SearchableSnapshotDirectoryTests.testIndexSearcher can fail with assertion error

[jtibshirani]

The failure consistently reproduces for me. Command:

./gradlew ':x-pack:plugin:searchable-snapshots:test' \
  --tests "org.elasticsearch.index.store.SearchableSnapshotDirectoryTests.testIndexSearcher" \
  -Dtests.seed=4ADEC076A04B379C -Dtests.security.manager=true -Dtests.locale=fr-FR \
  -Dtests.timezone=America/Hermosillo -Dcompiler.java=14 -Druntime.java=11

Build scan: https://gradle-enterprise.elastic.co/s/gee7fullo3xhm

Relevant excerpt from the logs:

java.lang.AssertionError: current thread [Thread[LuceneTestCase-1-thread-2,5,TGRP-SearchableSnapshotDirectoryTests]] may not read [name: __UmWBMwYMTo6pUM37x8biLg, numberOfParts: 1, partSize: 868b, partBytes: 868, metadata: name [_0_Lucene84_1.doc], length [682], checksum [1pi9tjs], writtenBy [8.5.1]]
    at org.elasticsearch.index.store.BaseSearchableSnapshotIndexInput.assertCurrentThreadMayAccessBlobStore(BaseSearchableSnapshotIndexInput.java:148)
    at org.elasticsearch.index.store.direct.DirectBlobContainerIndexInput.openBlobStream(DirectBlobContainerIndexInput.java:343)
    at org.elasticsearch.index.store.direct.DirectBlobContainerIndexInput.readInternalBytes(DirectBlobContainerIndexInput.java:133)
    at org.elasticsearch.index.store.direct.DirectBlobContainerIndexInput.readInternal(DirectBlobContainerIndexInput.java:105)

[elasticmachine]

Pinging @elastic/es-distributed (:Distributed/Snapshot/Restore)

[jtibshirani]

Muted the test:

• eddbc78 (master)
• 793f265 (7.x)