branchcache: explicitly track inheritence "state"

We move from a binary "dirty" flag to a three value "state": "clean", "inherited", "dirty".

The "inherited" means that the branch cache is not only "clean", but it is a
duplicate of its parent filter.

If a branch cache is "inherited", we can non only skip writing its value on
disk, but it is a good idea to delete any stale value on disk, as those will
just waste time (and possibly induce bug) in the future.

We only do this in the update related to transaction or explicit cache update
(e.g `hg debugupdatecache`). Deleting the file when we simply detected a stall
cache during a read only operation seems more dangerous.

We rename `copy` to `inherit_for` to clarify we associate a stronger semantic
to the operation.

contrib/perf.py

@@ -4303,8 +4303,16 b' def perfbranchmapupdate(ui, repo, base=('
         baserepo = repo.filtered(b'__perf_branchmap_update_base')
         targetrepo = repo.filtered(b'__perf_branchmap_update_target')
 
+        bcache = repo.branchmap()
+        copy_method = 'copy'
+
         copy_base_kwargs = copy_base_kwargs = {}
-        if 'repo' in getargspec(repo.branchmap().copy).args:
+        if hasattr(bcache, 'copy'):
+            if 'repo' in getargspec(bcache.copy).args:
+                copy_base_kwargs = {"repo": baserepo}
+                copy_target_kwargs = {"repo": targetrepo}
+        else:
+            copy_method = 'inherit_for'
             copy_base_kwargs = {"repo": baserepo}
             copy_target_kwargs = {"repo": targetrepo}
 
@@ -4316,7 +4324,7 b' def perfbranchmapupdate(ui, repo, base=('
             if candidatebm.validfor(baserepo):
                 filtered = repoview.filterrevs(repo, candidatefilter)
                 missing = [r for r in allbaserevs if r in filtered]
-                base = candidatebm.copy(**copy_base_kwargs)
+                base = getattr(candidatebm, copy_method)(**copy_base_kwargs)
                 base.update(baserepo, missing)
                 break
             candidatefilter = subsettable.get(candidatefilter)
@@ -4326,7 +4334,7 b' def perfbranchmapupdate(ui, repo, base=('
             base.update(baserepo, allbaserevs)
 
         def setup():
-            x[0] = base.copy(**copy_target_kwargs)
+            x[0] = getattr(base, copy_method)(**copy_target_kwargs)
             if clearcaches:
                 unfi._revbranchcache = None
                 clearchangelog(repo)

mercurial/branchmap.py

@@ -85,8 +85,7 b' class BranchMapCache:'
             bcache._filtername,
             repo.filtername,
         )
-        if bcache._dirty:
-            bcache.write(repo)
+        bcache.sync_disk(repo)
 
     def updatecache(self, repo):
         """Update the cache for the given filtered view on a repository"""
@@ -109,7 +108,7 b' class BranchMapCache:'
             subsetname = subsettable.get(filtername)
             if subsetname is not None:
                 subset = repo.filtered(subsetname)
-                bcache = self[subset].copy(repo)
+                bcache = self[subset].inherit_for(repo)
                 extrarevs = subset.changelog.filteredrevs - cl.filteredrevs
                 revs.extend(r for r in extrarevs if r <= bcache.tiprev)
             else:
@@ -160,7 +159,7 b' class BranchMapCache:'
                 if cache.validfor(rview):
                     cache._filtername = candidate
                     self._per_filter[candidate] = cache
-                    cache._dirty = True
+                    cache._state = STATE_DIRTY
                     cache.write(rview)
                     return
 
@@ -173,12 +172,11 b' class BranchMapCache:'
             cache = self._per_filter.get(filtername)
             if cache is None:
                 continue
-            if cache._dirty:
-                if filtername is None:
-                    repo = unfi
-                else:
-                    repo = unfi.filtered(filtername)
-                cache.write(repo)
+            if filtername is None:
+                repo = unfi
+            else:
+                repo = unfi.filtered(filtername)
+            cache.sync_disk(repo)
 
 
 def _unknownnode(node):
@@ -414,6 +412,11 b' class _BaseBranchCache:'
         return max_rev
 
