Before this change, bisync proactively converted modtime precision when greater
than what the destination backend supported.
This dates back to a time before bisync considered the modifyWindow for same-side
comparisons. Back then, it was problematic to save a listing with 12:54:49.7 for
a backend that can't handle that precision, as on the next run the backend would
report the time as 12:54:50 and bisync would think the file had changed. So the
truncation was a workaround to anticipate this and proactively record the time
with the precision we expect to receive next time.
However, this caused problems for backends (such as dropbox) that round instead
of truncating as bisync expected.
After this change, bisync preserves the original precision in the listing
(without conversion), even when greater than what the backend supports, to avoid
rounding error. On the next run, bisync will compare it to the rounded time
reported by the backend, and if it's within the modifyWindow, it will treat them
as equivalent.
Before this change, the path1 version of a file always prevailed during
--resync, and many users requested options to automatically select the winner
based on characteristics such as newer, older, larger, and smaller. This change
adds support for such options.
Note that ideally this feature would have been implemented by allowing the
existing `--resync` flag to optionally accept string values such as `--resync
newer`. However, this would have been a breaking change, as the existing flag
is a `bool` and it does not seem to be possible to have a `string` flag that
accepts both `--resync newer` and `--resync` (with no argument.) (`NoOptDefVal`
does not work for this, as it would force an `=` like `--resync=newer`.) So
instead, the best compromise to avoid a breaking change was to add a new
`--resync-mode CHOICE` flag that implies `--resync`, while maintaining the
existing behavior of `--resync` (which implies `--resync-mode path1`. i.e. both
flags are now valid, and either can be used without the other.
--resync-mode CHOICE
In the event that a file differs on both sides during a `--resync`,
`--resync-mode` controls which version will overwrite the other. The supported
options are similar to `--conflict-resolve`. For all of the following options,
the version that is kept is referred to as the "winner", and the version that
is overwritten (deleted) is referred to as the "loser". The options are named
after the "winner":
- `path1` - (the default) - the version from Path1 is unconditionally
considered the winner (regardless of `modtime` and `size`, if any). This can be
useful if one side is more trusted or up-to-date than the other, at the time of
the `--resync`.
- `path2` - same as `path1`, except the path2 version is considered the winner.
- `newer` - the newer file (by `modtime`) is considered the winner, regardless
of which side it came from. This may result in having a mix of some winners
from Path1, and some winners from Path2. (The implementation is analagous to
running `rclone copy --update` in both directions.)
- `older` - same as `newer`, except the older file is considered the winner,
and the newer file is considered the loser.
- `larger` - the larger file (by `size`) is considered the winner (regardless
of `modtime`, if any). This can be a useful option for remotes without
`modtime` support, or with the kinds of files (such as logs) that tend to grow
but not shrink, over time.
- `smaller` - the smaller file (by `size`) is considered the winner (regardless
of `modtime`, if any).
For all of the above options, note the following:
- If either of the underlying remotes lacks support for the chosen method, it
will be ignored and will fall back to the default of `path1`. (For example, if
`--resync-mode newer` is set, but one of the paths uses a remote that doesn't
support `modtime`.)
- If a winner can't be determined because the chosen method's attribute is
missing or equal, it will be ignored, and bisync will instead try to determine
whether the files differ by looking at the other `--compare` methods in effect.
(For example, if `--resync-mode newer` is set, but the Path1 and Path2 modtimes
are identical, bisync will compare the sizes.) If bisync concludes that they
differ, preference is given to whichever is the "source" at that moment. (In
practice, this gives a slight advantage to Path2, as the 2to1 copy comes before
the 1to2 copy.) If the files _do not_ differ, nothing is copied (as both sides
are already correct).
- These options apply only to files that exist on both sides (with the same
name and relative path). Files that exist *only* on one side and not the other
are *always* copied to the other, during `--resync` (this is one of the main
differences between resync and non-resync runs.).
- `--conflict-resolve`, `--conflict-loser`, and `--conflict-suffix` do not
apply during `--resync`, and unlike these flags, nothing is renamed during
`--resync`. When a file differs on both sides during `--resync`, one version
always overwrites the other (much like in `rclone copy`.) (Consider using
`--backup-dir` to retain a backup of the losing version.)
