Add support for atomic locking

cs3org / wopiserver

A vendor-neutral application gateway compatible with the WOPI specifications.

Apache License 2.0

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Add support for atomic locking #25

Closed glpatcern closed 4 years ago

glpatcern commented 4 years ago

This is to better support lock operations in the /wopi/cbox/lock and /wopi/cbox/unlock WOPI extensions.

Work to do:

[x] Pass the unit test suite
[x] Modify the cboxLock() call to make use of this call as opposed to stat and write, which is not atomic and prone to race conditions.
[x] Test the race with multiple OnlyOffice sessions
[x] Validate WOPI Lock

glpatcern commented 4 years ago

~~This is pending a fix on eos as the race with O_EXCL is not correctly handled there.~~ Edit: independently from the ongoing fix, the proper fix here is to not use atomic writes together with O_EXCL as an atomic would always create a new unique filename, and it's only at close time that the operation fails, not at open.

glpatcern commented 4 years ago

This is merged as tests are passing, though we're going to execute further stress tests.

To be noted that until https://github.com/cs3org/cs3apis/pull/87 is completed and implemented in Reva, atomic uploads do NOT work with Reva and the test suite consistently fails.