Your aim is to write simulator of LRU cache for hard drive. System provides availability for concurrent users to read and write key-value data. Integers from 0 to 1000 can be used as keys in this task. Strings are used as values.
Data is physically stored on the group of hard drives. Each hard drive is split into blocks. In this task each drive is presented as file on the user’s machine. Blocks are written to files one by one. Each block has it’s address in format disk_no:block_no.
Clients are working with disk via LRU cache.
Reads config from config.txt file. Sets up variables for other modules.
Each "disk" is splitted into blocks of size N. Provides function get_block(disk_no, block_no) that gets data from disk block and set_block(disk_no, block_no, value) to write data on disk.
Work with disk operations is done through LRU cache. Up to M blocks are loaded to the cache. Data is commited to disk only when block is dropped from LRU Cache.
provides get_cached_block(disk_no, block_no) and set_cached_block(disk_no, block_no) functions.
Stores mapping from keys to sequence of blocks where value is stored. Also stores list of all free blocks.
{
‘UNUSED_BLOCKS’: shuffled list of unused blocks,
Key1: list with addresses of blocks where data of ‘Key1’ is stored,
Key2: list with addresses of blocks where data of ‘Key2’ is stored,
…
}
Provides end user with functions write(key, text) read(key) and delete(key) to create, update and delete values assigned to some keys. Values are splitted to blocks and written to files.
To test itself system starts different threads that are performing some data. All actions are logged to console.
Writer thread generates random integer key, and tries to store under that key random poem from poems list.
Reader thread generates random integer key, and tries to read poem from those key and print it.
Takes random key and tries to delete it.
256 # block size in bytes
500 # number of blocks in each file
100 # blocks in LRU cache
16 # Readers threads running during test
5 # Writers threads running during test
2 # Deleters threads running during test
#Mappings file
/home/user/dk/disks/mappings.bytes
# Disks are listed one by one next
/home/user/dk/disks/disk1.bytes
/home/user/dk/disks/disk2.bytes
/home/user/dk/disks/disk3.bytes
/home/user/dk/disks/disk4.bytese