arp7 commented on a change in pull request #1100: HDDS-1802. Add Eviction
policy for table cache.
URL: https://github.com/apache/hadoop/pull/1100#discussion_r303692949
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File path:
hadoop-hdds/common/src/main/java/org/apache/hadoop/utils/db/TypedTable.java
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@@ -104,14 +148,25 @@ public boolean isExist(KEY key) throws IOException {
public VALUE get(KEY key) throws IOException {
// Here the metadata lock will guarantee that cache is not updated for same
// key during get key.
- CacheValue< VALUE > cacheValue = cache.get(new CacheKey<>(key));
- if (cacheValue == null) {
- // If no cache for the table or if it does not exist in cache get from
- // RocksDB table.
+
+ // First get from cache. If it has return value.
+ // If it does not have
+ // If cache cleanup policy is NEVER return null. Because cache here is
+ // full table data in-memory, so no need to get from underlying rocksdb
+ // table.
+ // If cache cleanup policy is AFTER_FLUSH return from underlying rocksdb
+ // table. As it might have been cleaned up from cache, might be there in
+ // DB.
+ CacheValue<VALUE> cacheValue =
+ Optional.fromNullable(cache.get(new CacheKey<>(key))).orNull();
+ if (cacheValue != null) {
+ return cacheValue.getCacheValue();
+ }
+
+ if (cacheCleanupPolicy == TableCacheImpl.CacheCleanupPolicy.AFTER_FLUSH) {
Review comment:
Same here.. we should not have these checks here.
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