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.. _rl-multi-site-origin-qht:

***************************
Configure Multi Site Origin
***************************

1) Create "cachegroups" for the origin locations, and assign the appropriate parent-child relationship between the mid cg's and org cgs (click the image to see full size):

.. image:: C5C4CD22-949A-48FD-8976-C673083E2177.png
	:scale: 100%
	:align: center

2) Create a profile to assign to each of the origins:

.. image:: 19BB6EC1-B6E8-4D22-BFA0-B7D6A9708B42.png
	:scale: 100%
	:align: center

3) Create server entries for the origination vips:

.. image:: D28614AA-9758-45ED-9EFD-3A284FC4218E.png
	:scale: 100%
	:align: center

4) Check the multi-site check box in the delivery service screen:

.. image:: mso-enable.png
	:scale: 100%
	:align: center

5) Assign the org servers to the delivery service that will have the multi site feature:

.. image:: 066CEF4F-C1A3-4A89-8B52-4F72B0531367.png
	:scale: 100%
	:align: center

.. Note:: “Origin Server Base URL” uniqueness: In order to enable MID caches to distinguish delivery services by different MSO algorithms while performing parent failover, it requires that “Origin Server Base URL” (OFQDN) for each MSO enabled delivery service is unique unless the exceptions listed afterwards. This means that the OFQDN of a MSO enabled delivery service should be different with the OFQDNs of any other delivery service, regardless of whether they are MSO enabled or not. The exceptions are: 
       1) If there are multiple CDNs created on the same Traffic Ops, delivery services across different CDNs may have the same OFQDN configured.
       2) If several delivery services in the same CDN have the same MSO algorithm configured, they may share the same OFQDN.
       3) If delivery services are assigned with different MID cache groups respectively, they can share the same OFQDN.

6) Select an option from the "Multi Site Origin Algorithm" drop-down list. Four MSO algorithms are supported:

+------------------+--------------------------------------------------------------------------------------------------------------------+
|     Option       |                                                            Description                                             |
+==================+====================================================================================================================+
| Consistent hash  | Origin server selection is based on the consistent hash of requested URLs.                                         |
+------------------+--------------------------------------------------------------------------------------------------------------------+
| Primary/back     | Round robin selection does not occur. The first origin server is selected unless it fails.                         |
|                  | If the first fails, the second and other following origin servers will be tried by order.                          |
|                  | Order is defined by 2 factors - if the origin server's cachegroup is configured as the                             |
|                  | parent cachegroup for the mid, then this server will be used as the primary. The same rules                        |
|                  | apply for secondary parents, in order.  Within the cachegroups, the rank parameter will sort                       |
|                  | order further. If no parents are defined at the mid, then only rank is considered.                                 |  
+------------------+--------------------------------------------------------------------------------------------------------------------+
| Strict           | MID caches serve requests strictly in turn. For example: origin server 1 serves the first request,                 |
| round-robin      | origin server 2 serves the second request, and so on.                                                              |
+------------------+--------------------------------------------------------------------------------------------------------------------+
| IP based         | MID cache goes through the origin server list in a round robin-based on the IP address of EDGE cache.              |
| round-robin      |                                                                                                                    |
+------------------+--------------------------------------------------------------------------------------------------------------------+

7) Optionally, there are two configuration options that can set the order of the origins used if "Primary/backup" is selected for "Multi Site Origin Algorithm". By creating location-based cachegroups and assigning the origin servers accordingly and defining these cachegroups as parents for specific mids, location-based primary/secondary selection can be made.   If primary/secondary selection should be the same for all mids, then a new parameter “rank” should be configured for each origin server profile. Origin servers with lower values of rank have higher ranking in the origin server list on MID caches, e.g. OS with rank of "2" precedes OS with the rank of "5". For any OS, if rank value is not defined in its profile, its rank value will default to “1”.  In the event that both location based cachegroups are used alongside rank, sorting will be by cachegroup first and rank second.  In this way it is possible to have specific backup servers for use at specific locations.

.. image:: mso-rank.png
	:scale: 60%
	:align: center

8) Assign the parent.config location parameter to the MID profile:

.. image:: D22DCAA3-18CC-48F4-965B-5312993F9820.png
	:scale: 100%
	:align: center


9) Configure the mid hdr_rewrite on the delivery service, example: ::

	cond %{REMAP_PSEUDO_HOOK} __RETURN__ set-config proxy.config.http.parent_origin.dead_server_retry_enabled 1 __RETURN__ set-config proxy.config.http.parent_origin.simple_retry_enabled 1 __RETURN__ set-config proxy.config.http.parent_origin.simple_retry_response_codes "400,404,412" __RETURN__ set-config proxy.config.http.parent_origin.dead_server_retry_response_codes "502,503" __RETURN__ set-config proxy.config.http.connect_attempts_timeout 2 __RETURN__ set-config proxy.config.http.connect_attempts_max_retries 2 __RETURN__ set-config proxy.config.http.connect_attempts_max_retries_dead_server 1 __RETURN__ set-config proxy.config.http.transaction_active_timeout_in 5 [L] __RETURN__

10) Turn on parent_proxy_routing in the MID profile.