Global read write lock

[gopal]

I have just noticed that Mongodb has a database read write lock means whenever you try to do the write operations on a particluar collection  the database gets locked and same for read operations is it true?

[Andreas Jung]

http://www.mongodb.org/display/DOCS/How+does+concurrency+work

-aj

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[Sam Millman]

Rad operations can run concurrently but yes write takes lock.

On 1 May 2012 18:23, Andreas Jung <and...@andreas-jung.com> wrote:

gopal wrote:
> I have just noticed that Mongodb has a database read write lock means
> whenever you try to do the write operations on a particluar collection
>  the database gets locked and same for read operations is it true?

http://www.mongodb.org/display/DOCS/How+does+concurrency+work

-aj

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[Tad Marshall]

In versions up to 2.0.x, there is a global write lock for each mongod server, so activity in any collection on any database on that server will affect all other collections (in any database) on that server.  Starting with version 2.2, there is one lock per database, so multiple locks per server if there is more than one database being used, so concurrency can be greater if activity is spread across more more than one database.  We may move to collection-level concurrency in a future version, but we don't have a schedule for this yet.

The general pattern is that many readers can all read at the same time if no writes are taking place, but a mix of readers and writers will force queuing.