet these requirements, **Storage** and **Database** must be set as bellow.
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### Storage
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**Storage** is meant as disc space with some commonly used filesystem. We'll use `ext4`, but the other ones should work too. **Storage** file structure is:
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```
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.
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├── submits
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│ └── user_id
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│ └── advanced_dot_net_1
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│ └── submit_id
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│ ├── eval.yml
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│ └── source.cs
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├── submit_archives
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│ └── submit_id.tar.gz
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├── tasks
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│ ├── a
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│ │ ├── a014ed2abb56371bfaf2b4298a85d5dfb56509ed
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│ │ └── a5edbd8b12e670ed1e3110d6c0524000cd4c3c7a
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│ └── b
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│ └── b1696358b8540923eb79b68f95c0f94c13a83fa7
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└── temp
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└── 1795184136b8bdddabe50453cc2cc2d46f0f7c5e
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```
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- **submits** keep information about all files submited by users to ReCodEx.
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There are subdirectories _user_id_ and _advanced_dot_net_1_ which groups
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submits by users and courses the submits are for. This structure is easy to
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maintain for new and deleted users.
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- **submit_archives** contains the student submissions in compressed archives so
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that they can be easily downloaded by workers.
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- **tasks** contains supplementary files (such as test inputs or helper
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programs) for all existing task in ReCodEx. To avoid too many files in one
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directory, files are separated to subfolders by first character of their name.
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- **temp** directory is dedicated to temporary storing outputs of programs on teachers' demand. This directory will be erased by cron job on daily basis.
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### Database
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For user friendly access and modifying tasks following information should be stored in database:
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- list of tasks with their newest version number
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- for every task and version list of used files (their hashed names)
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- for every hash name one human readable filename
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### Conclusion
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Files are internally stored by their `sha1sum` hashes, so it's easy to implement
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versioning and get rid of files with duplicate content (multiple files can have
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the same content, which is only stored once). **Worker** also uses files by
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their hashes, which is great for local caching without worries about actual
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version number of given file. On the other hand, **Database** stores information
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about human readable names, so that the files are presented in a friendly way to
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users (teachers) in **WebApp**.
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