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Error Class Hierarchy

Title: Error Class Hierarchy

Authors: Warren James, Andy Mina

Advisory Group: Daria Purdue, Eric Adum, Neal Beeken

Contents

Errors

All errors are derived from the MongoError class which should never be instantiated. There are four main error classes which stem from MongoError: MongoDriverError, MongoNetworkError, MongoServerError, and MongoSystemError.

MongoError

The base class from which all errors in the Node driver subclass. MongoError should never be be directly instantiated.

graph TD
    MongoError --- MongoDriverError
    MongoError --- MongoNetworkError
    MongoError --- MongoServerError
    MongoError --- MongoSystemError
    MongoDriverError --- MongoAPIError
    MongoDriverError --- MongoRuntimeError

linkStyle 0 stroke:#116149
linkStyle 1 stroke:#116149
linkStyle 2 stroke:#116149
linkStyle 3 stroke:#116149
linkStyle 4 stroke:#116149
linkStyle 5 stroke:#116149

style MongoError fill:#13aa52,stroke:#21313c,color:#FAFBFC
style MongoSystemError fill:#13aa52,stroke:#21313c,color:#FAFBFC
style MongoNetworkError fill:#13aa52,stroke:#21313c,color:#FAFBFC
style MongoServerError fill:#13aa52,stroke:#21313c,color:#FAFBFC
style MongoDriverError fill:#13aa52,stroke:#21313c,color:#FAFBFC
style MongoAPIError fill:#13aa52,stroke:#21313c,color:#FAFBFC
style MongoRuntimeError fill:#13aa52,stroke:#21313c,color:#FAFBFC

Children of MongoError include:

MongoDriverError

This class represents errors which originate in the driver itself or when the user incorrectly uses the driver. This class should never be directly instantiated. Its children are the main classes of errors that most users will interact with: MongoAPIError and MongoRuntimeError.

MongoAPIError

This class represents errors which originate from misuse of the driver API and will generally be thrown before making contact with the server. This class should never be directly instantiated.

Children of MongoAPIError

Error Name Description
MongoInvalidArgumentError Thrown when the user supplies malformed or unexpected arguments or failed to provide a required argument or field.
MongoCompatibilityError Thrown when a feature that is not enabled or allowed for the current server configuration is used.
MongoMissingCredentialsError Thrown when a user fails to provide authentication credentials before attempting to connect.
MongoMissingDependencyError Thrown when a required module or dependency is not present.
MongoExpiredSessionError Thrown when the user attempts to operate on a session that is expired or closed.
MongoTransactionError Thrown when the user makes a mistake in the usage of transactions (e.g.: attempting to commit a transaction with a readPreference other than primary).
MongoTailableCursorError Thrown when the user calls a function or method that is not supported on a tailable cursor.
MongoCursorExhaustedError Thrown when an attempt is made to read from a cursor that is exhausted.
MongoCursorInUseError Thrown when the user attempts to add options to an already initialized cursor.
MongoServerClosedError Thrown when an attempt is made to operate on a closed server.
MongoTopologyClosedError Thrown when an attempt is made to operate on a dropped, or otherwise unavailable, database.
MongoNotConnectedError Thrown when the user attempts to perform operations on a client that has not yet connected.
MongoBatchReExecutionError Thrown when a user attempts to re-execute a batch command when one of the constituent commands has failed.
MongoConnectionStringError Thrown when a user supplies an incorrect URI to the driver.
MongoConnectionPoolClosedError Thrown when a user attempts to operate on a connection pool that is expired or closed.

MongoRuntimeError

This class represents errors which occur when the driver encounters unexpected input or reaches an unexpected/invalid internal state. This class should never be directly instantiated.

Children of MongoRuntimeError

Error Name Description
MongoDecompressionError Thrown when the driver fails to decompress data received from the server.
MongoChangeStreamError Thrown when an error is encountered when operating on a ChangeStream.
MongoGridFSStreamError Thrown when an unexpected state is reached when operating on a GridFS Stream.
MongoGridFSChunkError Thrown when a malformed or invalid chunk is encountered when reading from a GridFS Stream.
MongoUnexpectedServerResponseError Thrown when the driver receives a parsable response it did not expect from the server.

MongoUnexpectedServerResponseError

Intended for the scenario where the MongoDB returns an unexpected response in relation to some state the driver is in. This error should NOT represent a response that couldn't be parsed due to errors in protocol formatting.

Ex. Server selection results in a feature detection change: this is not usually an unexpected response, but if while retrying an operation serverSelection returns a server with a lower wireVersion than expected, we can no longer proceed with the retry, so the response is unexpected in that case.

MongoNetworkError

These are errors which prevent the driver from connecting to a mongo server instance. Children of this class include:

  • MongoNetworkTimeoutError

    • Thrown when a timeout expires while attempting to connect to the mongo server

MongoServerError

These are errors which wrap error responses received from the server.

MongoSystemError

These are errors which originate from faulty environment setup.

  • MongoServerSelectionError

    • Thrown when the driver fails to select a server to complete an operation

Test Plan

The test plan consists of a series of prose tests. As numerous errors are being introduced, select classes will be tested. The classes to be tested will be selected based on three characteristics:

  1. The frequency with which users may encounter this error. Errors that users will likely run into, including but not limited to MongoInvalidArgumentError and MongoNetworkTimeoutError, are a part of the test plan. Note: Error classes that should never be instantiated, such as MongoAPIError and MongoRuntimeError, will not be tested as the user should not encounter them.
  2. The scope of the error. Errors that tackle a large subset of issues, including but not limited to MongoServerError and MongoSystemError, will not be a part of the test plan.
  3. The existing coverage of the error. Errors that are already covered in existing tests will not be a part of the test plan to avoid redundancy.

MongoAPIError

MongoInvalidArgumentError

  • Create a MongoClient object and supply a number in place of the connection string when calling .connect()
    • Assert that MongoInvalidArgumentError is thrown.

MongoMissingCredentialsError

  • Fail to provide credentials when authenticating with the x509 mechanism.
    • Assert that MongoMissingCredentialsError is thrown.

MongoNotConnectedError

  • Attempt to access a database without establishing a connection to a MongoDB server.
    • Assert that MongoNotConnectedError is thrown.

MongoTopologyClosedError

  • Attempt to execute createCollection() against a database that has been closed.
    • Assert that MongoTopologyClosedError is thrown.

MongoCursorExhaustedError

  • Attempt to continue reading a cursor after it has reached the end of the batch.
    • Assert that MongoCursorExhaustedError is thrown.

MongoServerClosedError

  • Attempt to execute a query against a server that has closed.
    • Assert that MongoServerClosedError is thrown.

MongoNetworkError

MongoNetworkTimeoutError

  • Create a MongoClient object and set the connectTimeoutMS option to 1.
    • Assert that a MongoNetworkTimeoutError is thrown.