This blog post details setting up a highly available Mosquitto MQTT broker on Kubernetes. It leverages a StatefulSet to manage persistent storage and pod identity, ensuring data persistence across restarts. The setup uses a headless service for internal communication and an external LoadBalancer service to expose the broker to clients. Persistence is achieved with a PersistentVolumeClaim, while a ConfigMap manages configuration files. The post also covers generating a self-signed certificate for secure communication and emphasizes the importance of a proper Kubernetes DNS configuration for service discovery. Finally, it offers a simplified deployment using a single YAML file and provides instructions for testing the setup with mosquitto_sub
and mosquitto_pub
clients.
"Understanding Machine Learning: From Theory to Algorithms" provides a comprehensive overview of machine learning, bridging the gap between theoretical principles and practical applications. The book covers a wide range of topics, from basic concepts like supervised and unsupervised learning to advanced techniques like Support Vector Machines, boosting, and dimensionality reduction. It emphasizes the theoretical foundations, including statistical learning theory and PAC learning, to provide a deep understanding of why and when different algorithms work. Practical aspects are also addressed through the presentation of efficient algorithms and their implementation considerations. The book aims to equip readers with the necessary tools to both analyze existing learning algorithms and design new ones.
HN users largely praised Shai Shalev-Shwartz and Shai Ben-David's "Understanding Machine Learning" as a highly accessible and comprehensive introduction to the field. Commenters highlighted the book's clear explanations of fundamental concepts, its rigorous yet approachable mathematical treatment, and the helpful inclusion of exercises. Several pointed out its value for both beginners and those with prior ML experience seeking a deeper theoretical understanding. Some compared it favorably to other popular ML resources, noting its superior balance between theory and practice. A few commenters also shared specific chapters or sections they found particularly insightful, such as the treatment of PAC learning and the VC dimension. There was a brief discussion on the book's coverage (or lack thereof) of certain advanced topics like deep learning, but the overall sentiment remained strongly positive.
The paper "Stop using the elbow criterion for k-means" argues against the common practice of using the elbow method to determine the optimal number of clusters (k) in k-means clustering. The authors demonstrate that the elbow method is unreliable, often identifying spurious elbows or missing genuine ones. They show this through theoretical analysis and empirical examples across various datasets and distance metrics, revealing how the within-cluster sum of squares (WCSS) curve, on which the elbow method relies, can behave unexpectedly. The paper advocates for abandoning the elbow method entirely in favor of more robust and theoretically grounded alternatives like the gap statistic, silhouette analysis, or information criteria, which offer statistically sound approaches to k selection.
HN users discuss the problems with the elbow method for determining the optimal number of clusters in k-means, agreeing it's often unreliable and subjective. Several commenters suggest superior alternatives, such as the silhouette coefficient, gap statistic, and information criteria like AIC/BIC. Some highlight the importance of considering the practical context and the "business need" when choosing the number of clusters, rather than relying solely on statistical methods. Others point out that k-means itself may not be the best clustering algorithm for all datasets, recommending DBSCAN and hierarchical clustering as potentially better suited for certain situations, particularly those with non-spherical clusters. A few users mention the difficulty in visualizing high-dimensional data and interpreting the results of these metrics, emphasizing the iterative nature of cluster analysis.
This paper provides a comprehensive overview of percolation theory, focusing on its mathematical aspects. It explores bond and site percolation on lattices, examining key concepts like critical probability, the existence of infinite clusters, and critical exponents characterizing the behavior near the phase transition. The text delves into various methods used to study percolation, including duality, renormalization group techniques, and series expansions. It also discusses different percolation models beyond regular lattices, like continuum percolation and directed percolation, highlighting their unique features and applications. Finally, the paper connects percolation theory to other areas like random graphs, interacting particle systems, and the study of disordered media, showcasing its broad relevance in statistical physics and mathematics.
