unblock cache bucket drop (#406)

* don't hold exclusive locks while deleting files from a dropped bucket/namespace
* cleaner detection of missing namespace when issuing a drop

1 files changed, 28 insertions, 14 deletions

diff --git a/src/zenstore/cache/structuredcachestore.cpp b/src/zenstore/cache/structuredcachestore.cpp
index 7d277329e..5ce254fac 100644
--- a/src/zenstore/cache/structuredcachestore.cpp
+++ b/src/zenstore/cache/structuredcachestore.cpp
@@ -277,11 +277,14 @@ ZenCacheNamespace::DropBucket(std::string_view Bucket)
 {
 	ZEN_INFO("dropping bucket '{}'", Bucket);
 
-	const bool Dropped = m_DiskLayer.DropBucket(Bucket);
-
-	ZEN_INFO("bucket '{}' was {}", Bucket, Dropped ? "dropped" : "not found");
-
-	return Dropped;
+	std::function<void()> PostDropOp = m_DiskLayer.DropBucket(Bucket);
+	if (!PostDropOp)
+	{
+		ZEN_INFO("bucket '{}' was not found in {}", Bucket, m_RootDir);
+		return false;
+	}
+	PostDropOp();
+	return true;
 }
 
 void
@@ -291,7 +294,7 @@ ZenCacheNamespace::EnumerateBucketContents(std::string_view
 	m_DiskLayer.EnumerateBucketContents(Bucket, Fn);
 }
 
-bool
+std::function<void()>
 ZenCacheNamespace::Drop()
 {
 	return m_DiskLayer.Drop();
@@ -786,16 +789,27 @@ ZenCacheStore::DropBucket(std::string_view Namespace, std::string_view Bucket)
 bool
 ZenCacheStore::DropNamespace(std::string_view InNamespace)
 {
-	RwLock::SharedLockScope _(m_NamespacesLock);
-	if (auto It = m_Namespaces.find(std::string(InNamespace)); It != m_Namespaces.end())
+	std::function<void()> PostDropOp;
 	{
-		ZenCacheNamespace& Namespace = *It->second;
-		m_DroppedNamespaces.push_back(std::move(It->second));
-		m_Namespaces.erase(It);
-		return Namespace.Drop();
+		RwLock::SharedLockScope _(m_NamespacesLock);
+		if (auto It = m_Namespaces.find(std::string(InNamespace)); It != m_Namespaces.end())
+		{
+			ZenCacheNamespace& Namespace = *It->second;
+			m_DroppedNamespaces.push_back(std::move(It->second));
+			m_Namespaces.erase(It);
+			PostDropOp = Namespace.Drop();
+		}
+		else
+		{
+			ZEN_WARN("request for unknown namespace '{}' in ZenCacheStore::DropNamespace", InNamespace);
+			return false;
+		}
 	}
-	ZEN_WARN("request for unknown namespace '{}' in ZenCacheStore::DropNamespace", InNamespace);
-	return false;
+	if (PostDropOp)
+	{
+		PostDropOp();
+	}
+	return true;
 }
 
 void