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Client-Server Monitoring

Client-Server monitoring focuses on validating the interaction between client applications (web browsers, mobile apps) and back-end servers.

It ensures that transactions are completed successfully and that end-user experience remains optimal under load.

Why do we do Client-Server Monitoring?

  • To ensure seamless communication between client and server under load.
  • To identify performance bottlenecks across network, server, and application layers.
  • To validate end-user experience by monitoring real user metrics and system responses.
  • To prevent failures caused by latency, timeouts, or resource exhaustion.

What We Monitor on Client Side

Time to First Byte (TTFB)

Time taken from sending request to receiving the first byte of response.

Target: < 200 ms
Page Load Time

Total time taken to fully load the page, including all resources.

Target: < 3 sec
JSP/Servlet Response Time

Time taken by server-side components to process request.

Target: < 500 ms
API Calls (AJAX/REST)

Total number of API calls from client.

Should not exceed:
• 50 calls per page
• Error rate < 1%

JS Errors

Number of JavaScript errors on the page.

Should be: 0
File Download (ZIP, PDF, etc.)

Download time for files.

Target: < 5 sec
Size limit: < 50 MB
File Upload

Upload time for files.

Target: < 5 sec
Size limit: < 50 MB
Page Weight

Total size of page resources (HTML, CSS, JS, Images).

Should be: < 2 MB
Number of Requests

Total number of requests sent by browser.

Should not exceed: 100 per page
Connection Errors

Failed requests due to network/server issues.

Should be: 0

Client Side Monitoring Thresholds

Metric Description Threshold Why It Matters
TTFB Time to First Byte < 200 ms Higher TTFB indicates server or network latency.
Page Load Time Total time to fully load the page < 3 sec Affects user experience and page abandonment.
JSP/Servlet Response Time Server-side processing time < 500 ms High time impacts overall application performance.
API Calls Total API calls made by page <= 50 calls Too many calls increase load and latency.
JS Errors JavaScript errors on page 0 JS errors break functionality and user experience.
File Download Time to download files (ZIP, PDF, etc.) < 5 sec (Size < 50MB) Large/slow downloads degrade user experience.
File Upload Time to upload files < 5 sec (Size < 50MB) Slow uploads affect productivity and satisfaction.
Page Weight Total size of page resources < 2 MB Heavy pages take longer to load.
Number of Requests Total requests from browser <= 100 Too many requests increase server load.
Connection Errors Failed requests 0 Errors impact functionality and trust.

End-to-End Client-Server Flow

Client/Browser
Mobile App
DNS Lookup
TCP Connection
SSL Handshake
Send Request
Server Processing
(JSP/Servlet)
Database Query
Response to Client
Monitoring each step helps identify the exact point of delay or failure.

Real-Time Monitoring (Examples)

TTFB (ms)
10:0010:1510:3010:4511:00
TTFB (ms)
Page Load Time (sec)
10:0010:1510:3010:4511:00
Page Load Time (sec)
API Calls (count)
10:0010:1510:3010:4511:00
API Calls (count) Threshold (50)
Error Rate (%)
10:0010:1510:3010:4511:00
Error Rate (%) Threshold (1%)

Best Practices

Set realistic thresholds based on user expectations.
Track trends, not just single values.
Alert when thresholds are breached.
Monitor under different network conditions.
Correlate client-side metrics with server performance.
Continuously optimize based on monitoring insights.
Effective client-server monitoring ensures optimal end-user experience, system reliability, and better performance under all load conditions.