Add docs for multi-dc support

mesosphere-backup · Aug 7, 2015 · cd5b33d · cd5b33d
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diff --git a/docs/_layouts/docs.html b/docs/_layouts/docs.html
@@ -44,6 +44,16 @@ <h5>Reference</h5>
             REST API
         </a>
       </li>
+      <li>
+        <a href="{{ site.baseurl }}/docs/mesos-dns.html">
+            Mesos DNS
+        </a>
+      </li>
+      <li>
+        <a href="{{ site.baseurl }}/docs/multi-dc.html">
+            Multi Datacenter
+        </a>
+      </li>
       <li>
         <a href="{{ site.baseurl }}/docs/faq.html">
             FAQ

diff --git a/docs/docs/multi-dc.md b/docs/docs/multi-dc.md
@@ -0,0 +1,178 @@
+---
+title: Multi Datacenter
+---
+
+# Multi Datacenter
+
+Beginning with Cassandra on Mesos version 0.2.0, Cassandra on Mesos can be configured so that multiple datacenters are aware of each other.
+
+See [Deploying Cassandra across Multiple Data Centers](http://www.datastax.com/dev/blog/deploying-cassandra-across-multiple-data-centers) for motivations regarding running Cassandra in multiple datacenters.
+
+## How it works
+
+Cassandra on Mesos can be configured to provide datacenter and rack information to Cassandra upon starting each server.
+
+Cassandra on Mesos can also be configured to query other Cassandra instances to provide seed sets across multiple clusters so that each of the clusters can coordinate and replicate data.
+
+
+## Requirements
+
+1. Every cluster must be able to reach the IP addresses of every other cluster.
+2. All clusters must have the same cluster name.
+3. Datacenters must be defined before starting the framework. New datacenters cannot be added after a cluster has initialized.
+4. Node sizes and counts must be the same across all clusters. **Note:** Cassandra on Mesos does not enforce or validate this, so be certain that this is configured correctly.
+
+## Configuration
+
+### DC and Rack
+
+Configuration is provided via environment variables.
+
+```
+# Value to be used as the default DC name
+CASSANDRA_DEFAULT_DC=DC1
+
+# Value to be used as the default RACK name
+CASSANDRA_DEFAULT_RACK=RAC1
+
+```
+
+### Other instances of Cassandra on Mesos
+
+Cassandra on Mesos is informed of other Cassandra on Mesos instances running in other Mesos clusters by
+environment variables in the format `CASSANDRA_EXTERNAL_DC_<dcName>=<cassandraOnMesosUrl>`.
+
+## Example on Mesos
+
+In this example, three datacenters dc0, dc1, dc2 are running three different Mesos clusters.
+
+The following configuration would be used for each instance of Cassandra on Mesos:
+
+##### dc0
+```
+CASSANDRA_CLUSTER_NAME=multi-dc
+CASSANDRA_DEFAULT_DC=dc0
+CASSANDRA_EXTERNAL_DC_dc1=http://multi-dc.cassandra.marathon.mesos1:10001
+CASSANDRA_EXTERNAL_DC_dc2=http://multi-dc.cassandra.marathon.mesos2:10002
+```
+
+##### dc1
+```
+CASSANDRA_CLUSTER_NAME=multi-dc
+CASSANDRA_DEFAULT_DC=dc1
+CASSANDRA_EXTERNAL_DC_dc0=http://multi-dc.cassandra.marathon.mesos0:10000
+CASSANDRA_EXTERNAL_DC_dc2=http://multi-dc.cassandra.marathon.mesos2:10002
+```
+
+##### dc2
+```
+CASSANDRA_CLUSTER_NAME=multi-dc
+CASSANDRA_DEFAULT_DC=dc2
+CASSANDRA_EXTERNAL_DC_dc0=http://multi-dc.cassandra.marathon.mesos0:10000
+CASSANDRA_EXTERNAL_DC_dc1=http://multi-dc.cassandra.marathon.mesos1:10001
+```
+
+1. Ensure there are TCP routes allowing for traffic flow between each of the Mesos clusters.
+2. Start each cluster with the necessary configuration.
+3. Wait for each cluster to allocate its seed nodes.
