I'm glad to hear that somebody has been working on this issue!
After read your proposal and previous dicussion, I realized that such
locking mechanism doesn't have to be tied to specific storage mechanism,
and a promise-based API
is more general than a synchronous API.
在 2015年07月16日 01:12, Joshua Bell 写道:
Based on similar feedback, I've been noodling on this too. Here are my
current thoughts:
https://gist.github.com/inexorabletash/a53c6add9fbc8b9b1191
Feedback welcome - I was planning to send this around shortly anyway.
On Wed, Jul 15, 2015 at 3:07 AM, 段垚 <duan...@ustc.edu
<mailto:duan...@ustc.edu>> wrote:
Hi all,
I'm developing an web-based editor which can edit HTML documents
locally (stored in indexedDB).
An issue I encountered is that there is no reliable way to ensure
that at most one editor instance (an instance is a web page) can
open a document at the same time.
* An editor instance may create a flag entry in indexedDB or
localStorage for each opened document to indicate "this document
is locked", and remove this flag when the document is closed.
However, if the editor is closed forcibly, this flag won't be
removed, and the document can't be opened any more!
* An editor instance may use storage event of localStorage to ask
"is this document has been opened by any other editor instance".
If there is no response for a while, it can open the document.
However, storage event is async so we are not sure about how long
the editor has to wait before opening the document.
* IndexedDB and FileHandle do have locks, but such locks can only
live for a short time, so can't lock an object during the entire
lifetime of an editor instance.
In a native editor application, it may use file locking
(https://en.wikipedia.org/wiki/File_locking) to achieve this purpose.
So maybe it is valuable to add similar locking mechanism to
indexedDB/web storage/FileHandle?
I propose a locking API of web storage:
try {
localStorage.lock('file1.html');
myEditor.open('file1.html'); // open and edit the document
} catch (e) {
alert('file1.html is already opened by another editor');
}
Storage.lock() lock an entry if it has not been locked, and throw
if it has been locked by another page.
The locked entry is unlocked automatically after the page holding
the lock is unloaded. It can also be unlocked by calling
Storage.unlock().
What do you think?
Regards,
Duan Yao
