Python API: improve request ID usage in ChunkReader

Relates to #1346

oio/api/io.py

@@ -196,6 +196,13 @@ def __init__(self, chunk_iter, buf_size, headers,
         self.read_timeout = read_timeout or CHUNK_TIMEOUT
         self._resp_by_chunk = dict()
 
+    @property
+    def reqid(self):
+        """:returns: the request ID or None"""
+        if not self.request_headers:
+            return None
+        return self.request_headers.get('X-oio-req-id')
+
     def recover(self, nb_bytes):
         """
         Recover the request.
@@ -254,7 +261,8 @@ def _get_request(self, chunk):
                 source = conn.getresponse()
                 source.conn = conn
         except (Exception, Timeout) as error:
-            logger.exception('Connection failed to %s', chunk)
+            logger.exception('Connection failed to %s (reqid=%s)',
+                             chunk, self.reqid)
             self._resp_by_chunk[chunk["url"]] = (0, str(error))
             return False
 
@@ -264,8 +272,8 @@ def _get_request(self, chunk):
             self.sources.append((source, chunk))
             return True
         else:
-            logger.warn("Invalid response from %s: %d %s",
-                        chunk, source.status, source.reason)
+            logger.warn("Invalid response from %s (reqid=%s): %d %s",
+                        chunk, self.reqid, source.status, source.reason)
             self._resp_by_chunk[chunk["url"]] = (source.status,
                                                  str(source.reason))
         return False
@@ -298,8 +306,11 @@ def get_iter(self):
                                      self._resp_by_chunk)
 
     def stream(self):
-        # Calling that right now will make `headers` field available
-        # before the caller starts reading the stream
+        """
+        Get a generator over chunk data.
+        After calling this method, the `headers` field will be available
+        (even if no data is read from the generator).
+        """
         parts_iter = self.get_iter()
 
         def _iter():
@@ -377,8 +388,9 @@ def iter_from_resp(self, source, parts_iter, part, chunk):
                 new_source, new_chunk = self._get_source()
                 if new_source:
                     logger.warn(
-                        "Failed to read from %s (%s), retrying from %s",
-                        chunk, crto, new_chunk)
+                        "Failed to read from %s (%s), "
+                        "retrying from %s (reqid=%s)",
+                        chunk, crto, new_chunk, self.reqid)
                     close_source(source[0])
                     # switch source
                     source[0] = new_source
@@ -393,7 +405,8 @@ def iter_from_resp(self, source, parts_iter, part, chunk):
                         return
 
                 else:
-                    logger.warn("Failed to read from %s (%s)", chunk, crto)
+                    logger.warn("Failed to read from %s (%s, reqid=%s)",
+                                chunk, crto, self.reqid)
                     # no valid source found to recover
                     raise
             else:
@@ -456,7 +469,8 @@ def _get_iter(self, chunk, source):
                     body_iter.close()
 
         except green.ChunkReadTimeout:
-            logger.exception("Failure during chunk read")
+            logger.exception("Failure during chunk read (reqid=%s)",
+                             self.reqid)
             raise
         except GeneratorExit:
             pass