RGW Multisite

This document contains directions for configuring the RGW Multisite in ceph-ansible. Multisite replication can be configured either over multiple Ceph clusters or in a single Ceph cluster to isolate RGWs from each other.

The first two sections are refreshers on working with ansible inventory and RGW Multisite. The next 4 sections are instructions on deploying the following multisite scenarios:

• Scenario #1: Single Realm with Multiple Ceph Clusters
• Scenario #2: Single Ceph Cluster with Multiple Realms
• Scenario #3: Multiple Realms over Multiple Ceph Clusters
• Scenario #4: Multiple Realms over Multiple Ceph Clusters with Multiple Instances on a Host

Working with Ansible Inventory

If you are familiar with basic ansible terminology, working with inventory files, and variable precedence feel free to skip this section.

The Inventory File

ceph-ansible starts up all the different daemons in a Ceph cluster. Each daemon (osd.0, mon.1, rgw.a) is given a line in the inventory file. Each line is called a host in ansible. Each type of daemon (osd, mon, rgw, mgr, etc.) is given a group with its respective daemons in the ansible inventory file.

Here is an example of an inventory file (in .ini format) for a ceph cluster with 1 ceph-mgr, 4 rgws, 3 osds, and 2 mons:

[mgrs]
mgr-001 ansible_ssh_host=192.168.224.48 ansible_ssh_port=22

[rgws]
rgw-001 ansible_ssh_host=192.168.216.145 ansible_ssh_port=22 radosgw_address=192.168.216.145
rgw-002 ansible_ssh_host=192.168.215.178 ansible_ssh_port=22 radosgw_address=192.168.215.178

[osds]
osd-001 ansible_ssh_host=192.168.230.196 ansible_ssh_port=22
osd-002 ansible_ssh_host=192.168.226.21 ansible_ssh_port=22
osd-003 ansible_ssh_host=192.168.176.118 ansible_ssh_port=22

[mons]
mon-001 ansible_ssh_host=192.168.210.155 ansible_ssh_port=22 monitor_address=192.168.210.155
mon-002 ansible_ssh_host=192.168.179.111 ansible_ssh_port=22 monitor_address=192.168.179.111

Notice there are 4 groups defined here: mgrs, rgws, osds, mons. There is one host (mgr-001) in mgrs, 2 hosts (rgw-001, rgw-002) in rgws, 3 hosts (osd-001, osd-002, osd-003) in osds, and 2 hosts (mon-001, mon-002) in mons.

group_vars

In the ceph-ansible tree there is a directory called group_vars. This directory has a collection of .yml files for variables set for each of the groups. The rgw multisite specific variables are defined in all.yml. This file has variables that apply to all groups in the inventory. When a variable, for example if rgw_realm: usa, is set in group_vars/all.yml, usa will be the value for rgw_realm for all of the rgws.

host_vars

If you want to set any of the variables defined in group_vars for a specific host you have two options. One option is to edit the line in the inventory file for the host you want to configure. In the above inventory each mon and rgw has a host specific variable for its address.

The preferred option is to create a directory called host_vars at the root of the ceph-ansible tree. In host_vars/ there can be files with the same name as the host (ex: osd-001, mgr-001, rgw-001) that set variables for each host. The values for the variables set in host_vars have a higher precedence than the values in group_var.

Consider this the file host_vars/rgw-001:

rgw_realm: usa
rgw_zonegroup: alaska
rgw_zone: juneau

rgw_zonemaster: true
rgw_zonesecondary: false
system_access_key: alaskaaccesskey
system_secret_key: alaskasecretkey

Even if rgw_realm is set to france in group_vars/all.yml, rgw_realm will evaluate to usa for tasks run on rgw-001. This is because Ansible gives higher precedence to the values set in host_vars over group_vars.

For more information on working with inventory in Ansible please visit: https://docs.ansible.com/ansible/latest/user_guide/intro_inventory.html.

Brief Multisite Overview

RGW Multisite terminology

If you are familiar with RGW multisite in detail, feel free to skip this section.

Rados gateways (RGWs) in multisite replication are grouped into zones.

A group of 1 or more RGWs can be grouped into a zone.\ A group of 1 or more zones can be grouped into a zonegroup.\ A group of 1 or more zonegroups can be grouped into a realm.\ A Ceph cluster in multisite has 1 or more rgws that use the same backend OSDs.

There can be multiple clusters in one realm, multiple realms in a single cluster, or multiple realms over multiple clusters.

RGW Realms

A realm allows the RGWs inside of it to be independent and isolated from RGWs outside of the realm. A realm contains one or more zonegroups.

