MongoDB C Client Library / Threaded (libmongoc)

[J-EC]

Hello,

While reading the Mongo C Client library documentation regarding threading & connection pooling (mongoc_client_pool_t), it seems clear that an application using this library will likely need to be multi-threaded for best performance.  I understand there won't be a single-threaded async client as discussed in this "won't fix" JIRA:

https://jira.mongodb.org/browse/CDRIVER-27

I'm thinking that my application will need to implement a thread pool + producer / consumer model to interwork with the Mongo C Client library.  But I'd like to see how other open-source apps make use of the C Client library to confirm that this is the right track, and to hopefully avoid pitfalls.  I've searched and searched and come up empty. 

Anyone know of open-source apps that use the Mongo C Client library?

Thanks!

[A. Jesse Jiryu Davis]

Hi, there's no need for anything as complex as you're suggesting. Here's an example that uses a mongocxx::pool simultaneously in 3 threads:

https://github.com/mongodb/mongo-cxx-driver/blob/master/examples/mongocxx/pool.cpp

Just make sure that each mongocxx::client is used by only one thread at a time. The same rule applies to any database, collection, or cursor object you create from that client.

[A. Jesse Jiryu Davis]

Oh I'm sorry, you asked about C, not C++. For C, here's an example that uses a mongoc_client_pool_t with 10 threads at a time for 10 seconds:

https://github.com/mongodb/mongo-c-driver/blob/master/examples/example-pool.c

The basic idea is the same again: mongoc_client_pool_t is thread-safe, but mongoc_client_t is not, and you must use the client and any database, collection, or cursor you create from the client all in the same thread.