Operation Error Handling

Overview

This page describes errors you might encounter when using the MongoDB Rust Driver to perform MongoDB operations. Once you understand the types of operation errors that the driver raises, you can take appropriate actions to either handle them or correct the error-causing code.

Error Type

If the driver encounters an error while performing an operation, it returns an error of the Error type.

The Error type contains the kind field, which describes the type of error that occurred. The kind field has a value of enum ErrorKind. The ErrorKind enum has variants for different kinds of errors, including the following:

• InvalidArgument: you provided an invalid argument to a method

• Authentication: the driver encountered an error during authentication

• ServerSelection: the client couldn't select a server for the operation

• Write: an error occurred during a write operation

• Transaction: an error occurred during a transaction

For example, if you attempt to perform an insert operation that duplicates an _id field value that is already in the collection, the driver returns an Error instance and prints the following error message:

Error: Error { kind: Write(WriteError(WriteError { code: 11000,
code_name: None, message: "E11000 duplicate key error collection:
db.test_coll index: _id_ dup key: { _id: 1 }", details: None })), labels:
{}, wire_version: None, source: None }

In the preceding error message, the value of the kind field is Write. To learn more about this type of error, see the Write Error Types section of this guide.

Connection Errors

A concurrent operation error might clear the connection pool, interrupting your connection to the server. In this situation, the driver raises an Error type in which the value of the kind field is ConnectionPoolCleared. The error message describes the reason that the concurrent operation failed.

To learn how to adjust your connection pool to address this error, see Tuning Your Connection Pool Settings in the Server manual.

Depending on the circumstances that produce the error, the driver might add a RetryableWriteError label to the error, as shown in the following error message:

Error { kind: ConnectionPoolCleared { message: "Connection pool for
localhost:27017 cleared because another operation failed with: Kind:
I/O error: timed out, labels: {}" }, labels: {"RetryableWriteError"},
wire_version: None, source: None }

This label indicates that the error is write-retryable, which means that the driver makes one retry attempt.

Write Error Types

When the driver experiences an error while performing a write operation, it raises an Error instance with a kind field value of Write. The body of the Write variant is the enum WriteFailure, which takes a value of type WriteError or WriteConcernError.

Error: Error { kind: Write(WriteError(WriteError { code: 121, code_name:
None, message: "Document failed validation", details:
Some(Document({"failingDocumentId": Int32(1), "details":
Document({"operatorName": String("$jsonSchema"), "title":
String("Numerical Validation"), "schemaRulesNotSatisfied":
Array(...)})})) })), labels: {},
wire_version: None, source: None }