remote: separate cloud remote and cloud cache classes (iterative#4019)

* remote: move get_file_checksum() into tree

* makes RemoteTree and RepoTree consistent with regard to checksum
  calculation

* remote: save() now takes explicit tree parameter

* when tree is remote.tree, save will be a move + link operation
  (same as default existing behavior)
* when saving path from a different tree, save will be a copy operation

* tests: update for moved remote/tree functions

* remote: move get_checksum into tree

* remote: separate cloud remote and cache classes

* tests: update unit tests for remote/cache separation

* remote: cloud cache should extend cloud remote

* remote: move LocalRemote.get

* tests: update func tests

* dependency: update for moved get_checksum

* remote: fix state lookup bug

dvc/cache.py

@@ -28,13 +28,13 @@ def _make_remote_property(name):
     """
 
     def getter(self):
-        from dvc.remote import Remote
+        from dvc.remote import Cache as CloudCache
 
         remote = self.config.get(name)
         if not remote:
             return None
 
-        return Remote(self.repo, name=remote)
+        return CloudCache(self.repo, name=remote)
 
     getter.__name__ = name
     return cached_property(getter)
@@ -50,7 +50,7 @@ class Cache:
     CACHE_DIR = "cache"
 
     def __init__(self, repo):
-        from dvc.remote import Remote
+        from dvc.remote import Cache as CloudCache
 
         self.repo = repo
         self.config = config = repo.config["cache"]
@@ -62,7 +62,7 @@ def __init__(self, repo):
         else:
             settings = {**config, "url": config["dir"]}
 
-        self.local = Remote(repo, **settings)
+        self.local = CloudCache(repo, **settings)
 
     s3 = _make_remote_property("s3")
     gs = _make_remote_property("gs")

dvc/dependency/repo.py

@@ -64,9 +64,7 @@ def _get_checksum(self, locked=True):
 
                 # We are polluting our repo cache with some dir listing here
                 if tree.isdir(path):
-                    return self.repo.cache.local.get_dir_checksum(
-                        path, tree=tree
-                    )
+                    return self.repo.cache.local.get_checksum(path, tree)
                 return tree.get_file_checksum(path)
 
     def status(self):

dvc/external_repo.py

@@ -126,8 +126,9 @@ def download_update(result):
                 raise PathMissingError(path, self.url)
             save_info = self.local_cache.save(
                 path,
+                self.repo_tree,
                 None,
-                tree=self.repo_tree,
+                save_link=False,
                 download_callback=download_update,
             )
             save_infos.append(save_info)

dvc/output/base.py

@@ -267,7 +267,7 @@ def save(self):
 
     def commit(self):
         if self.use_cache:
-            self.cache.save(self.path_info, self.info)
+            self.cache.save(self.path_info, self.cache.tree, self.info)
 
     def dumpd(self):
         ret = copy(self.info)

dvc/remote/__init__.py

@@ -1,16 +1,25 @@
 import posixpath
 from urllib.parse import urlparse
 
-from dvc.remote.azure import AzureRemote
+from dvc.remote.azure import AzureCache, AzureRemote
 from dvc.remote.gdrive import GDriveRemote
-from dvc.remote.gs import GSRemote
-from dvc.remote.hdfs import HDFSRemote
+from dvc.remote.gs import GSCache, GSRemote
+from dvc.remote.hdfs import HDFSCache, HDFSRemote
 from dvc.remote.http import HTTPRemote
 from dvc.remote.https import HTTPSRemote
-from dvc.remote.local import LocalRemote
+from dvc.remote.local import LocalCache, LocalRemote
 from dvc.remote.oss import OSSRemote
-from dvc.remote.s3 import S3Remote
-from dvc.remote.ssh import SSHRemote
+from dvc.remote.s3 import S3Cache, S3Remote
+from dvc.remote.ssh import SSHCache, SSHRemote
+
+CACHES = [
+    AzureCache,
+    GSCache,
+    HDFSCache,
+    S3Cache,
+    SSHCache,
+    # LocalCache is the default
+]
 
 REMOTES = [
     AzureRemote,
@@ -26,21 +35,30 @@
 ]
 
 
-def _get(remote_conf):
-    for remote in REMOTES:
+def _get(remote_conf, remotes, default):
+    for remote in remotes:
         if remote.supported(remote_conf):
             return remote
-    return LocalRemote
+    return default
 
 
-def Remote(repo, **kwargs):
+def _get_conf(repo, **kwargs):
     name = kwargs.get("name")
     if name:
         remote_conf = repo.config["remote"][name.lower()]
     else:
         remote_conf = kwargs
-    remote_conf = _resolve_remote_refs(repo.config, remote_conf)
-    return _get(remote_conf)(repo, remote_conf)
+    return _resolve_remote_refs(repo.config, remote_conf)
+
+
+def Remote(repo, **kwargs):
+    remote_conf = _get_conf(repo, **kwargs)
+    return _get(remote_conf, REMOTES, LocalRemote)(repo, remote_conf)
+
+
+def Cache(repo, **kwargs):
+    remote_conf = _get_conf(repo, **kwargs)
+    return _get(remote_conf, CACHES, LocalCache)(repo, remote_conf)
 
 
 def _resolve_remote_refs(config, remote_conf):

dvc/remote/azure.py

@@ -7,7 +7,7 @@
 
 from dvc.path_info import CloudURLInfo
 from dvc.progress import Tqdm
-from dvc.remote.base import BaseRemote, BaseRemoteTree
+from dvc.remote.base import BaseRemote, BaseRemoteTree, CacheMixin
 from dvc.scheme import Schemes
 
 logger = logging.getLogger(__name__)
@@ -108,6 +108,9 @@ def remove(self, path_info):
         logger.debug(f"Removing {path_info}")
         self.blob_service.delete_blob(path_info.bucket, path_info.path)
 
+    def get_file_checksum(self, path_info):
+        return self.get_etag(path_info)
+
     def _upload(
         self, from_file, to_info, name=None, no_progress_bar=False, **_kwargs
     ):
@@ -134,10 +137,11 @@ def _download(
 class AzureRemote(BaseRemote):
     scheme = Schemes.AZURE
     REQUIRES = {"azure-storage-blob": "azure.storage.blob"}
+    TREE_CLS = AzureRemoteTree
     PARAM_CHECKSUM = "etag"
     COPY_POLL_SECONDS = 5
     LIST_OBJECT_PAGE_SIZE = 5000
-    TREE_CLS = AzureRemoteTree
 
-    def get_file_checksum(self, path_info):
-        return self.tree.get_etag(path_info)
+
+class AzureCache(AzureRemote, CacheMixin):
+    pass