Synnefo

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Asynchronous communication with Ganeti backends

Synnefo uses Google Ganeti backends for VM cluster management. In order Cyclades

to be able to handle thousand of user requests, Cyclades and Ganeti communicate

asynchronously. Briefly, requests are submitted to Ganeti, and asynchronous

Cyclades API server is responsible for handling user requests. Read-only

requests are directly served by looking up the Cyclades DB. If the request

needs an action in the Ganeti backend, Cyclades submit jobs to the Ganeti

While Ganeti executes the job, snf-ganeti-eventd, snf-ganeti-hook and

snf-progress-monitor are monitoring the progress of the job and send

* *snf-ganeti-eventd* sends messages about operations affecting the operating

  state of instances and networks. Works by monitoring Ganeti job queue.

* *snf-ganeti_hook* sends messages about the NIC of instances. It includes a

* *snf-progress_monitor* sends messages about the progress of building a new

  instance and image deployment, triggered by snf-image.

messages and properly updates the state of Cyclades DB. Subsequent requests in

Cyclades API, will retrieve the updated state from the DB.

Prereqs

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Managing Ganeti Backends

Since v0.11 Synnefo is able to manage multiple Ganeti clusters (backends)

making it capable to scale to thousand of VMs. Backends can be dynamically be

be connected to the same private network.

Listing existing backend

To find out the available Ganeti backends, run:

.. code-block:: console

   $ snf-manage backend-list

Adding a new Ganeti backend

Backends are dynamically added under the control of Synnefo with `snf-manage

backend-add` command. In this section it is assumed that a Ganeti cluster,

named cluster.example.com is already up and running and configured to be able

to host Synnefo VMs.

To add the Ganeti cluster, run:

.. code-block:: console

   $ snf-manage backend-add --clustername=cluster.example.com --user="synnefo_user" --pass="synnefo_pass"

associated with it.

Removing an existing Ganeti backend

In order to remove an existing backend, run:

.. code-block:: console

   # snf-manage backend-remove ID

will be left.

Allocation of VMS in Ganneti backends

As already mentioned, the backend allocator is responsible allocating new VMs

to backends. This allocator is not concerned about the Ganeti node that will

host the VM, which is chosen by the Ganeti allocator.

resources. The allocator computes a score for each backend, that shows its load

factor, and the one with the minimum score is chosen. The admin can exclude

backends from the allocation phase by marking them as drained by running:

.. code-block:: console

   $ snf-manage backend-modify --drained ID

the `BACKEND_PER_USER` setting.

Managing Network Resources

Proper operation of of Cyclades Network Service depends on unique assignment of

specific resources to each virtual network. Specifically, these resources are:

  management command.

Creating a new Pool

Pools are created using the `snf-manage pool-create` command.

.. code-block:: console

   # snf-manage pool-create --type=bridge --base=prv --size=20

will create a pool of bridges, containing bridges prv1, prv2,..prv21.

You can verify the creation of the pool, and check its contents by running:

.. code-block:: console

   # snf-manage pool-list

   # snf-manage pool-show --type=bridge 1

With the same commands you can handle the pool of MAC prefixes. For example:

.. code-block:: console

   # snf-manage pool-create --type=mac-prefix --base=aa:00:0 --size=65536

for reconciling VMs and Networks

Reconciling VirtualMachine

Reconciliation of VMs detects the following conditions:

 * Stale DB servers without corresponding Ganeti instances

 * Orphan Ganeti instances, without corresponding DB entries

 * Out-of-sync state for DB entries wrt to Ganeti instances

To detect all inconsistencies you can just run:

.. code-block:: console

  $ snf-manage reconcile --detect-all

Adding the `--fix-all` option, will do the actual synchronization:

.. code-block:: console

  $ snf-manage reconcile --detect-all --fix-all

Reconciling Networks

Reconciliation of Networks detects the following conditions:

  * Stale DB networks without corresponding Ganeti networks

  * Orphan Ganeti networks, without corresponding DB entries

  * Unsynchronized IP pools

To detect all inconsistencies you can just run:

.. code-block:: console

  $ snf-manage reconcile-networks

Adding the `--fix-all` option, will do the actual synchronization:

.. code-block:: console

  $ snf-manage reconcile-networks --fix-all