Source code for SCons.CacheDir

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"""CacheDir support
"""

import atexit
import json
import os
import stat
import sys
import uuid

import SCons.Action
import SCons.Errors
import SCons.Warnings
import SCons

cache_enabled = True
cache_debug = False
cache_force = False
cache_show = False
cache_readonly = False
cache_tmp_uuid = uuid.uuid4().hex

[docs]def CacheRetrieveFunc(target, source, env): t = target[0] fs = t.fs cd = env.get_CacheDir() cd.requests += 1 cachedir, cachefile = cd.cachepath(t) if not fs.exists(cachefile): cd.CacheDebug('CacheRetrieve(%s): %s not in cache\n', t, cachefile) return 1 cd.hits += 1 cd.CacheDebug('CacheRetrieve(%s): retrieving from %s\n', t, cachefile) if SCons.Action.execute_actions: if fs.islink(cachefile): fs.symlink(fs.readlink(cachefile), t.get_internal_path()) else: cd.copy_from_cache(env, cachefile, t.get_internal_path()) try: os.utime(cachefile, None) except OSError: pass st = fs.stat(cachefile) fs.chmod(t.get_internal_path(), stat.S_IMODE(st[stat.ST_MODE]) | stat.S_IWRITE) return 0
[docs]def CacheRetrieveString(target, source, env): t = target[0] fs = t.fs cd = env.get_CacheDir() cachedir, cachefile = cd.cachepath(t) if t.fs.exists(cachefile): return "Retrieved `%s' from cache" % t.get_internal_path() return None
CacheRetrieve = SCons.Action.Action(CacheRetrieveFunc, CacheRetrieveString) CacheRetrieveSilent = SCons.Action.Action(CacheRetrieveFunc, None)
[docs]def CachePushFunc(target, source, env): if cache_readonly: return t = target[0] if t.nocache: return fs = t.fs cd = env.get_CacheDir() cachedir, cachefile = cd.cachepath(t) if fs.exists(cachefile): # Don't bother copying it if it's already there. Note that # usually this "shouldn't happen" because if the file already # existed in cache, we'd have retrieved the file from there, # not built it. This can happen, though, in a race, if some # other person running the same build pushes their copy to # the cache after we decide we need to build it but before our # build completes. cd.CacheDebug('CachePush(%s): %s already exists in cache\n', t, cachefile) return cd.CacheDebug('CachePush(%s): pushing to %s\n', t, cachefile) tempfile = "%s.tmp%s"%(cachefile,cache_tmp_uuid) errfmt = "Unable to copy %s to cache. Cache file is %s" try: fs.makedirs(cachedir, exist_ok=True) except OSError: msg = errfmt % (str(target), cachefile) raise SCons.Errors.SConsEnvironmentError(msg) try: if fs.islink(t.get_internal_path()): fs.symlink(fs.readlink(t.get_internal_path()), tempfile) else: cd.copy_to_cache(env, t.get_internal_path(), tempfile) fs.rename(tempfile, cachefile) except EnvironmentError: # It's possible someone else tried writing the file at the # same time we did, or else that there was some problem like # the CacheDir being on a separate file system that's full. # In any case, inability to push a file to cache doesn't affect # the correctness of the build, so just print a warning. msg = errfmt % (str(t), cachefile) cd.CacheDebug(errfmt + '\n', str(t), cachefile) SCons.Warnings.warn(SCons.Warnings.CacheWriteErrorWarning, msg)
CachePush = SCons.Action.Action(CachePushFunc, None)
[docs]class CacheDir: def __init__(self, path): """ Initialize a CacheDir object. The cache configuration is stored in the object. It is read from the config file in the supplied path if one exists, if not the config file is created and the default config is written, as well as saved in the object. """ self.requests = 0 self.hits = 0 self.path = path self.current_cache_debug = None self.debugFP = None self.config = dict() if path is None: return self._readconfig(path)
[docs] def _readconfig(self, path): """ Read the cache config. If directory or config file do not exist, create. Take advantage of Py3 capability in os.makedirs() and in file open(): just try the operation and handle failure appropriately. Omit the check for old cache format, assume that's old enough there will be none of those left to worry about. :param path: path to the cache directory """ config_file = os.path.join(path, 'config') try: os.makedirs(path, exist_ok=True) except FileExistsError: pass except OSError: msg = "Failed to create cache directory " + path raise SCons.Errors.SConsEnvironmentError(msg) try: with open(config_file, 'x') as config: self.config['prefix_len'] = 2 try: json.dump(self.config, config) except Exception: msg = "Failed to write cache configuration for " + path raise SCons.Errors.SConsEnvironmentError(msg) except FileExistsError: try: with open(config_file) as config: self.config = json.load(config) except ValueError: msg = "Failed to read cache configuration for " + path raise SCons.Errors.SConsEnvironmentError(msg)
