After you put a Tomcat site live, the first 24 to 72 hours are the most important for spotting issues early. A Java application can appear healthy in a browser while still having problems in the background, such as high memory use, slow startup, failed deploys, expired certificates, or requests being handled by the wrong app context. In a hosted Tomcat setup, especially when you manage the service through Plesk and a control-panel extension such as My App Server, the goal is to confirm that the site is not only reachable, but also stable, responsive, and behaving as expected under real traffic.
If you are running a WAR-based application, a JSP site, a servlet app, or a private JVM on shared hosting, the checks below will help you watch the right signals without overcomplicating things. The focus is practical uptime monitoring for UK hosting customers: availability, response time, logs, restarts, resource usage, and alerts that tell you when action is needed.
What to check first after going live
Right after launch, verify the basics in the same order a visitor would experience them. This helps you catch configuration issues quickly before you start looking at deeper Tomcat metrics.
1. Confirm the site opens on the expected URL
Test the exact public URL that visitors will use, including:
- the correct domain name
- the right protocol, usually HTTPS
- the expected application path, if the app is not on the root domain
- redirects from HTTP to HTTPS, if enabled
Make sure the page loads without browser warnings, mixed-content errors, or unexpected redirects to an old host name or temporary address.
2. Check the Tomcat application context
For Tomcat hosting, a common launch issue is the app being deployed under the wrong context path. Confirm that the application starts in the intended location and that links, forms, and API endpoints resolve correctly. A JSP or servlet app may render the homepage correctly while deeper paths still fail if the context mapping is wrong.
3. Verify login, forms, and session-based features
If your site has authentication, checkout flows, admin pages, or any function that depends on session state, test them immediately. Problems with session persistence, cookies, or application configuration often appear only after a few clicks, not on the landing page.
4. Check static assets and front-end resources
Confirm that CSS, JavaScript, images, and uploaded files are served correctly. Missing assets can happen when the deployment path changes or when file permissions are not aligned with the Java process running the app.
Monitor availability, not just a successful page load
Uptime monitoring should tell you more than whether one URL responded once. A Tomcat app can return a 200 response while still being slow, half-broken, or intermittently failing under load. For a practical monitoring setup, watch multiple signals.
HTTP status codes
Track the status codes returned by the app. Repeated 5xx responses usually mean application errors, deployment problems, or JVM issues. Frequent 4xx responses may point to broken routes, incorrect rewriting rules, or changed URLs after deployment.
Response time
Response time is one of the best early indicators of trouble. If a page starts taking significantly longer to load after launch, it may indicate:
- insufficient heap memory
- slow database calls
- thread contention
- too many open sessions
- an expensive startup task running during requests
Set a baseline when the app is healthy so you can spot slowdowns before users complain.
Availability from more than one check point
Where possible, monitor from more than one external location or monitoring service. This helps distinguish a local connectivity issue from a true application outage. Even on managed hosting, external checks are useful because they reflect what users can reach from the internet.
Content validation
For a Tomcat site, it is worth monitoring not only that the page responds, but also that the returned content is correct. A login page, maintenance page, or proxy error can all return a normal status code. A content check can confirm the page contains a known phrase, title, or application marker.
Watch the Tomcat service itself in Plesk
If your hosting plan includes My App Server or a similar Plesk extension for Java hosting, the service layer is as important as the web layer. You should know whether Tomcat is running, whether it restarted cleanly, and whether the selected Java version is still the one your app expects.
Service state
Check that the Tomcat service is running after deployment and after any restart. If the service stops unexpectedly, the site may appear unavailable or may show a generic error page depending on how Apache and the application are integrated.
Restart history
Unexpected restarts can indicate deployment problems, memory pressure, or configuration changes. A healthy app should not need repeated restarts to stay online. If restarts become frequent, review logs and memory use before the issue becomes user-visible.
Java version consistency
One of the advantages of hosted Java and Tomcat management through Plesk is the ability to choose the Java version that matches the application. After going live, confirm that the app is actually running on the intended JVM version. A mismatch can cause subtle runtime errors, class loading problems, or dependency failures even if deployment succeeded.
Custom app server settings
If you manually uploaded or configured a custom Tomcat or JVM instance, monitor the startup parameters and environment variables as well. A wrong port, path, heap setting, or runtime argument can make the app unstable even when the service appears to be enabled.