- Unlike for `--conflict-resolve`, `--resync-mode none` is not a valid option
(or rather, it will be interpreted as "no resync", unless `--resync` has also
been specified, in which case it will be ignored.)
- Winners and losers are decided at the individual file-level only (there is
not currently an option to pick an entire winning directory atomically,
although the `path1` and `path2` options typically produce a similar result.)
- To maintain backward-compatibility, the `--resync` flag implies
`--resync-mode path1` unless a different `--resync-mode` is explicitly
specified. Similarly, all `--resync-mode` options (except `none`) imply
`--resync`, so it is not necessary to use both the `--resync` and
`--resync-mode` flags simultaneously -- either one is sufficient without the
other.
Before this change, when a file was new/changed on both paths (relative to the
prior sync), and the versions on each side were not identical, bisync would
keep both versions, renaming them with ..path1 and ..path2 suffixes,
respectively. Many users have requested more control over how bisync handles
such conflicts -- including an option to automatically select one version as
the "winner" and rename or delete the "loser". This change introduces support
for such options.
--conflict-resolve CHOICE
In bisync, a "conflict" is a file that is *new* or *changed* on *both sides*
(relative to the prior run) AND is *not currently identical* on both sides.
`--conflict-resolve` controls how bisync handles such a scenario. The currently
supported options are:
- `none` - (the default) - do not attempt to pick a winner, keep and rename
both files according to `--conflict-loser` and
`--conflict-suffix` settings. For example, with the default
settings, `file.txt` on Path1 is renamed `file.txt.conflict1` and `file.txt` on
Path2 is renamed `file.txt.conflict2`. Both are copied to the opposite path
during the run, so both sides end up with a copy of both files. (As `none` is
the default, it is not necessary to specify `--conflict-resolve none` -- you
can just omit the flag.)
- `newer` - the newer file (by `modtime`) is considered the winner and is
copied without renaming. The older file (the "loser") is handled according to
`--conflict-loser` and `--conflict-suffix` settings (either renamed or
deleted.) For example, if `file.txt` on Path1 is newer than `file.txt` on
Path2, the result on both sides (with other default settings) will be `file.txt`
(winner from Path1) and `file.txt.conflict1` (loser from Path2).
- `older` - same as `newer`, except the older file is considered the winner,
and the newer file is considered the loser.
- `larger` - the larger file (by `size`) is considered the winner (regardless
of `modtime`, if any).
- `smaller` - the smaller file (by `size`) is considered the winner (regardless
of `modtime`, if any).
- `path1` - the version from Path1 is unconditionally considered the winner
(regardless of `modtime` and `size`, if any). This can be useful if one side is
usually more trusted or up-to-date than the other.
- `path2` - same as `path1`, except the path2 version is considered the
winner.
For all of the above options, note the following:
- If either of the underlying remotes lacks support for the chosen method, it
will be ignored and fall back to `none`. (For example, if `--conflict-resolve
newer` is set, but one of the paths uses a remote that doesn't support
`modtime`.)
- If a winner can't be determined because the chosen method's attribute is
missing or equal, it will be ignored and fall back to `none`. (For example, if
`--conflict-resolve newer` is set, but the Path1 and Path2 modtimes are
identical, even if the sizes may differ.)
- If the file's content is currently identical on both sides, it is not
considered a "conflict", even if new or changed on both sides since the prior
sync. (For example, if you made a change on one side and then synced it to the
other side by other means.) Therefore, none of the conflict resolution flags
apply in this scenario.
- The conflict resolution flags do not apply during a `--resync`, as there is
no "prior run" to speak of (but see `--resync-mode` for similar
options.)
--conflict-loser CHOICE
`--conflict-loser` determines what happens to the "loser" of a sync conflict
(when `--conflict-resolve` determines a winner) or to both
files (when there is no winner.) The currently supported options are:
- `num` - (the default) - auto-number the conflicts by automatically appending
the next available number to the `--conflict-suffix`, in chronological order.
