fix(storage): add retry mechanism to recover from a full input queue

If the client writes data too quickly, the agent may see its input queue
full. Give ourselves up to 30 seconds to submit the data to be written to
the shared storage before giving up. Refactor the code between local and
s3 sources to make error handling consistent.

Signed-off-by: Cedric Hombourger <cedric.hombourger@siemens.com>

mtda/client.py

@@ -491,6 +491,24 @@ def progress(self):
     def size(self):
         return None
 
+    def _write_to_storage(self, data):
+        max_tries = int(CONSTS.STORAGE.TIMEOUT / CONSTS.STORAGE.RETRY_INTERVAL)
+
+        for _ in range(max_tries):
+            result = self._agent.storage_write(data, self._session)
+            if result != 0:
+                break
+            time.sleep(CONSTS.STORAGE.RETRY_INTERVAL)
+
+        if result > 0:
+            return result
+        elif result < 0:
+            exc = 'write or decompression error from shared storage'
+            raise IOError(exc)
+        else:
+            exc = 'timeout from shared storage'
+            raise IOError(exc)
+
 
 class ImageLocal(ImageFile):
     """ An image from the local file-system to be copied over to the shared
@@ -519,24 +537,10 @@ def copy(self):
             inputstream = image
 
         try:
-            data = inputstream.read(self._blksz)
-            while data:
+            while (data := inputstream.read(self._blksz)):
                 self._totalread = image.tell()
                 self.progress()
-
-                # Write block to shared storage device
-                bytes_wanted = self._agent.storage_write(data, self._session)
-
-                # Check what to do next
-                if bytes_wanted < 0:
-                    raise IOError('write or decompression error from the '
-                                  'shared storage')
-                elif bytes_wanted > 0:
-                    # Read next block
-                    data = inputstream.read(bytes_wanted)
-                else:
-                    # Agent may continue without further data
-                    data = b''
+                self._write_to_storage(data)
 
         finally:
             if comp_on_the_fly:
@@ -612,19 +616,8 @@ def write(self, data):
         self._totalread += dataread
 
         # Write block to shared storage device
-        bytes_wanted = 0
-        while bytes_wanted == 0:
-            # Report progress
-            self.progress()
-
-            # Write downloaded data to storage
-            bytes_wanted = self._agent.storage_write(data, self._session)
-            if bytes_wanted == 0:
-                # Agent may continue without further data
-                data = b''
-            elif bytes_wanted < 0:
-                # Write failure
-                raise IOError('write or decompression error')
+        self.progress()
+        self._write_to_storage(data)
 
         return dataread
 

mtda/constants.py

@@ -67,6 +67,8 @@ class STORAGE:
     LOCKED = "LOCKED"
     UNLOCKED = "UNLOCKED"
     UNKNOWN = "???"
+    RETRY_INTERVAL = 0.5
+    TIMEOUT = 30
 
 
 class WRITER: