Hi All,

I have a quick question which seems to be a common topic here but I
cant find a clear answer. Hope you can help.

My application allows users to download a blob of data and edit it.
The blob cannot be merged so while the data is in use I need to "lock"
the data allowing others read only access.

I concerned that there is no guaranteed way to grant a user this
lock.

Is this possible? Is there preferable strategy?

I was thinking something like this

write --> attempt to take ownership of file by appending my email to a
list
read <-- check that lock was granted to me and only me. Only my email
in the list.

read <-- grab the blob
do my work
write --> save the blob and clear the owner list

I can make this work if the read is guaranteed to happen _after_ the
write of ownership info.

Are read write operations guaranteed to occur in the order I call them
in the script. ?
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