{"record":{"id":"5f7ba178284f3ad7","repo":"apache/cassandra","slug":"failed-to-dump-trie-to-due-to-exception","errorCode":null,"errorMessage":"Failed to dump trie to {} due to exception","messagePattern":"Failed to dump trie to (.+?) due to exception","errorType":"console","errorClass":null,"httpStatus":null,"severity":"warning","filePath":"src/java/org/apache/cassandra/io/sstable/format/bti/PartitionIndex.java","lineNumber":443,"sourceCode":"\n            pos = INVALID; // make sure next time we call nextPayloadedNode() again\n            return getIndexPos(buf, payloadPosition(), payloadFlags()); // this should not throw\n        }\n    }\n\n    /**\n     * debug/test code\n     */\n    @VisibleForTesting\n    public void dumpTrie(String fileName)\n    {\n        try(PrintStream ps = new PrintStream(fileName))\n        {\n            dumpTrie(ps);\n        }\n        catch (Throwable t)\n        {\n            logger.warn(\"Failed to dump trie to {} due to exception\", fileName, t);\n        }\n    }\n\n    private void dumpTrie(PrintStream out) throws IOException\n    {\n        try (Reader rdr = openReader())\n        {\n            rdr.dumpTrie(out, (buf, ppos, pbits, version) -> Long.toString(getIndexPos(buf, ppos, pbits)), null);\n        }\n    }\n\n}\n","sourceCodeStart":425,"sourceCodeEnd":456,"githubUrl":"https://github.com/apache/cassandra/blob/88fd0f6a0eaed8943f05ac9e8f947882b8ddc8f1/src/java/org/apache/cassandra/io/sstable/format/bti/PartitionIndex.java#L425-L456","documentation":"PartitionIndex.dumpTrie(fileName) writes a human-readable dump of the BTI partition index trie to a file, mainly for debugging support tickets. Any exception during the dump (unwritable path, I/O error, corruption while reading the trie) is swallowed with this WARN log — it never affects normal operation since dumping is a diagnostic side feature.","triggerScenarios":"Calling PartitionIndex.dumpTrie(path) (used by debugging tooling / support diagnostics on a BTI sstable's Index.db) when the target path is unwritable, the disk is full, or reading the trie via openReader() fails.","commonSituations":"Engineers dumping index tries for Cassandra support; read-only filesystem or wrong permissions on the output path; dumping an index from a corrupt or partially-open sstable.","solutions":["Check the logged exception to see whether it's a file-write problem or an index-read problem.","Verify the output directory is writable and has free space; retry the dump to a different path (e.g. /tmp).","If the trie itself fails to read, run `nodetool scrub`/compact on the sstable first, then retry the dump.","If only diagnostics failed, no data-path action is needed — the sstable keeps serving normally."],"exampleFix":"// before: dumpTrie('/read-only-dir/index.dump') fails silently\n// after: choose a writable destination\nPartitionIndex idx = ...;\nidx.dumpTrie(\"/tmp/bti-index-dump.txt\"); // writable location","handlingStrategy":"try-catch","validationCode":"// Ensure destination is writable before dumping\nFile f = new File(fileName);\nif (!f.getParentFile().canWrite()) throw new IllegalStateException(\"Cannot write trie dump to \" + fileName);","typeGuard":null,"tryCatchPattern":"// dumpTrie already swallows exceptions; treat WARN as non-fatal\npartitionIndex.dumpTrie(\"/tmp/index-dump.txt\");\n// verify output exists if the dump is required\nif (!new File(\"/tmp/index-dump.txt\").exists()) logger.warn(\"Trie dump not produced\");","preventionTips":["Dump tries only to writable, spacious locations like /tmp.","Remember dumpTrie is diagnostic — never rely on it for data-path behavior.","Run scrub/compact first if the index itself is suspect, then dump.","Check log level configuration so the WARN from a failed dump is visible."],"tags":["cassandra","bti","index","diagnostics"],"backgroundTag":"file-write-failed","analyzedSha":"88fd0f6a0eaed8943f05ac9e8f947882b8ddc8f1","analyzedAt":"2026-09-10T07:29:22.284Z","contentChangedAt":"2026-09-10T07:29:22.284Z","schemaVersion":2},"datasetVersion":"2026-09-17T15:17:12.973Z"}