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  1. C# Driver
  2. CSHARP-2277

Provide Transactions example for Docs

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    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 2.7.0
    • Component/s: None
    • Labels:
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      Description

      Hi –
      for the manual – would like to pop in driver examples in
      Drivers section and Retry section

      If we could get the corresponding driver examples.

      • The Intro example will be for the Drivers section – where it's to highlight – how to use a transaction, and the section will be emphasizing the passing of the session to the operations in the txn.
      • The retry examples will of course be in the retry section.

      // Start Transactions Intro Example 1
       
      function updateEmployeeInfo(session) {
          employeesCollection = session.getDatabase("hr").employees;
          eventsCollection = session.getDatabase("reporting").events;
       
          session.startTransaction( { readConcern: { level: "snapshot" }, writeConcern: { w: "majority" } } );
       
          try{
              employeesCollection.updateOne( { employee: 3 }, { $set: { status: "Inactive" } } );
              eventsCollection.insertOne( { employee: 3, status: { new: "Inactive", old: "Active" } } );
          } catch (error) {
              print("Caught exception during transaction, aborting.");
              session.abortTransaction();
              throw error;
          }
       
          while (true) {
              try {
                  session.commitTransaction(); // Uses write concern set at transaction start.
                  print("Transaction committed.");
                  break;
              } catch (error) {
                  // Can retry commit
                  if (error.hasOwnProperty("errorLabels") && error.errorLabels.includes("UnknownTransactionCommitResult") ) {
                      print("UnknownTransactionCommitResult, retrying commit operation ...");
                      continue;
                  } else {
                      print("Error during commit ...");
                      throw error;
                  }
             }
          }
      }
      // End Transactions Intro Example 1
       
       
      // Start Transactions Retry Example 1
      function runTransactionWithRetry(txnFunc, session) {
          while (true) {
              try {
                  txnFunc(session);  // performs transaction
                  break;
              } catch (error) {
                  print("Transaction aborted. Caught exception during transaction.");
       
                  // If transient error, retry the whole transaction
                  if ( error.hasOwnProperty("errorLabels") && error.errorLabels.includes( "TransientTransactionError")  ) {
                      print("TransientTransactionError, retrying transaction ...");
                      continue;
                  } else {
                      throw error;
                  }
              }
          }
      }
      // End Transactions Retry Example 1
       
      // Start Transactions Retry Example 2
       
      function commitWithRetry(session) {
          while (true) {
              try {
                  session.commitTransaction(); // Uses write concern set at transaction start.
                  print("Transaction committed.");
                  break;
              } catch (error) {
                  // Can retry commit
                  if (error.hasOwnProperty("errorLabels") && error.errorLabels.includes( "UnknownTransactionCommitResult") ) {
                      print("UnknownTransactionCommitResult, retrying commit operation ...");
                      continue;
                  } else {
                      print("Error during commit ...");
                      throw error;
                  }
             }
          }
      }
      // End Transactions Retry Example 2
       
      // Start Transactions Retry Example 3
       
      function runTransactionWithRetry(txnFunc, session) {
          while (true) {
              try {
                  txnFunc(session);  // performs transaction
                  break;
              } catch (error) {
                  // If transient error, retry the whole transaction
                  if ( error.hasOwnProperty("errorLabels") && error.errorLabels.includes("TransientTransactionError")  ) {
                      print("TransientTransactionError, retrying transaction ...");
                      continue;
                  } else {
                      throw error;
                  }
              }
          }
      }
       
      function commitWithRetry(session) {
          while (true) {
              try {
                  session.commitTransaction(); // Uses write concern set at transaction start.
                  print("Transaction committed.");
                  break;
              } catch (error) {
                  // Can retry commit
                  if (error.hasOwnProperty("errorLabels") && error.errorLabels.includes("UnknownTransactionCommitResult") ) {
                      print("UnknownTransactionCommitResult, retrying commit operation ...");
                      continue;
                  } else {
                      print("Error during commit ...");
                      throw error;
                  }
             }
          }
      }
       
      // Updates two collections in a transactions
       
      function updateEmployeeInfo(session) {
          employeesCollection = session.getDatabase("hr").employees;
          eventsCollection = session.getDatabase("reporting").events;
       
          session.startTransaction( { readConcern: { level: "snapshot" }, writeConcern: { w: "majority" } } );
       
          try{
              employeesCollection.updateOne( { employee: 3 }, { $set: { status: "Inactive" } } );
              eventsCollection.insertOne( { employee: 3, status: { new: "Inactive", old: "Active" } } );
          } catch (error) {
              print("Caught exception during transaction, aborting.");
              session.abortTransaction();
              throw error;
          }
       
          commitWithRetry(session);
      }
       
      // Start a session.
      session = db.getMongo("myRepl/mongodb0.example.net:27017,mongodb1.example.net:27017,mongodb2.example.net:27017").startSession( { mode: "primary" } );
       
      try{
         runTransactionWithRetry(updateEmployeeInfo, session);
      } catch (error) {
         // Do something with error
      } finally {
         session.endSession();
      }
       
      // End Transactions Retry Example 3
      
      

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                  Updated:
                  Resolved: