From 215eb06b11e917d21fd2560583b230026cb47495 Mon Sep 17 00:00:00 2001
From: Bojan Serafimov <bojan.serafimov7@gmail.com>
Date: Wed, 17 May 2023 09:52:17 -0400
Subject: [PATCH] Add test

---
 pageserver/src/tenant/timeline.rs            |  4 ++
 test_runner/regress/test_duplicate_layers.py | 42 ++++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 test_runner/regress/test_duplicate_layers.py

diff --git a/pageserver/src/tenant/timeline.rs b/pageserver/src/tenant/timeline.rs
index 6ae23c584b..eab7b63f97 100644
--- a/pageserver/src/tenant/timeline.rs
+++ b/pageserver/src/tenant/timeline.rs
@@ -2839,6 +2839,10 @@ impl Timeline {
 
         drop(all_keys_iter); // So that deltas_to_compact is no longer borrowed
 
+        fail_point!("compact-level0-phase1-finish", |_| {
+            Err(anyhow::anyhow!("failpoint compact-level0-phase1-finish").into())
+        });
+
         Ok(CompactLevel0Phase1Result {
             new_layers,
             deltas_to_compact,
diff --git a/test_runner/regress/test_duplicate_layers.py b/test_runner/regress/test_duplicate_layers.py
new file mode 100644
index 0000000000..77d79cfcc0
--- /dev/null
+++ b/test_runner/regress/test_duplicate_layers.py
@@ -0,0 +1,42 @@
+import time
+
+import pytest
+from fixtures.neon_fixtures import NeonEnvBuilder, PgBin
+
+
+# Test duplicate layer detection
+#
+# This test sets fail point at the end of first compaction phase:
+# after flushing new L1 layers but before deletion of L0 layes
+# It should cause generation of duplicate L1 layer by compaction after restart
+@pytest.mark.timeout(600)
+def test_duplicate_layers(neon_env_builder: NeonEnvBuilder, pg_bin: PgBin):
+    env = neon_env_builder.init_start()
+
+    # These warnings are expected, when the pageserver is restarted abruptly
+    env.pageserver.allowed_errors.append(".*found future image layer.*")
+    env.pageserver.allowed_errors.append(".*found future delta layer.*")
+    env.pageserver.allowed_errors.append(".*duplicate layer.*")
+
+    pageserver_http = env.pageserver.http_client()
+
+    # Use aggressive compaction and checkpoint settings
+    tenant_id, _ = env.neon_cli.create_tenant(
+        conf={
+            "checkpoint_distance": f"{1024 ** 2}",
+            "compaction_target_size": f"{1024 ** 2}",
+            "compaction_period": "1 s",
+            "compaction_threshold": "3",
+        }
+    )
+    endpoint = env.endpoints.create_start("main", tenant_id=tenant_id)
+    connstr = endpoint.connstr(options="-csynchronous_commit=off")
+    pg_bin.run_capture(["pgbench", "-i", "-s10", connstr])
+
+    pageserver_http.configure_failpoints(("compact-level0-phase1-finish", "exit"))
+
+    with pytest.raises(Exception):
+        pg_bin.run_capture(["pgbench", "-P1", "-N", "-c5", "-T500", "-Mprepared", connstr])
+    env.pageserver.stop()
+    env.pageserver.start()
+    time.sleep(10)  # let compaction to be performed