zeroinstall/injector/solver.py

   1 """
   2 Chooses a set of components to make a running program.
   3 """
   4
   5 # Copyright (C) 2009, Thomas Leonard
   6 # See the README file for details, or visit http://0install.net.
   7
   8 from zeroinstall import _
   9 import os
  10 from logging import debug, warn, info
  11
  12 from zeroinstall.zerostore import BadDigest, NotStored
  13
  14 from zeroinstall.injector.arch import machine_groups
  15 from zeroinstall.injector import model
  16
  17 class Solver(object):
  18         """Chooses a set of implementations to satisfy the requirements of a program and its user.
  19         Typical use:
  20          1. Create a Solver object and configure it
  21          2. Call L{solve}.
  22          3. If any of the returned feeds_used are stale or missing, you may like to start downloading them
  23          4. If it is 'ready' then you can download and run the chosen versions.
  24         @ivar selections: the chosen implementation of each interface
  25         @type selections: {L{model.Interface}: Implementation}
  26         @ivar requires: the selected dependencies for each chosen version
  27         @type requires: {L{model.Interface}: [L{model.Dependency}]}
  28         @ivar feeds_used: the feeds which contributed to the choice in L{selections}
  29         @type feeds_used: set(str)
  30         @ivar record_details: whether to record information about unselected implementations
  31         @type record_details: {L{Interface}: [(L{Implementation}, str)]}
  32         @ivar details: extra information, if record_details mode was used
  33         @type details: {str: [(Implementation, comment)]}
  34         """
  35         __slots__ = ['selections', 'requires', 'feeds_used', 'details', 'record_details', 'ready']
  36
  37         def __init__(self):
  38                 self.selections = self.requires = self.feeds_used = self.details = None
  39                 self.record_details = False
  40                 self.ready = False
  41
  42         def solve(self, root_interface, arch):
  43                 """Get the best implementation of root_interface and all of its dependencies.
  44                 @param root_interface: the URI of the program to be solved
  45                 @type root_interface: str
  46                 @param arch: the desired target architecture
  47                 @type arch: L{arch.Architecture}
  48                 @postcondition: self.ready, self.selections and self.feeds_used are updated"""
  49                 raise NotImplementedError("Abstract")
  50
  51 class DefaultSolver(Solver):
  52         """The standard (rather naive) Zero Install solver."""
  53         def __init__(self, network_use, iface_cache, stores, extra_restrictions = None):
  54                 """
  55                 @param network_use: how much use to make of the network
  56                 @type network_use: L{model.network_levels}
  57                 @param iface_cache: a cache of feeds containing information about available versions
  58                 @type iface_cache: L{iface_cache.IfaceCache}
  59                 @param stores: a cached of implementations (affects choice when offline or when minimising network use)
  60                 @type stores: L{zerostore.Stores}
  61                 @param extra_restrictions: extra restrictions on the chosen implementations
  62                 @type extra_restrictions: {L{model.Interface}: [L{model.Restriction}]}
  63                 """
  64                 Solver.__init__(self)
  65                 self.network_use = network_use
  66                 self.iface_cache = iface_cache
  67                 self.stores = stores
  68                 self.help_with_testing = False
  69                 self.extra_restrictions = extra_restrictions or {}
  70
  71         def solve(self, root_interface, arch):
  72                 self.selections = {}
  73                 self.requires = {}
  74                 self.feeds_used = set()
  75                 self.details = self.record_details and {}
  76                 self._machine_group = None
  77
  78                 restrictions = {}
  79                 debug(_("Solve! root = %s"), root_interface)
  80                 def process(dep, arch):
  81                         ready = True
  82                         iface = self.iface_cache.get_interface(dep.interface)
  83
  84                         if iface in self.selections:
  85                                 debug("Interface requested twice; skipping second %s", iface)
  86                                 if dep.restrictions:
  87                                         warn("Interface requested twice; I've already chosen an implementation "
  88                                                 "of '%s' but there are more restrictions! Ignoring the second set.", iface)
  89                                 return ready
  90                         self.selections[iface] = None   # Avoid cycles
  91                         self.requires[iface] = selected_requires = []
  92
  93                         assert iface not in restrictions
  94                         restrictions[iface] = dep.restrictions
