Troubleshooting kSar: Common Errors and Quick FixeskSar is a popular Java-based tool that parses sar (System Activity Report) output and generates visual reports (graphs and PDFs) to help analyze historical system performance on Linux and UNIX systems. While kSar is powerful and useful, users sometimes encounter issues related to Java environment, sar file formats, resource limits, or application bugs. This article walks through common errors, diagnostics, and reliable fixes so you can get kSar back to producing clear performance charts quickly.
Table of contents
- Overview of common problem areas
- Preparing your environment (Java, sar versions, file formats)
- Error: kSar fails to start / Java exceptions on launch
- Error: “Cannot parse input file” / malformed lines in sar output
- Error: Incorrect or missing metrics in graphs
- Error: High memory usage / OutOfMemoryError when loading large sar files
- Error: Charts rendering incorrectly or missing labels
- Tips for automation, logging, and advanced debugging
- When to report a bug and how to prepare reproducible reports
Overview of common problem areas
Common kSar problems typically fall into these categories:
- Java runtime issues (wrong version, incompatible vendor, missing libraries)
- sar output format differences or corrupted files
- Locale/encoding mismatches affecting numeric parsing
- Resource constraints (memory, CPU) when processing large sar files
- UI rendering issues or PDF generation problems
- User errors in selecting the correct input type (raw sar vs. post-processed)
Preparing your environment
Before troubleshooting specific errors, confirm the basics:
- Java: kSar is Java-based and typically runs on Java 8+ (many users run it on Java 8–11). Use a stable JDK/JRE such as OpenJDK or Oracle JRE.
- Check with: java -version
- kSar version: Use the latest stable kSar release; older versions may lack fixes for newer sar formats.
- sar version / sysstat: kSar expects sar output produced by the sysstat package. Standard sar command versions differ; note your sar version with sar -V or check package manager.
- Locale/encoding: Ensure UTF-8 locale (LANG, LC_NUMERIC) to avoid decimal comma/period parsing issues.
- Input type: Know whether you’re supplying a raw binary sar file (usually created by sysstat) or a text sar output. kSar supports raw files and textual sar outputs but you must pick the correct import option.
Error: kSar fails to start / Java exceptions on launch
Symptoms:
- kSar window doesn’t open; terminal shows Java stack trace.
- Errors mention NoClassDefFoundError, UnsupportedClassVersionError, or ClassNotFoundException.
Diagnostics & fixes:
- UnsupportedClassVersionError: indicates kSar was compiled for a newer Java than the one installed. Install a newer JRE/JDK (e.g., Java 11) or use a kSar build compatible with your Java version.
- NoClassDefFoundError / ClassNotFoundException: corrupted or incomplete kSar jar. Re-download kSar from a trusted source and verify file integrity.
- Permission denied when launching: check executable bit and file ownership; run with java -jar kSar.jar from a terminal to see full errors.
- If you see AWT/Swing exceptions on headless servers (no display), run kSar in headless mode or use X forwarding / virtual framebuffer (Xvfb). Example: xvfb-run java -jar kSar.jar
Error: “Cannot parse input file” / malformed lines in sar output
Symptoms:
- kSar reports parse errors, shows a line number, or skips data silently.
- Imported graphs are empty or have large gaps.
Causes & fixes:
- sar locale mismatches: If sar output uses commas for decimal separators (LC_NUMERIC), numeric parsing fails. Generate sar with C or en_US.UTF-8 locale: LC_ALL=C sar -A -f /var/log/sa/saXX
- Different sar versions change column headers or add/remove fields. kSar maps columns by header names — if headers don’t match expected patterns, parsing fails. Use sar -A or standard sar textual output, or upgrade kSar to a version that recognizes your sar format.
- Corrupted or truncated sar file: validate with sar -f file or try parsing smaller chunks. If binary sar is corrupted, regenerate sar data if possible.
- Mixed content (timestamps in different formats): normalize timestamps or export sar to plain text: sar -A -f /var/log/sa/saXX > sa.txt and import the text file.
- Missing timezone or DST adjustments: ensure consistent timezone when comparing multiple files—convert or set TZ environment variable before running sar.
Example: Convert problematic file to standard textual format then import
LC_ALL=C sar -A -f /var/log/sa/sa01 > /tmp/sa01.txt java -jar kSar.jar /tmp/sa01.txt Error: Incorrect or missing metrics in graphs
Symptoms:
- CPU graph shows zeroes, network graph missing RX/TX lines, or memory panels are blank.
Causes & fixes:
- Some sar records are optional depending on kernel configuration or sar options used. Confirm the sar collection included the metrics (e.g., enable network statistics collection).
- kSar may misinterpret columns after sar updates. Update kSar or manually edit the text sar output so headers match expected names.
- Ensure you imported the correct file (binary sar vs. textual). Some users accidentally import sar binary into the textual importer.
- Time granularity: if sar collected at long intervals, graphs may appear sparse; use higher frequency collection for finer detail.
Error: High memory usage / OutOfMemoryError when loading large sar files
Symptoms:
- Java heap space errors, system becomes unresponsive when opening very large sar datasets.
Fixes:
- Increase Java heap size when launching kSar:
java -Xmx4g -jar kSar.jarAdjust -Xmx to available RAM (e.g., 2g, 4g).
- Pre-filter sar to narrower time ranges before importing: sar -f file | awk ‘/^15:00:00/,/^16:00:00/’ > subset.txt
- Use a machine with more RAM or process files in segments.
- Reportedly, newer kSar builds have memory optimizations—try the latest version.
Error: Charts rendering incorrectly or missing labels
Symptoms:
- Axis labels missing, overlapping text, or exported PDF graphs distorted.
Causes & fixes:
- Font or rendering issues in headless environments: ensure Java has access to fonts. Install font packages (e.g., dejavu-fonts) in minimal containers.
- PDF generation problems: try exporting to PNG first to verify rendering, or run kSar with a local display/Xvfb.
- Scale and DPI issues: when exporting to PDF, specify higher DPI or larger canvas if available in options.
Tips for automation, logging, and advanced debugging
- Run kSar from terminal to capture stderr/stdout; save logs for later examination.
- Use sar -A -f to produce consistent textual output for portability.
- For repetitive tasks, script sar extraction and kSar invocation, and limit time ranges to reduce memory use.
- When testing parsing issues, create minimal reproducer files (small time window) to speed debugging.
- Keep Java and kSar up to date; many parsing bugs are resolved in newer releases.
When to report a bug and how to prepare reproducible reports
Report to the kSar issue tracker when:
- You can reproduce parsing errors with an unmodified sar output and the latest kSar.
- There’s a Java exception or stack trace pointing to kSar code.
Provide:
- kSar version and java -version output (include vendor and runtime).
- A small anonymized sample of the sar input that reproduces the issue (trim to minimal lines).
- Exact command lines used to produce sar and launch kSar.
- Screenshots of errors and full stack traces from terminal.
Troubleshooting kSar usually revolves around matching sar output format and ensuring a compatible Java environment. Start with locale and Java version checks, try converting to standard textual sar output, and increase Java heap for large files. If problems persist with the latest kSar, create a minimal reproducible example and report it with Java and kSar version details.
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