caddyserver/caddy · error

server block %v: %v

Error message

server block %v: %v

What it means

A wrapper error from compileEncodedMatcherSets: encoding one of the server block's compiled matcher sets into a caddy.ModuleMap failed. The inner error typically comes from encodeMatcherSet rejecting a matcher module whose JSON cannot be produced, and the message prefixes the block's keys so you know which site block is at fault.

Source

Thrown at caddyconfig/httpcaddyfile/httptype.go:1663

	for _, mp := range matcherPairs {
		matcherSet := make(map[string]caddyhttp.RequestMatcherWithError)
		if len(mp.hostm) > 0 {
			matcherSet["host"] = mp.hostm
		}
		if len(mp.pathm) > 0 {
			matcherSet["path"] = mp.pathm
		}
		if len(matcherSet) > 0 {
			matcherSets = append(matcherSets, matcherSet)
		}
	}

	// finally, encode each of the matcher sets
	matcherSetsEnc := make([]caddy.ModuleMap, 0, len(matcherSets))
	for _, ms := range matcherSets {
		msEncoded, err := encodeMatcherSet(ms)
		if err != nil {
			return nil, fmt.Errorf("server block %v: %v", sblock.block.Keys, err)
		}
		matcherSetsEnc = append(matcherSetsEnc, msEncoded)
	}

	return matcherSetsEnc, nil
}

func parseMatcherDefinitions(d *caddyfile.Dispenser, matchers map[string]caddy.ModuleMap) error {
	d.Next() // advance to the first token

	// this is the "name" for "named matchers"
	definitionName := d.Val()

	if _, ok := matchers[definitionName]; ok {
		return fmt.Errorf("matcher is defined more than once: %s", definitionName)
	}
	matchers[definitionName] = make(caddy.ModuleMap)

View on GitHub (pinned to 50e54ee279)

Solutions

1. Read the inner error — it identifies the failing matcher value; correct it in the named site block
2. If a custom matcher plugin is involved, fix its JSON marshaling or update the plugin
3. Reproduce with `caddy adapt` on the single block to minimize input
4. Simplify the block's matchers and re-add them one by one to isolate the bad one

// Programmatically: round-trip each matcher set before use
if _, err := json.Marshal(matcherSet); err != nil {
    return fmt.Errorf("block %v: unencodable matcher: %w", keys, err)
}

msEncoded, err := encodeMatcherSet(ms)
if err != nil {
    return nil, fmt.Errorf("server block %v: %w", sblock.block.Keys, err)
}

When it happens

Trigger: A site block whose host/path matcher combination includes values that fail encoding — e.g. a placeholder or regexp that cannot marshal into the module map; practically rare with stock matchers, more likely with custom matcher modules returning non-serializable configs from their UnmarshalCaddyfile.

Common situations: Custom matcher plugins with broken MarshalJSON, or malformed hostnames/placeholders in site keys; also seen when a config generated by tooling feeds unexpected values into matcher fields.

Related errors

• unrecognized matcher name: %+v
• matcher is defined more than once: %s
• missing 'req' argument
• unsupported type
• private key does not match issuer public key

AI-assisted analysis of caddyserver/caddy@50e54ee279 (2026-08-15). Data as JSON: /api/errors/4b1f58e0a1739e00. Report an issue: GitHub.