Review logs early and regularly
Logs are often the fastest way to understand what is happening after launch. For a hosted Tomcat application, watch both the application logs and the service-related logs available in your control panel or hosting account.
Tomcat startup logs
Look for clear signs that startup completed successfully. Pay attention to:
- deployment success messages
- class loading errors
- missing file or permission errors
- port binding problems
- JVM warnings during startup
If startup ends with warnings, do not ignore them just because the app opens in a browser. Some warnings become failures later under real traffic.
Application error logs
After release, watch for stack traces, SQL errors, null pointer exceptions, and configuration warnings. A burst of errors after go-live often indicates a hidden code path that was not exercised in testing.
Apache and proxy logs, if relevant
In many hosting setups, Apache sits in front of Tomcat. If traffic reaches Apache but not the app, or if redirects behave strangely, Apache logs can help you identify rewrite issues, proxy failures, or blocked requests.
Access logs for pattern changes
Access logs help you see real traffic patterns. They can reveal repeated requests to missing pages, a sudden rise in 404 errors, bot traffic, or unusual request spikes after launch.
Track memory and CPU usage after deployment
One of the most common post-launch problems in Java hosting is resource use that looks fine at first but grows over time. Even a small or medium Tomcat application can become unstable if the JVM is sized poorly or if the app leaks memory.
Memory usage
Watch for steadily increasing memory use, frequent garbage collection, or the app approaching its configured limit. Signs of memory pressure include:
- slower responses over time
- random application errors
- timeouts during heavier traffic
- service restarts after reaching limits
If your hosting platform exposes JVM-related information or service usage details, review them after each deployment and again during peak usage.
CPU usage
High CPU can be caused by repeated errors, expensive queries, inefficient loops, or background jobs that run too often. A Tomcat app may still serve pages while CPU is elevated, but sustained high CPU is usually a warning that the site will not remain predictable under growth.
Request spikes and background tasks
Some applications perform scheduled work such as report generation, cache refreshes, or sync jobs. These tasks can interfere with interactive traffic if they run too frequently or with poor limits. Monitor whether the site slows down at the same time each hour or day.
Set sensible uptime alerts
A good alerting setup should notify you early without flooding you with false alarms. For hosted Tomcat applications, alerts should focus on actionable events.
Alert on true downtime
Send alerts when the app is unreachable, when the health check fails repeatedly, or when the Tomcat service is down. A single failed check may be a temporary network issue, so use a short retry window before alerting.
Alert on slow response time
Do not wait for a full outage. If response times rise above your normal baseline for several checks in a row, that usually deserves attention. Slowdowns often appear before a full failure.
Alert on repeated restart events
Repeated restarts are important to catch because they often indicate a deeper problem such as memory exhaustion, configuration errors, or a failing deployment package.
Alert on error-rate changes
If your monitoring system can check log patterns or application metrics, watch for sudden increases in 5xx errors, application exceptions, or failed health endpoints.
Use a simple health endpoint or lightweight check page
For Tomcat and Java hosting, a dedicated health endpoint is often more useful than checking a complex page. A lightweight URL should return quickly and reflect whether the app is functioning.
What a good health check should do
- respond quickly
- avoid heavy database work
- not require login unless that is deliberate
- confirm the application is actually running
- return a clear success signal
What to avoid
- using a slow homepage with many images or scripts
- calling external services that may fail for unrelated reasons
- running expensive queries on every check
- depending on cached content that can mask issues
The best health check is simple enough to be reliable and strict enough to fail when the app genuinely has a problem.
Watch SSL, domain, and DNS-related issues
After launch, many “site down” reports are really certificate, DNS, or redirect problems. These are especially important to watch right after switching an application live.
Certificate validity
Make sure the SSL certificate is valid, installed correctly, and covering the right hostname. Expired or misconfigured certificates can make a healthy Tomcat app look unavailable to visitors.
DNS propagation and record changes
If the domain was recently updated, some visitors may still resolve an old address for a short period. Monitor availability from different networks and keep an eye on whether traffic is reaching the expected hosting service.
Redirect loops
Watch for HTTPS redirect loops, www/non-www loops, or application-level redirects that conflict with Apache rules. These problems often appear only after the site is live and the browser starts applying cached redirect behavior.
