monitor pg connection when uploading chunks

pghoard/basebackup/base.py

@@ -35,6 +35,7 @@
     set_subprocess_stdout_and_stderr_nonblocking, terminate_subprocess
 )
 from pghoard.compressor import CompressionEvent
+from pghoard.pgutil import check_if_pg_connection_is_alive
 from pghoard.transfer import UploadEvent
 
 BASEBACKUP_NAME = "pghoard_base_backup"
@@ -543,6 +544,7 @@ def run_local_tar_basebackup(self, delta: bool = False, with_delta_stats: bool =
         self.log.debug("Connecting to database to start backup process")
         connection_string = connection_string_using_pgpass(self.connection_info)
         with psycopg2.connect(connection_string) as db_conn:
+            conn_polling = lambda: check_if_pg_connection_is_alive(db_conn)
             cursor = db_conn.cursor()
 
             if self.pg_version_server < 90600:
@@ -589,6 +591,7 @@ def run_local_tar_basebackup(self, delta: bool = False, with_delta_stats: bool =
                             for item in self.find_files_to_backup(pgdata=pgdata, tablespaces=tablespaces)
                             if not item[1].endswith(".pem")  # Exclude such files like "dh1024.pem"
                         ),
+                        conn_polling=conn_polling,
                     )
                     chunks_count = len(chunk_files)
                     control_files_metadata_extra["chunks"] = chunk_files
@@ -607,11 +610,12 @@ def run_local_tar_basebackup(self, delta: bool = False, with_delta_stats: bool =
                     # Tar up the chunks and submit them for upload; note that we start from chunk 1 here; chunk 0
                     # is reserved for special files and metadata and will be generated last.
                     chunk_files = self.chunk_uploader.create_and_upload_chunks(
-                        chunks,
-                        data_file_format,
-                        compressed_base,
+                        chunks=chunks,
+                        data_file_format=data_file_format,
+                        temp_base_dir=compressed_base,
                         delta_stats=delta_stats,
-                        file_type=FileType.Basebackup_chunk
+                        file_type=FileType.Basebackup_chunk,
+                        conn_polling=conn_polling,
                     )
 
                     total_size_plain = sum(item["input_size"] for item in chunk_files)

pghoard/basebackup/chunks.py

@@ -62,8 +62,16 @@ class DeltaStats:
 
 class ChunkUploader:
     def __init__(
-        self, metrics: Metrics, chunks_on_disk: int, encryption_data: EncryptionData, compression_data: CompressionData,
-        site_config: Dict[str, Any], site: str, is_running: Callable[[], bool], transfer_queue: TransferQueue
+        self,
+        *,
+        metrics: Metrics,
+        chunks_on_disk: int,
+        encryption_data: EncryptionData,
+        compression_data: CompressionData,
+        site_config: Dict[str, Any],
+        site: str,
+        is_running: Callable[[], bool],
+        transfer_queue: TransferQueue,
     ):
         self.log = logging.getLogger("ChunkUploader")
         self.metrics = metrics
@@ -216,9 +224,15 @@ def handle_single_chunk(
         chunks,
         index: int,
         temp_dir: Path,
+        conn_polling: Callable[[], bool],
         delta_stats: Optional[DeltaStats] = None,
-        file_type: FileType = FileType.Basebackup_chunk
+        file_type: FileType = FileType.Basebackup_chunk,
     ) -> Dict[str, Any]:
+        # if the chunk is dependent on a PG connection and connection
+        # is not alive then abort the task
+        if not conn_polling():
+            raise RuntimeError("ERROR: PostgreSQL connection was lost during backup process.")
+
         one_chunk_files = chunks[index]
         chunk_name, input_size, result_size = self.tar_one_file(
             callback_queue=chunk_callback_queue,
@@ -260,12 +274,14 @@ def wait_for_chunk_transfer_to_complete(
 
     def create_and_upload_chunks(
         self,
+        *,
         chunks,
         data_file_format: Callable[[int], str],
+        conn_polling: Callable[[], bool],
         temp_base_dir: Path,
         delta_stats: Optional[DeltaStats] = None,
         file_type: FileType = FileType.Basebackup_chunk,
-        chunks_max_progress: float = 100.0
+        chunks_max_progress: float = 100.0,
     ) -> List[Dict[str, Any]]:
         start_time = time.monotonic()
         chunk_files = []
@@ -299,8 +315,9 @@ def create_and_upload_chunks(
                         chunks=chunks,
                         index=i,
                         temp_dir=temp_base_dir,
+                        conn_polling=conn_polling,
                         delta_stats=delta_stats,
-                        file_type=file_type
+                        file_type=file_type,
                     )
                     pending_compress_and_encrypt_tasks.append(task)
                     self.chunks_on_disk += 1

pghoard/basebackup/delta.py

@@ -55,10 +55,21 @@ class HasReadAndSeek(HasRead, HasSeek, Protocol):
 
 class DeltaBaseBackup:
     def __init__(
-        self, *, storage: BaseTransfer, site: str, site_config: Dict[str, Any], transfer_queue: TransferQueue,
-        metrics: Metrics, encryption_data: EncryptionData, compression_data: CompressionData,
-        get_remote_basebackups_info: Callable[[str], List[Dict[str, Any]]], parallel: int, temp_base_dir: Path,
-        compressed_base: Path, chunk_uploader: ChunkUploader, data_file_format: Callable[[int], str]
+        self,
+        *,
+        storage: BaseTransfer,
+        site: str,
+        site_config: Dict[str, Any],
+        transfer_queue: TransferQueue,
+        metrics: Metrics,
+        encryption_data: EncryptionData,
+        compression_data: CompressionData,
+        get_remote_basebackups_info: Callable[[str], List[Dict[str, Any]]],
+        parallel: int,
+        temp_base_dir: Path,
+        compressed_base: Path,
+        chunk_uploader: ChunkUploader,
+        data_file_format: Callable[[int], str],
     ):
         self.log = logging.getLogger("DeltaBaseBackup")
         self.storage = storage
@@ -384,11 +395,14 @@ def _split_files_for_upload(
 
