SSH tunnel support for S3Store

docs/getting_started/using_ssh_tunnel.md

@@ -0,0 +1,56 @@
+# Using `SSHTunnel` to conect to remote database 
+
+One of the typical scenarios to use `maggma` is to connect to a remote database that is behind a firewall and thus cannot be accessed directly from your local computer (as shown below, [image credits](https://github.com/pahaz/sshtunnel/)). 
+
+In this case, you can use `SSHTunnel` to first connect to the remote server, and then connect to the database from the server. 
+
+```
+----------------------------------------------------------------------
+
+                            |
+-------------+              |    +----------+               +---------
+    LOCAL    |              |    |  REMOTE  |               | PRIVATE
+  COMPUTER   | <== SSH ========> |  SERVER  | <== local ==> | SERVER
+-------------+              |    +----------+               +---------
+                            |
+                         FIREWALL (only port 22 is open)
+
+----------------------------------------------------------------------
+
+Note, the `local` indicates that the connction to the PRIVATE SERVER can only be made from the REMOTE SERVER.
+```
+
+
+Below is an example of how to use `SSHTunnel` to connect to an AWS `S3Store` hosted on a private server.
+
+Let's assume that, from you local computer, you can ssh to the remote server using the following command with your credentials (e.g. <USER_CREDENTIAL>):
+
+```bash
+ssh <USERNAME>@<REMOTE_SERVER_ADDRESS>
+```
+
+and then from the remote server, you can access your database using, e.g., the following information:
+```
+private_server_address: COMPUTE_NODE_1
+private_server_port: 9000
+```
+
+You can create an `SSHTunnel` object as follows:
+
+```python
+from maggma.stores.ssh_tunnel import SSHTunnel
+
+tunnel = SSHTunnel(
+    tunnel_server_address = "<REMOTE_SERVER_ADDRESS>:22",
+    username = "<USERNAME>",
+    password= "<USER_CREDENTIAL>",
+    remote_server_address = "COMPUTE_NODE_1:9000", 
+    local_port = 9000,
+)
+```
+and then pass it to the `S3Store` to connect to the database. 
+By doing so, you can access the database at the localhost address `http://127.0.0.1:9000` from your local computer as if it is hosted on your local computer. 
+
+The arguments of the `SSHTunnel` are self-explanatory, but `local_port` needs more explanation. We assume that on the local computer, we want t o connect to the localhost address `http://127.0.0.1`, so we do not need to provide the address, but only the port number (`9000` in this case.)
+
+In essence, `SSHTunnel` allows you to connect to `COMPUTE_NODE_1:9000` on the private server from `http://127.0.0.1:9000` on your local computer.

docs/reference/stores.md

@@ -9,3 +9,5 @@
 ::: maggma.stores.advanced_stores
 
 ::: maggma.stores.compound_stores
+
+::: maggma.stores.ssh_tunnel

mkdocs.yml

@@ -17,6 +17,7 @@ nav:
     - Working with MapBuilder: getting_started/map_builder.md
     - Working with GroupBuilder: getting_started/group_builder.md
     - Setting up MongoDB: getting_started/mongodb.md
+    - Using SSHTunnel: getting_started/using_ssh_tunnel.md
   - Reference:
       Core:
         Store: reference/core_store.md