Is Lock on File Required When Reading a File
Locking
Subversion generally works best without locking, using the "Re-create-Modify-Merge" methods described before in the department called "The Re-create-Modify-Merge Solution". Even so there are a few instances when yous may need to implement some form of locking policy.
-
Y'all are using "unmergeable" files, for example, graphics files. If ii people modify the same file, merging is not possible, so one of you volition lose their changes.
-
Your visitor has always used a locking revision control arrangement in the past and there has been a management conclusion that "locking is best".
Firstly you need to ensure that your Subversion server is upgraded to at least version 1.2. Earlier versions practise not support locking at all. If you are using file:// admission, and so of course only your client needs to exist updated.
The Three Meanings of "Lock"
In this section, and almost everywhere in this book, the words "lock" and "locking" draw a mechanism for common exclusion between users to avoid clashing commits. Unfortunately, there are two other sorts of "lock" with which Subversion, and therefore this volume, sometimes needs to be concerned.
The 2d is working re-create locks, used internally by Subversion to foreclose clashes between multiple Subversion clients operating on the same working copy. Usually yous go these locks whenever a command similar update/commit/... is interrupted due to an error. These locks can be removed by running the cleanup command on the working copy, as described in the section called "Cleanup".
And third, files and folders tin can get locked if they're in use by another process, for instance if you have a word certificate opened in Word, that file is locked and can not be accessed by TortoiseSVN.
You lot can by and large forget about these other kinds of locks until something goes incorrect that requires you lot to intendance virtually them. In this book, "lock" means the outset sort unless the contrary is either clear from context or explicitly stated.
How Locking Works in Subversion
By default, zero is locked and anyone who has commit access can commit changes to any file at any time. Others will update their working copies periodically and changes in the repository will be merged with local changes.
If you Get a Lock on a file, then only yous can commit that file. Commits by all other users will be blocked until you release the lock. A locked file cannot exist modified in any way in the repository, so it cannot exist deleted or renamed either, except by the lock owner.
Important
A lock is non assigned to a specific user, merely to a specific user and a working copy. Having a lock in one working re-create too prevents the same user from committing the locked file from some other working re-create.
As an example, imagine that user Jon has a working copy on his office PC. There he starts working on an image, and therefore acquires a lock on that file. When he leaves his role he's not finished all the same with that file, so he doesn't release that lock. Back at home Jon also has a working copy and decides to piece of work a little more on the projection. But he tin can't alter or commit that same epitome file, because the lock for that file resides in his working copy in the part.
However, other users will non necessarily know that you accept taken out a lock. Unless they check the lock status regularly, the first they will know about it is when their commit fails, which in nigh cases is not very useful. To brand it easier to manage locks, at that place is a new Subversion property svn:needs-lock. When this property is set up (to any value) on a file, whenever the file is checked out or updated, the local copy is made read-but unless that working copy holds a lock for the file. This acts as a warning that you should not edit that file unless you lot have starting time caused a lock. Files which are versioned and read-merely are marked with a special overlay in TortoiseSVN to signal that y'all need to acquire a lock before editing.
Locks are recorded by working copy location too as by owner. If you have several working copies (at home, at work) so you tin but hold a lock in ane of those working copies.
If one of your co-workers acquires a lock and so goes on holiday without releasing it, what do you do? Subversion provides a means to force locks. Releasing a lock held by someone else is referred to every bit Breaking the lock, and forcibly acquiring a lock which someone else already holds is referred to equally Stealing the lock. Naturally these are not things y'all should do lightly if you lot desire to remain friends with your co-workers.
Locks are recorded in the repository, and a lock token is created in your local working copy. If there is a discrepancy, for case if someone else has cleaved the lock, the local lock token becomes invalid. The repository is always the definitive reference.
Getting a Lock
Select the file(due south) in your working copy for which y'all want to learn a lock, then select the command → .
Figure four.61. The Locking Dialog
A dialog appears, assuasive yous to enter a comment, so others can meet why you take locked the file. The comment is optional and currently merely used with Svnserve based repositories. If (and merely if) you lot need to steal the lock from someone else, check the Steal lock box, then click on .
You can set the project holding tsvn:logtemplatelock to provide a message template for users to fill in every bit the lock bulletin. Refer to the section called "Project Settings" for instructions on how to set properties.
If you lot select a binder and then employ → the lock dialog will open with every file in every sub-folder selected for locking. If you really want to lock an entire hierarchy, that is the style to practise it, just you could become very unpopular with your co-workers if you lock them out of the whole project. Utilize with intendance ...
Releasing a Lock
To brand sure you don't forget to release a lock you don't need any more, locked files are shown in the commit dialog and selected by default. If you lot continue with the commit, locks you hold on the selected files are removed, even if the files oasis't been modified. If yous don't want to release a lock on certain files, yous can uncheck them (if they're not modified). If you desire to keep a lock on a file y'all've modified, you take to enable the Go on locks checkbox before you lot commit your changes.
To release a lock manually, select the file(s) in your working copy for which you want to release the lock, then select the command → There is nothing further to enter so TortoiseSVN will contact the repository and release the locks. You tin also apply this command on a folder to release all locks recursively.
Checking Lock Status
Figure iv.62. The Check for Modifications Dialog
To see what locks you and others hold, you tin can utilise → . Locally held lock tokens prove up immediately. To bank check for locks held by others (and to see if any of your locks are broken or stolen) yous demand to click on .
From the context card here, you can also go and release locks, also as breaking and stealing locks held by others.
Avert Breaking and Stealing Locks
If you break or steal someone else'due south lock without telling them, y'all could potentially cause loss of work. If yous are working with unmergeable file types and you steal someone else'due south lock, one time you lot release the lock they are gratis to check in their changes and overwrite yours. Subversion doesn't lose data, simply you lot have lost the team-working protection that locking gave you.
Making Non-locked Files Read-Simply
As mentioned above, the most constructive way to employ locking is to fix the svn:needs-lock property on files. Refer to the department chosen "Project Settings" for instructions on how to set properties. Files with this property set volition always exist checked out and updated with the read-only flag ready unless your working re-create holds a lock.
Every bit a reminder, TortoiseSVN uses a special overlay to betoken this.
If you operate a policy where every file has to be locked and so you lot may observe it easier to employ Subversion's automobile-props feature to set the property automatically every time you add new files. Read the section called "Automatic holding setting" for farther information.
The Locking Hook Scripts
When you create a new repository with Subversion one.two or higher, iv hook templates are created in the repository hooks directory. These are called earlier and afterwards getting a lock, and before and afterwards releasing a lock.
Information technology is a good idea to install a post-lock and mail service-unlock claw script on the server which sends out an email indicating the file which has been locked. With such a script in place, all your users can exist notified if someone locks/unlocks a file. You can find an example hook script hooks/mail service-lock.tmpl in your repository binder.
You might also utilise hooks to disallow breaking or stealing of locks, or perhaps limit information technology to a named administrator. Or maybe y'all desire to electronic mail the owner when one of their locks is broken or stolen.
Read the section chosen "Server side claw scripts" to find out more.
Source: https://tortoisesvn.net/docs/release/TortoiseSVN_en/tsvn-dug-locking.html
0 Response to "Is Lock on File Required When Reading a File"
Post a Comment