         return delta_chunks, todo_hexdigests
 
-    def _upload_chunks(self, delta_chunks, chunks_max_progress: float) -> Tuple[UploadedFilesMetric, List[Dict[str, Any]]]:
+    def _upload_chunks(
+        self, delta_chunks, chunks_max_progress: float, conn_polling: Callable[[], bool],
+    ) -> Tuple[UploadedFilesMetric, List[Dict[str, Any]]]:
         """Upload small files grouped into chunks to save on latency and requests costs"""
         chunk_files = self.chunk_uploader.create_and_upload_chunks(
             chunks=delta_chunks,
             data_file_format=self.data_file_format,
+            conn_polling=conn_polling,
             temp_base_dir=self.compressed_base,
             file_type=FileType.Basebackup_delta_chunk,
             chunks_max_progress=chunks_max_progress,
@@ -426,7 +440,7 @@ def _read_delta_sizes(self, snapshot_result: SnapshotResult) -> Tuple[UploadedFi
         return digests_metric, embed_metric
 
     def run(
-        self, pgdata: str, src_iterate_func: Callable[[], Iterable[BackupPath]]
+        self, pgdata: str, src_iterate_func: Callable[[], Iterable[BackupPath]], conn_polling: Callable[[], bool],
     ) -> Tuple[int, int, BackupManifest, int, List[Dict[str, Any]]]:
         # NOTE: Hard links work only in the same FS, therefore using hopefully the same FS in PG home folder
         delta_dir = os.path.join(os.path.dirname(pgdata), "basebackup_delta")
@@ -459,7 +473,9 @@ def run(
                 sum(len(chunk) for chunk in delta_chunks)
             )
             chunks_max_progress = delta_chunks_count * 100.0 / (delta_chunks_count + len(todo_hexdigests))
-            chunks_metric, chunk_files = self._upload_chunks(delta_chunks, chunks_max_progress=chunks_max_progress)
+            chunks_metric, chunk_files = self._upload_chunks(
+                delta_chunks, chunks_max_progress=chunks_max_progress, conn_polling=conn_polling,
+            )
 
             self.log.info(
                 "Submitting hashes for upload: %r, total hashes in the snapshot: %r", len(todo_hexdigests),

pghoard/pgutil.py

@@ -5,10 +5,9 @@
 Copyright (c) 2015 Ohmu Ltd
 See LICENSE for details
 """
-
+from psycopg2 import OperationalError
 from urllib.parse import parse_qs, urlparse
 
-
 def create_connection_string(connection_info):
     return " ".join("{}='{}'".format(k, str(v).replace("'", "\\'")) for k, v in sorted(connection_info.items()))
 
@@ -92,3 +91,15 @@ def parse_connection_string_libpq(connection_string):
                 value, connection_string = rem, ""
         fields[key] = value
     return fields
+
+
+def check_if_pg_connection_is_alive(db_conn) -> bool:
+    alive = False
+    try:
+        with db_conn.cursor() as cursor:
+            cursor.execute("SELECT 1;")
+            alive = True
+    except OperationalError:
+        alive = False
+    finally:
+        return alive

test/basebackup/test_basebackup.py

@@ -946,3 +946,28 @@ def fake_download_backup_meta_file(basebackup_path: str, **kwargs):  # pylint: d
                 "7e0c70d50c0ccd9ca4cb8c6837fbfffb4ef7e885aa1c6370fcfc307541a03e27": 8192,
                 "7e0c70d50c0ccd9ca4cb8c6837fbfffb4ef7e885aa1c6370fcfc307541a03e28": 800
             }
+
+    @pytest.mark.parametrize(
+        "backup_mode", [BaseBackupMode.local_tar, BaseBackupMode.delta, BaseBackupMode.local_tar_delta_stats],
+    )
+    def test_create_basebackup_lost_pg_connection(self, capsys, db, pghoard, tmpdir, backup_mode: BaseBackupMode):
+        with patch("pghoard.basebackup.base.check_if_pg_connection_is_alive", return_value=False):
+            pghoard.create_backup_site_paths(pghoard.test_site)
+            basebackup_path = os.path.join(pghoard.config["backup_location"], pghoard.test_site, "basebackup")
+            q = Queue()
+
+            pghoard.config["backup_sites"][pghoard.test_site]["basebackup_mode"] = backup_mode
+            pghoard.config["backup_sites"][pghoard.test_site]["active_backup_mode"] = "archive_command"
+
+            now = datetime.datetime.now(datetime.timezone.utc)
+            metadata = {
+                "backup-reason": BackupReason.scheduled,
+                "backup-decision-time": now.isoformat(),
+                "normalized-backup-time": now.isoformat(),
+            }
+            pghoard.create_basebackup(pghoard.test_site, db.user, basebackup_path, q, metadata)
+            result = q.get(timeout=60)
+
+            assert result.success is False
+            assert result.exception and isinstance(result.exception, RuntimeError)
+            assert result.exception.args[0] == 'ERROR: PostgreSQL connection was lost during backup process.'