Implement replica prewarm

test_runner/regress/test_replica_prewarm.py

@@ -0,0 +1,53 @@
+from __future__ import annotations
+
+import pytest
+from fixtures.neon_fixtures import NeonEnv, wait_replica_caughtup
+from fixtures.pg_version import PgVersion
+
+
+def test_replica_prewarm(neon_simple_env: NeonEnv):
+    env = neon_simple_env
+    n_records = 1000000
+    if env.pg_version < PgVersion.V16:
+        pytest.skip("NEON_RM is available only in PG16")
+    primary = env.endpoints.create_start(
+        branch_name="main",
+        endpoint_id="primary",
+        config_lines=[
+            "autovacuum = off",
+            "shared_buffers=1MB",
+            "neon.max_file_cache_size=1GB",
+            "neon.file_cache_size_limit=1GB",
+            "neon.file_cache_prewarm_rate=1s",
+        ],
+    )
+    p_con = primary.connect()
+    p_cur = p_con.cursor()
+
+    p_cur.execute("create extension neon")
+    p_cur.execute("create table t(pk integer primary key, payload text default repeat('?', 128))")
+
+    secondary = env.endpoints.new_replica_start(
+        origin=primary,
+        endpoint_id="secondary",
+        config_lines=[
+            "autovacuum = off",
+            "shared_buffers=1MB",
+            "neon.max_file_cache_size=1GB",
+            "neon.file_cache_size_limit=1GB",
+            "neon.file_cache_prewarm_limit=1000",
+        ],
+    )
+    p_cur.execute(f"insert into t (pk) values (generate_series(1,{n_records}))")
+
+    wait_replica_caughtup(primary, secondary)
+
+    s_con = secondary.connect()
+    s_cur = s_con.cursor()
+
+    s_cur.execute("select lfc_value from neon_lfc_stats where lfc_key='file_cache_used_pages'")
+    lfc_used_pages = s_cur.fetchall()[0][0]
+    assert lfc_used_pages > 10000
+
+    s_cur.execute("select sum(pk) from t")
+    assert s_cur.fetchall()[0][0] == n_records * (n_records + 1) / 2