python
9 minDebugging Flaky Python Tests: Time, State, Concurrency, and Isolation
Find the hidden shared state, clock assumptions, race, or nondeterministic dependency behind tests that fail only sometimes.
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25 matching resultsArticles and interview answers
java
10 minJava Exception Debugging: Trace the Root Cause and Fix the Boundary
A practical method for investigating wrapped exceptions, null failures, resource exhaustion, and misleading catch blocks in JVM services.
Q&A
Q&AHow do TCP and UDP differ when debugging a service?
TCP establishes an ordered byte stream; UDP sends datagrams without delivery acknowledgement from the transport.
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TCP connection establishment and retransmission make a port-connectivity test meaningful, but application message boundaries still need framing. UDP has no handshake, so silence may mean a dropped packet, invalid request, or a service that does not answer probes. Test using a valid protocol request and inspect both ends when possible.
python
9 minPython Error Debugging: Tracebacks, Root Causes, and Safe Fixes
Turn Python exceptions into a reproducible diagnosis using traceback frames, minimal experiments, structured logging, and boundary validation.
unix
9 minShell Script Debugging: Trace Failures, Preserve Exit Codes, and Fix Safely
A root-cause workflow for shell failures involving quoting, pipelines, unset variables, traps, temporary files, and partial work.
unix
11 minTCP, UDP, ss, netstat, and tcpdump: A Layered Network Debugging Guide
Diagnose connection failures by separating DNS, routing, transport, listening sockets, and application protocol behavior.
java
9 minJava equals and hashCode: Fix Broken HashMap and HashSet Lookups
Diagnose collection bugs caused by inconsistent equality, mutable keys, inheritance, and accidental identity comparisons.
Q&A
Q&AWhy can COUNT(column) differ from COUNT(*)?
COUNT(column) excludes NULL values; COUNT(*) counts input rows.
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COUNT(*) counts each row in the group regardless of column values. COUNT(column) counts only rows where that expression is non-NULL. When aggregates look low, check nullability and join multiplication before changing the query.