Suspend MongoDB 4.4.2, 4.4.3, 4.4.4 version upgrade: there are serious bugs

According to MongoDB official website release: When upgrading from version 4.4.2~4.4.4 to version 4.4.8+ or 5.0.2+, there are serious bugs. Partners with upgrade plans please postpone the implementation.

Cause of

Even if the mongod instance is normally closed during the upgrade process, MongoDB may still use the error information in the WT engine metadata file, and thus use the wrong checkpoint, resulting in inconsistent data in MongoDB.

Problem Description

• Versions 4.4.2, 4.4.3, and 4.4.4 leave a piece of invalid metadata when they are completely closed.
• We discovered and fixed this error when we started using metadata for decision-making in 4.4.5.
• In version 4.4.8 and newer, we have added code that assumes that the metadata is correct. When it is incorrect, WiredTiger can delete the content that should be retained after the upgrade.

solution

Those who are using the above version do not upgrade for now, and wait for the problem to be fixed before upgrading.

Software introduction

MongoDB is a product between relational and non-relational databases. It is the most versatile and most like relational database among non-relational databases.

It supports a very loose data structure, which is a bjson format similar to json, so it can store more complex data types.

The query language it supports is very powerful, and its syntax is a bit similar to an object-oriented query language. It can almost achieve most of the functions similar to single-table queries in relational databases, and it also supports indexing of data.

The MongoDB server can run on Linux, Windows or OS X platforms and supports 32-bit and 64-bit applications. The default port is 27017. It is recommended to run on a 64-bit platform, because the maximum file size supported by MongoDB when running in 32-bit mode is 2GB.

Features

It is characterized by high performance, easy deployment, easy use, and very convenient data storage.

The main features are:

• For collection storage, it is easy to store object type data.
• Model freedom
• Support dynamic query
• Support full indexing, including internal objects
• Support query
• Supports replication and failure recovery
• Use efficient binary data storage, including large objects (such as videos, etc.)
• Automatically handle fragments to support scalability at the cloud computing level
• Support RUBY, PYTHON, JAVA, C++, PHP and other languages
• The file storage format is BSON (an extension of JSON)
• Can be accessed via the network

Overall structure

Internal structure