Check app-specific behaviour, not only infrastructure
Uptime monitoring for a Java/Tomcat app should include the application’s own business logic. Infrastructure can be healthy while the app still fails to complete its main tasks.
Forms and submissions
Test contact forms, registration forms, checkout steps, and file uploads. A site may load fine but fail when handling POST requests or multipart uploads.
Database-backed pages
If pages depend on a database, confirm the app can read and write data correctly. Watch for delayed queries, connection pool issues, and timeouts that may not appear on static pages.
Scheduled jobs and imports
If the app runs scheduled tasks, confirm they start at the expected times and do not block the main service. In a smaller hosted environment, poorly tuned background jobs can affect visible uptime.
Practical monitoring checklist for the first week
Use this checklist as a simple launch routine for a newly live Tomcat site:
- Open the public URL in a browser and confirm the correct page loads.
- Check HTTPS, redirects, and the final canonical URL.
- Verify the Tomcat service is running in the control panel.
- Confirm the selected Java version matches the application requirement.
- Review Tomcat startup logs for warnings or deployment errors.
- Test login, forms, and any page that uses session state.
- Check that CSS, JavaScript, images, and uploads are served correctly.
- Watch response time during a few different times of day.
- Monitor memory and CPU after real traffic begins.
- Set alerts for downtime, slow response, and repeated restarts.
Troubleshooting signs that mean you should act quickly
Certain symptoms suggest the site needs attention before users are affected more broadly:
- the app loads once, then fails on the next request
- Tomcat starts successfully but the app throws errors in logs
- response time increases after every deployment
- the service restarts on its own
- some pages work while others return 500 errors
- the app behaves differently after a Java version change
- login works, but sessions are lost after refresh
These patterns usually point to configuration, memory, deployment, or application-level issues rather than a simple browser problem.
Best practices for hosted Tomcat monitoring
For a managed hosting environment, keep monitoring realistic and maintainable. You do not need enterprise-grade observability to run a small or medium Java application well. You do need consistent checks that match the size and complexity of the site.
Keep checks lightweight
Use a small set of meaningful health checks rather than many expensive probes. This keeps the monitoring overhead low and avoids creating noise.
Document the expected baseline
Record normal response times, normal memory use, the expected Java version, and the application context path. When something changes, you will know whether it is a real issue or just normal variation.
Review after every deploy
Each release is a good time to re-check logs, service state, and response time. A deployment that succeeds technically can still introduce functional problems.
Keep a simple rollback option
If your hosting workflow supports it, keep the previous working WAR or configuration available. Fast rollback is often the easiest way to restore service while you investigate the root cause.
FAQ
How often should I check a newly live Tomcat site?
During the first few days, check it more often than usual. A one- to five-minute external uptime check is common, with alerts for repeated failures. Also review logs and service status manually during the first 24 hours.
What is the most important thing to monitor first?
Start with availability, response time, and Tomcat service status. Those three signals usually reveal the biggest problems earliest.
Should I monitor the homepage only?
No. A homepage check is useful, but it is better to also check a lightweight health endpoint or a key functional URL such as login or search, depending on the application.
Why does my Tomcat site look fine but still need monitoring?
Because many Java issues appear gradually: memory growth, slow queries, background tasks, and service restarts. A site can appear healthy in one browser test and still be unstable under real usage.
What should I do if Tomcat keeps restarting?
Check the startup and application logs first, then review memory usage, heap settings, and recent changes. Repeated restarts are usually a sign of a configuration or application issue, not normal behaviour.
Can Apache hide a Tomcat problem?
Yes. If Apache is fronting Tomcat, it may still respond even when the Java app behind it is failing. That is why you should monitor both the public URL and the Tomcat service itself.
Conclusion
After putting a Tomcat site live, the safest approach is to monitor both the public experience and the Java service behind it. Check that the site opens correctly, watch response time, review logs, confirm the Tomcat service stays running, and keep an eye on memory and CPU usage. In a hosted Plesk environment with My App Server, these checks are straightforward and give you early warning before minor issues become downtime.
For UK hosting customers running Java, JSP, servlet, or Tomcat-based sites, the goal is predictable availability rather than complex infrastructure. A small set of reliable checks, sensible alerts, and regular log review will usually provide everything you need to keep the application stable after launch.