Deploying WAR file on Tomcat requires correct port configuration

From DB Lock to Kernel OOM (A System Collapse and recovery Story) While working in a UAT environment, we migrated our application stack to: Red Hat Enterprise Linux 9 Java 17 Apache Tomcat 9 PostgreSQL 17 Post deployment, everything looked stable. The application was accessible, testing was smooth, and cron jobs were scheduled to simulate real-time transactions at intervals of 2,5,10, and 15 minutes. Then at midnight the application crashed. What we found RHEL’s OOM Killer terminated Tomcat RAM + swap fully exhausted Memory usage kept increasing over time The real issue It wasn’t Tomcat. It wasn’t Java.   Cron jobs were stacking. Jobs were triggered repeatedly,But not terminating Processes kept accumulating (memory exhaustion) Then we found the deeper problem: Database was locked,CRUD operations were blocked Cron jobs got stuck (never completed) Solution Restarted the database ,this released locks Cron jobs completed successfully Memory freed instantly System stabilized Realworld debugging is about connecting OS,Application and Database layers together. #Linux #RHEL #DevOps #Tomcat #Java #Troubleshooting #SRE #IncidentResponse #RootCauseAnalysis #ProductionIssues

Update on the #Jenkins / Java saga 🎉 A few days ago I posted about our struggle with Jenkins on legacy platforms — AIX and Solaris frozen on Java 11, while newer Jenkins requires Java 17+. Good news: we managed to get Java 17 installed on both SPARC and x86 #Solaris, and #AIX. Jenkins agents are already running on it. It's a temporary fix, but it buys us time to think through a proper long-term solution. And the best part? I posted about it on #Mastodon — and the community helped us figure it out in under 5 minutes. 🐘 That's open source for you. We're still looking for a long-term solution — as Peter Tribble (who maintains the very OpenJDK builds we're using!) put it, pushing the SPARC OpenJDK port past Java 17 is "somewhere between difficult and impossible." So the search continues. Thank you to everyone who commented and reached out, both here and on Mastodon! #DevOps #OpenSource #Java #NetXMS #AIX #Solaris

Setting up a classic CGI environment using Apache and Perl on RHEL is still useful for legacy systems, automation scripts, and lightweight backend tasks. Here’s a simple step-by-step approach I worked on: 🔹 Installed Apache (httpd) using DNF 🔹 Started and enabled the service 🔹 Configured httpd.conf to enable CGI execution 🔹 Created and deployed a sample Perl CGI script 🔹 Set proper execution permissions 🔹 Handled missing Perl CGI modules (if any) Once configured, you can access your script directly via browser using the /cgi-bin/ path. #linux #sysadmin #apache #CGI #perl #RHEL #Devops #configuration

Day 11: Install and Configure Tomcat Server | #100DaysOfDevOps with KodeKloud Continuing my DevOps journey with a focus on application deployment Today’s topic: Installing and Configure Tomcat Server This task helped me understand how to set up an application server, configure it to run on a custom port, and deploy a `.war` file so the application is accessible from the base URL. It also gave me clarity on how Tomcat handles deployments and how small configurations (like ports and ROOT apps) play a big role in real-world environments. 📌 I’ve documented the complete step-by-step process in my blog — check it out here: 👉 https://lnkd.in/g_YesNkp Looking forward to staying consistent and learning in public #DevOps #LearningInPublic #Linux #Tomcat #Java #WebServer #Deployment #KodeKloud 

Java profiling in Coroot now covers memory allocations and lock contention. It requires no code changes, no JVM flags, and works with any HotSpot JVM: https://lnkd.in/eMDFbwvH Enable it with a single environment variable for flamegraphs and time-series metrics. Learn on our blog how to set it up #opensource on your system, how it works, and how it can help diagnose incidents - with examples from intentionally breaking a few things. #observability #monitoring #kubernetes #tech #opensource #ebpf #linux #freesoftware #jvm #tech #AI #sre #devops #sysadmin

Unix timestamp driving you crazy? ⏱️ Convert any Unix timestamp to a readable date/time — or convert a date back to Unix. Instant. 👉 https://lnkd.in/gsjTPFxA Read: https://lnkd.in/gsKCqGGF #UnixTimestamp #Developer #WebDev #FreeTool #Coding

One glance, instant truth about a backup's footprint. Here's a one-liner that shows name, size, and mtime in one go 🔥 `stat -c '%n %s bytes %y' backup.tar.gz` In -c, format string. %n = name, %s = size in bytes, %y = last modification time. You're auditing a nightly backup; you need to confirm it's the right file, the size matches, and the timestamp is fresh. This prints a single line you can paste into notes or tickets ⚡ The terminal doesn't bluff: exact, fast, repeatable checks. Try it in your backup workflow and drop your output in the comments. #linux #terminal #oneliner #filesystem #stat #devops #sysadmin #programming #softwareengineering #opensource #productivity #scripting #backup #datamanagement #buildinpublic

Built FluxMon, a Linux process monitor written in Java from scratch. No libraries. No frameworks. Just raw /proc. What it does: → Reads per-process CPU, memory, and user data directly from the Linux kernel interfaces (/proc filesystem) — the same source htop uses → Renders a real-time TUI using ANSI escape codes and alternate screen buffer → Spring Boot REST API exposes live process data as JSON — GET /api/processes, /api/processes/top → Raw HTTP/1.1 server built from scratch using Java sockets — zero frameworks And the next step A web dashboard where you can monitor your own Linux machine's resources in real time — directly from the browser. The whole project goes from kernel interfaces → HTTP protocol → REST API → browser. Every layer built manually. GitHub: https://lnkd.in/dQf7b3gB Project structure: FluxMon/ ├── Core   → TUI, reads /proc directly ├── API    → Spring Boot REST layer └── Dashboard → coming soon #Java #Linux #SystemsProgramming #OpenSource #SoftwareEngineering

Day 11/100 — Deploy Java Application on Tomcat 🚀☕ Installed Tomcat on an app server, configured it to run on a custom port, transferred a WAR file from the jump host and deployed it as the root application. 🔑 Key Takeaway: Deploying a Java app isn't just about copying a file — the port config, WAR naming, and deployment directory all have to be exactly right. One wrong detail and the app simply won't load. Day 11 ✅ | 89 more to go! #DevOps #Java #Tomcat #KodeKloud #100DaysOfDevOps #LearningInPublic #WebServers