Client Sessions

Table of Contents

• Create a Client Session
  • Basic Usage
  • With Options
• Use a Client Session
  • Basic Usage
  • With Transactions

How to create and use client sessions.

Create a Client Session

Basic Usage

void example(mongocxx::client client) {
    mongocxx::client_session session = client.start_session();
 
    EXPECT(&session.client() == &client);
 
    EXPECT(session.id()["id"]);
    EXPECT(session.id()["id"].type() == bsoncxx::type::k_binary);
    EXPECT(session.id()["id"].get_binary().sub_type == bsoncxx::binary_sub_type::k_uuid);
}

With Options

void example(mongocxx::client client) {
    mongocxx::options::client_session opts;
 
    opts.snapshot(true);
    // ... other client session options.
 
    mongocxx::client_session session = client.start_session(opts);
 
    EXPECT(session.options().snapshot() == true);
}

Use a Client Session

See also

• Causal Consistency and Read and Write Concerns (MongoDB Manual)

Basic Usage

void example(mongocxx::client_session session, mongocxx::database db) {
    using bsoncxx::builder::basic::make_document;
 
    mongocxx::collection coll = db.create_collection(session, "coll");
 
    auto x1 = bsoncxx::from_json(R"({"x": 1})");
 
    EXPECT(coll.insert_one(session, x1.view()));
    EXPECT(coll.update_one(session, x1.view(), bsoncxx::from_json(R"({"$inc": {"x": 1}})")));
 
    auto doc_opt = coll.find_one(session, make_document());
 
    EXPECT(doc_opt);
 
    auto& doc = *doc_opt;
 
    EXPECT(doc["x"]);
    EXPECT(doc["x"].get_int32().value == 2);
}

With Transactions

void example(mongocxx::client_session session, mongocxx::collection coll) {
    using bsoncxx::builder::basic::make_document;
 
    using mongocxx::model::insert_one;
 
    auto x0 = bsoncxx::from_json(R"({"x": 0})");
    auto inc = bsoncxx::from_json(R"({"$inc": {"x": 1}})");
 
    session.start_transaction();
 
    {
        auto result_opt = coll.create_bulk_write(session)
                              .append(insert_one{x0.view()})
                              .append(insert_one{x0.view()})
                              .append(insert_one{x0.view()})
                              .execute();
 
        EXPECT(result_opt);
        EXPECT(result_opt->inserted_count() == 3);
    }
 
    {
        auto result_opt =
            coll.update_many(session, bsoncxx::from_json(R"({"x": {"$exists": 1}})"), inc.view());
 
        EXPECT(result_opt);
        EXPECT(result_opt->modified_count() == 3);
    }
 
    session.commit_transaction();
 
    EXPECT(coll.count_documents(session, bsoncxx::from_json(R"({"x": 1})")) == 3);
}