{"record":{"id":"f353d39d7d420f7a","repo":"elastic/elasticsearch","slug":"unable-to-find-pattern-in-grok-s-pattern-dict","errorCode":null,"errorMessage":"Unable to find pattern [{}] in Grok's pattern dictionary","messagePattern":"Unable to find pattern \\[(.+?)\\] in Grok's pattern dictionary","errorType":"validation","errorClass":"IllegalArgumentException","httpStatus":null,"severity":"error","filePath":"libs/grok/src/main/java/org/elasticsearch/grok/Grok.java","lineNumber":148,"sourceCode":"                result = matcher.search(0, grokPatternBytes.length, Option.NONE);\n            } finally {\n                matcherWatchdog.unregister(matcher);\n            }\n            handleInterrupted(result);\n            if (result < 0) {\n                return res.append(grokPattern).toString();\n            }\n\n            Region region = matcher.getEagerRegion();\n            String namedPatternRef = groupMatch(NAME_GROUP, region, grokPattern);\n            String subName = groupMatch(SUBNAME_GROUP, region, grokPattern);\n            // TODO(tal): Support definitions\n            @SuppressWarnings(\"unused\")\n            String definition = groupMatch(DEFINITION_GROUP, region, grokPattern);\n            String patternName = groupMatch(PATTERN_GROUP, region, grokPattern);\n            String pattern = patternBank.get(patternName);\n            if (pattern == null) {\n                throw new IllegalArgumentException(\"Unable to find pattern [\" + patternName + \"] in Grok's pattern dictionary\");\n            }\n            if (pattern.contains(\"%{\" + patternName + \"}\") || pattern.contains(\"%{\" + patternName + \":\")) {\n                throw new IllegalArgumentException(\"circular reference in pattern back [\" + patternName + \"]\");\n            }\n            String grokPart;\n            if (namedCaptures && subName != null) {\n                grokPart = String.format(Locale.US, \"(?<%s>%s)\", namedPatternRef, pattern);\n            } else if (namedCaptures) {\n                grokPart = String.format(Locale.US, \"(?:%s)\", pattern);\n            } else {\n                grokPart = String.format(Locale.US, \"(?<%s>%s)\", patternName + \"_\" + result, pattern);\n            }\n            String start = new String(grokPatternBytes, 0, result, StandardCharsets.UTF_8);\n            String rest = new String(\n                grokPatternBytes,\n                region.getEnd(0),\n                grokPatternBytes.length - region.getEnd(0),\n                StandardCharsets.UTF_8","sourceCodeStart":130,"sourceCodeEnd":166,"githubUrl":"https://github.com/elastic/elasticsearch/blob/db6a809a667c081ca1dc7500389d26975573215f/libs/grok/src/main/java/org/elasticsearch/grok/Grok.java#L130-L166","documentation":"Thrown by Grok.toRegex() during pattern compilation when a named pattern referenced via %{PATTERN_NAME:...} or %{PATTERN_NAME} is not found in the provided PatternBank. The Grok constructor calls toRegex() to expand all grok pattern references into a concrete regular expression. Each %{NAME} must resolve to an entry in the pattern bank.","triggerScenarios":"Constructing a new Grok(patternBank, grokPattern) where grokPattern contains a %{PATTERN_NAME} reference that does not exist in patternBank. Common with custom patterns that reference built-in pattern names that are only available in a specific ECS compatibility mode, or when the pattern bank was built with a different set of patterns.","commonSituations":"Using a grok pattern that references %{IP} or %{NUMBER} but loading patterns with a custom PatternBank that doesn't include those; misspelling a pattern name (e.g. %{IPORHOST} vs %{IPOR_HOST}); ECS v1 vs legacy pattern mismatch — some patterns exist only in one mode; using a third-party grok pattern file that references patterns not in the Elasticsearch built-in set.","solutions":["Pre-register the missing pattern in the PatternBank before constructing the Grok object.","Use GrokBuiltinPatterns.legacyPatterns() or ecsV1Patterns() to include standard built-in patterns.","Check the spelling of the pattern name in the grok expression — compare against the pattern definitions file.","Merge custom patterns with built-in patterns: create a combined PatternBank with both sets."],"exampleFix":"// before — missing pattern\nMap<String, String> custom = Map.of(\"MYCUSTOM\", \"\\\\d+\");\nPatternBank bank = new PatternBank(custom);\nnew Grok(bank, \"%{IP:client_ip} %{MYCUSTOM:count}\", null); // IP not in bank\n\n// after — merge with built-in patterns\nMap<String, String> custom = new LinkedHashMap<>(GrokBuiltinPatterns.legacyPatterns().patterns());\ncustom.put(\"MYCUSTOM\", \"\\\\d+\");\nPatternBank bank = new PatternBank(custom);\nnew Grok(bank, \"%{IP:client_ip} %{MYCUSTOM:count}\", null);","handlingStrategy":"validation","validationCode":"// Pre-check that all referenced patterns exist in the bank\nString[] refs = extractPatternReferences(grokPattern); // your utility\nfor (String ref : refs) {\n    if (patternBank.get(ref) == null) {\n        throw new IllegalArgumentException(\"Missing grok pattern: \" + ref);\n    }\n}\nnew Grok(patternBank, grokPattern, callback);","typeGuard":"static boolean allPatternsDefined(String grokPattern, PatternBank bank) {\n    // simplistic check — a full check requires parsing %{NAME} references\n    java.util.regex.Pattern ref = java.util.regex.Pattern.compile(\"%\\\\{(\\\\w+)\");\n    var m = ref.matcher(grokPattern);\n    while (m.find()) {\n        if (bank.get(m.group(1)) == null) return false;\n    }\n    return true;\n}","tryCatchPattern":"try {\n    new Grok(patternBank, grokPattern, callback);\n} catch (IllegalArgumentException e) {\n    if (e.getMessage().contains(\"Unable to find pattern\")) {\n        // extract pattern name, suggest registering it or merging built-in patterns\n    }\n    throw e;\n}","preventionTips":["Merge custom patterns with GrokBuiltinPatterns.legacyPatterns() or ecsV1Patterns() to include standard patterns.","Validate pattern references before constructing a Grok object.","Check pattern name spelling against the pattern definition files."],"tags":["grok","pattern-matching","validation","pattern-resolution","ingest"],"analyzedSha":"db6a809a667c081ca1dc7500389d26975573215f","analyzedAt":"2026-08-12T01:39:14.192Z","schemaVersion":2},"datasetVersion":"2026-08-12T06:17:24.410Z"}