{"record":{"id":"12bd0e6fad3b67ab","repo":"microsoft/FASTER","slug":"unable-to-recover-from-previous-commit-inner-exception","errorCode":null,"errorMessage":"Unable to recover from previous commit. Inner exception: ","messagePattern":"Unable to recover from previous commit\\. Inner exception: ","errorType":"exception","errorClass":"FasterException","httpStatus":null,"severity":"critical","filePath":"cs/src/core/FasterLog/FasterLogRecoveryInfo.cs","lineNumber":91,"sourceCode":"        /// <param name=\"reader\"></param>\n        public void Initialize(BinaryReader reader)\n        {\n            int version;\n            long checkSum;\n            try\n            {\n                version = reader.ReadInt32();\n                checkSum = reader.ReadInt64();\n                BeginAddress = reader.ReadInt64();\n                UntilAddress = reader.ReadInt64();\n                if (version > 0)\n                    CommitNum = reader.ReadInt64();\n                else\n                    CommitNum = -1;\n            }\n            catch (Exception e)\n            {\n                throw new FasterException(\"Unable to recover from previous commit. Inner exception: \" + e.ToString());\n            }\n            if (version < 0 || version > FasterLogRecoveryVersion)\n                throw new FasterException(\"Invalid version found during commit recovery\");\n\n            var iteratorCount = 0;\n            try\n            {\n                iteratorCount = reader.ReadInt32();\n            }\n            catch { }\n\n            if (iteratorCount > 0)\n            {\n                Iterators = new Dictionary<string, long>();\n                for (int i = 0; i < iteratorCount; i++)\n                {\n                    int len = reader.ReadInt32();\n                    byte[] bytes = reader.ReadBytes(len);","sourceCodeStart":73,"sourceCodeEnd":109,"githubUrl":"https://github.com/microsoft/FASTER/blob/321d872eabda6a0345c8bd76419f89723ed864ae/cs/src/core/FasterLog/FasterLogRecoveryInfo.cs#L73-L109","documentation":"FasterLogRecoveryInfo.Initialize failed while reading the persisted commit metadata stream (version/cookie/commit num) from the commit manager's recovery file (FasterLogRecoveryInfo.cs:91). The underlying I/O or format exception is wrapped in this FasterException to mark the log unrecoverable from the previous commit.","triggerScenarios":"Opening a FasterLog whose commit metadata file is missing bytes, truncated by a crash mid-write, or written in an unreadable format; I/O errors (permissions, disk failure) while reading the recovery info; deserializing a file from a different FasterLog version.","commonSituations":"Crash or power loss while CommitAsync was flushing metadata; hand-copied or partially synced log directories; committing metadata on one storage medium and reading from a stale replica.","solutions":["Inspect the inner exception (it is appended to the message) to identify whether it is I/O or format related and fix the underlying cause (permissions, disk, network storage).","Restore the commit metadata (and log) from the last good checkpoint.","Ensure the entire log directory (metadata + device files) is moved/restored atomically as a set.","Do not edit or truncate commit metadata files manually; use FasterLog APIs or delete the whole stale log set and start fresh if data loss is acceptable."],"exampleFix":"// before\nvar log = new FasterLog(new FasterLogOptions(path)); // throws on corrupt metadata\n\n// after\ntry { log = new FasterLog(new FasterLogOptions(path)); }\ncatch (FasterException ex) when (ex.Message.StartsWith(\"Unable to recover\"))\n{\n    // restore from checkpoint or reinitialize the log directory\n}","handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"try { log = new FasterLog(options); } catch (FasterException ex) when (ex.Message.StartsWith(\"Unable to recover from previous commit\")) { RestoreFromCheckpoint(); }","preventionTips":["Keep checkpoints and commit metadata together as one atomic set","Test crash-during-commit scenarios","Log and alert on the wrapped inner exception"],"tags":["fasterlog","recovery","metadata","corruption"],"backgroundTag":"file-read-failed","analyzedSha":"321d872eabda6a0345c8bd76419f89723ed864ae","analyzedAt":"2026-09-15T22:18:00.693Z","contentChangedAt":"2026-09-15T22:18:00.693Z","schemaVersion":2},"datasetVersion":"2026-09-16T04:17:20.429Z"}