A function is referred to as reentrant if it can be safely (and without side effects) invoked in the middle of its execution. Some single-threaded applications can work with non-reentrant functions. Because most applications don’t handle signals or have recursive, callback functions at all. …

Part 1 — Ext4 filesystem: data blocks, super blocks, inode structure Part 2 — Ext4 filesystem: extent, flex_bg, sparse_super Delayed Allocation The delayed allocation feature is enabled by default. That’s why the data may not be committed to the disk immediately when you try to write or modify a data block. I…

Part 1 — Ext4 filesystem: data blocks, super blocks, inode structure Part 3 — Ext4 file system: Delayed allocation, dirty data blocks You can examine your filesystem with dumpe2fs:

Part 2 — Ext4 filesystem: extent, flex_bg, sparse_super Part 3 — Ext4 file system: Delayed allocation, dirty data blocks ext4 was proposed to be added to Linux Kernel on 2006. It was added to Linux Kernel in 2008. …

TCP self-connect issue occurs when `src_ip:src_port == dst_ip:dst_port` You can try to access a local port to reproduce the self-connect issue. The application will likely connect to itself. This is my local port range: root@main:~# sysctl net.ipv4.ip_local_port_range net.ipv4.ip_local_port_range = 32768 60999 I randomly picked an even port number (why even…

You most probably know that TCP is reliable, and UDP is an unreliable protocol. Because TCP is a stream-oriented protocol. When a sender transmits some data to a receiver, the receiver will need to send an “acknowledge” to the sender. …

Google developed gVisor in 2018 and has been using it on Google Cloud for several years. gVisor is an application kernel that provides a secure environment for containers. Because it is OCI compatible, gVisor integrates with Kubernetes clusters and Docker containers. gVisor is a second layer that handles some syscalls…

When you need to create a mock object in Python, MagicMock comes in handy. However, there is a common issue that most people run into: Python returns MagicMock object instead of return_value Suppose your method calls another method, which in turn calls another method. …

There is a tricky feature in PostgreSQL: Unlogged Table I’ll quote the description of the Unlogged Table from PostgreSQL.org: Data written to unlogged tables is not written to the write-ahead log, which makes them considerably faster than ordinary tables. …