zeroinstall/injector/solver.py

   1 """
   2 Chooses a set of components to make a running program.
   3 """
   4
   5 import os
   6 from logging import debug, warn, info
   7
   8 from zeroinstall.zerostore import BadDigest, NotStored
   9
  10 from zeroinstall.injector import selections
  11 from zeroinstall.injector import model
  12
  13 # Copyright (C) 2008, Thomas Leonard
  14 # See the README file for details, or visit http://0install.net.
  15
  16 class Solver(object):
  17         """Chooses a set of implementations to satisfy the requirements of a program and its user.
  18         Typical use:
  19          1. Create a Solver object and configure it
  20          2. Call L{solve}.
  21          3. If any of the returned feeds_used are stale or missing, you may like to start downloading them
  22          4. If it is 'ready' then you can download and run the chosen versions.
  23         @ivar selections: the chosen implementation of each interface
  24         @type selections: {L{model.Interface}: Implementation}
  25         @ivar feeds_used: the feeds which contributed to the choice in L{selections}
  26         @type feeds_used: set(str)
  27         @ivar record_details: whether to record information about unselected implementations
  28         @type record_details: {L{Interface}: [(L{Implementation}, str)]}
  29         @ivar details: extra information, if record_details mode was used
  30         @type details: {str: [(Implementation, comment)]}
  31         """
  32         __slots__ = ['selections', 'feeds_used', 'details', 'record_details', 'ready']
  33
  34         def __init__(self):
  35                 self.selections = self.feeds_used = self.details = None
  36                 self.record_details = False
  37                 self.ready = False
  38
  39         def solve(self, root_interface, arch):
  40                 """Get the best implementation of root_interface and all of its dependencies.
  41                 @param root_interface: the URI of the program to be solved
  42                 @type root_interface: str
  43                 @param arch: the desired target architecture
  44                 @type arch: L{arch.Architecture}
  45                 @return: whether we have a viable selection
  46                 @rtype: bool
  47                 @postcondition: self.selections and self.feeds_used are updated"""
  48                 raise NotImplementedError("Abstract")
  49
  50 class DefaultSolver(Solver):
  51         """The standard (rather naive) Zero Install solver."""
  52         def __init__(self, network_use, iface_cache, stores, extra_restrictions = None):
  53                 """
  54                 @param network_use: how much use to make of the network
  55                 @type network_use: L{model.network_levels}
  56                 @param iface_cache: a cache of feeds containing information about available versions
  57                 @type iface_cache: L{iface_cache.IfaceCache}
  58                 @param stores: a cached of implementations (affects choice when offline or when minimising network use)
  59                 @type stores: L{zerostore.Stores}
  60                 @param extra_restrictions: extra restrictions on the chosen implementations
  61                 @type extra_restrictions: {L{model.Interface}: [L{model.Restriction}]}
  62                 """
  63                 Solver.__init__(self)
  64                 self.network_use = network_use
  65                 self.iface_cache = iface_cache
  66                 self.stores = stores
  67                 self.help_with_testing = False
  68                 self.extra_restrictions = extra_restrictions or {}
  69
  70         def solve(self, root_interface, arch):
  71                 self.selections = {}
  72                 self.feeds_used = set()
  73                 self.details = self.record_details and {}
  74
  75                 restrictions = {}
  76                 debug("Solve! root = %s", root_interface)
  77                 def process(dep, arch):
  78                         ready = True
  79                         iface = self.iface_cache.get_interface(dep.interface)
  80
  81                         if iface in self.selections:
  82                                 debug("Interface requested twice; skipping second %s", iface)
  83                                 if dep.restrictions:
  84                                         warn("Interface requested twice; I've already chosen an implementation "
  85                                                 "of '%s' but there are more restrictions! Ignoring the second set.", iface)
  86                                 return
  87                         self.selections[iface] = None   # Avoid cycles
  88
  89                         assert iface not in restrictions
  90                         restrictions[iface] = dep.restrictions
  91
  92                         impl = get_best_implementation(iface, arch)
  93                         if impl:
  94                                 debug("Will use implementation %s (version %s)", impl, impl.get_version())
  95                                 self.selections[iface] = impl
  96                                 for d in impl.requires:
  97                                         debug("Considering dependency %s", d)
  98                                         if not process(d, arch.child_arch):
  99                                                 ready = False
 100                         else:
 101                                 debug("No implementation chould be chosen yet");
 102                                 ready = False
 103
 104                         return ready
 105
 106                 def get_best_implementation(iface, arch):
 107                         debug("get_best_implementation(%s), with feeds: %s", iface, iface.feeds)
 108
 109                         iface_restrictions = restrictions.get(iface, [])
 110                         extra_restrictions = self.extra_restrictions.get(iface, None)
 111                         if extra_restrictions:
 112                                 # Don't modify original
 113                                 iface_restrictions = iface_restrictions + extra_restrictions
 114
 115                         impls = []
 116                         for f in usable_feeds(iface, arch):
 117                                 self.feeds_used.add(f)
 118                                 debug("Processing feed %s", f)
 119
 120                                 try:
 121                                         feed = self.iface_cache.get_interface(f)._main_feed
 122                                         if not feed.last_modified: continue     # DummyFeed
 123                                         if feed.name and iface.uri != feed.url and iface.uri not in feed.feed_for:
 124                                                 warn("Missing <feed-for> for '%s' in '%s'", iface.uri, f)
 125
 126                                         if feed.implementations:
 127                                                 impls.extend(feed.implementations.values())
 128                                 except Exception, ex:
 129                                         warn("Failed to load feed %s for %s: %s", f, iface, str(ex))
 130
 131                         if not impls:
 132                                 info("Interface %s has no implementations!", iface)
 133                                 return None
 134
 135                         if self.record_details:
 136                                 # In details mode, rank all the implementations and then choose the best
 137                                 impls.sort(lambda a, b: compare(iface, a, b, iface_restrictions, arch))
 138                                 best = impls[0]
 139                                 self.details[iface] = [(impl, get_unusable_reason(impl, iface_restrictions, arch)) for impl in impls]
 140                         else:
 141                                 # Otherwise, just choose the best without sorting
 142                                 best = impls[0]
 143                                 for x in impls[1:]:
 144                                         if compare(iface, x, best, iface_restrictions, arch) < 0:
 145                                                 best = x
 146                         unusable = get_unusable_reason(best, iface_restrictions, arch)
 147                         if unusable:
 148                                 info("Best implementation of %s is %s, but unusable (%s)", iface, best, unusable)
 149                                 return None
 150                         return best
 151
 152                 def compare(interface, b, a, iface_restrictions, arch):
 153                         """Compare a and b to see which would be chosen first.
