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Q&A
Q&AEvery later layer is invalidated when an earlier instruction input changes.
If the whole source tree is copied before dependency installation, any source edit changes that COPY layer and invalidates all subsequent build steps. Copy lockfiles first, install from them, then copy source. Confirm the result with build output and a clean build; cache reuse should improve speed, not alter correctness.
Q&A
Q&APreserve the logical job and intended window, not the retry start time.
A logical run names the business partition; attempt IDs name executions of that run. Commit completion with the effect when they share storage, and handle remote effects with an explicit duplicate or reconciliation protocol.
http
5 minKeep list traversal stable, validate cached representations, and bound retry work when networks fail at ambiguous points.
unix
18 minConnect kernel readiness APIs, resource limits, cgroups, socket queues, page cache, and inode behavior to production symptoms.
Q&A
Q&AA 304 validates a previously cached representation and does not provide a replacement body. Cache policy and authorization still control whether reuse is appropriate.
A 304 validates a previously cached representation and does not provide a replacement body. Cache policy and authorization still control whether reuse is appropriate.
devops
17 minOptimize Docker layers without breaking reproducibility, isolate CI execution, secure image provenance, and deploy compatible schema changes.
Q&A
Q&ATIME_WAIT is part of safe TCP teardown; verify actual ephemeral-port pressure before tuning sysctls.
TIME_WAIT helps prevent delayed packets from an old connection from contaminating a new one. A high count can be normal. Diagnose port exhaustion by checking outbound tuple reuse, NAT limits, ephemeral port range, and connection pooling. tcp_tw_reuse semantics vary by kernel and are not a universal first fix.
Q&A
Q&AIndependent hot fields on one cache line can cause cores to invalidate each other’s cache copies.
False sharing occurs when separate variables frequently written by different cores share a hardware cache line. The values are logically independent, but cache-coherence traffic makes updates contend. Confirm with profiling and workload measurements before padding or using specialized structures; layout optimizations are hardware- and JVM-sensitive.