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https://mrdrivingduck.github.io/blog/A collection of detailed technical study notes covering Nginx internals (including ngx_pool_t, event-driven frameworks, and IPC), Redis implementation (data structures and slow logs), Linux kernel development, process management, and Spring Cloud microservices with Netflix Hystrix and Spring Cloud Stream.
ScheduledExecutorService interface extends ExecutorService to allow tasks to be scheduled for execution after a specific delay or to be executed periodically. All scheduling methods use relative delays and periods rather than absolute dates or times. Tasks submitted via standard execute() or submit() methods are treated as having a delay of zero (immediate execution).FutureTask is a default implementation of the Future interface that represents a cancellable asynchronous computation. It can wrap a Callable or Runnable object and, because it implements RunnableFuture (and thus Runnable), it can be submitted to an Executor for execution.
Key capabilities include:
Once a computation completes, it cannot be restarted or cancelled unless it was invoked using runAndReset().
public class FutureTask<V> implements RunnableFuture<V> {
// Implementation details
}Introduced in JDK 9, the Java Platform Module System (JPMS) evolves the JAR concept from a simple code container to a structured module. JPMS provides a configurable encapsulation mechanism where the public keyword no longer grants global access. Instead, access control is fine-grained and must be explicitly declared.
Modules include the following metadata:
lsof is used to list all open files on a Linux system. Because 'everything is a file' in Linux, lsof reports on various types of open entities, including regular files, directories, character/block devices, and pipes.Pipes are a fundamental mechanism for inter-process communication (IPC). In this implementation, each pipe is associated with an inode and uses a single page of memory as a circular buffer. The inode stores the buffer address, a head pointer (for writing), and a tail pointer (for reading).
Key behaviors:
NavigableMap<K,V> interface extends SortedMap<K,V> to provide navigation methods that return the closest matches for given search targets. It allows the map to be accessed and traversed in either ascending or descending key order. Submaps created from a NavigableMap must also implement the NavigableMap interface. Note that entry-returning methods typically return snapshots of mappings and generally do not support Entry.setValue.public interface NavigableMap<K,V> extends SortedMap<K,V> {
// Navigation and boundary methods
}μC/OS-II uses a memory partitioning scheme instead of standard ANSI C malloc() and free() to prevent memory fragmentation and ensure deterministic execution time, which is critical for real-time operating systems.
In this system, a large contiguous block of memory (provided by the user as a static array or dynamically allocated memory) is divided into multiple partitions. Each partition consists of a fixed number of equal-sized memory blocks organized as a linked list. Multiple partitions with different block sizes can be created to meet various allocation needs.
TreeSet is a NavigableSet implementation based on a TreeMap. Elements are ordered using their natural ordering (Comparable) or by a provided Comparator. It provides guaranteed log(n) time cost for basic operations: add, remove, and contains.
Key characteristics:
Collections.synchronizedSortedSet.ConcurrentModificationException if the set is modified after the iterator is created (except through the iterator's own remove method).SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));paimon-cpp library, which provides pure C++ read/write capabilities for Paimon tables (including Snapshots, Manifests, and Parquet/ORC data files).