/** 5) Release the snapshot object for RocksDB and clean up. */
public void releaseSnapshotResources(boolean canceled) {
if (null != kvStateIterators) {
for (Tuple2<RocksIterator, Integer> kvStateIterator : kvStateIterators) {
kvStateIterator.f0.close();
}
kvStateIterators = null;
}
if (null != snapshot) {
if (null != stateBackend.db) {
stateBackend.db.releaseSnapshot(snapshot);
}
snapshot.close();
snapshot = null;
}
if (null != readOptions) {
readOptions.close();
readOptions = null;
}
if (canceled) {
try {
if (null != snapshotResultStateHandle) {
snapshotResultStateHandle.discardState();
}
} catch (Exception ignored) {
LOG.warn("Exception occurred during snapshot state handle cleanup: " + ignored);
}
}
}
private void writeKVStateMetaData() throws IOException, InterruptedException {
// write number of k/v states
outputView.writeInt(stateBackend.kvStateInformation.size());
int kvStateId = 0;
// iterate all column families, where each column family holds one k/v state, to write the
// metadata
for (Map.Entry<String, Tuple2<ColumnFamilyHandle, StateDescriptor<?, ?>>> column :
stateBackend.kvStateInformation.entrySet()) {
// be cooperative and check for interruption from time to time in the hot loop
checkInterrupted();
// write StateDescriptor for this k/v state
InstantiationUtil.serializeObject(outStream, column.getValue().f1);
// retrieve iterator for this k/v states
readOptions = new ReadOptions();
readOptions.setSnapshot(snapshot);
RocksIterator iterator = stateBackend.db.newIterator(column.getValue().f0, readOptions);
kvStateIterators.add(new Tuple2<>(iterator, kvStateId));
++kvStateId;
}
}
@Test
public void snapshots() throws RocksDBException {
RocksDB db = null;
Options options = null;
ReadOptions readOptions = null;
try {
options = new Options();
options.setCreateIfMissing(true);
db = RocksDB.open(options, dbFolder.getRoot().getAbsolutePath());
db.put("key".getBytes(), "value".getBytes());
// Get new Snapshot of database
Snapshot snapshot = db.getSnapshot();
readOptions = new ReadOptions();
// set snapshot in ReadOptions
readOptions.setSnapshot(snapshot);
// retrieve key value pair
assertThat(new String(db.get("key".getBytes()))).isEqualTo("value");
// retrieve key value pair created before
// the snapshot was made
assertThat(new String(db.get(readOptions, "key".getBytes()))).isEqualTo("value");
// add new key/value pair
db.put("newkey".getBytes(), "newvalue".getBytes());
// using no snapshot the latest db entries
// will be taken into account
assertThat(new String(db.get("newkey".getBytes()))).isEqualTo("newvalue");
// snapshopot was created before newkey
assertThat(db.get(readOptions, "newkey".getBytes())).isNull();
// Retrieve snapshot from read options
Snapshot sameSnapshot = readOptions.snapshot();
readOptions.setSnapshot(sameSnapshot);
// results must be the same with new Snapshot
// instance using the same native pointer
assertThat(new String(db.get(readOptions, "key".getBytes()))).isEqualTo("value");
// update key value pair to newvalue
db.put("key".getBytes(), "newvalue".getBytes());
// read with previously created snapshot will
// read previous version of key value pair
assertThat(new String(db.get(readOptions, "key".getBytes()))).isEqualTo("value");
// read for newkey using the snapshot must be
// null
assertThat(db.get(readOptions, "newkey".getBytes())).isNull();
// setting null to snapshot in ReadOptions leads
// to no Snapshot being used.
readOptions.setSnapshot(null);
assertThat(new String(db.get(readOptions, "newkey".getBytes()))).isEqualTo("newvalue");
// release Snapshot
db.releaseSnapshot(snapshot);
} finally {
if (db != null) {
db.close();
}
if (options != null) {
options.dispose();
}
if (readOptions != null) {
readOptions.dispose();
}
}
}