 
+STATE_CLEAN = 1
+STATE_INHERITED = 2
+STATE_DIRTY = 3
+
+
 class branchcache(_BaseBranchCache):
     """Branchmap info for a local repo or repoview"""
 
@@ -431,6 +434,7 b' class branchcache(_BaseBranchCache):'
         closednodes: Optional[Set[bytes]] = None,
         hasnode: Optional[Callable[[bytes], bool]] = None,
         verify_node: bool = False,
+        inherited: bool = False,
     ) -> None:
         """hasnode is a function which can be used to verify whether changelog
         has a given node or not. If it's not provided, we assume that every node
@@ -442,7 +446,9 b' class branchcache(_BaseBranchCache):'
             self.tipnode = tipnode
         self.tiprev = tiprev
         self.filteredhash = filteredhash
-        self._dirty = False
+        self._state = STATE_CLEAN
+        if inherited:
+            self._state = STATE_INHERITED
 
         super().__init__(repo=repo, entries=entries, closed_nodes=closednodes)
         # closednodes is a set of nodes that close their branch. If the branch
@@ -555,7 +561,7 b' class branchcache(_BaseBranchCache):'
             filename = b'%s-%s' % (filename, repo.filtername)
         return filename
 
-    def copy(self, repo):
+    def inherit_for(self, repo):
         """return a deep copy of the branchcache object"""
         assert repo.filtername != self._filtername
         other = type(self)(
@@ -569,16 +575,33 b' class branchcache(_BaseBranchCache):'
             filteredhash=self.filteredhash,
             closednodes=set(self._closednodes),
             verify_node=self._verify_node,
+            inherited=True,
         )
         # also copy information about the current verification state
         other._verifiedbranches = set(self._verifiedbranches)
         return other
 
+    def sync_disk(self, repo):
+        """synchronise the on disk file with the cache state
+
+        If new value specific to this filter level need to be written, the file
+        will be updated, if the state of the branchcache is inherited from a
+        subset, any stalled on disk file will be deleted.
+
+        That method does nothing if there is nothing to do.
+        """
+        if self._state == STATE_DIRTY:
+            self.write(repo)
+        elif self._state == STATE_INHERITED:
+            filename = self._filename(repo)
+            repo.cachevfs.tryunlink(filename)
+
     def write(self, repo):
         assert self._filtername == repo.filtername, (
             self._filtername,
             repo.filtername,
         )
+        assert self._state == STATE_DIRTY, self._state
         tr = repo.currenttransaction()
         if not getattr(tr, 'finalized', True):
             # Avoid premature writing.
@@ -597,7 +620,7 b' class branchcache(_BaseBranchCache):'
                 len(self._entries),
                 nodecount,
             )
-            self._dirty = False
+            self._state = STATE_CLEAN
         except (IOError, OSError, error.Abort) as inst:
             # Abort may be raised by read only opener, so log and continue
             repo.ui.debug(
@@ -707,7 +730,7 b' class branchcache(_BaseBranchCache):'
         self.filteredhash = scmutil.filteredhash(
             repo, self.tiprev, needobsolete=True
         )
-        self._dirty = True
+        self._state = STATE_DIRTY
         self.write(repo)
 
 

