viewssmh-lazy-election-redux

1 files changed, 91 insertions, 0 deletions

diff --git a/internal/praefect/datastore/migrations/20210521151941_valid_primaries_view.go b/internal/praefect/datastore/migrations/20210521151941_valid_primaries_view.go
new file mode 100644
index 000000000..d9f110b12
--- /dev/null
+++ b/internal/praefect/datastore/migrations/20210521151941_valid_primaries_view.go
@@ -0,0 +1,91 @@
+package migrations
+
+import migrate "github.com/rubenv/sql-migrate"
+
+func init() {
+	m := &migrate.Migration{
+		Id: "20210521151941_valid_primaries_view",
+		Up: []string{
+			`
+CREATE VIEW replicas AS
+	SELECT * FROM storage_repositories
+`,
+
+			`
+CREATE VIEW healthy_storages AS
+	SELECT shard_name AS virtual_storage, node_name AS storage
+	FROM node_status AS ns
+	WHERE last_seen_active_at >= NOW() - INTERVAL '10 SECOND'
+	GROUP BY shard_name, node_name
+	HAVING COUNT(praefect_name) >= (
+		SELECT CEIL(COUNT(DISTINCT praefect_name) / 2.0) AS quorum_count
+		FROM node_status
+		WHERE shard_name = ns.shard_name
+		AND last_contact_attempt_at >= NOW() - INTERVAL '60 SECOND'
+	)
+	ORDER BY shard_name, node_name
+`,
+
+			`
+CREATE VIEW replicas_pending_deletion AS
+	SELECT
+		job->>'virtual_storage' AS virtual_storage,
+		job->>'relative_path' AS relative_path,
+		job->>'target_node_storage' AS storage
+	FROM replication_queue
+	WHERE state NOT IN ('completed', 'dead', 'cancelled')
+	AND job->>'change' in ('delete_replica', 'delete')
+`,
+
+			`
+CREATE VIEW valid_primaries AS
+	SELECT virtual_storage, relative_path, storage
+	FROM repositories
+	JOIN healthy_storages USING (virtual_storage)
+	JOIN replicas USING (virtual_storage, relative_path, storage)
+	WHERE (
+		-- If assignments exist for the repository, only the assigned storages elected as primary.
+		-- If no assignments exist, any healthy node can be elected as the primary
+		SELECT COUNT(*) = 0 OR COUNT(*) FILTER (WHERE storage = healthy_storages.storage) = 1
+		FROM repository_assignments
+		WHERE repository_assignments.virtual_storage = repositories.virtual_storage
+		AND repository_assignments.relative_path = repositories.relative_path
+	) AND NOT EXISTS (
+		SELECT FROM replicas_pending_deletion
+		WHERE virtual_storage = repositories.virtual_storage
+		AND relative_path = repositories.relative_path
+		AND storage = healthy_storages.storage
+	)
+`,
+
+			`
+CREATE VIEW repository_generations AS
+	SELECT virtual_storage, relative_path, MAX(generation) AS generation
+	FROM replicas
+	GROUP BY virtual_storage, relative_path
+`,
+			`
+CREATE VIEW in_sync_replicas AS
+	SELECT virtual_storage, relative_path, storage
+	FROM (SELECT virtual_storage, relative_path FROM repositories) AS repositories
+	JOIN replicas USING (virtual_storage, relative_path)
+	JOIN repository_generations USING (virtual_storage, relative_path, generation)
+`,
+
+			`
+CREATE VIEW outdated_replicas AS
+	SELECT virtual_storage, relative_path, storage
+	FROM replicas
+	WHERE NOT EXISTS (
+		SELECT FROM in_sync_replicas
+		WHERE virtual_storage = replicas.virtual_storage
+		AND relative_path = replicas.relative_path
+		AND storage = replicas.storage
+	)
+`,
+		},
+		Down: []string{"DROP VIEW valid_primaries"},
+	}
+
+	allMigrations = append(allMigrations, m)
+}