## Backup manager ### Logs and error handling All scripts will have to use `try` and `except` to handle errors. The scripts should log (aka write) all actions and errors into a specific file in the `./log` directory. - The script `backup_manager.py` will log into `./logs/backup_manager.log`. - The script `backup_service.py` will log into `./logs/backup_service.log`. 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. > Check the examples in the list of arguments for `backup_manager.py` and the usage section to see what the logs should looks like. ### Instructions You will create two scripts that will manage and perform scheduled backups. #### First script: backup_manager.py 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: - `start`: Runs `backup_service.py` in the background. - Example of logs: - `[dd/mm/yyyy hh:mm] backup_service started` - `[dd/mm/yyyy hh:mm] Error: can't start backup_service` - `[dd/mm/yyyy hh:mm] Error: backup_service already running` - `stop`: Kills `backup_service.py` process. - Example of logs: - `[dd/mm/yyyy hh:mm] backup_service stopped` - `[dd/mm/yyyy hh:mm] Error: can't stop backup_service` - `[dd/mm/yyyy hh:mm] Error: backup_service not running` - `create [schedule]`: Adds a new backup schedule in `backup_schedules.txt`. - This schedule will have a specific format which is `"file_name;hour:minutes;backup_file_name"`. - Example of logs: - `[dd/mm/yyyy hh:mm] New schedule added: test2;16:07;office_docs` - `[dd/mm/yyyy hh:mm] Error: malformed schedule: test;` - `list`: Prints the scheduled backups in `backup_schedules.txt`, adding an index before each schedule. - Example of logs: - `[dd/mm/yyyy hh:mm] Show backups list` - `[dd/mm/yyyy hh:mm] Error: can't find backup_schedules.txt` - `delete [index]`: Delete the backup schedule at line `index` (starting by 0) in `backup_schedules.txt`. - Example of logs: - `[dd/mm/yyyy hh:mm] Schedule at index 3 deleted` - `[dd/mm/yyyy hh:mm] Error: can't find schedule at index 3` - `[dd/mm/yyyy hh:mm] Error: can't find backup_schedules.txt` - `backups`: List the backups files in `./backups`. - Example of logs: - `[dd/mm/yyyy hh:mm] Show backups list` - `[dd/mm/yyyy hh:mm] Error: can't find backups directory` #### Second script: backup_service.py The script `backup_service.py` will check the schedules in `backup_schedules.txt` and perform the daily backups at the proper time. - The service will run in an infinite loop. - On every cycle of the loop the service will check the schedules. - The service will perform the backup if the current time (hour and minute) matches the time of the schedule. - The format of the schedules is `path_to_save;time(hh:mm);backup_name`. - The backups will be saved in `./backups`. - The backups will be a compressed file (`.tar`) for the `path_to_save` directory. > At the end of each loop it would be wise to make the service sleep for about 45 seconds to save processor cycles. ### Usage Here is a little script to show how the backup system should work (assuming the script is ran at 16:07): ```bash echo "--> Create 3 new schedules" python3 ./backup_manager.py create "test;16:07;backup_test" python3 ./backup_manager.py create "test1;16:07;personal_data" python3 ./backup_manager.py create "test2;16:07;office_docs" echo "--> Try to add a malformed schedule" python3 ./backup_manager.py create "test;" echo "--> Instruction list" python3 ./backup_manager.py list python3 ./backup_manager.py start python3 ./backup_manager.py stop echo "--> Instruction backups" python3 ./backup_manager.py backups echo "--> Content of the directory" ls echo "--> cat on ./logs/backup_manager.log" cat ./logs/backup_manager.log echo "--> cat on ./logs/backup_service.log" cat ./logs/backup_service.log echo "--> Content of ./backups" ls ./backups ``` The output of this script should be similar to the following: ```console --> Create 3 new schedules --> Try to add a malformed schedule --> Instruction list 0: test;16:07;backup_test 1: test1;16:07;personal_data 2: test2;16:07;office_docs --> Instruction backups personal_data.tar office_docs.tar backup_test.tar --> Content of the directory backup_manager.py backups backup_schedules.txt backup_service.py logs --> cat on ./logs/backup_manager.log [dd/mm/yyyy 16:07] New schedule added: test;16:07;backup_test [dd/mm/yyyy 16:07] New schedule added: test1;16:07;personal_data [dd/mm/yyyy 16:07] New schedule added: test2;16:07;office_docs [dd/mm/yyyy 16:07] Error: malformed schedule: test; [dd/mm/yyyy 16:07] Show schedules list [dd/mm/yyyy 16:07] backup_service started [dd/mm/yyyy 16:07] backup_service stopped [dd/mm/yyyy 16:07] Show backups list --> cat on ./logs/backup_service.log [dd/mm/yyyy 16:07] Backup done for test in backups/backup_test.tar [dd/mm/yyyy 16:07] Backup done for test1 in backups/personal_data.tar [dd/mm/yyyy 16:07] Backup done for test2 in backups/office_docs.tar --> Content of ./backups backup_test.tar office_docs.tar personal_data.tar ``` ### Hints - Familiarize with Python, including modules such as `subprocess`, `shlex` and file `I/O` operations. - To run a script from another Python script you could use `subprocess.Popen` with the flag `start_new_session=True`. - To kill a process you should find its process id and call `os.kill`. - 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. - The standard library `tarfile` is very useful when trying to work with archives. - This starts to be quite a big project, try to be as modular as possible by creating single-task functions, this will save you a lot of time. > 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. ### References - [Error handling in Python](https://docs.python.org/3.10/tutorial/errors.html) - [Spawn a subprocess in Python](https://docs.python.org/3.10/library/subprocess.html) - [Simple lexical analysis, shlex](https://docs.python.org/3/library/shlex.html) - [Reading and writing files](https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files) - [Set handlers for asynchronous events, signal](https://docs.python.org/3/library/signal.html) - [Try and Except](https://pythonbasics.org/try-except/)