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Issue #1248: Avoid queueing multiple cluster discovers of the same type #1249

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merged 1 commit into from Apr 4, 2016
Merged

Issue #1248: Avoid queueing multiple cluster discovers of the same type #1249

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48 changes: 27 additions & 21 deletions src/main/java/redis/clients/jedis/JedisClusterInfoCache.java
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Expand Up @@ -22,6 +22,7 @@ public class JedisClusterInfoCache {
private final ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();
private final Lock r = rwl.readLock();
private final Lock w = rwl.writeLock();
private volatile boolean rediscovering;
private final GenericObjectPoolConfig poolConfig;

private int connectionTimeout;
Expand Down Expand Up @@ -79,36 +80,41 @@ public void discoverClusterNodesAndSlots(Jedis jedis) {
}

public void discoverClusterSlots(Jedis jedis) {
w.lock();
//If rediscovering is already in process - no need to start one more same rediscovering, just return
if (!rediscovering) {
w.lock();
rediscovering = true;
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Late to the party, but a possible perf enhancement here might be to check rediscovering again:

if (!rediscovering) {
  w.lock();
  if (rediscovering) {
    return;
  }

That way, if multiple threads make it past the initial check when under high load and block at lock acquisition, only the first one will do the work.

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It shouldn't help. We set it to true only after lock and to false before releasing lock, so if thread got write lock - it's always false in this var.

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Ah, right. This looks like a candidate for a double-checked locking pattern, but because we're resetting rediscovering it won't work. Darn. It'd be nice to be able to get rid of those extra rediscovers.

(And this, friends, is why I shouldn't read PRs before coffee.)

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👍


try {
this.slots.clear();
try {
this.slots.clear();

List<Object> slots = jedis.clusterSlots();
List<Object> slots = jedis.clusterSlots();

for (Object slotInfoObj : slots) {
List<Object> slotInfo = (List<Object>) slotInfoObj;
for (Object slotInfoObj : slots) {
List<Object> slotInfo = (List<Object>) slotInfoObj;

if (slotInfo.size() <= 2) {
continue;
}
if (slotInfo.size() <= 2) {
continue;
}

List<Integer> slotNums = getAssignedSlotArray(slotInfo);
List<Integer> slotNums = getAssignedSlotArray(slotInfo);

// hostInfos
List<Object> hostInfos = (List<Object>) slotInfo.get(2);
if (hostInfos.isEmpty()) {
continue;
}
// hostInfos
List<Object> hostInfos = (List<Object>) slotInfo.get(2);
if (hostInfos.isEmpty()) {
continue;
}

// at this time, we just use master, discard slave information
HostAndPort targetNode = generateHostAndPort(hostInfos);
// at this time, we just use master, discard slave information
HostAndPort targetNode = generateHostAndPort(hostInfos);

setNodeIfNotExist(targetNode);
assignSlotsToNode(slotNums, targetNode);
setNodeIfNotExist(targetNode);
assignSlotsToNode(slotNums, targetNode);
}
} finally {
rediscovering = false;
w.unlock();
}
} finally {
w.unlock();
}
}

Expand Down