apache/skywalking · error · IllegalArgumentException

Unclosed interpolation in: {s}

Error message

Unclosed interpolation in: {s}

What it means

Same unknown-function failure as the 3-arg create, but from the extended MeterSystem.create(metricsName, functionName, ScopeType, ClassPool, ClassLoader, StorageManipulationOpt) overload used by the MAL runtime compiler. The functionName lookup in functionRegister fails for identical reasons: no @MeterFunction class registered under that name.

Source

Thrown at oap-server/analyzer/log-analyzer/src/main/java/org/apache/skywalking/oap/log/analyzer/v2/compiler/LALScriptParser.java:1033

            }
            // Literal text before ${
            if (start > pos) {
                parts.add(InterpolationPart.ofLiteral(s.substring(pos, start)));
            }
            // Find matching closing brace, respecting nesting
            int depth = 1;
            int i = start + 2;
            while (i < s.length() && depth > 0) {
                final char c = s.charAt(i);
                if (c == '{') {
                    depth++;
                } else if (c == '}') {
                    depth--;
                }
                i++;
            }
            if (depth != 0) {
                throw new IllegalArgumentException(
                    "Unclosed interpolation in: " + s);
            }
            final String expr = s.substring(start + 2, i - 1);
            // Parse the expression as a valueAccess through ANTLR
            parts.add(InterpolationPart.ofExpression(parseValueAccessExpr(expr)));
            pos = i;
        }
        return parts;
    }

    /**
     * Parses a standalone valueAccess expression string by wrapping it in
     * a minimal LAL script and extracting the parsed ValueAccess.
     */
    private static ValueAccess parseValueAccessExpr(final String expr) {
        // Wrap in: filter { if (EXPR) { sink {} } }
        // The expression becomes a condition, parsed as ExprCondition
        // whose ValueAccess is what we want.

View on GitHub (pinned to 102af09b4a)

Solutions

1. Fix the function name in the MAL config to match an existing @MeterFunction functionName
2. Ensure custom function classes live under org.apache.skywalking and are on the OAP classpath
3. Check the OAP log at startup — the scan-based register is built in the MeterSystem constructor; load errors there explain empty entries

catch (IllegalArgumentException e) { throw new RuntimeException("MAL compilation failed for function '" + functionName + "'", e); }

When it happens

Trigger: The MAL analyzer compiles a rule and calls this overload with a function name absent from the register — typo'd name, custom function not on the classpath, or name drift after upgrading OAP where a function was renamed.

Common situations: Loading meter-analyzer-config YAML at boot or via dynamic configuration; custom MAL functions packaged outside the scanned org.apache.skywalking packages; mixing rule versions with the OAP binary.

Related errors

• {slot} value '{numText}' exceeds the supported range (must f
• Load meter analyzer configs failed
• Unsupported extractor statement in LAL rule at line {sourceL
• {slot} value '{numText}' exceeds the supported range (must f
• Cannot parse interpolation expression: {expr}

AI-assisted analysis of apache/skywalking@102af09b4a (2026-08-14). Data as JSON: /api/errors/8dfcd0a145ff91a8. Report an issue: GitHub.