[execution][docker] Implement database root folder sharing

A new property in the execution configuration allows to
mount the various databases in the algorithm container
in a similar fashion as the database container. It will
only work for containers that needs to access datasets.

Fixes #103

beat/core/execution/docker.py

@@ -384,6 +384,15 @@ class DockerExecutor(RemoteExecutor):
             file_path = result["path"]
             __add_writable_volume(file_path)
 
+    def __share_databases(self, algorithm_container, db_infos):
+        """Add volumes to the algorithm container for the datasets"""
+
+        for database_name, database in self.databases.items():
+            db_data = database.data
+            algorithm_container.add_volume(
+                db_data["root_folder"], os.path.join("/databases", database_name)
+            )
+
     def process(
         self, virtual_memory_in_megabytes=0, max_cpu_percent=0, timeout_in_minutes=0
     ):
@@ -472,6 +481,8 @@ class DockerExecutor(RemoteExecutor):
         network_name = self.data.pop("network_name", "bridge")
         databases_infos = {}
 
+        share_databases = self.data.pop("share_databases", False)
+
         if len(self.databases) > 0:
             databases_infos["db"] = self.__create_db_container(
                 datasets_uid, network_name
@@ -526,6 +537,9 @@ class DockerExecutor(RemoteExecutor):
                 loop_algorithm_container, volume_cache_mount_point, self.data["loop"]
             )
 
+            if share_databases:
+                self.__share_databases(loop_algorithm_container, databases_infos)
+
             # Start the container
             self.host.start(
                 loop_algorithm_container,
@@ -570,6 +584,9 @@ class DockerExecutor(RemoteExecutor):
             algorithm_container, volume_cache_mount_point, self.data
         )
 
+        if share_databases:
+            self.__share_databases(algorithm_container, databases_infos)
+
         # Start the container
         self.host.start(
             algorithm_container,