libra/doc/admin_api/schedulers.rst

Admin Schedulers

The Admin API has several schedulers to maintain the health of the Libra system. This section of the document goes into detail about each one.

Each Admin API server takes it in-turn to run these tasks. Which server is next is determined by the --number_of_servers and --server_id options.

Stats Scheduler

This scheduler is actually a monitoring scheduler and at a later date will also gather statistics for billing purposes. It is executed once a minute.

It sends a gearman 'ping' message to active Load Balancer device. There are three possible outcomes from the results:

It has support for multiple different stats-drivers.

1. If all is good, no action is taken
2. If a node connected to a load balancer has failed the node is marked as ERROR and the load balancer is marked as DEGRADED
3. If a device has failed the device will automatically be rebuilt on a new device and the associated floating IP will be re-pointed to that device. The old device will be marked for deletion.

Rebuild (AutoFailover)

Libra LBaaS supports auto-failover or auto-rebuild of a broken device.

This basically means typically re-allocating / re-building the device to a new device.

1. A ping is sent to each device (ping_lbs > _exec_ping)

2. Send failures to drivers (_exec_ping > _send_fails)

3. Driver does

   1. Marks the device as being in ERROR state.
   2. Triggers a rebuild
   3. Looks for a free device that is in OFFLINE state in the db.
   4. Assigns the failed device to the OFFLINE device
   5. Assigns the vip to the new device
   6. Marks device as DELETED
   7. Puts the new device into ACTIVE in the db.

4. A scheduled function remove the device from DB and unconfigures it.

5. A scheduled function ensures that there are standby device in the pool.

Delete Scheduler

This scheduler looks out for any devices marked for deletion after use or after an error state. It is executed once a minute.

It sends a gearman message to the Pool Manager to delete any devices that are to be deleted and removes them from the database.

Create Scheduler

This scheduler takes a look at the number of hot spare devices available. It is executed once a minute (after the delete scheduler).

If the number of available hot spare devices falls below the value specified by --node_pool_size it will request that new devices are built and those devices will be added to the database. It records how many are currently being built so long build times don't mean multiple Admin APIs are trying to fulfil the same quota.

VIP Scheduler

This scheduler takes a look at the number of hot spare floating IPs available. It is executed once a minute.

If the number of available floating IP address falls below the value specified by vip_pool_size it will request that new IPs are build and those will be added to the database.

Expunge Scheduler

This scheduler removes logical Load Balancers marked as DELETED from the database. It is executed once a day.

The DELETED logical Load Balancers remain in the database mainly for billing purposes. This clears out any that were deleted after the number of days specified by --expire-days.