apache/skywalking · error · ApplyException

YAML parse failure for {sourceName}

Error message

YAML parse failure for {sourceName}

What it means

ApplyException wrapping any non-ApplyException Throwable thrown while MalFileApplier.parse deserializes MAL YAML, defaults the rule name to sourceName, or stamps source lines via RuleSourceLines.assign. The empty/parse-null ApplyException is rethrown untouched; snakeyaml syntax errors and line-stamping failures are wrapped with the source name and an empty rollback set (nothing registered yet).

Source

Thrown at oap-server/server-admin/runtime-rule/src/main/java/org/apache/skywalking/oap/server/receiver/runtimerule/apply/MalFileApplier.java:293

            final Rule rule = new Yaml().loadAs(reader, Rule.class);
            if (rule == null) {
                throw new ApplyException("YAML parsed to null — empty or malformed rule file: "
                    + sourceName, null, Collections.emptySet());
            }
            if (rule.getName() == null || rule.getName().isEmpty()) {
                rule.setName(sourceName);
            }
            // Stamp YAML source anchors from the SAME text we just bound, so a hot-updated rule
            // gets the same line provenance a disk-loaded one does.
            RuleSourceLines.assign(rule, yamlContent);
            // layerDefinitions: are now permitted in runtime MAL rules; they're handled by
            // the layer registry on the apply path below. The rejection that used to live
            // here was removed when runtime dynamic layers became a first-class feature.
            return rule;
        } catch (final ApplyException e) {
            throw e;
        } catch (final Throwable t) {
            throw new ApplyException("YAML parse failure for " + sourceName, t, Collections.emptySet());
        }
    }

    /**
     * Build {@link LayerClaim}s for every {@code layerDefinitions:} entry in {@code rule}.
     * The list is ordered the same as the YAML for stable diagnostic output.
     *
     * <p>{@code ordinal:} is mandatory in runtime DSL — the registry-side validation rejects
     * any entry whose ordinal is below {@link Layer#RUNTIME_DYNAMIC_MIN_ORDINAL} (including
     * the default {@code 0} that an omitted-yaml-key produces) with applyStatus
     * {@code layer_ordinal_out_of_range}. {@code normal:} is optional and defaults to
     * {@code true} via {@link LayerDefinition}'s field initializer — same semantics as the
     * bundled {@code layerDefinitions:} blocks and {@code layer-extensions.yml}.
     *
     * <p>An empty {@code layerDefinitions:} block returns an empty list — callers may pass
     * it straight to {@link RuntimeLayerRegistry#apply}, which is a no-op for empty input.
     */
    private static List<LayerClaim> extractLayerClaims(final Rule rule) {

View on GitHub (pinned to 102af09b4a)

Solutions

1. Fix the syntax error at the line/column named by the wrapped cause
2. Quote all exp values and keep metricsRules as a block-style list of maps
3. Lint with Yaml().loadAs(new StringReader(content), Rule.class) locally before submit
4. After correcting, re-apply; no rollback is needed since the failure precedes registration

try (StringReader r = new StringReader(content)) {
    final Rule rule = new Yaml().loadAs(r, Rule.class);
    if (rule == null) reject("empty");
    RuleSourceLines.assign(rule, content); // exercises the same line-stamping step
}

catch (ApplyException e) when 'YAML parse failure for': surface e.getCause()'s mark; content defect — fix and re-submit, no state to unwind.

When it happens

Trigger: Applying MAL content with a YAML syntax error (tabs, bad indentation, unterminated string) or a structure Rule cannot be mapped onto — e.g. metricsRules as a map instead of a list. Also fires if RuleSourceLines cannot assign line anchors to a flow-style or anchor-using document.

Common situations: Unquoted expressions containing ': ' or leading special YAML characters; Windows line endings breaking block parsing; Renamed schema keys after upgrades (metricPrefix vs prefix) making mapping fail

Related errors

• LAL YAML parse failure for {sourceName}
• Load rule {} failed
• compile_failed
• LAL YAML parsed to empty/malformed — no rules list in {sourc
• MAL register failed for {sourceName} (partial)

AI-assisted analysis of apache/skywalking@102af09b4a (2026-08-14). Data as JSON: /api/errors/7ff662f6edf942a1. Report an issue: GitHub.