test/cql-pytest: test_select_from_mutation_fragments: bump timeout for slow test

The test test_many_partitions is very slow, as it tests a slow scan over
a lot of partitions. This was observed to time out on the slower ARM
machines, making the test flaky. To prevent this, create an
extra-patient cql connection with a 10 minutes timeout for the scan
itself.

Fixes: #16145

Closes scylladb/scylladb#16303

test/cql-pytest/test_select_from_mutation_fragments.py

@@ -182,7 +182,11 @@ def test_many_partition_scan(cql, test_keyspace, scylla_only):
         requests.post(f'{nodetool.rest_api_url(cql)}/system/drop_sstable_caches')
 
         # the real test here is that this scan completes without problems
-        res_all = list(cql.execute(f"SELECT pk, mutation_source, mutation_fragment_kind, metadata FROM MUTATION_FRAGMENTS({test_table});"))
+        # since this scan is very slow, we create an extra patient cql connection,
+        # with an abundant 10 minutes timeout
+        ep = cql.hosts[0].endpoint
+        with util.cql_session(ep.address, ep.port, False, 'cassandra', 'cassandra', 600) as patient_cql:
+            res_all = list(patient_cql.execute(f"SELECT pk, mutation_source, mutation_fragment_kind, metadata FROM MUTATION_FRAGMENTS({test_table});"))
 
         actual_partitions = []
         for r in res_all:

test/cql-pytest/util.py

@@ -159,7 +159,7 @@ def new_secondary_index(cql, table, column, name='', extra=''):
 
 # Helper function for establishing a connection with given username and password
 @contextmanager
-def cql_session(host, port, is_ssl, username, password):
+def cql_session(host, port, is_ssl, username, password, request_timeout=120):
     profile = ExecutionProfile(
         load_balancing_policy=RoundRobinPolicy(),
         consistency_level=ConsistencyLevel.LOCAL_QUORUM,
@@ -169,7 +169,7 @@ def cql_session(host, port, is_ssl, username, password):
         # very slow debug build running on a very busy machine and a very slow
         # request (e.g., a DROP KEYSPACE needing to drop multiple tables)
         # 10 seconds may not be enough, so let's increase it. See issue #7838.
-        request_timeout = 120)
+        request_timeout=request_timeout)
     if is_ssl:
         # Scylla does not support any earlier TLS protocol. If you try,
         # you will get mysterious EOF errors (see issue #6971) :-(