Examples with Cache io.pravega.segmentstore.storage.Cache used on opensource projects

Example 1 with Cache

use of io.pravega.segmentstore.storage.Cache in project pravega by pravega.

the class ContainerReadIndexTests method testCacheEviction.

/**
 * Tests the ability to evict entries from the ReadIndex under various conditions:
 * * If an entry is aged out
 * * If an entry is pushed out because of cache space pressure.
 * <p>
 * This also verifies that certain entries, such as RedirectReadIndexEntries and entries after the Storage Offset are
 * not removed.
 * <p>
 * The way this test goes is as follows (it's pretty subtle, because there aren't many ways to hook into the ReadIndex and see what it's doing)
 * 1. It creates a bunch of segments, and populates them in storage (each) up to offset N/2-1 (this is called pre-storage)
 * 2. It populates the ReadIndex for each of those segments from offset N/2 to offset N-1 (this is called post-storage)
 * 3. It loads all the data from Storage into the ReadIndex, in entries of size equal to those already loaded in step #2.
 * 3a. At this point, all the entries added in step #2 have Generations 0..A/4-1, and step #3 have generations A/4..A-1
 * 4. Append more data at the end. This forces the generation to increase to 1.25A.
 * 4a. Nothing should be evicted from the cache now, since the earliest items are all post-storage.
 * 5. We 'touch' (read) the first 1/3 of pre-storage entries (offsets 0..N/4).
 * 5a. At this point, those entries (offsets 0..N/6) will have the newest generations (1.25A..1.5A)
 * 6. We append more data (equivalent to the data we touched)
 * 6a. Nothing should be evicted, since those generations that were just eligible for removal were touched and bumped up.
 * 7. We forcefully increase the current generation by 1 (without touching the ReadIndex)
 * 7a. At this point, we expect all the pre-storage items, except the touched ones, to be evicted. This is generations 0.25A-0.75A.
 * 8. Update the metadata and indicate that all the post-storage entries are now pre-storage and bump the generation by 0.75A.
 * 8a. At this point, we expect all former post-storage items and pre-storage items to be evicted (in this order).
 * <p>
 * The final order of eviction (in terms of offsets, for each segment), is:
 * * 0.25N-0.75N, 0.75N..N, N..1.25N, 0..0.25N, 1.25N..1.5N (remember that we added quite a bunch of items after the initial run).
 */
@Test
@SuppressWarnings("checkstyle:CyclomaticComplexity")
public void testCacheEviction() throws Exception {
    // Create a CachePolicy with a set number of generations and a known max size.
    // Each generation contains exactly one entry, so the number of generations is also the number of entries.
    final int appendSize = 100;
    // This also doubles as number of generations (each generation, we add one append for each segment).
    final int entriesPerSegment = 100;
    final int cacheMaxSize = SEGMENT_COUNT * entriesPerSegment * appendSize;
    // 25% of the entries are beyond the StorageOffset
    final int postStorageEntryCount = entriesPerSegment / 4;
    // 75% of the entries are before the StorageOffset.
    final int preStorageEntryCount = entriesPerSegment - postStorageEntryCount;
    CachePolicy cachePolicy = new CachePolicy(cacheMaxSize, Duration.ofMillis(1000 * 2 * entriesPerSegment), Duration.ofMillis(1000));
    // To properly test this, we want predictable storage reads.
    ReadIndexConfig config = ConfigHelpers.withInfiniteCachePolicy(ReadIndexConfig.builder().with(ReadIndexConfig.STORAGE_READ_ALIGNMENT, appendSize)).build();
    ArrayList<CacheKey> removedKeys = new ArrayList<>();
    @Cleanup TestContext context = new TestContext(config, cachePolicy);
    // Record every cache removal.
    context.cacheFactory.cache.removeCallback = removedKeys::add;
    // Create the segments (metadata + storage).
    ArrayList<Long> segmentIds = createSegments(context);
    createSegmentsInStorage(context);
    // Populate the Storage with appropriate data.
    byte[] preStorageData = new byte[preStorageEntryCount * appendSize];
    for (long segmentId : segmentIds) {
        UpdateableSegmentMetadata sm = context.metadata.getStreamSegmentMetadata(segmentId);
        val handle = context.storage.openWrite(sm.getName()).join();
        context.storage.write(handle, 0, new ByteArrayInputStream(preStorageData), preStorageData.length, TIMEOUT).join();
        sm.setStorageLength(preStorageData.length);
        sm.setLength(preStorageData.length);
    }
    // Callback that appends one entry at the end of the given segment id.
    Consumer<Long> appendOneEntry = segmentId -> {
        UpdateableSegmentMetadata sm = context.metadata.getStreamSegmentMetadata(segmentId);
        byte[] data = new byte[appendSize];
        long offset = sm.getLength();
        sm.setLength(offset + data.length);
        try {
            context.readIndex.append(segmentId, offset, data);
        } catch (StreamSegmentNotExistsException ex) {
            throw new CompletionException(ex);
        }
    };
    // Populate the ReadIndex with the Append entries (post-StorageOffset)
    for (int i = 0; i < postStorageEntryCount; i++) {
        segmentIds.forEach(appendOneEntry);
        // Each time we make a round of appends (one per segment), we increment the generation in the CacheManager.
        context.cacheManager.applyCachePolicy();
    }
    // Read all the data from Storage, making sure we carefully associate them with the proper generation.
    for (int i = 0; i < preStorageEntryCount; i++) {