 154                         @param interface: The interface we are trying to resolve, which may
 155                         not be the interface of a or b if they are from feeds.
 156                         @rtype: int"""
 157                         a_stab = a.get_stability()
 158                         b_stab = b.get_stability()
 159
 160                         # Usable ones come first
 161                         r = cmp(is_unusable(b, iface_restrictions, arch), is_unusable(a, iface_restrictions, arch))
 162                         if r: return r
 163
 164                         # Preferred versions come first
 165                         r = cmp(a_stab == model.preferred, b_stab == model.preferred)
 166                         if r: return r
 167
 168                         if self.network_use != model.network_full:
 169                                 r = cmp(get_cached(a), get_cached(b))
 170                                 if r: return r
 171
 172                         # Stability
 173                         stab_policy = interface.stability_policy
 174                         if not stab_policy:
 175                                 if self.help_with_testing: stab_policy = model.testing
 176                                 else: stab_policy = model.stable
 177
 178                         if a_stab >= stab_policy: a_stab = model.preferred
 179                         if b_stab >= stab_policy: b_stab = model.preferred
 180
 181                         r = cmp(a_stab, b_stab)
 182                         if r: return r
 183
 184                         # Newer versions come before older ones
 185                         r = cmp(a.version, b.version)
 186                         if r: return r
 187
 188                         # Get best OS
 189                         r = cmp(arch.os_ranks.get(a.os, None),
 190                                 arch.os_ranks.get(b.os, None))
 191                         if r: return r
 192
 193                         # Get best machine
 194                         r = cmp(arch.machine_ranks.get(a.machine, None),
 195                                 arch.machine_ranks.get(b.machine, None))
 196                         if r: return r
 197
 198                         # Slightly prefer cached versions
 199                         if self.network_use == model.network_full:
 200                                 r = cmp(get_cached(a), get_cached(b))
 201                                 if r: return r
 202
 203                         return cmp(a.id, b.id)
 204
 205                 def usable_feeds(iface, arch):
 206                         """Return all feeds for iface that support arch.
 207                         @rtype: generator(ZeroInstallFeed)"""
 208                         yield iface.uri
 209
 210                         for f in iface.feeds:
 211                                 if f.os in arch.os_ranks and f.machine in arch.machine_ranks:
 212                                         yield f.uri
 213                                 else:
 214                                         debug("Skipping '%s'; unsupported architecture %s-%s",
 215                                                 f, f.os, f.machine)
 216
 217                 def is_unusable(impl, restrictions, arch):
 218                         """@return: whether this implementation is unusable.
 219                         @rtype: bool"""
 220                         return get_unusable_reason(impl, restrictions, arch) != None
 221
 222                 def get_unusable_reason(impl, restrictions, arch):
 223                         """
 224                         @param impl: Implementation to test.
 225                         @type restrictions: [L{model.Restriction}]
 226                         @return: The reason why this impl is unusable, or None if it's OK.
 227                         @rtype: str
 228                         @note: The restrictions are for the interface being requested, not the interface
 229                         of the implementation; they may be different when feeds are being used."""
 230                         for r in restrictions:
 231                                 if not r.meets_restriction(impl):
 232                                         return "Incompatible with another selected implementation"
 233                         stability = impl.get_stability()
 234                         if stability <= model.buggy:
 235                                 return stability.name
 236                         if self.network_use == model.network_offline and not get_cached(impl):
 237                                 return "Not cached and we are off-line"
 238                         if impl.os not in arch.os_ranks:
 239                                 return "Unsupported OS"
 240                         # When looking for source code, we need to known if we're
 241                         # looking at an implementation of the root interface, even if
 242                         # it's from a feed, hence the sneaky restrictions identity check.
 243                         if impl.machine not in arch.machine_ranks:
 244                                 if impl.machine == 'src':
 245                                         return "Source code"
 246                                 return "Unsupported machine type"
 247                         return None
 248
 249                 def get_cached(impl):
 250                         """Check whether an implementation is available locally.
 251                         @type impl: model.Implementation
 252                         @rtype: bool
 253                         """
 254                         if isinstance(impl, model.DistributionImplementation):
 255                                 return impl.installed
 256                         if impl.id.startswith('/'):
 257                                 return os.path.exists(impl.id)
 258                         else:
 259                                 try:
 260                                         path = self.stores.lookup(impl.id)
 261                                         assert path
 262                                         return True
 263                                 except BadDigest:
 264                                         return False
 265                                 except NotStored:
 266                                         return False
 267
 268                 self.ready = process(model.InterfaceDependency(root_interface), arch)