Realms can contain 1 or more clusters. There can also be more than 1 realm in a cluster.

RGW Zonegroups

Similar to zones a zonegroup can be either master zonegroup or a secondary zonegroup.

rgw_zonegroupmaster specifies whether the zonegroup will be the master zonegroup in a realm. There can only be one master zonegroup per realm. There can be any number of secondary zonegroups in a realm. Zonegroups that are not master must have rgw_zonegroupmaster set to false.

RGW Zones

A zone is a collection of RGW daemons. A zone can be either master zone or a secondary zone.

rgw_zonemaster specifies that the zone will be the master zone in a zonegroup. rgw_zonesecondary specifies that the zone will be a secondary zone in a zonegroup. Both rgw_zonemaster and rgw_zonesecondary need to be defined. They cannot have the same value.

A secondary zone pulls a realm in order to sync data to it.

Finally, The variable rgw_zone is set to "default" to enable compression for clusters configured without rgw multi-site. If multisite is configured rgw_zone should not be set to "default".

For more detail information on multisite please visit: https://docs.ceph.com/docs/master/radosgw/multisite/.

Deployment Scenario #1: Single Realm & Zonegroup with Multiple Ceph Clusters

Requirements

• At least 2 Ceph clusters
• 1 RGW per cluster
• Jewel or newer

Configuring the Master Zone in the Primary Cluster

This will setup a realm, master zonegroup and master zone in the Ceph cluster. Since there is only 1 realm, 1 zonegroup, and 1 zone for all the rgw hosts, only group_vars/all.yml needs to be edited for mulitsite conifguration. If there is one more that one rgw being deployed in this configuration, the rgw(s) will be added to the master zone.

1. Generate System Access and System Secret Keys

   bash echo system_access_key: $(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 20 | head -n 1) > multi-site-keys.txt echo system_secret_key: $(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 40 | head -n 1) >> multi-site-keys.txt

2. Edit group_vars/all.yml for the 1st cluster

   ```yaml rgw_multisite: true

   rgw_zone: juneau rgw_zonegroup: alaska rgw_realm: usa

   rgw_zonemaster: true rgw_zonesecondary: false

   rgw_zonegroupmaster: true

   rgw_multisite_proto: http rgw_zone_user: edward.lewis rgw_zone_user_display_name: "Edward Lewis"

   system_access_key: 6kWkikvapSnHyE22P7nO system_secret_key: MGecsMrWtKZgngOHZdrd6d3JxGO5CPWgT2lcnpSt ```

   Note: rgw_zonemaster should have the value of true and rgw_zonesecondary should be false. Both values always need to be defined when running multisite.

   Note: replace the system_access_key and system_secret_key values with the ones you generated.

3. Run the ceph-ansible playbook for the 1st cluster

Configuring the Secondary Zone in a Separate Cluster

This will setup a realm, master zonegroup and master zone in the secondary Ceph cluster. Since there is only 1 realm, 1 zonegroup, and 1 zone for all the rgw hosts, only group_vars/all.yml needs to be edited for mulitsite conifguration. If there is one more that one rgw being deployed in this configuration, the rgw(s) will be added to the secondary zone.

1. Edit group_vars/all.yml for the 2nd cluster

   ```yaml rgw_multisite: true

   rgw_zone: fairbanks rgw_zonegroup: alaska rgw_realm: usa

   rgw_zonemaster: false rgw_zonesecondary: true

   rgw_zonegroupmaster: true

   rgw_multisite_proto: http rgw_zone_user: edward.lewis rgw_zone_user_display_name: "Edward Lewis"

   system_access_key: 6kWkikvapSnHyE22P7nO system_secret_key: MGecsMrWtKZgngOHZdrd6d3JxGO5CPWgT2lcnpSt

   rgw_pull_proto: http rgw_pull_port: 8080 rgw_pullhost: rgw-001-hostname ```

   Note: rgw_zonemaster should have the value of false and rgw_zonesecondary should be true

   Note: The variables rgw_pull_port, rgw_pull_proto, rgw_pullhost, are joined together to make an endpoint string needed to create secondary zones. This endpoint is of one of the RGW endpoints in a master zone in the zonegroup and realm you want to create secondary zones in. This endpoint must be resolvable from the mons and rgws in the cluster the secondary zone(s) are being created in.

   Note: system_access_key, and system_secret_key should match what you used in the Primary Cluster

2. Run the ceph-ansible playbook on your 2nd cluster

Conclusion

You should now have a master zone on cluster0 and a secondary zone on cluster1 in an Active-Active mode.