  95
  96                         impl = get_best_implementation(iface, arch)
  97                         if impl:
  98                                 debug(_("Will use implementation %(implementation)s (version %(version)s)"), {'implementation': impl, 'version': impl.get_version()})
  99                                 self.selections[iface] = impl
 100                                 if self._machine_group is None and impl.machine and impl.machine != 'src':
 101                                         self._machine_group = machine_groups.get(impl.machine, 0)
 102                                         debug(_("Now restricted to architecture group %s"), self._machine_group)
 103                                 for d in impl.requires:
 104                                         debug(_("Considering dependency %s"), d)
 105                                         use = d.metadata.get("use", None)
 106                                         if use not in arch.use:
 107                                                 info("Skipping dependency; use='%s' not in %s", use, arch.use)
 108                                                 continue
 109                                         if not process(d, arch.child_arch):
 110                                                 ready = False
 111                                         selected_requires.append(d)
 112                         else:
 113                                 debug(_("No implementation chould be chosen yet"));
 114                                 ready = False
 115
 116                         return ready
 117
 118                 def get_best_implementation(iface, arch):
 119                         debug(_("get_best_implementation(%(interface)s), with feeds: %(feeds)s"), {'interface': iface, 'feeds': iface.feeds})
 120
 121                         iface_restrictions = restrictions.get(iface, [])
 122                         extra_restrictions = self.extra_restrictions.get(iface, None)
 123                         if extra_restrictions:
 124                                 # Don't modify original
 125                                 iface_restrictions = iface_restrictions + extra_restrictions
 126
 127                         impls = []
 128                         for f in usable_feeds(iface, arch):
 129                                 self.feeds_used.add(f)
 130                                 debug(_("Processing feed %s"), f)
 131
 132                                 try:
 133                                         feed = self.iface_cache.get_interface(f)._main_feed
 134                                         if not feed.last_modified: continue     # DummyFeed
 135                                         if feed.name and iface.uri != feed.url and iface.uri not in feed.feed_for:
 136                                                 info(_("Missing <feed-for> for '%(uri)s' in '%(feed)s'"), {'uri': iface.uri, 'feed': f})
 137
 138                                         if feed.implementations:
 139                                                 impls.extend(feed.implementations.values())
 140                                 except Exception, ex:
 141                                         warn(_("Failed to load feed %(feed)s for %(interface)s: %(exception)s"), {'feed': f, 'interface': iface, 'exception': str(ex)})
 142
 143                         if not impls:
 144                                 info(_("Interface %s has no implementations!"), iface)
 145                                 return None
 146
 147                         if self.record_details:
 148                                 # In details mode, rank all the implementations and then choose the best
 149                                 impls.sort(lambda a, b: compare(iface, a, b, iface_restrictions, arch))
 150                                 best = impls[0]
 151                                 self.details[iface] = [(impl, get_unusable_reason(impl, iface_restrictions, arch)) for impl in impls]
 152                         else:
 153                                 # Otherwise, just choose the best without sorting
 154                                 best = impls[0]
 155                                 for x in impls[1:]:
 156                                         if compare(iface, x, best, iface_restrictions, arch) < 0:
 157                                                 best = x
 158                         unusable = get_unusable_reason(best, iface_restrictions, arch)
 159                         if unusable:
 160                                 info(_("Best implementation of %(interface)s is %(best)s, but unusable (%(unusable)s)"), {'interface': iface, 'best': best, 'unusable': unusable})
 161                                 return None
 162                         return best
 163
 164                 def compare(interface, b, a, iface_restrictions, arch):
 165                         """Compare a and b to see which would be chosen first.
 166                         @param interface: The interface we are trying to resolve, which may
 167                         not be the interface of a or b if they are from feeds.
