Add design for simplified node-add process

Instead of initiating many SSH connections to copy files using “scp”, a
JSON structure is passed to a program running on the node to be added.
The design is similar to the one used for SSH setup.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

diff --git a/doc/design-node-add.rst b/doc/design-node-add.rst
index 7b5fe4c..4c52cea 100644 (file)
--- a/doc/design-node-add.rst
+++ b/doc/design-node-add.rst
@@ -20,10 +20,20 @@ requires a tight coupling and equality between nodes (e.g. paths to
 files being the same). Most of the logic and error handling is also done
 on the connecting machine.
 
 files being the same). Most of the logic and error handling is also done
 on the connecting machine.
 

+Once a node's SSH daemon has been configured, more than 25 files need to
+be copied using ``scp`` before the node daemon can be started. No
+verification is being done before files are copied. Once the node daemon
+is started, an opcode is submitted to the master daemon, which will then
+copy more files, such as the configuration and job queue for master
+candidates, using RPC. This process is somewhat fragile and requires
+initiating many SSH connections.

 
 Proposed changes
 ----------------
 
 
 Proposed changes
 ----------------
 

+SSH
+~~~
+

 The main goal is to move more logic to the newly added node. Instead of
 having a relatively large script executed on the master node, most of it
 is moved over to the added node.
 The main goal is to move more logic to the newly added node. Instead of
 having a relatively large script executed on the master node, most of it
 is moved over to the added node.

@@ -42,10 +52,37 @@ SSH client and to drop the dependency on Paramiko for Ganeti itself
 
 Eventually ``setup-ssh`` can be removed.
 
 
 Eventually ``setup-ssh`` can be removed.
 

+
+Node daemon
+~~~~~~~~~~~
+
+Similar to SSH setup changes, the process of copying files and starting
+the node daemon will be moved into a dedicated program. On its standard
+input it will receive a standardized JSON structure (defined :ref:`below
+<node-daemon-setup-json>`). Once the input data has been successfully
+decoded and the received values were verified for sanity, the program
+proceeds to write the values to files and then starts the node daemon
+(``ganeti-noded``).
+
+To add a new node to the cluster, the master node will have to gather
+all values, build the data structure, and then invoke the newly added
+``node-daemon-setup`` program via SSH. In this way only a single SSH
+connection is needed and the values can be verified before being written
+to files.
+
+If the program exits successfully, the node is ready to be added to the
+master daemon's configuration. The node daemon will be running, but
+``OpNodeAdd`` needs to be run before it becomes a full node. The opcode
+will copy more files, such as the :doc:`RAPI certificate <rapi>`.
+
+
+Data structures
+---------------
+

 .. _prepare-node-join-json:
 
 .. _prepare-node-join-json:
 

-JSON structure
-~~~~~~~~~~~~~~
+JSON structure for SSH setup
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 
 The data is given in an object containing the keys described below.
 Unless specified otherwise, all entries are optional.
 
 The data is given in an object containing the keys described below.
 Unless specified otherwise, all entries are optional.

@@ -78,6 +115,43 @@ and public part of the key. Example:
     ("dsa", "-----BEGIN DSA PRIVATE KEY-----...", "ssh-dss AAAA..."),
   ]
 
     ("dsa", "-----BEGIN DSA PRIVATE KEY-----...", "ssh-dss AAAA..."),
   ]
 

+
+.. _node-daemon-setup-json:
+
+JSON structure for node daemon setup
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The data is given in an object containing the keys described below.
+Unless specified otherwise, all entries are optional.
+
+``cluster_name``
+  Required string with the cluster name. If a local cluster name is
+  found, the join process is aborted unless the passed cluster name
+  matches the local name. The cluster name is also included in the
+  dictionary given via the ``ssconf`` entry.
+``node_daemon_certificate``
+  Public and private part of cluster's node daemon certificate in PEM
+  format. If a local node certificate is found, the process is aborted
+  unless it matches.
+``ssconf``
+  Dictionary with ssconf names and their values. Both are strings.
+  Example:
+
+  .. highlight:: javascript
+
+  ::
+
+    {
+      "cluster_name": "cluster.example.com",
+      "master_ip": "192.168.2.1",
+      "master_netdev": "br0",
+      # …
+    }
+
+``start_node_daemon``
+  Boolean denoting whether the node daemon should be started (or
+  restarted if it was running for some reason).
+

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