121 lines
3.9 KiB
Python
121 lines
3.9 KiB
Python
import json
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import os.path
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import threading
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import time
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from modules.paths import data_path, script_path
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cache_filename = os.path.join(data_path, "cache.json")
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cache_data = None
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cache_lock = threading.Lock()
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dump_cache_after = None
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dump_cache_thread = None
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def dump_cache():
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"""
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Marks cache for writing to disk. 5 seconds after no one else flags the cache for writing, it is written.
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"""
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global dump_cache_after
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global dump_cache_thread
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def thread_func():
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global dump_cache_after
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global dump_cache_thread
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while dump_cache_after is not None and time.time() < dump_cache_after:
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time.sleep(1)
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with cache_lock:
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with open(cache_filename, "w", encoding="utf8") as file:
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json.dump(cache_data, file, indent=4)
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dump_cache_after = None
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dump_cache_thread = None
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with cache_lock:
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dump_cache_after = time.time() + 5
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if dump_cache_thread is None:
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dump_cache_thread = threading.Thread(name='cache-writer', target=thread_func)
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dump_cache_thread.start()
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def cache(subsection):
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"""
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Retrieves or initializes a cache for a specific subsection.
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Parameters:
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subsection (str): The subsection identifier for the cache.
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Returns:
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dict: The cache data for the specified subsection.
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"""
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global cache_data
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if cache_data is None:
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with cache_lock:
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if cache_data is None:
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if not os.path.isfile(cache_filename):
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cache_data = {}
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else:
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try:
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with open(cache_filename, "r", encoding="utf8") as file:
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cache_data = json.load(file)
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except Exception:
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os.replace(cache_filename, os.path.join(script_path, "tmp", "cache.json"))
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print('[ERROR] issue occurred while trying to read cache.json, move current cache to tmp/cache.json and create new cache')
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cache_data = {}
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s = cache_data.get(subsection, {})
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cache_data[subsection] = s
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return s
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def cached_data_for_file(subsection, title, filename, func):
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"""
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Retrieves or generates data for a specific file, using a caching mechanism.
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Parameters:
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subsection (str): The subsection of the cache to use.
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title (str): The title of the data entry in the subsection of the cache.
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filename (str): The path to the file to be checked for modifications.
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func (callable): A function that generates the data if it is not available in the cache.
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Returns:
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dict or None: The cached or generated data, or None if data generation fails.
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The `cached_data_for_file` function implements a caching mechanism for data stored in files.
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It checks if the data associated with the given `title` is present in the cache and compares the
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modification time of the file with the cached modification time. If the file has been modified,
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the cache is considered invalid and the data is regenerated using the provided `func`.
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Otherwise, the cached data is returned.
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If the data generation fails, None is returned to indicate the failure. Otherwise, the generated
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or cached data is returned as a dictionary.
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"""
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existing_cache = cache(subsection)
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ondisk_mtime = os.path.getmtime(filename)
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entry = existing_cache.get(title)
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if entry:
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cached_mtime = entry.get("mtime", 0)
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if ondisk_mtime > cached_mtime:
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entry = None
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if not entry or 'value' not in entry:
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value = func()
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if value is None:
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return None
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entry = {'mtime': ondisk_mtime, 'value': value}
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existing_cache[title] = entry
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dump_cache()
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return entry['value']
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