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SOLR-13418 - safer synchronization and zk version checking for collection properties

This commit is contained in:
Gus Heck 2019-04-23 12:29:08 -04:00
parent 2261b4e8e1
commit 80d3ac8709
1 changed files with 76 additions and 60 deletions
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68
solr/solrj/src/java/org/apache/solr/common/cloud/ZkStateReader.java
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@ -167,7 +167,7 @@ public class ZkStateReader implements SolrCloseable {
private final ConcurrentHashMap<String, LazyCollectionRef> lazyCollectionStates = new ConcurrentHashMap<>();
/** Collection properties being actively watched */
private final ConcurrentHashMap<String, Map<String, String>> watchedCollectionProps = new ConcurrentHashMap<>();
private final ConcurrentHashMap<String, VersionedCollectionProps> watchedCollectionProps = new ConcurrentHashMap<>();
private volatile SortedSet<String> liveNodes = emptySortedSet();
@ -1074,17 +1074,30 @@ public class ZkStateReader implements SolrCloseable {
* otherwise fetch it directly from zookeeper.
*/
public Map<String, String> getCollectionProperties(final String collection) {
Map<String, String> properties = watchedCollectionProps.get(collection);
if (properties == null) {
try {
properties = fetchCollectionProperties(collection, null);
// Not storing the value in watchedCollectionProps, because it can gat stale, since we have no watcher set.
} catch (Exception e) {
throw new SolrException(ErrorCode.SERVER_ERROR, "Error reading collection properties", SolrZkClient.checkInterrupted(e));
synchronized (watchedCollectionProps) { // making decisions based on the result of a get...
VersionedCollectionProps vprops = watchedCollectionProps.get(collection);
Map<String, String> properties = vprops != null ? vprops.props : null;
if (properties == null) {
try {
// todo: maybe we want to store/watch since if someone's calling this it's probably going to get called again?
// Not storing the value in watchedCollectionProps, because it can gat stale, since we have no watcher set.
properties = fetchCollectionProperties(collection, null ).props;
} catch (Exception e) {
throw new SolrException(ErrorCode.SERVER_ERROR, "Error reading collection properties", SolrZkClient.checkInterrupted(e));
}
}
return properties;
}
}
private class VersionedCollectionProps {
public VersionedCollectionProps(int zkVersion, Map<String, String> props) {
this.zkVersion = zkVersion;
this.props = props;
}
return properties;
int zkVersion;
Map<String,String> props;
}
static String getCollectionPropsPath(final String collection) {
@ -1092,12 +1105,13 @@ public class ZkStateReader implements SolrCloseable {
}
@SuppressWarnings("unchecked")
private Map<String, String> fetchCollectionProperties(String collection, Watcher watcher) throws KeeperException, InterruptedException {
private VersionedCollectionProps fetchCollectionProperties(String collection, Watcher watcher) throws KeeperException, InterruptedException {
final String znodePath = getCollectionPropsPath(collection);
while (true) {
try {
byte[] data = zkClient.getData(znodePath, watcher, null, true);
return (Map<String, String>) Utils.fromJSON(data);
Stat stat = new Stat();
byte[] data = zkClient.getData(znodePath, watcher, stat, true);
return new VersionedCollectionProps(stat.getVersion(),(Map<String, String>) Utils.fromJSON(data));
} catch (ClassCastException e) {
throw new SolrException(ErrorCode.SERVER_ERROR, "Unable to parse collection properties for collection " + collection, e);
} catch (KeeperException.NoNodeException e) {
@ -1110,7 +1124,7 @@ public class ZkStateReader implements SolrCloseable {
continue;
}
}
return Collections.emptyMap();
return new VersionedCollectionProps(-1, EMPTY_MAP);
}
}
}
@ -1272,18 +1286,17 @@ public class ZkStateReader implements SolrCloseable {
*/
void refreshAndWatch(boolean notifyWatchers) {
try {
synchronized (coll) { // We only have one PropsWatcher instance per collection, so it's fine to sync on coll
Map<String, String> properties = fetchCollectionProperties(coll, this);
watchedCollectionProps.put(coll, properties);
/*
* Note that if two events were fired close to each other and the second one arrived first, we would read the collectionprops.json
* twice for the same data and notify watchers (in case of notifyWatchers==true) twice for the same data, however it's guaranteed
* that after processing both events, watchedCollectionProps will have the latest data written to ZooKeeper and that the watchers
* won't be called with out of order data
*
*/
if (notifyWatchers) {
notifyPropsWatchers(coll, properties);
synchronized (watchedCollectionProps) { // making decisions based on the result of a get...
VersionedCollectionProps vcp = fetchCollectionProperties(coll, this);
Map<String, String> properties = vcp.props;
VersionedCollectionProps existingVcp = watchedCollectionProps.get(coll);
if (existingVcp == null || // never called before, record what we found
vcp.zkVersion > existingVcp.zkVersion || // newer info we should update
vcp.zkVersion == -1) { // node was deleted start over
watchedCollectionProps.put(coll, vcp);
if (notifyWatchers) {
notifyPropsWatchers(coll, properties);
}
}
}
} catch (KeeperException.SessionExpiredException | KeeperException.ConnectionLossException e) {
@ -1692,7 +1705,10 @@ public class ZkStateReader implements SolrCloseable {
return null;
v.stateWatchers.remove(watcher);
if (v.canBeRemoved()) {
watchedCollectionProps.remove(collection);
// don't want this to happen in middle of other blocks that might add it back.
synchronized (watchedCollectionProps) {
watchedCollectionProps.remove(collection);
}
return null;
}
return v;