For example, with the default settings, the first conflict for `file.txt` will
be renamed `file.txt.conflict1`. If `file.txt.conflict1` already exists,
`file.txt.conflict2` will be used instead (etc., up to a maximum of
9223372036854775807 conflicts.)
- `pathname` - rename the conflicts according to which side they came from,
which was the default behavior prior to `v1.66`. For example, with
`--conflict-suffix path`, `file.txt` from Path1 will be renamed
`file.txt.path1`, and `file.txt` from Path2 will be renamed `file.txt.path2`.
If two non-identical suffixes are provided (ex. `--conflict-suffix
cloud,local`), the trailing digit is omitted. Importantly, note that with
`pathname`, there is no auto-numbering beyond `2`, so if `file.txt.path2`
somehow already exists, it will be overwritten. Using a dynamic date variable
in your `--conflict-suffix` (see below) is one possible way to avoid this. Note
also that conflicts-of-conflicts are possible, if the original conflict is not
manually resolved -- for example, if for some reason you edited
`file.txt.path1` on both sides, and those edits were different, the result
would be `file.txt.path1.path1` and `file.txt.path1.path2` (in addition to
`file.txt.path2`.)
- `delete` - keep the winner only and delete the loser, instead of renaming it.
If a winner cannot be determined (see `--conflict-resolve` for details on how
this could happen), `delete` is ignored and the default `num` is used instead
(i.e. both versions are kept and renamed, and neither is deleted.) `delete` is
inherently the most destructive option, so use it only with care.
For all of the above options, note that if a winner cannot be determined (see
`--conflict-resolve` for details on how this could happen), or if
`--conflict-resolve` is not in use, *both* files will be renamed.
--conflict-suffix STRING[,STRING]
`--conflict-suffix` controls the suffix that is appended when bisync renames a
`--conflict-loser` (default: `conflict`).
`--conflict-suffix` will accept either one string or two comma-separated
strings to assign different suffixes to Path1 vs. Path2. This may be helpful
later in identifying the source of the conflict. (For example,
`--conflict-suffix dropboxconflict,laptopconflict`)
With `--conflict-loser num`, a number is always appended to the suffix. With
`--conflict-loser pathname`, a number is appended only when one suffix is
specified (or when two identical suffixes are specified.) i.e. with
`--conflict-loser pathname`, all of the following would produce exactly the
same result:
```
--conflict-suffix path
--conflict-suffix path,path
--conflict-suffix path1,path2
```
Suffixes may be as short as 1 character. By default, the suffix is appended
after any other extensions (ex. `file.jpg.conflict1`), however, this can be
changed with the `--suffix-keep-extension` flag (i.e. to instead result in
`file.conflict1.jpg`).
`--conflict-suffix` supports several *dynamic date variables* when enclosed in
curly braces as globs. This can be helpful to track the date and/or time that
each conflict was handled by bisync. For example:
```
--conflict-suffix {DateOnly}-conflict
// result: myfile.txt.2006-01-02-conflict1
```
All of the formats described [here](https://pkg.go.dev/time#pkg-constants) and
[here](https://pkg.go.dev/time#example-Time.Format) are supported, but take
care to ensure that your chosen format does not use any characters that are
illegal on your remotes (for example, macOS does not allow colons in
filenames, and slashes are also best avoided as they are often interpreted as
directory separators.) To address this particular issue, an additional
`{MacFriendlyTime}` (or just `{mac}`) option is supported, which results in
`2006-01-02 0304PM`.
Note that `--conflict-suffix` is entirely separate from rclone's main `--sufix`
flag. This is intentional, as users may wish to use both flags simultaneously,
if also using `--backup-dir`.
Finally, note that the default in bisync prior to `v1.66` was to rename
conflicts with `..path1` and `..path2` (with two periods, and `path` instead of
`conflict`.) Bisync now defaults to a single dot instead of a double dot, but
additional dots can be added by including them in the specified suffix string.
For example, for behavior equivalent to the previous default, use:
```
[--conflict-resolve none] --conflict-loser pathname --conflict-suffix .path
```
Background: Bisync uses lock files as a safety feature to prevent
interference from other bisync runs while it is running. Bisync normally
removes these lock files at the end of a run, but if bisync is abruptly
interrupted, these files will be left behind. By default, they will lock out
all future runs, until the user has a chance to manually check things out and
remove the lock.
