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|
"""A size cap for the saved tiles (a public server on a shared disk): past the cap, the tiles used least recently
are deleted down to (1 − SLACK) × cap, so a sweep is rare. Tiles of the kept layers at zooms ≤ keep_z (the
prerendered map shipped with the server) are never deleted and do not count; other layers at those zooms do (they
render on demand, and fifteen layers' worth would outgrow any disk). "Used" = the file's mtime: a tile read from disk is touched
(the data disk may be mounted noatime). Only files shaped <layer>/<z>/<x>/<y>.<ext> are ever touched or deleted."""
from __future__ import annotations
import os
import threading
from pathlib import Path
SLACK = 0.1
TILE_EXTS = (".jpg", ".png", ".bin")
KEEP_LAYERS = ("relief", "mesh") # what a public deploy prerenders
def tile_key(path) -> tuple[str, int] | None:
"""(layer, zoom) of a saved tile's path, or None when it is not one (manifests, .part files, anything else)."""
p = Path(path)
if p.suffix not in TILE_EXTS or not p.stem.isdigit():
return None
parts = p.parts
if len(parts) < 5 or not (parts[-2].isdigit() and parts[-3].isdigit()):
return None
return parts[-4], int(parts[-3])
class TileCap:
def __init__(self, cap_bytes: int, keep_z: int = -1, keep_layers=KEEP_LAYERS):
self.cap, self.keep_z, self.keep_layers = int(cap_bytes), int(keep_z), tuple(keep_layers)
self.roots: list[Path] = []
self.total = None # counted bytes; None until the first sweep
self.lock = threading.Lock()
self.sweeping = False
def add_root(self, root) -> None:
root = Path(root)
with self.lock:
if root not in self.roots:
self.roots.append(root)
def counts(self, path) -> bool:
k = tile_key(path)
return k is not None and not (k[0] in self.keep_layers and k[1] <= self.keep_z)
def used(self, path) -> None:
"""A tile was read from disk: it is now the most recently used."""
if self.counts(path):
try:
os.utime(path)
except OSError:
pass
def saved(self, path, nbytes: int) -> None:
"""A tile was written: count it, and sweep in the background once past the cap."""
if not self.counts(path):
return
with self.lock:
if self.total is None:
return # the first sweep counts it
self.total += nbytes
over = self.total > self.cap
if over:
self.start()
def start(self) -> None:
with self.lock:
if self.sweeping:
return
self.sweeping = True
threading.Thread(target=self.sweep, daemon=True).start()
def _files(self):
for root in list(self.roots):
for d, _, names in os.walk(root):
for n in names:
f = os.path.join(d, n)
if self.counts(f):
try:
st = os.stat(f)
except OSError:
continue
yield st.st_mtime_ns, st.st_size, f
def sweep(self) -> int:
"""Count the tiles; past the cap, delete the least recently used down to (1 − SLACK) × cap.
Returns the bytes deleted."""
with self.lock:
self.sweeping = True
freed = 0
try:
files = list(self._files())
total = sum(s for _, s, _ in files)
if total > self.cap:
goal = self.cap * (1 - SLACK)
files.sort()
for _, size, f in files:
if total <= goal:
break
try:
os.unlink(f)
except FileNotFoundError:
pass
except OSError:
continue
total -= size
freed += size
for parent in (Path(f).parent, Path(f).parent.parent): # empty <x>/ and <z>/ folders go too
try:
parent.rmdir()
except OSError:
break
with self.lock:
self.total = total
finally:
with self.lock:
self.sweeping = False
return freed
|
