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116 lines
4.8 KiB
116 lines
4.8 KiB
2 years ago
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## Backup manager
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### Instructions
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You will create two scripts that will manage and perform scheduled backups.
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#### First script: backup_manager.py
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The script `backup_manager.py` will orchestrate the backup service and if necessary update the file `backup_schedules.txt`. In order to do so it will accept the following command-line arguments:
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- `start`: run `backup_service.py` in the background.
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- `stop`: stop the process `backup_service.py`.
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- `create [schedule]`: add a new backup schedule in `backup_schedules.txt`.
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- `delete [index]`: delete the backup schedule at line `index` (starting by 0) in `backup_schedules.txt`.
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- `list`: print the scheduled backups in `backup_schedules.txt`, adding an index before each schedule.
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- `backups`: list the backups files in `./backups`.
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#### Second script: backup_service.py
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The script `backup_service.py` will check the schedules in `backup_schedules.txt` and perform the daily backups at the proper time.
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- The service will run in an infinite loop.
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- On every cycle of the loop the service will check the schedules.
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- The service will perform the backup if the current time (hour and minute) matches the time of the schedule.
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- The format of the schedules is `path_to_save;time(hh:mm);backup_name`.
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- The backups will be saved in `./backups`.
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- The backups will be a compressed file (`.tar`) for the `path_to_save` directory.
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> At the end of each loop it would be wise to make the service sleep for about 45 seconds to save processor cycles.
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### Logs and error handling
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Both scripts will have to use `try` and `except` to handle errors.
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All actions and errors should be logged into a specific file in the `./log` directory.
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- `backup_manager.py` will log into `./logs/backup_manager.log`.
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- `backup_service.py` will log into `./logs/backup_service.log`.
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You can choose to phrase your logs as you prefer, however it would be smart to start with a timestamp and try to be as specific as you can.
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### Usage
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Here is a little script to show how the backup system should work:
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```bash
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echo "--> Create 3 new schedules"
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python3 ./backup_manager.py create "test;16:07;backup_test"
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python3 ./backup_manager.py create "test1;16:07;personal_data"
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python3 ./backup_manager.py create "test2;16:07;office_docs"
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echo "--> Try to add a malformed schedule"
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python3 ./backup_manager.py create "test;"
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echo "--> Instruction list"
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python3 ./backup_manager.py list
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python3 ./backup_manager.py start
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python3 ./backup_manager.py stop
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echo "--> Instruction backups"
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python3 ./backup_manager.py backups
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echo "--> Content of the directory"
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ls
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echo "--> cat on ./logs/backup_manager.log"
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cat ./logs/backup_manager.log
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echo "--> cat on ./logs/backup_service.log"
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cat ./logs/backup_service.log
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echo "--> Content of ./backups"
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ls ./backups
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```
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The output of this script should be similar to the following:
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```console
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--> Create 3 new schedules
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--> Try to add a malformed schedule
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--> Instruction list
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0: test;16:07;backup_test
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1: test1;16:07;personal_data
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2: test2;16:07;office_docs
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--> Instruction backups
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personal_data.tar
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office_docs.tar
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backup_test.tar
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--> Content of the directory
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backup_manager.py backups backup_schedules.txt backup_service.py logs
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--> cat on ./logs/backup_manager.log
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[08/02/2023 16:07] New schedule added: test;16:07;backup_test
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[08/02/2023 16:07] New schedule added: test1;16:07;personal_data
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[08/02/2023 16:07] New schedule added: test2;16:07;office_docs
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[08/02/2023 16:07] Error: malformed schedule: test;
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[08/02/2023 16:07] Show schedules list
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[08/02/2023 16:07] backup_service started
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[08/02/2023 16:07] backup_service stopped
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[08/02/2023 16:07] Show backups list
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--> cat on ./logs/backup_service.log
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[08/02/2023 16:07] Backup done for test in backups/backup_test.tar
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[08/02/2023 16:07] Backup done for test1 in backups/personal_data.tar
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[08/02/2023 16:07] Backup done for test2 in backups/office_docs.tar
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--> Content of ./backups
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backup_test.tar office_docs.tar personal_data.tar
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```
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### Hints
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- To run a script from another python script you could use `subprocess.Popen` with the flag `start_new_session=True`.
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- To kill a process you should find its process id and call `os.kill`.
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- Play with the command `ps -A -f`, it will show a list of all active processes with the arguments attached to them and their process ids.
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- The standard library `tarfile` is very useful when trying to work with archives.
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- This starts to be quite a big project, try to be as modular as you can by creating single-task functions, this will save you a lot of time.
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> There is many ways to run tasks in background and to perform actions on a specific time, the implementation proposed in this exercise is good for learning but should not be your preferred choice for production environments.
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### References
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- [Error handling in Python](https://docs.python.org/3.10/tutorial/errors.html)
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- [Spawn a subprocess in Python](https://docs.python.org/3.10/library/subprocess.html)
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