Before this change, lock files blocked future runs indefinitely, so a single
interrupted run would lock out all future runs forever (absent user
intervention), and there was no way to change this behavior.
After this change, a new --max-lock flag can be used to make lock files
automatically expire after a certain period of time, so that future runs are
not locked out forever, and auto-recovery is possible. --max-lock can be any
duration 2m or greater (or 0 to disable). If set, lock files older than this
will be considered "expired", and future runs will be allowed to disregard them
and proceed. (Note that the --max-lock duration must be set by the process that
left the lock file -- not the later one interpreting it.)
If set, bisync will also "renew" these lock files every
--max-lock_minus_one_minute throughout a run, for extra safety. (For example,
with --max-lock 5m, bisync would renew the lock file (for another 5 minutes)
every 4 minutes until the run has completed.) In other words, it should not be
possible for a lock file to pass its expiration time while the process that
created it is still running -- and you can therefore be reasonably sure that
any _expired_ lock file you may find was left there by an interrupted run, not
one that is still running and just taking awhile.
If --max-lock is 0 or not set, the default is that lock files will never
expire, and will block future runs (of these same two bisync paths)
indefinitely.
For maximum resilience from disruptions, consider setting a relatively short
duration like --max-lock 2m along with --resilient and --recover, and a
relatively frequent cron schedule. The result will be a very robust
"set-it-and-forget-it" bisync run that can automatically bounce back from
almost any interruption it might encounter, without requiring the user to get
involved and run a --resync.
Before this change, bisync had no mechanism to gracefully cancel a sync early
and exit in a clean state. Additionally, there was no way to recover on the
next run -- any interruption at all would cause bisync to require a --resync,
which made bisync more difficult to use as a scheduled background process.
This change introduces a "Graceful Shutdown" mode and --recover flag to
robustly recover from even un-graceful shutdowns.
If --recover is set, in the event of a sudden interruption or other un-graceful
shutdown, bisync will attempt to automatically recover on the next run, instead
of requiring --resync. Bisync is able to recover robustly by keeping one
"backup" listing at all times, representing the state of both paths after the
last known successful sync. Bisync can then compare the current state with this
snapshot to determine which changes it needs to retry. Changes that were synced
after this snapshot (during the run that was later interrupted) will appear to
bisync as if they are "new or changed on both sides", but in most cases this is
not a problem, as bisync will simply do its usual "equality check" and learn
that no action needs to be taken on these files, since they are already
identical on both sides.
In the rare event that a file is synced successfully during a run that later
aborts, and then that same file changes AGAIN before the next run, bisync will
think it is a sync conflict, and handle it accordingly. (From bisync's
perspective, the file has changed on both sides since the last trusted sync,
and the files on either side are not currently identical.) Therefore, --recover
carries with it a slightly increased chance of having conflicts -- though in
practice this is pretty rare, as the conditions required to cause it are quite
specific. This risk can be reduced by using bisync's "Graceful Shutdown" mode
(triggered by sending SIGINT or Ctrl+C), when you have the choice, instead of
forcing a sudden termination.
--recover and --resilient are similar, but distinct -- the main difference is
that --resilient is about _retrying_, while --recover is about _recovering_.
Most users will probably want both. --resilient allows retrying when bisync has
chosen to abort itself due to safety features such as failing --check-access or
detecting a filter change. --resilient does not cover external interruptions
such as a user shutting down their computer in the middle of a sync -- that is
what --recover is for.
"Graceful Shutdown" mode is activated by sending SIGINT or pressing Ctrl+C
during a run. Once triggered, bisync will use best efforts to exit cleanly
before the timer runs out. If bisync is in the middle of transferring files, it
will attempt to cleanly empty its queue by finishing what it has started but
not taking more. If it cannot do so within 30 seconds, it will cancel the
in-progress transfers at that point and then give itself a maximum of 60
seconds to wrap up, save its state for next time, and exit. With the -vP flags
you will see constant status updates and a final confirmation of whether or not
the graceful shutdown was successful.