HN commenters discuss the applications of percolation theory, mentioning its relevance to forest fires, disease spread, and network resilience. Some highlight the beauty and elegance of the theory itself, while others note its accessibility despite being a relatively advanced topic. A few users share personal experiences using percolation theory in their work, including modeling concrete porosity and analyzing social networks. The concept of universality in percolation, where different systems exhibit similar behavior near the critical threshold, is also pointed out. One commenter links to an interactive percolation simulation, allowing others to experiment with the concepts discussed. Finally, the historical context and development of percolation theory are briefly touched upon.
Sort_Memories is a Python script that automatically sorts group photos based on the number of specified individuals present in each picture. Leveraging face detection and recognition, the script analyzes images, identifies faces, and groups photos based on the user-defined 'N' number of people desired in each output folder. This allows users to easily organize their photo collections by separating pictures of individuals, couples, small groups, or larger gatherings, automating a tedious manual process.
Hacker News commenters generally praised the project for its clever use of facial recognition to solve a common problem. Several users pointed out potential improvements, such as handling images where faces are partially obscured or not clearly visible, and suggested alternative approaches like clustering algorithms. Some discussed the privacy implications of using facial recognition technology, even locally. There was also interest in expanding the functionality to include features like identifying the best photo out of a burst or sorting based on other criteria like smiles or open eyes. Overall, the reception was positive, with commenters recognizing the project's practical value and potential.
Summary of Comments ( 15 )
https://news.ycombinator.com/item?id=43988975
HN users generally found the tutorial lacking important details for a true HA setup. Several commenters pointed out that using a single persistent volume claim wouldn't provide redundancy and suggested using a distributed storage solution instead. Others questioned the choice of a StatefulSet without discussing scaling or the need for a headless service. The external database dependency was also criticized as a potential single point of failure. A few users offered alternative approaches, including using a managed MQTT service or simpler clustering methods outside of Kubernetes. Overall, the sentiment was that while the tutorial offered a starting point, it oversimplified HA and omitted crucial considerations for production environments.
The Hacker News post titled "High Available Mosquitto MQTT on Kubernetes" linking to a tutorial on setting up a highly available Mosquitto MQTT broker using Kubernetes has generated a modest number of comments, primarily focusing on alternative approaches and concerns regarding the complexity introduced by Kubernetes for this specific use case.
One commenter suggests exploring VerneMQ as an alternative MQTT broker, highlighting its built-in clustering capabilities, potentially simplifying the setup and avoiding the overhead of Kubernetes. This comment sparks a brief discussion about the pros and cons of VerneMQ compared to Mosquitto, touching upon aspects like performance and ease of use. Another user echoes this sentiment, recommending against using Kubernetes unless absolutely necessary, emphasizing the added operational complexity. They propose a simpler approach using a systemd service with two Mosquitto instances and a shared persistent storage, arguing this would suffice for most use cases and be significantly easier to manage.
A separate thread emerges discussing the challenges of persistent storage in Kubernetes, particularly in the context of stateful applications like MQTT brokers. Commenters mention the potential complexities and performance implications of using persistent volumes, especially when dealing with high throughput scenarios. This discussion touches upon the importance of carefully considering storage solutions and their impact on the overall performance and reliability of the MQTT broker.
Finally, a commenter expresses their preference for a simpler approach using Docker Compose, suggesting it provides a suitable level of resilience without the operational overhead of Kubernetes. They argue that for many applications, the added complexity of Kubernetes isn't justified and a more streamlined solution like Docker Compose is often sufficient.
Overall, the comments reflect a general sentiment that while Kubernetes offers robust features for high availability and scalability, it might be overkill for certain applications like a Mosquitto MQTT broker. The commenters advocate for carefully evaluating the complexity and operational overhead introduced by Kubernetes and considering simpler alternatives if they adequately address the specific requirements. They highlight the importance of choosing the right tool for the job, balancing complexity with the actual needs of the application and infrastructure.