tests/test-acl.t

@@ -167,7 +167,6 b' Extension disabled for lack of acl.sourc'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -187,7 +186,6 b' Extension disabled for lack of acl.sourc'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -237,7 +235,6 b' No [acl.allow]/[acl.deny]'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -257,7 +254,6 b' No [acl.allow]/[acl.deny]'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -317,7 +313,6 b' Empty [acl.allow]'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -337,7 +332,6 b' Empty [acl.allow]'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -388,7 +382,6 b' fred is allowed inside foo/'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -408,7 +401,6 b' fred is allowed inside foo/'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -463,7 +455,6 b' Empty [acl.deny]'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -483,7 +474,6 b' Empty [acl.deny]'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -535,7 +525,6 b' fred is allowed inside foo/, but not foo'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -555,7 +544,6 b' fred is allowed inside foo/, but not foo'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -612,7 +600,6 b' fred is allowed inside foo/, but not foo'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -632,7 +619,6 b' fred is allowed inside foo/, but not foo'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -686,7 +672,6 b' fred is allowed inside foo/, but not foo'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -706,7 +691,6 b' fred is allowed inside foo/, but not foo'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -761,7 +745,6 b' fred is not blocked from moving bookmark'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   1 changesets found
   list of changesets:
@@ -783,7 +766,6 b' fred is not blocked from moving bookmark'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -849,7 +831,6 b' fred is not allowed to move bookmarks'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   1 changesets found
   list of changesets:
@@ -871,7 +852,6 b' fred is not allowed to move bookmarks'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -938,7 +918,6 b' barney is allowed everywhere'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -958,7 +937,6 b' barney is allowed everywhere'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -1024,7 +1002,6 b' wilma can change files with a .txt exten'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -1044,7 +1021,6 b' wilma can change files with a .txt exten'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -1108,7 +1084,6 b' file specified by acl.config does not ex'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -1128,7 +1103,6 b' file specified by acl.config does not ex'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -1186,7 +1160,6 b' betty is allowed inside foo/ by a acl.co'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -1206,7 +1179,6 b' betty is allowed inside foo/ by a acl.co'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -1275,7 +1247,6 b' acl.config can set only [acl.allow]/[acl'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -1295,7 +1266,6 b' acl.config can set only [acl.allow]/[acl'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -1365,7 +1335,6 b' fred is always allowed'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -1385,7 +1354,6 b' fred is always allowed'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -1452,7 +1420,6 b' no one is allowed inside foo/Bar/'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -1472,7 +1439,6 b' no one is allowed inside foo/Bar/'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -1535,7 +1501,6 b' OS-level groups'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -1555,7 +1520,6 b' OS-level groups'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374
@@ -1622,7 +1586,6 b' OS-level groups'
   listing keys for "phases"
   checking for updated bookmarks
   listing keys for "bookmarks"
-  invalid branch cache (served): tip differs
   listing keys for "bookmarks"
   3 changesets found
   list of changesets:
@@ -1642,7 +1605,6 b' OS-level groups'
   bundle2-input-part: total payload size * (glob)
   bundle2-input-part: "check:updated-heads" supported
   bundle2-input-part: total payload size * (glob)
-  invalid branch cache (served): tip differs
   bundle2-input-part: "changegroup" (params: 1 mandatory) supported
   adding changesets
   add changeset ef1ea85a6374

tests/test-blackbox.t

@@ -188,13 +188,11 b' backup bundles get logged'
   $ hg strip tip
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved
   saved backup bundle to $TESTTMP/blackboxtest2/.hg/strip-backup/*-backup.hg (glob)
-  $ hg blackbox -l 6
+  $ hg blackbox -l 4
   1970-01-01 00:00:00.000 bob @73f6ee326b27d820b0472f1a825e3a50f3dc489b (5000)> strip tip
   1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> saved backup bundle to $TESTTMP/blackboxtest2/.hg/strip-backup/73f6ee326b27-7612e004-backup.hg
-  1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> updated branch cache (base) in * seconds (glob)
-  1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> wrote branch cache (base) with 1 labels and 2 nodes
   1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> strip tip exited 0 after * seconds (glob)
-  1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> blackbox -l 6
+  1970-01-01 00:00:00.000 bob @6563da9dcf87b1949716e38ff3e3dfaa3198eb06 (5000)> blackbox -l 4
 
 extension and python hooks - use the eol extension for a pythonhook
 

tests/test-strip-branch-cache.t

@@ -43,11 +43,9 b' older one have been actively deleted.'
 
   $ ls -1 .hg/cache/branch?*
   .hg/cache/branch2-base
-  .hg/cache/branch2-served
-  $ cat .hg/cache/branch?-served
-  222ae9789a75703f9836e44de7db179cbfd420ee 2
-  a3498d6e39376d2456425dd8c692367bdbf00fa2 o default
-  222ae9789a75703f9836e44de7db179cbfd420ee o default
+  $ cat .hg/cache/branch?-base
+  7ab0a3bd758a58b9f79557ce708533e627776cce 0
+  7ab0a3bd758a58b9f79557ce708533e627776cce o default
 
 We do a new commit and we get a new valid branchmap for the served version