Avoid `git-annex sync --content` etc from operating on cluster nodes by default
since syncing with a cluster implicitly syncs with its nodes. This avoids a
lot of unncessary work when a cluster has a lot of nodes just in checking
if each node's preferred content is satisfied. And it avoids content
being sent to nodes individually, so instead syncing with clusters always
fanout uploads to nodes.
The downside is that there are situations where a cluster's preferred content
settings can be met, but those of its nodes are not. Or where a node does not
contain a key, but the cluster does, and there are not enough copies of the key
yet, so it would be desirable the send it there. I think that's an acceptable
tradeoff. These kind of situations are ones where the cluster itself should
probably be responsible for copying content to the node. Which it can do much
less expensively than a client can. Part of the balanced preferred content
design that I will be working on in a couple of months involves rebalancing
clusters, so I expect to revisit this.
The use of annex-sync config does allow running git-annex sync with a specific
node, or nodes, and it will sync with it. And it's also possible to set
annex-sync git configs to make it sync with a node by default. (Although that
will require setting up an explicit git remote for the node rather than relying
on the proxied remote.)
Logs.Cluster.Basic is needed because Remote.Git cannot import Logs.Cluster
due to a cycle. And the Annex.Startup load of clusters happens
too late for Remote.Git to use that. This does mean one redundant load
of the cluster log, though only when there is a proxy.
Works down to P2P protocol.
The question now is, how to handle protocol version negotiation for
clusters? Connecting to each node to find their protocol versions and
using the lowest would be too expensive with a lot of nodes. So it seems
that the cluster needs to pick its own protocol version to use with the
client.
Then it can either negotiate that same version with the nodes when
it comes time to use them, or it can translate between multiple protocol
versions. That seems complicated. Thinking it would be ok to refuse to
use a node if it is not able to negotiate the same protocol version with
it as with the client. That will mean that sometimes need nodes to be
upgraded when upgrading the cluster's proxy. But protocol versions
rarely change.
This is to avoid inserting a cluster uuid into the location log when
only dead nodes in the cluster contain the content of a key.
One reason why this is necessary is Remote.keyLocations, which excludes
dead repositories from the list. But there are probably many more.
Implementing this was challenging, because Logs.Location importing
Logs.Cluster which imports Logs.Trust which imports Remote.List resulted
in an import cycle through several other modules.
Resorted to making Logs.Location not import Logs.Cluster, and instead
it assumes that Annex.clusters gets populated when necessary before it's
called.
That's done in Annex.Startup, which is run by the git-annex command
(but not other commands) at early startup in initialized repos. Or,
is run after initialization.
Note that is Remote.Git, it is unable to import Annex.Startup, because
Remote.Git importing Logs.Cluster leads the the same import cycle.
So ensureInitialized is not passed annexStartup in there.
Other commands, like git-annex-shell currently don't run annexStartup
either.
So there are cases where Logs.Location will not see clusters. So it won't add
any cluster UUIDs when loading the log. That's ok, the only reason to do
that is to make display of where objects are located include clusters,
and to make commands like git-annex get --from treat keys as being located
in a cluster. git-annex-shell certainly does not do anything like that,
and I'm pretty sure Remote.Git (and callers to Remote.Git.onLocalRepo)
don't either.
A cluster UUID is a version 8 UUID, with first octets 'a' and 'c'.
The rest of the content will be random.
This avoids a class of attack where the UUID of a repository is used as
the UUID of a cluster, which will prevent git-annex from updating
location logs for that repository. I don't know why someone would want
to do that, but let's prevent it.
Also, isClusterUUID make it easy to filter out cluster UUIDs when
writing the location logs.
Not used yet. (Or tested.)
I did consider making the log start with the uuid of the node, followed
by the cluster uuid (or uuids). That would perhaps mean a smaller write
to the git-annex branch when adding a node, but overall the log file
would be larger, and it will be read and cached near to startup on most
git-annex runs.
It was possible for the export.log to get written and then git-annex was
interrupted, before it could graft in the exported tree. Which could
result in export.log referencing a tree that got garbage collected.
Untested, but this should be close to working. The proxied remotes have
the same url but a different uuid. When talking to current
git-annex-shell, it will fail due to a uuid mismatch. Once it supports
proxies, it will know that the presented uuid is for a remote that it
proxies for.
The check for any git config settings for a remote with the same name as
the proxied remote is there for several reasons. One is security:
Writing a name to the proxy log should not cause changes to
how an existing, configured git remote operates in a different clone of
the repo.