At any point during the "Graceful Shutdown" sequence, a second SIGINT or Ctrl+C
will trigger an immediate, un-graceful exit, which will leave things in a
messier state. Usually a robust recovery will still be possible if using
--recover mode, otherwise you will need to do a --resync.
If you plan to use Graceful Shutdown mode, it is recommended to use --resilient
and --recover, and it is important to NOT use --inplace, otherwise you risk
leaving partially-written files on one side, which may be confused for real
files on the next run. Note also that in the event of an abrupt interruption, a
lock file will be left behind to block concurrent runs. You will need to delete
it before you can proceed with the next run (or wait for it to expire on its
own, if using --max-lock.)
Before this change, bisync could only detect changes based on modtime, and
would refuse to run if either path lacked modtime support. This made bisync
unavailable for many of rclone's backends. Additionally, bisync did not account
for the Fs's precision when comparing modtimes, meaning that they could only be
reliably compared within the same side -- not against the opposite side. Size
and checksum (even when available) were ignored completely for deltas.
After this change, bisync now fully supports comparing based on any combination
of size, modtime, and checksum, lifting the prior restriction on backends
without modtime support. The comparison logic considers the backend's
precision, hash types, and other features as appropriate.
The comparison features optionally use a new --compare flag (which takes any
combination of size,modtime,checksum) and even supports some combinations not
otherwise supported in `sync` (like comparing all three at the same time.) By
default (without the --compare flag), bisync inherits the same comparison
options as `sync` (that is: size and modtime by default, unless modified with
flags such as --checksum or --size-only.) If the --compare flag is set, it will
override these defaults.
If --compare includes checksum and both remotes support checksums but have no
hash types in common with each other, checksums will be considered only for
comparisons within the same side (to determine what has changed since the prior
sync), but not for comparisons against the opposite side. If one side supports
checksums and the other does not, checksums will only be considered on the side
that supports them. When comparing with checksum and/or size without modtime,
bisync cannot determine whether a file is newer or older -- only whether it is
changed or unchanged. (If it is changed on both sides, bisync still does the
standard equality-check to avoid declaring a sync conflict unless it absolutely
has to.)
Also included are some new flags to customize the checksum comparison behavior
on backends where hashes are slow or unavailable. --no-slow-hash and
--slow-hash-sync-only allow selectively ignoring checksums on backends such as
local where they are slow. --download-hash allows computing them by downloading
when (and only when) they're otherwise not available. Of course, this option
probably won't be practical with large files, but may be a good option for
syncing small-but-important files with maximum accuracy (for example, a source
code repo on a crypt remote.) An additional advantage over methods like
cryptcheck is that the original file is not required for comparison (for
example, --download-hash can be used to bisync two different crypt remotes with
different passwords.)
Additionally, all of the above are now considered during the final --check-sync
for much-improved accuracy (before this change, it only compared filenames!)
Many other details are explained in the included docs.
Before this change, bisync used the "canonical" Fs name in the filename for its
listing files, including any {hexstring} suffix. An unintended consequence of
this was that if a user added a backend-specific flag from the command line
(thus "overriding" the config), bisync would fail to find the listing files it
created during the prior run without this flag, due to the path now having a
{hexstring} suffix that wasn't there before (or vice versa, if the flag was
present when the session was established, and later removed.) This would
sometimes cause bisync to fail with a critical error (if no listing existed
with the alternate name), or worse -- it would sometimes cause bisync to use an
old, incorrect listing (if old listings with the alternate name DID still
exist, from before the user changed their flags.)
After this change, the issue is fixed by always normalizing the SessionName to
the non-canonical version (no {hexstring} suffix), regardless of the flags. To
avoid a breaking change, we first check if a suffixed listing exists. If so, we
rename it (and overwrite the non-suffixed version, if any.) If not, we carry on
with the non-suffixed version. (We should only find a suffixed version if
created prior to this commit.)
The result for the user is that the same pair of paths will always use the same
.lst filenames, with or without backend-specific flags.
