tests: make test cql environment use volatile system keyspace

Prevents hangs due to the database not being able to persist a memtable.

Tested-by: Asias He <asias@cloudius-systems.com>

database.cc

@@ -666,7 +666,7 @@ database::database(const db::config& cfg)
     , _version(empty_version)
 {
     bool durable = cfg.data_file_directories().size() > 0;
-    db::system_keyspace::make(*this, durable);
+    db::system_keyspace::make(*this, durable, _cfg->volatile_system_keyspace_for_testing());
     // Start compaction manager with two tasks for handling compaction jobs.
     _compaction_manager.start(2);
     setup_collectd();

database.hh

@@ -71,7 +71,7 @@ class commitlog;
 class config;
 
 namespace system_keyspace {
-void make(database& db, bool durable);
+void make(database& db, bool durable, bool volatile_testing_only);
 }
 }
 
@@ -385,7 +385,7 @@ private:
     // not be using this directly.  Go for the public create_keyspace instead.
     void add_keyspace(sstring name, keyspace k);
     void create_in_memory_keyspace(const lw_shared_ptr<keyspace_metadata>& ksm);
-    friend void db::system_keyspace::make(database& db, bool durable);
+    friend void db::system_keyspace::make(database& db, bool durable, bool volatile_testing_only);
     void setup_collectd();
 public:
     static utils::UUID empty_version;

db/config.hh

@@ -690,6 +690,7 @@ public:
     val(enable_in_memory_data_store, bool, false, Used, "Enable in memory mode (system tables are always persisted)") \
     val(enable_cache, bool, true, Used, "Enable cache") \
     val(enable_commitlog, bool, true, Used, "Enable commitlog") \
+    val(volatile_system_keyspace_for_testing, bool, false, Used, "Don't persist system keyspace - testing only!") \
     /* done! */
 
 #define _make_value_member(name, type, deflt, status, desc, ...)    \

db/system_keyspace.cc

@@ -813,16 +813,16 @@ std::vector<schema_ptr> all_tables() {
     return r;
 }
 
-void make(database& db, bool durable) {
+void make(database& db, bool durable, bool volatile_testing_only) {
     auto ksm = make_lw_shared<keyspace_metadata>(NAME,
             "org.apache.cassandra.locator.LocalStrategy",
             std::map<sstring, sstring>{},
             durable
             );
     auto kscfg = db.make_keyspace_config(*ksm);
-    kscfg.enable_disk_reads = true;
-    kscfg.enable_disk_writes = true;
-    kscfg.enable_commitlog = true;
+    kscfg.enable_disk_reads = !volatile_testing_only;
+    kscfg.enable_disk_writes = !volatile_testing_only;
+    kscfg.enable_commitlog = !volatile_testing_only;
     kscfg.enable_cache = true;
     keyspace _ks{ksm, std::move(kscfg)};
     auto rs(locator::abstract_replication_strategy::create_replication_strategy(NAME, "LocalStrategy", service::get_local_storage_service().get_token_metadata(), ksm->strategy_options()));

db/system_keyspace.hh

@@ -83,7 +83,7 @@ future<> remove_endpoint(gms::inet_address ep);
 future<> update_hints_dropped(gms::inet_address ep, utils::UUID time_period, int value);
 
 std::vector<schema_ptr> all_tables();
-void make(database& db, bool durable);
+void make(database& db, bool durable, bool volatile_testing_only = false);
 
 future<foreign_ptr<lw_shared_ptr<reconcilable_result>>>
 query_mutations(service::storage_proxy& proxy, const sstring& cf_name);

tests/cql_test_env.cc

@@ -216,6 +216,7 @@ future<::shared_ptr<cql_test_env>> make_env_for_test() {
             return seastar::async([db] {
                 auto cfg = make_lw_shared<db::config>();
                 cfg->data_file_directories() = {};
+                cfg->volatile_system_keyspace_for_testing() = true;
                 db->start(std::move(*cfg)).get();
 
                 distributed<service::storage_proxy>& proxy = service::get_storage_proxy();