It's possible that the user has been using a proxied remote, and decides
to set a git config for it. We can't tell the difference between that
scenario and an evil remote trying to eg, intercept a file upload
by replacing their remote with a proxied remote.
Also, if the user sets some git config, does it override the config
inherited from the proxy remote? Seems a difficult question. Luckily,
the above means we don't need to think through it.
This does mean though, that in order for a user to change the config of
a proxy remote, they have to manually set its annex-uuid and url, as
well as the config they want to change. They may also have to set any of
the inherited configs that they were relying on.
While redundant concurrent transfers were already prevented in most
cases, it failed to prevent the case where two different repositories were
sending the same content to the same repository. By removing the uuid
from the transfer lock file for Download transfers, one repository
sending content will block the other one from also sending the same
content.
In order to interoperate with old git-annex, the old lock file is still
locked, as well as locking the new one. That added a lot of extra code
and work, and the plan is to eventually stop locking the old lock file,
at some point in time when an old git-annex process is unlikely to be
running at the same time.
Note that in the case of 2 repositories both doing eg
`git-annex copy foo --to origin`
the output is not that great:
copy b (to origin...)
transfer already in progress, or unable to take transfer lock
git-annex: transfer already in progress, or unable to take transfer lock
97% 966.81 MiB 534 GiB/s 0sp2pstdio: 1 failed
Lost connection (fd:14: hPutBuf: resource vanished (Broken pipe))
Transfer failed
Perhaps that output could be cleaned up? Anyway, it's a lot better than letting
the redundant transfer happen and then failing with an obscure error about
a temp file, which is what it did before. And it seems users don't often
try to do this, since nobody ever reported this bug to me before.
(The "97%" there is actually how far along the *other* transfer is.)
Sponsored-by: Joshua Antonishen on Patreon
When downloading a VURL from the web, make sure that the equivilant key
log is populated.
Unfortunately, this does not hash the content while it's being
downloaded from the web. There is not an interface in Backend currently
for incrementally hash generation, only for incremental verification of an
existing hash. So this might add a noticiable delay, and it has to show
a "(checksum...") message. This could stand to be improved.
But, that separate hashing step only has to happen on the first download
of new content from the web. Once the hash is known, the VURL key can have
its hash verified incrementally while downloading except when the
content in the web has changed. (Doesn't happen yet because
verifyKeyContentIncrementally is not implemented yet for VURL keys.)
Note that the equivilant key log file is formatted as a presence log.
This adds a tiny bit of overhead (eg "1 ") per line over just listing the
urls. The reason I chose to use that format is it seems possible that
there will need to be a way to remove an equivilant key at some point in
the future. I don't know why that would be necessary, but it seemed wise
to allow for the possibility.
Downloads of VURL keys from other special remotes that claim urls,
like bittorrent for example, does not popilate the equivilant key log.
So for now, no checksum verification will be done for those.
Sponsored-by: Nicholas Golder-Manning on Patreon
When importing from a special remote, support preferred content expressions
that use terms that match on keys (eg "present", "copies=1"). Such terms
are ignored when importing, since the key is not known yet.
When "standard" or "groupwanted" is used, the terms in those
expressions also get pruned accordingly.
This does allow setting preferred content to "not (copies=1)" to make a
special remote into a "source" type of repository. Importing from it will
import all files. Then exporting to it will drop all files from it.
In the case of setting preferred content to "present", it's pruned on
import, so everything gets imported from it. Then on export, it's applied,
and everything in it is left on it, and no new content is exported to it.
Since the old behavior on these preferred content expressions was for
importtree to error out, there's no backwards compatability to worry about.
Except that sync/pull/etc will now import where before it errored out.
And avoid migrate --update/--aply migrating when the new key was already
present in the repository, and got dropped. Luckily, the location log
allows distinguishing from the new key never having been present!
That is mostly useful for --apply because otherwise dropped files would
keep coming back until the old objects were reaped as unused. But it
seemed to make sense to also do it for --update. for consistency in edge
cases if nothing else. One case where --update can use it is when one
branch got migrated earlier, and we dropped the file, and now another
branch has migrated the same file.
Sponsored-by: Jack Hill on Patreon
The git log is outputting the diff, but this only looks at the new
files. When we have a new file, we can get the old filename by just
replacing "new" with "old". And then use branchFileRef to refer to it
allows catting the old key.