Bisync checks file equality before renaming sync conflicts by comparing
checksums. Before this change, backends without checksum support (notably
Crypt) would fall back to --size-only for these checks, which is not a very
safe method (differing files can sometimes have the same size, especially if
they're small.) After this change, Crypt remotes fallback to using Cryptcheck
so that checksums can be compared. As a last resort when neither Check nor
Cryptcheck are available, files are compared using --download so that we can be
certain the files are identical regardless of checksum support.
Before this change, bisync supported `--backup-dir` only when `Path1` and
`Path2` were different paths on the same remote. With this change, bisync
introduces new `--backup-dir1` and `--backup-dir2` flags to support separate
backup-dirs for `Path1` and `Path2`.
`--backup-dir1` and `--backup-dir2` can use different remotes from each other,
but `--backup-dir1` must use the same remote as `Path1`, and `--backup-dir2`
must use the same remote as `Path2`. Each backup directory must not overlap its
respective bisync Path without being excluded by a filter rule.
The standard `--backup-dir` will also work, if both paths use the same remote
(but note that deleted files from both paths would be mixed together in the
same dir). If either `--backup-dir1` and `--backup-dir2` are set, they will
override `--backup-dir`.
Before this change, bisync intentionally ignored Google Docs (albeit in a
buggy way that caused problems during --resync.) After this change, Google Docs
(including Google Sheets, Slides, etc.) are now supported in bisync, subject to
the same options, defaults, and limitations as in `rclone sync`. When bisyncing
drive with non-drive backends, the drive -> non-drive direction is controlled
by `--drive-export-formats` (default `"docx,xlsx,pptx,svg"`) and the non-drive
-> drive direction is controlled by `--drive-import-formats` (default none.)
For example, with the default export/import formats, a Google Sheet on the
drive side will be synced to an `.xlsx` file on the non-drive side. In the
reverse direction, `.xlsx` files with filenames that match an existing Google
Sheet will be synced to that Google Sheet, while `.xlsx` files that do NOT
match an existing Google Sheet will be copied to drive as normal `.xlsx` files
(without conversion to Sheets, although the Google Drive web browser UI may
still give you the option to open it as one.)
If `--drive-import-formats` is set (it's not, by default), then all of the
specified formats will be converted to Google Docs, if there is no existing
Google Doc with a matching name. Caution: such conversion can be quite lossy,
and in most cases it's probably not what you want!
To bisync Google Docs as URL shortcut links (in a manner similar to "Drive for
Desktop"), use: `--drive-export-formats url` (or alternatives.)
Note that these link files cannot be edited on the non-drive side -- you will
get errors if you try to sync an edited link file back to drive. They CAN be
deleted (it will result in deleting the corresponding Google Doc.) If you
create a `.url` file on the non-drive side that does not match an existing
Google Doc, bisyncing it will just result in copying the literal `.url` file
over to drive (no Google Doc will be created.) So, as a general rule of thumb,
think of them as read-only placeholders on the non-drive side, and make all
your changes on the drive side.
Likewise, even with other export-formats, it is best to only move/rename Google
Docs on the drive side. This is because otherwise, bisync will interpret this
as a file deleted and another created, and accordingly, it will delete the
Google Doc and create a new file at the new path. (Whether or not that new file
is a Google Doc depends on `--drive-import-formats`.)
Lastly, take note that all Google Docs on the drive side have a size of `-1`
and no checksum. Therefore, they cannot be reliably synced with the
`--checksum` or `--size-only` flags. (To be exact: they will still get
created/deleted, and bisync's delta engine will notice changes and queue them
for syncing, but the underlying sync function will consider them identical and
skip them.) To work around this, use the default (modtime and size) instead of
`--checksum` or `--size-only`.
To ignore Google Docs entirely, use `--drive-skip-gdocs`.
Nearly all of the Google Docs logic is outsourced to the Drive backend, so
future changes should also be supported by bisync.
Refactored the case / unicode normalization logic to be much more efficient,
and fix the last outstanding issue from #7270. Before this change, we were
doing lots of for loops and re-normalizing strings we had already normalized
earlier. Now, we leave the normalizing entirely to March and avoid
re-transforming later, which seems to make a large difference in terms of
performance.