        long offset = i * appendSize;
        for (long segmentId : segmentIds) {
            @Cleanup ReadResult result = context.readIndex.read(segmentId, offset, appendSize, TIMEOUT);
            ReadResultEntry resultEntry = result.next();
            Assert.assertEquals("Unexpected type of ReadResultEntry when trying to load up data into the ReadIndex Cache.", ReadResultEntryType.Storage, resultEntry.getType());
            resultEntry.requestContent(TIMEOUT);
            ReadResultEntryContents contents = resultEntry.getContent().get(TIMEOUT.toMillis(), TimeUnit.MILLISECONDS);
            Assert.assertFalse("Not expecting more data to be available for reading.", result.hasNext());
            Assert.assertEquals("Unexpected ReadResultEntry length when trying to load up data into the ReadIndex Cache.", appendSize, contents.getLength());
        }
        context.cacheManager.applyCachePolicy();
    }
    Assert.assertEquals("Not expecting any removed Cache entries at this point (cache is not full).", 0, removedKeys.size());
    // Append more data (equivalent to all post-storage entries), and verify that NO entries are being evicted (we cannot evict post-storage entries).
    for (int i = 0; i < postStorageEntryCount; i++) {
        segmentIds.forEach(appendOneEntry);
        context.cacheManager.applyCachePolicy();
    }
    Assert.assertEquals("Not expecting any removed Cache entries at this point (only eligible entries were post-storage).", 0, removedKeys.size());
    // 'Touch' the first few entries read from storage. This should move them to the back of the queue (they won't be the first ones to be evicted).
    int touchCount = preStorageEntryCount / 3;
    for (int i = 0; i < touchCount; i++) {
        long offset = i * appendSize;
        for (long segmentId : segmentIds) {
            @Cleanup ReadResult result = context.readIndex.read(segmentId, offset, appendSize, TIMEOUT);
            ReadResultEntry resultEntry = result.next();
            Assert.assertEquals("Unexpected type of ReadResultEntry when trying to load up data into the ReadIndex Cache.", ReadResultEntryType.Cache, resultEntry.getType());
        }
    }
    // Append more data (equivalent to the amount of data we 'touched'), and verify that the entries we just touched are not being removed..
    for (int i = 0; i < touchCount; i++) {
        segmentIds.forEach(appendOneEntry);
        context.cacheManager.applyCachePolicy();
    }
    Assert.assertEquals("Not expecting any removed Cache entries at this point (we touched old entries and they now have the newest generation).", 0, removedKeys.size());
    // Increment the generations so that we are caught up to just before the generation where the "touched" items now live.
    context.cacheManager.applyCachePolicy();
    // We expect all but the 'touchCount' pre-Storage entries to be removed.
    int expectedRemovalCount = (preStorageEntryCount - touchCount) * SEGMENT_COUNT;
    Assert.assertEquals("Unexpected number of removed entries after having forced out all pre-storage entries.", expectedRemovalCount, removedKeys.size());
    // Now update the metadata and indicate that all the post-storage data has been moved to storage.
    segmentIds.forEach(segmentId -> {
        UpdateableSegmentMetadata sm = context.metadata.getStreamSegmentMetadata(segmentId);
        sm.setStorageLength(sm.getLength());
    });
    // We add one artificial entry, which we'll be touching forever and ever; this forces the CacheManager to
    // update its current generation every time. We will be ignoring this entry for our test.
    SegmentMetadata readSegment = context.metadata.getStreamSegmentMetadata(segmentIds.get(0));
    appendOneEntry.accept(readSegment.getId());
    // Now evict everything (whether by size of by aging out).
    for (int i = 0; i < cachePolicy.getMaxGenerations(); i++) {
        @Cleanup ReadResult result = context.readIndex.read(readSegment.getId(), readSegment.getLength() - appendSize, appendSize, TIMEOUT);
        result.next();
        context.cacheManager.applyCachePolicy();
    }
    int expectedRemovalCountPerSegment = entriesPerSegment + touchCount + postStorageEntryCount;
    int expectedTotalRemovalCount = SEGMENT_COUNT * expectedRemovalCountPerSegment;
    Assert.assertEquals("Unexpected number of removed entries after having forced out all the entries.", expectedTotalRemovalCount, removedKeys.size());
    // Finally, verify that the evicted items are in the correct order (for each segment). See this test's description for details.
    for (long segmentId : segmentIds) {
        List<CacheKey> segmentRemovedKeys = removedKeys.stream().filter(key -> key.getStreamSegmentId() == segmentId).collect(Collectors.toList());
        Assert.assertEquals("Unexpected number of removed entries for segment " + segmentId, expectedRemovalCountPerSegment, segmentRemovedKeys.size());
        // The correct order of eviction (N=entriesPerSegment) is: 0.25N-0.75N, 0.75N..N, N..1.25N, 0..0.25N, 1.25N..1.5N.
        // This is equivalent to the following tests
        // 0.25N-1.25N
        checkOffsets(segmentRemovedKeys, segmentId, 0, entriesPerSegment, entriesPerSegment * appendSize / 4, appendSize);
        // 0..0.25N
        checkOffsets(segmentRemovedKeys, segmentId, entriesPerSegment, entriesPerSegment / 4, 0, appendSize);
        // 1.25N..1.5N
        checkOffsets(segmentRemovedKeys, segmentId, entriesPerSegment + entriesPerSegment / 4, entriesPerSegment / 4, (int) (entriesPerSegment * appendSize * 1.25), appendSize);
    }
}