Packer PACKER_LOG alert threshold without losing step completion signals

Question

Goal is to surface only actionable build problems to notification channels while keeping normal build progress in logs. Packer controls verbosity via PACKER_LOG with levels debug, info, warn, error, and the -debug flag forces full trace output regardless of the environment variable.

With PACKER_LOG at warn or error, informational step messages are suppressed, which reduces noise but also removes step-completion signals some CI systems use for alerting and progress tracking. The -debug flag overrides PACKER_LOG and can flood downstream notifications if not filtered.

Packer does not document a dedicated alert-only mode that emits warnings and errors on a separate stream from the main build log. This leaves an unresolved decision about how to keep useful alerts without losing progress context.

Does Packer provide a documented way to emit warnings and errors independently of the main log verbosity? How does the interaction between PACKER_LOG and -debug affect external alert thresholds? Is there a supported pattern for alert-only output without suppressing step completion information?

Tasadduq Burney · Answer

AnswerPacker does not provide a separate alert‑only stream. The only way to keep step‑completion (INFO) messages while still surfacing warnings and errors is to retain a normal log level (INFO or higher) and filter the output downstream for WARN/ERROR lines.Confirmed factsPACKER_LOG controls the overall verbosity (debug, info, warn, error).The -debug flag forces full trace output and overrides PACKER_LOG.Step‑completion messages are emitted at the INFO level; setting PACKER_LOG=warn or error hides them.No built‑in option splits alerts from the main log.Steps for this caseSet the environment variable to a level that includes INFO, e.g.:export PACKER_LOG=infoRun Packer as usual:packer build template.pkr.hclPipe the combined stdout/stderr through a simple filter that extracts only warning and error lines for your notification channel:packer build template.pkr.hcl 2>&1 | grep -E 'WARN|ERROR'If you need the full debug trace for troubleshooting, add -debug and apply the same filter:packer build -debug template.pkr.hcl 2>&1 | grep -E 'WARN|ERROR'Missing diagnostic detailTo tailor the filter to your CI system’s expectations, please confirm the exact pattern your CI uses to recognise step‑completion signals (e.g., a specific prefix, ANSI colour code, or structured log field). This detail determines whether a simple grep is sufficient or if a more sophisticated parser is required.

Packer PACKER_LOG alert threshold without losing step completion signals

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Missing diagnostic detail

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