+4. After the seeds have been allocated, restart all of the nodes that have already been started. Send a `POST` to the http API at `/cluster/rolling-restart/start` and the framework will restart each of the nodes so that the new seed set will take effect.
+
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Your clusters should now be able to replicate data between each other.
+
+## Example on DCOS
+
+In this example, three datacenters dcos0, dcos1, dcos2 are running three different DCOS clusters.
+
+To install each instance of Cassandra on DCOS using the DCOS CLI:
+
+1. On DCOS Cluster 0, install with `dcos package install cassandra --options=dcos0.json`
+
+    ```json
+    {
+      "cassandra": {
+        "cluster-name": "multi-dc",
+        "resources": {
+          "cpus": 1.0,
+          "mem": 2048,
+          "disk": 6144
+        },
+        "dc": {
+          "default-dc": "dcos0",
+          "default-rack": "rack0",
+          "external-dcs": [
+            {
+              "name": "dcos1",
+              "url": "http://dcos1/service/cassandra.multi-dc"
+            },
+            {
+              "name": "dcos2",
+              "url": "http://dcos2/service/cassandra.multi-dc"
+            }
+          ]
+        }
+      }
+    }
+    ```
+
+2. On DCOS Cluster 1, install with `dcos package install cassandra --options=dcos1.json`
+
+    ```json
+    {
+      "cassandra": {
+        "cluster-name": "multi-dc",
+        "resources": {
+          "cpus": 1.0,
+          "mem": 2048,
+          "disk": 6144
+        },
+        "dc": {
+          "default-dc": "dcos1",
+          "default-rack": "rack1",
+          "external-dcs": [
+            {
+              "name": "dcos0",
+              "url": "http://dcos0/service/cassandra.multi-dc"
+            },
+            {
+              "name": "dcos2",
+              "url": "http://dcos2/service/cassandra.multi-dc"
+            }
+          ]
+        }
+      }
+    }
+    ```
+
+3. On DCOS Cluster 2 install with `dcos package install cassandra --options=dcos2.json`
+
+    ```json
+    {
+      "cassandra": {
+        "cluster-name": "multi-dc",
+        "resources": {
+          "cpus": 1.0,
+          "mem": 2048,
+          "disk": 6144
+        },
+        "dc": {
+          "default-dc": "dcos2",
+          "default-rack": "rack2",
+          "external-dcs": [
+            {
+              "name": "dcos0",
+              "url": "http://dcos0/service/cassandra.multi-dc"
+            },
+            {
+              "name": "dcos1",
+              "url": "http://dcos1/service/cassandra.multi-dc"
+            }
+          ]
+        }
+      }
+    }
+    ```
+
+4. Wait for each cluster to allocate its seed nodes.
+5. After the seeds have been allocated, restart all of the nodes that have already been started. Send a `POST` to the http API at `/cluster/rolling-restart/start` and the framework will restart each of the nodes so that the new seed set will take effect.
+
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Your clusters should now be able to replicate data between each other.
diff --git a/docs/index.md b/docs/index.md
@@ -94,15 +94,14 @@ The Custom Mesos Executor will be responsible for providing a high-fidelity mean
 #### Nodes
 1. Static Port configuration for all ports listed in [10](#resources) below
 
-## Out of Scope for Version 0.1.0
+## Out of Scope for Version 0.2.0
 
 * Support for reducing the size of a ring
 * Data backup
 * Automatic Upgrades
 * Auto-scaling
 * Performance Optimizations
 * Dynamic Ports
-* Multi-DataCenter support
 * Support vertically scaling nodes (increase RAM or CPU resources for a node)
   * Depends on MESOS-1279 [[6]](#resources)
 * Automatically scheduled `nodetool cleanup`