Deployment Scenario #2: Single Ceph Cluster with Multiple Realms

Requirements

• Jewel or newer

Configuring Multiple Realms in a Single Cluster

This configuration will a single Ceph cluster with multiple realms. Each of the rgws in the inventory should have a file in host_vars where the realm, zone, and zonegroup can be set for the rgw along with other variables.

1. Generate System Access and System Secret Keys for each realm

   ```bash echo system_access_key: $(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 20 | head -n 1) > multi-site-keys-realm-1.txt echo system_secret_key: $(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 40 | head -n 1) >> multi-site-keys-realm-1.txt

   echo system_access_key: $(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 20 | head -n 1) > multi-site-keys-realm-2.txt echo system_secret_key: $(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 40 | head -n 1) >> multi-site-keys-realm-2.txt ```

2. Edit group_vars/all.yml for the cluster

   yaml rgw_multisite: true

   As previously learned, all values set here will be set on all rgw hosts. rgw_multisite be set to true for all rgw hosts so multisite playbooks can run on all rgws.

3. Create & edit files in host_vars/ to create realms, zonegroups, and master zones.

   Here is an example of the file host_vars/rgw-001 for the rgw-001 entry in the [rgws] section of for the example ansible inventory.

   yaml rgw_zonemaster: true rgw_zonesecondary: false rgw_zonegroupmaster: true rgw_multisite_proto: http rgw_realm: france rgw_zonegroup: idf rgw_zone: paris radosgw_address: "{{ _radosgw_address }}" radosgw_frontend_port: 8080 rgw_zone_user: jacques.chirac rgw_zone_user_display_name: "Jacques Chirac" system_access_key: P9Eb6S8XNyo4dtZZUUMy system_secret_key: qqHCUtfdNnpHq3PZRHW5un9l0bEBM812Uhow0XfB

   Here is an example of the file host_vars/rgw-002 for the rgw-002 entry in the [rgws] section of for the example ansible inventory.

   yaml rgw_zonemaster: true rgw_zonesecondary: false rgw_zonegroupmaster: true rgw_multisite_proto: http rgw_realm: usa rgw_zonegroup: alaska rgw_zone: juneau radosgw_address: "{{ _radosgw_address }}" radosgw_frontend_port: 8080 rgw_zone_user: edward.lewis rgw_zone_user_display_name: "Edward Lewis" system_access_key: yu17wkvAx3B8Wyn08XoF system_secret_key: 5YZfaSUPqxSNIkZQQA3lBZ495hnIV6k2HAz710BY

   Note: Since rgw_realm, rgw_zonegroup, and rgw_zone differ between files, a new realm, zonegroup, and master zone are created containing rgw-001 and rgw-002 respectively.

   Note: rgw_zonegroupmaster is set to true in each of the files since it will be the only zonegroup in each realm.

   Note: rgw_zonemaster should have the value of true and rgw_zonesecondary should be false.

   Note: replace the system_access_key and system_secret_key values with the ones you generated.

4. Run the ceph-ansible playbook on your cluster

Conclusion

The RGWs in the deployed cluster will be split up into 2 realms: france and usa. France has a zonegroup named idf and usa has one called alaska. Idf has a master zone called paris. Alaska has a master zone called juneau.

Deployment Scenario #3: Multiple Realms over Multiple Ceph Clusters

The multisite playbooks in ceph-ansible are flexible enough to create many realms, zonegroups, and zones that span many clusters.

A multisite configuration consisting of multiple realms across multiple clusters can be configured by having files in host_vars for the rgws in each cluster similar to scenario #2.

The host_vars for the rgws in the second cluster would have rgw_zonesecondary set to true and the additional rgw_pull variables as seen in scenario #2

The inventory for the rgws section of the master cluster for this example looks like:

[rgws]
rgw-001 ansible_ssh_host=192.168.216.145 ansible_ssh_port=22 radosgw_address=192.168.216.145
rgw-002 ansible_ssh_host=192.168.215.178 ansible_ssh_port=22 radosgw_address=192.168.215.178

The inventory for the rgws section of the secondary cluster for this example looks like:

[rgws]
rgw-003 ansible_ssh_host=192.168.215.178 ansible_ssh_port=22 radosgw_address=192.168.215.199
rgw-004 ansible_ssh_host=192.168.215.178 ansible_ssh_port=22 radosgw_address=192.168.194.109

Requirements

• At least 2 Ceph clusters
• at least 2 RGW in the master cluster and the secondary clusters
• Jewel or newer