While this does have to skip past the old files in the diff, it's still
faster than calling git diff separately.
Sponsored-by: Nicholas Golder-Manning on Patreon
This is most of the way there, but not quite working.
The layout of migrate.tree/ needs to be changed to follow this approach.
git log will list all the files in tree order, so the new layout needs
to alternate old and new keys. Can that be done? git may not document
tree order, or may not preserve it here.
Alternatively, change to using git log --format=raw and extract
the tree header from that, then use
git diff --raw $tree:migrate.tree/old $tree:migrate.tree/new
That will be a little more expensive, but only when there are lots of
migrations.
Sponsored-by: Joshua Antonishen on Patreon
This will allow distributed migration: Start a migration in one clone of
a repo, and then update other clones.
commitMigration is a bit of a bear.. There is some inversion of control
that needs some TMVars. Also streamLogFile's finalizer does not handle
recording the trees, so an interrupt at just the wrong time can cause
migration.log to be emptied but the git-annex branch not updated.
Sponsored-by: Graham Spencer on Patreon
Noticed that Semigroup instance of Map is not suitable to use
for MapLog. For example, it behaved like this:
ghci> parseTrustLog "foo 1 timestamp=10\nfoo 2 timestamp=11" <> parseTrustLog "foo X timestamp=12"
fromList [(UUID "foo",LogEntry {changed = VectorClock 11s, value = SemiTrusted})]
Which was wrong, it lost the newer DeadTrusted value.
Luckily, nothing used that Semigroup when operating on a MapLog. And this
provides a safe instance.
Sponsored-by: Graham Spencer on Patreon
This can take a lot of memory. I decided to violate the usual rule in
git-annex that it operate in constant memory no matter how many annexed
objects. In this case, it would be hard to be fast without using a big
map of the location logs. The main difficulty here is that there can be
many git-annex branches and it needs to display a consistent view at a
point in time, which means merging information from multiple git-annex
branches.
I have not checked if there are any laziness leaks in this code. It
takes 1 gb to run in my big repo, which is around what I estimated
before writing it.
2 options that are documented are not yet implemented.
Small bug: With eg --when=1h, it will display at 12:00 then 1:10 if the
next change after 12:59 is then. Then it waits until after 2:10 to
display the next change. It ought to wait until after 2:00.
Sponsored-by: Brock Spratlen on Patreon
Factored out overLocationLogs from CmdLine.Seek, which can calculate this
pretty fast even in a large repo. In my big repo, the time to run git-annex
info went up from 1.33s to 8.5s.
Note that the "backend usage" stats are for annexed files in the working
tree only, not all annexed files. This new data source would let that be
changed, but that would be a confusing behavior change. And I cannot
retitle it either, out of fear something uses the current title (eg parsing
the json).
Also note that, while time says "402108maxresident" in my big repo now,
up from "54092maxresident", top shows the RES constant at 64mb, and it
was 48mb before. So I don't think there is a memory leak. I tried using
deepseq to force full evaluation of addKeyCopies and memory use didn't
change, which also says no memory leak. And indeed, not even calling
addKeyCopies resulted in the same memory use. Probably the increased memory
usage is buffering the stream of data from git in overLocationLogs.
Sponsored-by: Brett Eisenberg on Patreon
In particular, the mergedrefs file was written with CR added to each line,
but read without CRLF handling. This resulted in each update of the file
adding CR to each line in it, growing the number of lines, while also
preventing the optimisation from working, so it remerged unncessarily.
writeFile and readFile do NewlineMode translation on Windows. But the
ByteString conversion prevented that from happening any longer.
I've audited for other cases of this, and found three more
(.git/annex/index.lck, .git/annex/ignoredrefs, and .git/annex/import/). All
of those also only prevent optimisations from working. Some other files are
currently both read and written with ByteString, but old git-annex may have
written them with NewlineMode translation. Other files are at risk for
breakage later if the reader gets converted to ByteString.
This is a minimal fix, but should be enough, as long as I remember to use
fileLines when splitting a ByteString into lines. This leaves files written
using ByteString without CR added, but that's ok because old git-annex has
no difficulty reading such files.
When the mergedrefs file has gotten lines that end with "\r\r\r\n", this
will eventually clean it up. Each update will remove a single trailing CR.
Note that S8.lines is still used in eg Command.Unused, where it is parsing
git show-ref, and similar in Git/*. git commands don't include CR in their
output so that's ok.