[docs] def CacheDebug(self, fmt, target, cachefile): if cache_debug != self.current_cache_debug: if cache_debug == '-': self.debugFP = sys.stdout elif cache_debug: def debug_cleanup(debugFP): debugFP.close() self.debugFP = open(cache_debug, 'w') atexit.register(debug_cleanup, self.debugFP) else: self.debugFP = None self.current_cache_debug = cache_debug if self.debugFP: self.debugFP.write(fmt % (target, os.path.split(cachefile)[1])) self.debugFP.write("requests: %d, hits: %d, misses: %d, hit rate: %.2f%%\n" % (self.requests, self.hits, self.misses, self.hit_ratio))
[docs] @classmethod def copy_from_cache(cls, env, src, dst) -> str: """Copy a file from cache.""" if env.cache_timestamp_newer: return env.fs.copy(src, dst) else: return env.fs.copy2(src, dst)
[docs] @classmethod def copy_to_cache(cls, env, src, dst) -> str: """Copy a file to cache. Just use the FS copy2 ("with metadata") method, except do an additional check and if necessary a chmod to ensure the cachefile is writeable, to forestall permission problems if the cache entry is later updated. """ try: result = env.fs.copy2(src, dst) st = stat.S_IMODE(os.stat(result).st_mode) if not st | stat.S_IWRITE: os.chmod(dst, st | stat.S_IWRITE) return result except AttributeError as ex: raise EnvironmentError from ex
@property def hit_ratio(self) -> float: return (100.0 * self.hits / self.requests if self.requests > 0 else 100) @property def misses(self) -> int: return self.requests - self.hits
[docs] def is_enabled(self) -> bool: return cache_enabled and self.path is not None
[docs] def is_readonly(self) -> bool: return cache_readonly
[docs] def get_cachedir_csig(self, node): cachedir, cachefile = self.cachepath(node) if cachefile and os.path.exists(cachefile): return SCons.Util.hash_file_signature(cachefile, SCons.Node.FS.File.hash_chunksize)
[docs] def cachepath(self, node) -> tuple: """Return where to cache a file. Given a Node, obtain the configured cache directory and the path to the cached file, which is generated from the node's build signature. If caching is not enabled for the None, return a tuple of None. """ if not self.is_enabled(): return None, None sig = node.get_cachedir_bsig() subdir = sig[:self.config['prefix_len']].upper() cachedir = os.path.join(self.path, subdir) return cachedir, os.path.join(cachedir, sig)
[docs] def retrieve(self, node): """ This method is called from multiple threads in a parallel build, so only do thread safe stuff here. Do thread unsafe stuff in built(). Note that there's a special trick here with the execute flag (one that's not normally done for other actions). Basically if the user requested a no_exec (-n) build, then SCons.Action.execute_actions is set to 0 and when any action is called, it does its showing but then just returns zero instead of actually calling the action execution operation. The problem for caching is that if the file does NOT exist in cache then the CacheRetrieveString won't return anything to show for the task, but the Action.__call__ won't call CacheRetrieveFunc; instead it just returns zero, which makes the code below think that the file *was* successfully retrieved from the cache, therefore it doesn't do any subsequent building. However, the CacheRetrieveString didn't print anything because it didn't actually exist in the cache, and no more build actions will be performed, so the user just sees nothing. The fix is to tell Action.__call__ to always execute the CacheRetrieveFunc and then have the latter explicitly check SCons.Action.execute_actions itself. """ if not self.is_enabled(): return False env = node.get_build_env() if cache_show: if CacheRetrieveSilent(node, [], env, execute=1) == 0: node.build(presub=0, execute=0) return True else: if CacheRetrieve(node, [], env, execute=1) == 0: return True return False
[docs] def push(self, node): if self.is_readonly() or not self.is_enabled(): return return CachePush(node, [], node.get_build_env())
[docs] def push_if_forced(self, node): if cache_force: return self.push(node)
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