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Logging

confd logs everything to stdout. You can control the types of messages that get printed by using the --log-level flag and corresponding configuration file settings. See the Configuration Guide for more details.

Note: confd now uses Go's standard library log/slog for logging, providing better performance and structured logging capabilities.

Log Levels

Use the --log-level flag to set the verbosity. Valid levels are: panic, fatal, error, warn, info, and debug.

Log Formats

confd supports two log formats, controlled by the --log-format flag:

Text Format (default)

The default text format includes timestamp, hostname, process name, PID, level, and message. When using structured logging, attributes are appended as key-value pairs:

2013-11-03T19:04:53-08:00 confd[21356]: INFO SRV domain set to confd.io
2013-11-03T19:04:53-08:00 confd[21356]: INFO Starting confd
2013-11-03T19:04:53-08:00 confd[21356]: INFO etcd nodes set to http://etcd0.confd.io:4001, http://etcd1.confd.io:4001
2013-11-03T19:04:54-08:00 confd[21356]: INFO Target config /tmp/myconf2.conf out of sync
2013-11-03T19:04:54-08:00 confd[21356]: INFO Target config /tmp/myconf2.conf has been updated

With structured logging attributes:

2024-01-14T10:30:00-08:00 hostname confd[21356]: INFO Backend configured backend=etcd node_count=3

JSON Format

Use --log-format=json for structured JSON output, which is easier to parse with log indexing solutions (ELK, Splunk, etc.):

confd env --log-format=json --onetime
{"time":"2024-01-14T10:30:00Z","level":"INFO","msg":"Backend set to env"}
{"time":"2024-01-14T10:30:00Z","level":"INFO","msg":"Starting confd"}
{"time":"2024-01-14T10:30:01Z","level":"INFO","msg":"Target config /tmp/myconf.conf has been updated"}

Or set in confd.toml:

log-format = "json"

Structured Logging

confd supports structured logging using Go's log/slog package. This allows you to attach key-value pairs to log messages for better searchability and analysis:

// Traditional printf-style (still supported)
log.Info("Processing template %s", templatePath)

// Structured logging with context
log.InfoContext(ctx, "Processing template", 
    "path", templatePath,
    "backend", backendName,
    "duration_ms", elapsed.Milliseconds())

// Creating a logger with persistent attributes
templateLogger := log.With("template", "app.conf", "component", "renderer")
templateLogger.Info("Template rendered successfully")

Structured logging benefits:

  • Better searchability: Query logs by specific field values
  • Machine-readable: Easy to parse and analyze programmatically
  • Performance: Efficient key-value encoding with minimal allocations
  • Context propagation: Automatic trace/span ID extraction from context