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#include "ZooKeeperNodeCache.h"
namespace DB
{
namespace ErrorCodes
{
extern const int NO_ZOOKEEPER;
}
}
namespace zkutil
{
ZooKeeperNodeCache::ZooKeeperNodeCache(GetZooKeeper get_zookeeper_)
: get_zookeeper(std::move(get_zookeeper_))
, context(std::make_shared<Context>())
{
}
ZooKeeperNodeCache::ZNode ZooKeeperNodeCache::get(const std::string & path, EventPtr watch_event)
{
Coordination::WatchCallback watch_callback;
if (watch_event)
watch_callback = [watch_event](const Coordination::WatchResponse &) { watch_event->set(); };
return get(path, watch_callback);
}
ZooKeeperNodeCache::ZNode ZooKeeperNodeCache::get(const std::string & path, Coordination::WatchCallback caller_watch_callback)
{
std::unordered_set<std::string> invalidated_paths;
{
std::lock_guard lock(context->mutex);
if (context->all_paths_invalidated)
{
/// Possibly, there was a previous session and it has expired. Clear the cache.
path_to_cached_znode.clear();
context->all_paths_invalidated = false;
}
invalidated_paths.swap(context->invalidated_paths);
}
zkutil::ZooKeeperPtr zookeeper = get_zookeeper();
if (!zookeeper)
throw DB::Exception(DB::ErrorCodes::NO_ZOOKEEPER, "Could not get znode: '{}'. ZooKeeper not configured.", path);
for (const auto & invalidated_path : invalidated_paths)
path_to_cached_znode.erase(invalidated_path);
auto cache_it = path_to_cached_znode.find(path);
if (cache_it != path_to_cached_znode.end())
return cache_it->second;
std::weak_ptr<Context> weak_context(context);
auto watch_callback = [weak_context, caller_watch_callback](const Coordination::WatchResponse & response)
{
if (!(response.type != Coordination::SESSION || response.state == Coordination::EXPIRED_SESSION))
return;
auto owned_context = weak_context.lock();
if (!owned_context)
return;
bool changed = false;
{
std::lock_guard lock(owned_context->mutex);
if (response.type != Coordination::SESSION)
changed = owned_context->invalidated_paths.emplace(response.path).second;
else if (response.state == Coordination::EXPIRED_SESSION)
{
owned_context->invalidated_paths.clear();
owned_context->all_paths_invalidated = true;
changed = true;
}
}
if (changed && caller_watch_callback)
caller_watch_callback(response);
};
ZNode result;
result.exists = zookeeper->tryGetWatch(path, result.contents, &result.stat, watch_callback);
if (result.exists)
{
path_to_cached_znode.emplace(path, result);
return result;
}
/// Node doesn't exist. We must set a watch on node creation (because it wasn't set by tryGetWatch).
result.exists = zookeeper->existsWatch(path, &result.stat, watch_callback);
if (!result.exists)
{
path_to_cached_znode.emplace(path, result);
return result;
}
/// Node was created between the two previous calls, try again. Watch is already set.
result.exists = zookeeper->tryGet(path, result.contents, &result.stat);
path_to_cached_znode.emplace(path, result);
return result;
}
}
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