documented how we avoid the MongoDB cloud replica in ap-northeast-1 to become primary, setting its priority to 0

Axel Uhl commited 2021-06-01 12:41:09 +0200 commit 628ab99ef96454b14f04b6c249d2d9391a8b1521

				wiki/info/landscape/olympic-setup.md
			
          @@ -328,6 +328,15 @@ Three MongoDB nodes are intended to run during regular operations: sap-p1-1:1020

           	mongodb://localhost:10201,localhost:10202,localhost:10203/tokyo2020?replicaSet=tokyo2020&retryWrites=true&readPreference=nearest

           ```

          +The cloud replica is not supposed to become primary, except for maybe in the unlikely event where operations would move entirely to the cloud. To achieve this, the cloud replica has priority 0 which can be configured like this:

          +

          +```

          +    tokyo2020:PRIMARY> cfg = rs.conf()

          +    # Then search for the member localhost:10203; let's assume, it's in cfg.members[1]:

          +    cfg.members[1].priority=0

          +    rs.reconfig(cfg)

          +```

          +

           All cloud replicas shall use a MongoDB database name ``tokyo2020-replica``. In those regions where we don't have dedicated MongoDB support established (basically all but eu-west-1 currently), an image should be used that has a MongoDB server configured to use ``/home/sailing/mongo`` as its data directory and ``replica`` as its replica set name. See AMI SAP Sailing Analytics App HVM with MongoDB 1.137 (ami-05b6c7b1244f49d54) in ap-northeast-1 (already copied to the other peered regions except eu-west-1).

           One way to monitor the health and replication status of the replica set is running the following command:

...	...	@@ -328,6 +328,15 @@ Three MongoDB nodes are intended to run during regular operations: sap-p1-1:1020
328	328	mongodb://localhost:10201,localhost:10202,localhost:10203/tokyo2020?replicaSet=tokyo2020&retryWrites=true&readPreference=nearest
329	329	```
330	330
	331	+The cloud replica is not supposed to become primary, except for maybe in the unlikely event where operations would move entirely to the cloud. To achieve this, the cloud replica has priority 0 which can be configured like this:
	332	+
	333	+```
	334	+ tokyo2020:PRIMARY> cfg = rs.conf()
	335	+ # Then search for the member localhost:10203; let's assume, it's in cfg.members[1]:
	336	+ cfg.members[1].priority=0
	337	+ rs.reconfig(cfg)
	338	+```
	339	+
331	340	All cloud replicas shall use a MongoDB database name ``tokyo2020-replica``. In those regions where we don't have dedicated MongoDB support established (basically all but eu-west-1 currently), an image should be used that has a MongoDB server configured to use ``/home/sailing/mongo`` as its data directory and ``replica`` as its replica set name. See AMI SAP Sailing Analytics App HVM with MongoDB 1.137 (ami-05b6c7b1244f49d54) in ap-northeast-1 (already copied to the other peered regions except eu-west-1).
332	341
333	342	One way to monitor the health and replication status of the replica set is running the following command: