mongorestore 100.17.0 fails to restore timeseries collection dumped with mongodump 100.10.0

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    • Type: Bug
    • Resolution: Won't Do
    • None
    • Affects Version/s: None
    • Component/s: None
    • None
    • Tools and Replicator

      A gzipped archive dump of a time-series collection taken with mongodump 100.10.0 cannot be restored with mongorestore 100.17.0. The restore creates the collection successfully but then fails when reading the documents from the archive with:

      Failed: test.ts: error restoring from archive ...: reading bson input: error demultiplexing archive; archive io error

      No documents are restored (0 document(s) restored successfully).

      Environment

      • Dump:
        • MongoDB server: 8.0.26 (replica set)
        • mongodump: 100.10.0
      • Restore:
        • MongoDB server: 9.0.0 (replica set)
        • mongorestore: 100.17.0

      Steps to reproduce

      1. Create a time-series collection and insert some documents:
      db.createCollection("ts", {timeseries: {timeField: 'tf', metaField: 'mf'}})
db.ts.insertMany([
  { tf: ISODate('2025-03-08T16:40:39.239Z'), mf: "cpu",  temp: 45 },
  { tf: ISODate('2025-03-08T16:41:20.000Z'), mf: "disk", temp: 30 },
  { tf: ISODate('2025-03-08T16:42:30.131Z'), mf: "gpu",  temp: 80 },
  { tf: ISODate('2025-03-08T16:43:40.283Z'), mf: "cpu",  temp: 50, other: true }
])
      1. Dump with mongodump 100.10.0:
      mongodump --gzip --archive=mongo-dump-v80-timeseries-100.10.0.gzip --db=test
      1. Restore with mongorestore 100.17.0:
      mongorestore -vvv --numInsertionWorkersPerCollection=6 --bypassDocumentValidation --gzip --archive=mongo-dump-v80-timeseries-100.10.0.gzip

      Verbose restore output

      archive tool version `100.10.0`
...
demux namespaceHeader: {test system.buckets.ts false 0}
received `test.system.buckets.ts` from namespaceChan
first non special collection `test.ts` found. The demultiplexer will handle it and the remainder
...
creating collection `test.ts` using options from metadata
using collection options: bson.D{... "timeseries" ... "granularity":"seconds", "bucketMaxSpanSeconds":3600 ...}
restoring `test.ts` from archive ...
using 6 insertion workers
finished restoring `test.ts` (0 documents, 0 failures)
Failed: test.ts: error restoring from archive ...: reading bson input: error demultiplexing archive; archive io error
0 document(s) restored successfully. 0 document(s) failed to restore.

      Analysis

      The archive stores the data under the system.buckets.ts namespace, but the demultiplexer appears unable to route the bucket documents to the newly created time-series collection, suggesting a backward-compatibility regression in how the 100.17.0 demultiplexer handles archives produced by older (100.10.0) tooling for time-series collections.

            Assignee:
            Dave Rolsky
            Reporter:
            Tommaso Tocci
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            Watchers:
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              Created:
              Updated:
              Resolved: