Guance Learn

Observability questions

Focused answers for definitions, architecture choices, troubleshooting, pricing, and evaluation.

Illustration of cooperating application modules
Technical guide

Fix “Cannot set headers after they are sent” in Node.js

Find response paths that write headers twice, stop branch fallthrough, and hand Express errors to the right middleware.

  • Engineering
  • Technical guide
3 min read
Illustration of cooperating application modules
Technical guide

Fix EACCES during a global npm installation

Identify the path npm cannot write, then choose a user-owned Node installation or global prefix without broadly changing system permissions.

  • Engineering
  • Technical guide
3 min read
Data organization and search illustration
Technical guide

Troubleshoot Elasticsearch index_not_found_exception

Resolve missing index errors by checking the cluster, aliases, data streams, permissions, and lifecycle before creating anything.

  • Engineering
  • Technical guide
2 min read
Illustration of scheduled jobs, logs and Linux operations
Explainer

Fix “errors in crontab file, can’t install”

Repair rejected crontab files while preserving the current schedule, and distinguish parsing errors from runtime failures.

  • Engineering
  • Explainer
3 min read
Illustration of log collection and monitoring
Explainer

Exclude logs from a Fluentd match

Discard unwanted tags or record contents in Fluentd, order routes correctly, and use version-aware regular expressions for tag exclusion.

  • Engineering
  • Explainer
2 min read
Log monitoring illustration
Explainer

Export Kibana data to CSV for Excel

Export Discover results or Lens tables as CSV, understand reporting limits, and choose an API workflow for larger datasets.

  • Engineering
  • Explainer
2 min read
Log monitoring illustration
Explainer

Match a leading digit in Filebeat with a regular expression

Use Filebeat regexp conditions to drop or retain messages that start with a digit, and configure multiline parsing separately.

  • Engineering
  • Explainer
2 min read
Log monitoring illustration
Explainer

Fix Filebeat “data path already locked by another beat”

Find the Filebeat process using a data directory, resolve overlapping instances, and preserve registry state when troubleshooting locks.

  • Engineering
  • Explainer
2 min read
Log monitoring illustration
Explainer

Should Filebeat send directly to Elasticsearch or through Logstash?

Choose an ingestion path based on parsing, enrichment, routing, and recovery requirements rather than traffic volume alone.

  • Engineering
  • Explainer
2 min read
Log monitoring illustration
Explainer

Parse fields from a Filebeat message

Decode JSON or dissect fixed-format text in Filebeat, and use an Elasticsearch ingest pipeline when you need grok parsing.

  • Engineering
  • Explainer
2 min read
Illustration of log collection and monitoring
Explainer

Filebeat vs. rsyslog for forwarding logs

Choose between Filebeat and rsyslog by input protocol, destination, parsing needs, restart behavior, and the workload you can actually test.

  • Engineering
  • Explainer
3 min read
Illustration of Git branches and version history
Technical guide

Find the upstream branch of a local Git branch

Use git branch -vv and upstream references to inspect tracking relationships, refresh ahead/behind counts, and change a branch upstream.

  • Engineering
  • Technical guide
2 min read