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How do I lock a document in MongoDB?
MongoDB does not provide mechanism for a lock. But this can be easily implemented at application level (i.e. in your code): The granularity of the lock can be different: global, collection-specific, record/document-specific.
How many locking modes are supported in MongoDB?
MongoDB uses multi-granularity locking in different levels and modes of locking to achieve this. In this article we are going to discuss about locks and how we can monitor them. There are four different levels of locking in MongoDB.
What is write lock in database?
Write Locks: When a row/table has a write lock, it cannot be read by another thread if they have a read lock implemented in them but can be read by other threads if no read lock is implemented (i.e simple Select query)
What is Mongod lock?
Mongodb always creates the mongodb. lock file when the server starts and drops it before mongodb is stopped. Removing mongodb. lock does not affect any data it just means that mongodb was not stopped correctly. So, you are correct in removing this file and running with the -repair option should fix database.
What kind of write lock does MongoDB use?
MongoDB uses a readers-writer [ed: also known as “multi-reader” or “shared exclusive”] lock that allows concurrent reads access to a database but gives exclusive access to a single write operation. When a read lock exists, many read operations may use this lock. However, when a write lock exists,…
When do you need global lock for mongod?
Some global operations, typically short lived operations involving multiple databases, still require a global “instance” wide lock. Before 2.2, there is only one “global” lock per mongod instance. For example, if you have six databases and one takes a write lock, the other five are still available for read and write.
What happens when there is a write conflict in MongoDB?
When the storage engine detects conflicts between two operations, one will incur a write conflict causing MongoDB to transparently retry that operation. Some global operations, typically short lived operations involving multiple databases, still require a global “instance-wide” lock.
Why does MongoDB use multi granularity locking?
MongoDB uses multi-granularity locking [ 1] that allows operations to lock at the global, database or collection level, and allows for individual storage engines to implement their own concurrency control below the collection level (e.g., at the document-level in WiredTiger).