Add a function to change postgresql.conf in python tests. Add test_config as an example

test_runner/fixtures/zenith_fixtures.py

@@ -126,26 +126,43 @@ def pageserver(zenith_cli):
 class Postgres:
     """ An object representing a running postgres daemon. """
 
-    def __init__(self, zenith_cli):
+    def __init__(self, zenith_cli, repo_dir):
         self.zenith_cli = zenith_cli
         self.running = False
+        self.host = 'localhost'
+        self.port = 55432
+        self.repo_dir = repo_dir
         # path to conf is <repo_dir>/pgdatadirs/pg1/postgresql.conf
 
-    def create_start(self):
+    def create_start(self, config_lines=None):
         """ create the pg data directory, and start the server """
         self.zenith_cli.run(['pg', 'create'])
+        if config_lines is None:
+            config_lines = []
+        self.config(config_lines)
         # FIXME: where did the name pg1 come from?
         self.zenith_cli.run(['pg', 'start', 'pg1'])
         self.running = True
 
+
+    #lines should be an array of valid postgresql.conf rows
+    def config(self, lines):
+        #TODO use real node name, not just guessed pg1
+        filename = 'pgdatadirs/pg1/postgresql.conf'
+        config_name = os.path.join(self.repo_dir, filename)
+        with open(config_name, 'a') as conf:
+            for line in lines:
+                conf.write(line)
+                conf.write('\n')
+
     def stop(self):
         if self.running:
             self.zenith_cli.run(['pg', 'stop', 'pg1'])
 
 
 @zenfixture
-def postgres(zenith_cli):
-    pg = Postgres(zenith_cli)
+def postgres(zenith_cli, repo_dir):
+    pg = Postgres(zenith_cli, repo_dir)
     yield pg
     # After the yield comes any cleanup code we need.
     print('Starting postgres cleanup')

test_runner/test_config.py

@@ -0,0 +1,33 @@
+import pytest
+import os
+import getpass
+import psycopg2
+
+pytest_plugins = ("fixtures.zenith_fixtures")
+
+
+def test_config(zenith_cli, pageserver, postgres, pg_bin):
+    zenith_cli.run_init()
+    pageserver.start()
+    print('pageserver is running')
+
+    # change config
+    postgres.create_start(['log_min_messages=debug1'])
+
+    print('postgres is running')
+
+    username = getpass.getuser()
+    conn_str = 'host={} port={} dbname=postgres user={}'.format(
+        postgres.host, postgres.port, username)
+    print('conn_str is', conn_str)
+    pg_conn = psycopg2.connect(conn_str)
+    pg_conn.set_isolation_level(psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT)
+    cur = pg_conn.cursor()
+
+    #check that config change was applied
+    cur.execute('SELECT name, setting from pg_settings WHERE source!=%s and source!=%s', ("default","override",))
+    for record in cur:
+        if record[0] == 'log_min_messages':
+            assert(record[1] == 'debug1')
+
+    pg_conn.close()