Split out the local backend (#2052)

This splits the backend into two parts: the local backend for desktop cellxgene and the AWS backend for hosted cellxgene. The local backend is in local_server while the hosted remains in server. The general idea is to copy everything from server to local_server, pull unneeded stuff out of local_server, and keep server as-is for this PR. Not touching server means all the infra and deployment code will continue working just as it did before so we can make those changes incrementally.

local_server/common/config/base_config.py

@@ -0,0 +1,99 @@
+import copy
+
+from flatten_dict import flatten
+from local_server.common.errors import ConfigurationError
+
+
+class BaseConfig(object):
+    """
+    This class handles the mechanics of updating and checking attributes.
+    Derived classes are expected to store the actual attributes
+    Currently DatasetConfig and ServerConfig both inherit from BaseConfig.
+    """
+
+    def __init__(self, app_config, default_config):
+        # reference back to the app_config
+        self.app_config = app_config
+        # the complete set of attributes and their default values (unflattened)
+        self.default_config = default_config
+        # used to make sure every attribute value is checked
+        self.attr_checked = {key_name: False for key_name in self.create_mapping(default_config).keys()}
+
+    def create_mapping(self, config):
+        """
+        Create a dictionary where the keys are the name of attributes (using double underscore convention)
+        For example: authentication__type
+
+        The values are a tuple,
+        - the first item of the tuple is a tuple of path elements (location in config 'tree')
+        - the second item is the value of the config parameter
+
+        For example: (('authentication', 'type'), 'session'))
+        """
+        config_copy = copy.deepcopy(config)
+        mapping = {}
+
+        flat_config = flatten(config_copy)
+        for key, value in flat_config.items():
+            # name of the attribute
+            attr = "__".join(key)
+            mapping[attr] = (key, value)
+
+        return mapping
+
+    def validate_correct_type_of_configuration_attribute(self, attrname, vtype):
+        val = getattr(self, attrname)
+        if type(vtype) in (list, tuple):
+            if type(val) not in vtype:
+                tnames = ",".join([x.__name__ for x in vtype])
+                raise ConfigurationError(
+                    f"Invalid type for attribute: {attrname}, expected types ({tnames}), got {type(val).__name__}"
+                )
+        else:
+            if type(val) != vtype:
+                raise ConfigurationError(
+                    f"Invalid type for attribute: {attrname}, "
+                    f"expected type {vtype.__name__}, got {type(val).__name__}"
+                )
+
+        self.attr_checked[attrname] = True
+
+    def check_config(self):
+        mapping = self.create_mapping(self.default_config)
+        for key in mapping.keys():
+            if not self.attr_checked[key]:
+                raise ConfigurationError(f"The attr '{key}' has not been checked")
+
+    def update(self, **kw):
+        """Update the attributes defined in kw with their new values."""
+        for key, value in kw.items():
+            if not hasattr(self, key):
+                raise ConfigurationError(f"unknown config parameter {key}.")
+            try:
+                if type(value) == tuple:
+                    # convert tuple values to list values
+                    value = list(value)
+                setattr(self, key, value)
+            except KeyError:
+                raise ConfigurationError(f"Unable to set config parameter {key}.")
+
+            self.attr_checked[key] = False
+
+    def update_from_config(self, config, prefix):
+        mapping = self.create_mapping(config)
+        for attr, (key, value) in mapping.items():
+            if not hasattr(self, attr):
+                raise ConfigurationError(f"Unknown key from config file: {prefix}__{attr}")
+            setattr(self, attr, value)
+
+            self.attr_checked[attr] = False
+
+    def changes_from_default(self):
+        """Return all the attribute that are different from the default"""
+        mapping = self.create_mapping(self.default_config)
+        diff = []
+        for attrname, (key, defval) in mapping.items():
+            curval = getattr(self, attrname)
+            if curval != defval:
+                diff.append((attrname, curval, defval))
+        return diff