Before this change, --resync was handled in three steps, and needed to do a lot
of unnecessary work to implement its own --ignore-existing logic, which also
caused problems with unicode normalization, in addition to being pretty slow.
After this change, it is refactored to produce the same result much more
efficiently, by reducing the three steps to two and letting ci.IgnoreExisting
do the work instead of reinventing the wheel.
The behavior and sync order remain unchanged for now -- just faster (but see
the ongoing lively discussions about potential future changes in #5681!)
Before this change, Bisync sometimes normalized NFD to NFC and sometimes
did not, causing errors in some scenarios (particularly for users of macOS).
It was similarly inconsistent in its handling of case-insensitivity.
There were three main places where Bisync should have normalized, but didn't:
1. When building the list of files that need to be transferred during --resync
2. When building the list of deltas during a non-resync
3. When comparing Path1 to Path2 during --check-sync
After this change, 1 and 3 are resolved, and bisync supports
--no-unicode-normalization and --ignore-case-sync in the same way as sync.
2 will be addressed in a future update.
Before this change, bisync needed to build a full listing for Path1, then a
full listing for Path2, then compare them -- and each of those tasks needed to
finish before the next one could start. In addition to being slow and
inefficient, it also caused real problems if a file changed between the time
bisync checked it on Path1 and the time it checked the corresponding file on
Path2.
This change solves these problems by listing both paths concurrently, using
the same March infrastructure that check and sync use to traverse two
directories in lock-step, optimized by Go's robust concurrency support.
Listings should now be much faster, and any given path is now checked
nearly-instantaneously on both sides, minimizing room for error.
Further discussion:
https://forum.rclone.org/t/bisync-bugs-and-feature-requests/37636#:~:text=4.%20Listings%20should%20alternate%20between%20paths%20to%20minimize%20errors
Before this change, bisync had no mechanism for "retrying" a file again next
time, in the event of an unexpected and possibly temporary error. After this
change, bisync is now essentially able to mark a file as needing to be
rechecked next time. Bisync does this by keeping one prior listing on hand at
all times. In a low-confidence situation, bisync can revert a given file row
back to its state at the end of the last known successful sync, ensuring that
any subsequent changes will be re-noticed on the next run.
This can potentially be helpful for a dynamically changing file system, where
files may be changing quickly while bisync is working with them.
Before this change, if there were changes to sync, bisync listed each path
twice: once before the sync and once after. The second listing caused quite
a lot of problems, in addition to making each run much slower and more
expensive. A serious side-effect was that file changes could slip through
undetected, if they happened to occur while a sync was running (between the
first and second listing snapshots.)
After this change, the second listing is eliminated by getting the underlying
sync operation to report back a list of what it changed. Not only is this more
efficient, but also much more robust to concurrent modifications. It should no
longer be necessary to avoid make changes while it's running -- bisync will
simply learn about those changes next time and handle them on the next run.
Additionally, this also makes --check-sync usable again.
For further discussion, see:
https://forum.rclone.org/t/bisync-bugs-and-feature-requests/37636#:~:text=5.%20Final%20listings%20should%20be%20created%20from%20initial%20snapshot%20%2B%20deltas%2C%20not%20full%20re%2Dscans%2C%20to%20avoid%20errors%20if%20files%20changed%20during%20sync
Before this change, bisync handled copies and deletes in separate operations.
After this change, they are combined in one sync operation, which is faster
and also allows bisync to support --track-renames and --backup-dir.
Bisync uses a --files-from filter containing only the paths bisync has
determined need to be synced. Just like in sync (but in both directions),
if a path is present on the dst but not the src, it's interpreted as a delete
rather than a copy.
This commit documents my learnings after having encountered a failure
I reported in the rclone forum[0].
I may be a fool for having failed to understand the previous
documentation, but I am likely not the only fool to get snared by it.
This commit therefore adds details to clarify what the user must do in
order to allow `--check-access` to succeed.
While at it, I've also added some basic documentation for `--check-filename`.
[0]: https://forum.rclone.org/t/bisync-check-file-check-failed/35682