Sponsored-by: Joshua Antonishen on Patreon
Minor optimisation, but a win in every case, except for a couple where
it's a wash.
Note that replaceFile still takes a FilePath, because it needs to
operate on Chars to truncate unicode filenames properly.
Note the use of fromString and toString from Data.ByteString.UTF8 dated
back to commit 9b93278e8a. Back then it
was using the dataenc package for base64, which operated on Word8 and
String. But with the switch to sandi, it uses ByteString, and indeed
fromB64' and toB64' were already using ByteString without that
complication. So I think there is no risk of such an encoding related
breakage.
I also tested the case that 9b93278e8a
fixed:
git-annex metadata -s foo='a …' x
git-annex metadata x
metadata x
foo=a …
In Remote.Helper.Encryptable, it was avoiding using Utility.Base64
because of that UTF8 conversion. Since that's no longer done, it can
just use it now.
Avoid conversion from ByteString to String for urls that will just be
converted right back to ByteString to go into the database.
Also setTempUrl is not used by importfeed, so avoid checking for temp
urls in this code path.
This benchmarks as only a small improvement. From 2.99s to 2.78s
when populating a database with 33k urls.
Note that it does not seem worth replacing URLString with URLByteString
generally, because the ways urls are used all entails either parseURI,
which takes a string, or passing a parameter to eg curl, which also is
currently a string.
Sponsored-by: Leon Schuermann on Patreon
Fix behavior when importing a tree from a directory remote when the
directory does not exist. An empty tree was imported, rather than the
import failing. Merging that tree would delete every file in the
branch, if those files had been exported to the directory before.
The problem was that dirContentsRecursive returned [] when the directory
did not exist. Better for it to throw an exception. But in commit
74f0d67aa3 back in 2012, I made it never
theow exceptions, because exceptions throw inside unsafeInterleaveIO become
untrappable when the list is being traversed.
So, changed it to list the contents of the directory before entering
unsafeInterleaveIO. So exceptions are thrown for the directory. But still
not if it's unable to list the contents of a subdirectory. That's less of a
problem, because the subdirectory does exist (or if not, it got removed
after being listed, and it's ok to not include it in the list). A
subdirectory that has permissions that don't allow listing it will have its
contents omitted from the list still.
(Might be better to have it return a type that includes indications of
errors listing contents of subdirectories?)
The rest of the changes are making callers of dirContentsRecursive
use emptyWhenDoesNotExist when they relied on the behavior of it not
throwing an exception when the directory does not exist. Note that
it's possible some callers of dirContentsRecursive that used to ignore
permissions problems listing a directory will now start throwing exceptions
on them.
The fix to the directory special remote consisted of not making its
call in listImportableContentsM use emptyWhenDoesNotExist. So it will
throw an exception as desired.
Sponsored-by: Joshua Antonishen on Patreon
And annex.largefiles and annex.addunlocked.
Also git-annex matchexpression --explain explains why its input
expression matches or fails to match.
When there is no limit, avoid explaining why the lack of limit
matches. This is also done when no preferred content expression is set,
although in a few cases it defaults to a non-empty matcher, which will
be explained.
Sponsored-by: Dartmouth College's DANDI project
Speeds up sync in an adjusted branch by avoiding re-adjusting the branch
unncessarily, particularly when it is adjusted with --hide-missing or
--unlock-present.
When there are a lot of files, that was the majority of the time of a
--no-content sync.
Uses a log file, which is updated when content presence changes. This
adds a little bit of overhead to every file get/drop when on such an
adjusted branch. The overhead is minimal for get of any size of file,
but might be noticable for drop in some cases. It seems like a reasonable
trade-off. It would be possible to update the log file only at the end, but
then it would not happen if the command is interrupted.
When not in an adjusted branch, there should be no additional overhead.
(getCurrentBranch is an MVar read, and it avoids the MVar read of
getGitConfig.)
Note that this does not deal with situations such as:
git checkout master, git-annex get, git checkout adjusted branch,
git-annex sync. The sync won't know that the adjusted branch needs to be
updated. Dealing with that would add overhead to operation in non-adjusted
branches, which I don't like. Also, there are other situations like having
two adjusted branches that both need to be updated like this, and switching
between them and sync not updating.
This does mean a behavior change to sync, since it did previously deal
with those situations. But, the documentation did not say that it did.
The man pages only talk about sync updating the adjusted branch after
it transfers content.
I did consider making sync keep track of content it transferred (and
dropped) and only update the adjusted branch then, not to catch up to other
changes made previously. That would perform better. But it seemed rather
hard to implement, and also it would have problems with races with a
concurrent get/drop, which this implementation avoids.
And it seemed pretty likely someone had gotten used to get/drop followed by
sync updating the branch. It seems much less likely someone is switching
branches, doing get/drop, and then switching back and expecting sync to update
the branch.
Re-running git-annex adjust still does a full re-adjusting of the branch,
for anyone who needs that.
Sponsored-by: Leon Schuermann on Patreon
Speeds up eg git-annex sync --content by up to 50%. When it does not need
to transfer or drop anything, it now noops a lot more quickly.
I didn't see anything else in sync --content noop loop that could really
be sped up. It has to cat git objects to keys, stat object files, etc.
Sponsored-by: unqueued on Patreon
For simplicity, I've not tried to make it handle History yet, so when
there is a history, a full import will still be done. Probably the right
way to handle history is to first diff from the current tree to the last
imported tree. Then, diff from the current tree to each of the
historical trees, and recurse through the history diffing from child tree
to parent tree.
I don't think that will need a record of the previously imported
historical trees, and so Logs.Import doesn't store them. Although I did
leave room for future expansion in that log just in case.
Next step will be to change importTree to importChanges and modify
recordImportTree et all to handle it, by using adjustTree.
Sponsored-by: Brett Eisenberg on Patreon
This does, as a side effect, make long notes in json output not
be indented. The indentation is only needed to offset them
underneath the display of the file they apply to, so that's ok.
Sponsored-by: Brock Spratlen on Patreon
This is by no means complete, but escaping filenames in actionItemDesc does
cover most commands.
Note that for ActionItemBranchFilePath, the value is branch:file, and I
choose to only quote the file part (if necessary). I considered quoting the
whole thing. But, branch names cannot contain control characters, and while
they can contain unicode, git coes not quote unicode when displaying branch
names. So, it would be surprising for git-annex to quote unicode in a
branch name.
The find command is the most obvious command that still needs to be
dealt with. There are probably other places that filenames also get
displayed, eg embedded in error messages.
Some other commands use ActionItemOther with a filename, I think that
ActionItemOther should either be pre-sanitized, or should explicitly not
be used for filenames, so that needs more work.
When --json is used, unicode does not get escaped, but control
characters were already escaped in json.
(Key escaping may turn out to be needed, but I'm ignoring that for now.)
Sponsored-by: unqueued on Patreon
A repository can have a newline in its description due to being in a
directory containing a newline, or due to git-annex describe being
passed a string with a newline in it for some reason. Putting that
newline in uuid.log breaks its format.
So, escape the newline when it enters uuid.log, to \n
This is a one-way escaping, it is not converted back to a newline
when reading the log. If it were, commands like git-annex info and
whereis would display a multi-line description, which could be confusing
to read.
And, implementing roundtripping would necessarily cause problems if an
old version of git-annex were used to set a description that contained
whatever special character is used to escape the \n. Eg, a \ or if
it used the ! prefix before base64 data that is used in some other logs,
the ! character. Then the description set by the old git-annex would not
roundtrip.
There just doesn't seem to be any benefit of roundtripping newlines through,
so why bother? And, git often displays \n for newline when a filename
contains a newline, so git-annex doing it in this case seems sorta ok
by analogy to git.
(Some other git-annex logs can also have newlines put into them if the
user really wants to break git-annex. For example:
git-annex config annex.largefiles "foo
bar"
The full list is probably config.log, remote.log, group.log,
preferred-content.log, required-content.log,
group-preferred-content.log, schedule.log. Probably there is no
good reason to use a newline in any of these, and the breakage is
probably limited to the bad data the user put in not coming back out.
And users can write any garbage to log files themselves manually in any
case. So, I am not going to address all of those at this time. If a
problem such as this one with the newline in the repository path comes
up, it can be dealt with on a case by case basis.)
Sponsored-by: Dartmouth College's Datalad project
An adjusted view branch has a name like
"refs/heads/adjusted/views/master(author=_)(unlocked)", so it is a view
branch that has been converted to an adjusted branch.
Made Logs.View support such branch names. So now git-annex sync and
pre-commit handle updating metadata on commit in such a branch.
Much remains to be done to fully support adjusted view branches,
including actually applying the adjustment when updating the view branch.
Sponsored-by: Graham Spencer on Patreon
* sync: Avoid pushing view branches to remotes.
* Changed the name of view branches to include the parent branch.
Existing view branches checked out using an old name will still work.
It does not seem useful for sync to push view branches around, because
the information in a view branch can entirely be derived from other
information in git. And sync doesn't push adjusted branches around either.
The better view branch names make it more in line with adjusted branch
names, but were also needed to make fromViewBranch be able to return the
original branch name.
Kept the old view branch names still working. But, when those branches
exist in a repo, sync will still try to push them as before. Avoiding
that would need more complicated and/or expensive changes to sync.
Sponsored-By: Boyd Stephen Smith Jr. on Patreon
* view: New field?=glob and ?tag syntax that includes a directory "_"
in the view for files that do not have the specified metadata set.
* Added annex.viewunsetdirectory git config to change the name of the
"_" directory in a view.
When in a view using the new syntax, old git-annex will fail to parse the
view log. It errors with "Not in a view.", which is not ideal. But that
only affects view commands.
annex.viewunsetdirectory is included in the View for a couple of reasons.
One is to avoid needing to warn the user that it should not be changed when
in a view, since that would confuse git-annex. Another reason is that it
helped with plumbing the value through to some pure functions.
annex.viewunsetdirectory is actually mangled the same as any other view
directory. So if it's configured to something like "N/A", there won't be
multiple levels of directories, which would also confuse git-annex.
Sponsored-By: Jack Hill on Patreon
Fix a hang that occasionally occurred during commands such as move.
(A bug introduced in 10.20220927, in
commit 6a3bd283b8)
The restage.log was kept locked while running a complex index refresh
action. In an unusual situation, that action could need to write to the
restage log, which caused a deadlock.
The solution is a two-stage process. First the restage.log is moved to a
work file, which is done with the lock held. Then the content of the work
file is read and processed, which happens without the lock being held.
This is all done in a crash-safe manner.
Note that streamRestageLog may not be fully safe to run concurrently
with itself. That's ok, because restagePointerFiles uses it with the
index lock held, so only one can be run at a time.
streamRestageLog does delete the restage.old file at the end without
locking. If a calcRestageLog is run concurrently, it will either see the
file content before it was deleted, or will see it's missing. Either is
ok, because at most this will cause calcRestageLog to report more
work remains to be done than there is.
Sponsored-by: Dartmouth College's Datalad project
move: Fix openFile crash with -J
This does make them a bit slower, although usually the log file is not
very big, so even when it's being rewritten, they will not block for
long taking the lock. Still, little slowdowns may add up when moving a lot
file files.
A less expensive fix would be to use something lower level than openFile
that does not check if the file is already open for write by another
thread. But GHC does not seem to provide anything convenient; even mkFD
checks for a writing thread.
fullLines is no longer necessary since these functions no longer will
read the file while it's being written.
Sponsored-by: Dartmouth College's DANDI project
When pointer files need to be restaged, they're first written to the
log, and then when the restage operation runs, it reads the log. This
way, if the git-annex process is interrupted before it can do the
restaging, a later git-annex process can do it.
Currently, this lets a git-annex get/drop command be interrupted and
then re-ran, and as long as it gets/drops additional files, it will
clean up after the interrupted command. But more changes are
needed to make it easier to restage after an interrupted process.
Kept using the git queue to run the restage action, even though the
list of files that it builds up for that action is not actually used by
the action. This could perhaps be simplified to make restaging a cleanup
action that gets registered, rather than using the git queue for it. But
I wasn't sure if that would cause visible behavior changes, when eg
dropping a large number of files, currently the git queue flushes
periodically, and so it restages incrementally, rather than all at the
end.
In restagePointerFiles, it reads the restage log twice, once to get
the number of files and size, and a second time to process it.
This seemed better than reading the whole file into memory, since
potentially a huge number of files could be in there. Probably the OS
will cache the file in memory and there will not be much performance
impact. It might be better to keep running tallies in another file
though. But updating that atomically with the log seems hard.
Also note that it's possible for calcRestageLog to see a different file
than streamRestageLog does. More files may be added to the log in
between. That is ok, it will only cause the filterprocessfaster heuristic to
operate with slightly out of date information, so it may make the wrong
choice for the files that got added and be a little slower than ideal.
Sponsored-by: Dartmouth College's DANDI project
