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Clarify corner cases in the conflict/overwrite decision.

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Signed-off-by: Daira Hopwood <daira@jacaranda.org>
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Daira Hopwood 2015-11-04 13:00:32 +00:00
parent a41cf014d1
commit 71c65125d7
1 changed files with 11 additions and 11 deletions
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22
docs/proposed/magic-folder/remote-to-local-sync.rst
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@ -690,9 +690,9 @@ Fire Dragons: Distinguishing conflicts from overwrites
When synchronizing a file that has changed remotely, the Magic Folder When synchronizing a file that has changed remotely, the Magic Folder
client needs to distinguish between overwrites, in which the remote client needs to distinguish between overwrites, in which the remote
side was aware of your most recent version and overwrote it with a side was aware of your most recent version (if any) and overwrote it
new version, and conflicts, in which the remote side was unaware of with a new version, and conflicts, in which the remote side was unaware
your most recent version when it published its new version. Those two of your most recent version when it published its new version. Those two
cases have to be handled differently — the latter needs to be raised cases have to be handled differently — the latter needs to be raised
to the user as an issue the user will have to resolve and the former to the user as an issue the user will have to resolve and the former
must not bother the user. must not bother the user.
@ -776,12 +776,11 @@ Let ``last_downloaded_uri`` be the field of that name obtained from
the directory entry metadata for ``foo`` in Bob's DMD (this field the directory entry metadata for ``foo`` in Bob's DMD (this field
may be absent). Then the algorithm is: may be absent). Then the algorithm is:
* 2a. If Alice has no local copy of ``foo``, classify as an overwrite. * 2a. Attempt to "stat" ``foo`` to get its *current statinfo* (size
in bytes, ``mtime``, and ``ctime``). If Alice has no local copy
of ``foo``, classify as an overwrite.
* 2b. Otherwise, "stat" ``foo`` to get its *current statinfo* (size * 2b. Read the following information for the path ``foo`` from the
in bytes, ``mtime``, and ``ctime``).
* 2c. Read the following information for the path ``foo`` from the
local magic folder db: local magic folder db:
* the *last-uploaded statinfo*, if any (this is the size in * the *last-uploaded statinfo*, if any (this is the size in
@ -791,11 +790,12 @@ may be absent). Then the algorithm is:
for this file, which is the URI under which the file was last for this file, which is the URI under which the file was last
uploaded. uploaded.
* 2d. If any of the following are true, then classify as a conflict: * 2c. If any of the following are true, then classify as a conflict:
* there are pending notifications of changes to ``foo``; * there are pending notifications of changes to ``foo``;
* the last-uploaded statinfo is either absent, or different * the last-uploaded statinfo is either absent (i.e. there is no
from the current statinfo; entry in the database for this path), or different from the
current statinfo;
* either ``last_downloaded_uri`` or ``last_uploaded_uri`` * either ``last_downloaded_uri`` or ``last_uploaded_uri``
(or both) are absent, or they are different. (or both) are absent, or they are different.