**Build scan:**
https://gradle-enterprise.elastic.co/s/xow72etevme2m/tests/:x-pack:plugin:searchable-snapshots:test/org.elasticsearch.xpack.searchablesnapshots.cache.full.CacheServiceTests/testProcessShardEviction

**Reproduction line:**
```
./gradlew ':x-pack:plugin:searchable-snapshots:test' --tests "org.elasticsearch.xpack.searchablesnapshots.cache.full.CacheServiceTests.testProcessShardEviction" -Dtests.seed=4A4817D6257EF2CB -Dtests.locale=fi-FI -Dtests.timezone=America/Argentina/San_Luis -Druntime.java=17
```

**Applicable branches:**
8.5

**Reproduces locally?:**
Didn't try

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.xpack.searchablesnapshots.cache.full.CacheServiceTests&tests.test=testProcessShardEviction

**Failure excerpt:**
```
java.lang.AssertionError: (No message provided)

  at __randomizedtesting.SeedInfo.seed([4A4817D6257EF2CB:B2D9476556ADF10]:0)
  at org.junit.Assert.fail(Assert.java:86)
  at org.junit.Assert.assertTrue(Assert.java:41)
  at org.junit.Assert.assertTrue(Assert.java:52)
  at org.elasticsearch.xpack.searchablesnapshots.cache.full.CacheServiceTests.testProcessShardEviction(CacheServiceTests.java:324)
  at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:-2)
  at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
  at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:568)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.invoke(RandomizedRunner.java:1758)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$8.evaluate(RandomizedRunner.java:946)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$9.evaluate(RandomizedRunner.java:982)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$10.evaluate(RandomizedRunner.java:996)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleSetupTeardownChained$1.evaluate(TestRuleSetupTeardownChained.java:44)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.tests.util.TestRuleThreadAndTestName$1.evaluate(TestRuleThreadAndTestName.java:45)
  at org.apache.lucene.tests.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.tests.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:390)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.forkTimeoutingTask(ThreadLeakControl.java:843)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$3.evaluate(ThreadLeakControl.java:490)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.runSingleTest(RandomizedRunner.java:955)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$5.evaluate(RandomizedRunner.java:840)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$6.evaluate(RandomizedRunner.java:891)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$7.evaluate(RandomizedRunner.java:902)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleStoreClassName$1.evaluate(TestRuleStoreClassName.java:38)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleAssertionsRequired$1.evaluate(TestRuleAssertionsRequired.java:53)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.tests.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at org.apache.lucene.tests.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.tests.util.TestRuleIgnoreTestSuites$1.evaluate(TestRuleIgnoreTestSuites.java:47)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:390)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.lambda$forkTimeoutingTask$0(ThreadLeakControl.java:850)
  at java.lang.Thread.run(Thread.java:833)

```
x-pack/plugin/searchable-snapshots/src/main/java/org/elasticsearch/xpack/searchablesnapshots/cache/full/CacheService.java
* associated with a {@link CacheFile}, this method creates a new instance using the given file length and cache directory.
     *
     * @param cacheKey   the cache key whose associated {@link CacheFile} instance is to be returned or computed for if non-existent
     * @param fileLength the length of the cache file (required to compute a new instance)
     * @param cacheDir   the cache directory where the cache file on disk is created  (required to compute a new instance)
     * @return the current  {@link CacheFile} instance (existing or computed)
     * @throws Exception if this method is used when the {@link CacheService} is not started
     */
    public CacheFile get(final CacheKey cacheKey, final long fileLength, final Path cacheDir) throws Exception {
        ensureLifecycleStarted();
        return cache.computeIfAbsent(cacheKey, key -> {
            ensureLifecycleStarted();
            
            final String uuid = UUIDs.randomBase64UUID();
            
            final Path path = cacheDir.resolve(uuid);
            assert Files.notExists(path) : "cache file already exists " + path;
            return new CacheFile(key, fileLength, path, this.cacheFilesListener);
        });
    }
    /**
     * Get the number of bytes cached for the given shard id in the given snapshot id.
     * @param shardId    shard id
     * @param snapshotId snapshot id
     * @return number of bytes cached
     */
    public long getCachedSize(ShardId shardId, SnapshotId snapshotId) {
        return persistentCache.getCacheSize(shardId, snapshotId);
    }
    /**