change dict to dataclass for pendind_download_ops

pghoard/webserver.py

@@ -14,6 +14,7 @@
 from collections import deque
 from concurrent.futures import ThreadPoolExecutor
 from contextlib import contextmanager, suppress
+from dataclasses import dataclass
 from http.server import BaseHTTPRequestHandler, HTTPServer
 from pathlib import Path
 from queue import Empty, Queue
@@ -29,6 +30,14 @@
 from pghoard.version import __version__
 
 
+@dataclass(frozen=True)
+class PendingDownloadOp:
+    started_at: float
+    target_path: str
+    filetype: str
+    filename: str
+
+
 class PoolMixIn(ThreadingMixIn):
     def process_request(self, request, client_address):
         self.pool.submit(self.process_request_thread, request, client_address)
@@ -100,15 +109,15 @@ def process_queue_item(self, download_result):
                         os.unlink(download_result.payload["target_path"])
                 return
             if download_result.success:
-                if os.path.isfile(op["target_path"]):
+                if os.path.isfile(op.target_path):
                     self.log.warning("Target path for %r already exists, skipping", key)
                     return
                 # verify wal
                 src_tmp_file_path = download_result.payload["target_path"]
-                dst_file_path = op["target_path"]
-                if op["filetype"] == "xlog":
+                dst_file_path = op.target_path
+                if op.filetype == "xlog":
                     try:
-                        wal.verify_wal(wal_name=op["filename"], filepath=src_tmp_file_path)
+                        wal.verify_wal(wal_name=op.filename, filepath=src_tmp_file_path)
                         self.log.info("WAL verification successful %s", src_tmp_file_path)
                     except ValueError:
                         self.log.warning("WAL verification failed %s. Unlink file", src_tmp_file_path)
@@ -119,7 +128,7 @@ def process_queue_item(self, download_result):
                 metadata = download_result.payload["metadata"] or {}
                 self.log.info(
                     "Renamed %s to %s. Original upload from %r, hash %s:%s", download_result.payload["target_path"],
-                    op["target_path"], metadata.get("host"), metadata.get("hash-algorithm"), metadata.get("hash")
+                    op.target_path, metadata.get("host"), metadata.get("hash-algorithm"), metadata.get("hash")
                 )
             else:
                 ex = download_result.exception or Error
@@ -129,7 +138,7 @@ def process_queue_item(self, download_result):
                 else:
                     self.log.warning(
                         "Fetching %r failed (%s), took: %.3fs", key, ex.__class__.__name__,
-                        time.monotonic() - op["started_at"]
+                        time.monotonic() - op.started_at
                     )
 
     def stop(self):
@@ -379,7 +388,7 @@ def _create_fetch_operation(self, key, site, filetype, filename, max_age=-1, sup
             # Don't fetch again if we already have pending fetch operation unless the operation
             # has been ongoing longer than given max age and has potentially became stale
             existing = self.server.pending_download_ops.get(key)
-            if existing and (max_age < 0 or time.monotonic() - existing["started_at"] <= max_age):
+            if existing and (max_age < 0 or time.monotonic() - existing.started_at <= max_age):
                 return
 
         xlog_dir = get_pg_wal_directory(self.server.config["backup_sites"][site])
@@ -403,7 +412,7 @@ def _create_fetch_operation(self, key, site, filetype, filename, max_age=-1, sup
             "Fetching site: %r, filename: %r, filetype: %r, tmp_target_path: %r", site, filename, filetype, tmp_target_path
         )
         target_path = os.path.join(xlog_dir, "{}.pghoard.prefetch".format(filename))
-        self.server.pending_download_ops[key] = dict(
+        self.server.pending_download_ops[key] = PendingDownloadOp(
             started_at=time.monotonic(), target_path=target_path, filetype=filetype, filename=filename
         )
         self.server.transfer_queue.put(