 168                         @rtype: int"""
 169                         a_stab = a.get_stability()
 170                         b_stab = b.get_stability()
 171
 172                         # Usable ones come first
 173                         r = cmp(is_unusable(b, iface_restrictions, arch), is_unusable(a, iface_restrictions, arch))
 174                         if r: return r
 175
 176                         # Preferred versions come first
 177                         r = cmp(a_stab == model.preferred, b_stab == model.preferred)
 178                         if r: return r
 179
 180                         if self.network_use != model.network_full:
 181                                 r = cmp(get_cached(a), get_cached(b))
 182                                 if r: return r
 183
 184                         # Stability
 185                         stab_policy = interface.stability_policy
 186                         if not stab_policy:
 187                                 if self.help_with_testing: stab_policy = model.testing
 188                                 else: stab_policy = model.stable
 189
 190                         if a_stab >= stab_policy: a_stab = model.preferred
 191                         if b_stab >= stab_policy: b_stab = model.preferred
 192
 193                         r = cmp(a_stab, b_stab)
 194                         if r: return r
 195
 196                         # Newer versions come before older ones
 197                         r = cmp(a.version, b.version)
 198                         if r: return r
 199
 200                         # Get best OS
 201                         r = cmp(arch.os_ranks.get(b.os, None),
 202                                 arch.os_ranks.get(a.os, None))
 203                         if r: return r
 204
 205                         # Get best machine
 206                         r = cmp(arch.machine_ranks.get(b.machine, None),
 207                                 arch.machine_ranks.get(a.machine, None))
 208                         if r: return r
 209
 210                         # Slightly prefer cached versions
 211                         if self.network_use == model.network_full:
 212                                 r = cmp(get_cached(a), get_cached(b))
 213                                 if r: return r
 214
 215                         return cmp(a.id, b.id)
 216
 217                 def usable_feeds(iface, arch):
 218                         """Return all feeds for iface that support arch.
 219                         @rtype: generator(ZeroInstallFeed)"""
 220                         yield iface.uri
 221
 222                         for f in iface.feeds:
 223                                 # Note: when searching for src, None is not in machine_ranks
 224                                 if f.os in arch.os_ranks and \
 225                                    (f.machine is None or f.machine in arch.machine_ranks):
 226                                         yield f.uri
 227                                 else:
 228                                         debug(_("Skipping '%(feed)s'; unsupported architecture %(os)s-%(machine)s"),
 229                                                 {'feed': f, 'os': f.os, 'machine': f.machine})
 230
 231                 def is_unusable(impl, restrictions, arch):
 232                         """@return: whether this implementation is unusable.
 233                         @rtype: bool"""
 234                         return get_unusable_reason(impl, restrictions, arch) != None
 235
 236                 def get_unusable_reason(impl, restrictions, arch):
 237                         """
 238                         @param impl: Implementation to test.
 239                         @type restrictions: [L{model.Restriction}]
 240                         @return: The reason why this impl is unusable, or None if it's OK.
 241                         @rtype: str
 242                         @note: The restrictions are for the interface being requested, not the interface
 243                         of the implementation; they may be different when feeds are being used."""
 244                         machine = impl.machine
 245                         if machine and self._machine_group is not None:
 246                                 if machine_groups.get(machine, 0) != self._machine_group:
 247                                         return _("Incompatible with another selection from a different architecture group")
 248
 249                         for r in restrictions:
 250                                 if not r.meets_restriction(impl):
 251                                         return _("Incompatible with another selected implementation")
 252                         stability = impl.get_stability()
 253                         if stability <= model.buggy:
 254                                 return stability.name
 255                         if self.network_use == model.network_offline and not get_cached(impl):
 256                                 return _("Not cached and we are off-line")
 257                         if impl.os not in arch.os_ranks:
 258                                 return _("Unsupported OS")
 259                         # When looking for source code, we need to known if we're
 260                         # looking at an implementation of the root interface, even if
 261                         # it's from a feed, hence the sneaky restrictions identity check.
 262                         if machine not in arch.machine_ranks:
 263                                 if machine == 'src':
 264                                         return _("Source code")
 265                                 return _("Unsupported machine type")
 266                         return None
 267
 268                 def get_cached(impl):
 269                         """Check whether an implementation is available locally.
 270                         @type impl: model.Implementation
 271                         @rtype: bool
 272                         """
 273                         if isinstance(impl, model.DistributionImplementation):
 274                                 return impl.installed
 275                         if impl.local_path:
 276                                 return os.path.exists(impl.local_path)
 277                         else:
 278                                 try:
 279                                         path = self.stores.lookup_any(impl.digests)
 280                                         assert path
 281                                         return True
 282                                 except BadDigest:
 283                                         return False
 284                                 except NotStored:
 285                                         return False
 286
 287                 self.ready = process(model.InterfaceDependency(root_interface), arch)