You can ensure that your organization provides reliable services to your employees without downtime by using the high availability features that OpenText Cloud Bridge offers.
OpenText Cloud Bridge addresses both instance and site failover scenarios as follows:
Instance failover: If the hardware or container hosting the Agent fails, OpenText Cloud Bridge can immediately switch to another Agent instance with the same data center configuration that has access to the same data sources.
Site failover: If an entire data center location becomes inoperative due to a catastrophic event, OpenText Cloud Bridge can immediately switch to an Agent instance at another site that has access to the same data sources.
When you install an Agent, you specify the following properties. These properties are saved to the bridge-agent.yml configuration file for the Agent:
Instance ID - Specifies a unique identifier for that instance
Site Priority - Specifies the priority (Primary, Secondary, or Backup) of the site in relation to other data center sites
In the event of failure, all Agent instances within a Primary site take precedence over Agent instances with a Secondary site configuration, and the Secondary site instances take precedence over Agent instances with a Backup site configuration.
Instance Priority - Specifies the priority (Primary, Secondary, or Backup) of the instance in relation to other Agent instances
In the event of failure, all Agent instances (within the same site) with a Primary instance weight take precedence over Agent instances with a Secondary instance configuration, and the Secondary instances take precedence over Agent instances with a Backup instance configuration.
OpenText Cloud Bridge calculates the configured site priority and instance priority into a single weight value. When a shutdown takes place, whether planned or unplanned, OpenText Cloud Bridge uses a simple numerical comparison of the weight values from all active Agent instances to determine which Agent instance becomes the target Agent instance. OpenText Cloud Bridge fails over to the highest weighted instance that it finds. You can use any combination of weights you choose.
For a site, the weight values are as follows:
Primary = 30
Secondary = 20
Backup = 10
For an instance, the weight values are as follows:
Primary = 5
Secondary = 3
Backup = 1
So, for example, if you configured nine Agent instances in total, with a single Agent instance at each possible weight, failover would occur in the following order:
Table 2-2 Configuration Combinations
|
Order |
Site |
Instance |
Calculated haWeight Value |
|---|---|---|---|
|
1. |
Primary (30) |
Primary (5) |
35 |
|
2. |
Primary (30) |
Secondary (3) |
33 |
|
3. |
Primary (30) |
Backup (1) |
31 |
|
4. |
Secondary (20) |
Primary (5) |
25 |
|
5. |
Secondary (20) |
Secondary (3) |
23 |
|
6. |
Secondary (20) |
Backup (1) |
21 |
|
7. |
Backup (10) |
Primary (5) |
15 |
|
8. |
Backup (10) |
Secondary (3) |
13 |
|
9. |
Backup (10) |
Backup (1) |
11 |
NOTE:
OpenText Cloud Bridge does not prevent you from configuring multiple Agent instances with the same site and instance priority. For example, if you configure three Agent instances as Primary sites and instances, in a failover scenario the OpenText Cloud Bridge Client will select the first instance with that priority that it detects.
Secondary and Backup sites and instances provide additional layers for failover in larger environments, and you can have multiple sites and instances at each level if needed. However, you do not need to assign both Secondary and Backup site and instance roles if your organization does not need this level of complexity.
Each active OpenText™ Cloud Bridge Agent sends a heartbeat message when it starts up and every 30 seconds thereafter. The OpenText Cloud Bridge Client (“the Client”) monitors these heartbeats and is able to quickly detect an instance outage.
In a scenario where an administrator intentionally shuts down an Agent instance – for example, for maintenance or re-hosting – the Agent sends a heartbeat immediately to the OpenText Cloud Bridge Client. The Client immediately performs the necessary steps for failover to a new Agent target.
In an unplanned shutdown scenario where the target Agent instance is no longer able to communicate its heartbeat to the OpenText Cloud Bridge Client, the Client detects when a target Agent has not communicated within a configured timeframe (with a default of one minute). It then attempts to ping the Agent. If the ping attempt fails, the Client marks the target Agent as unresponsive and initiates the Agent target selection process.
Whether the shutdown was planned or unplanned, the following process takes place:
The OpenText™ Cloud Bridge Client selects a new target Agent from the current list of active Agent instances.
The Client sends a ping command to all Agent instances to inform them of the new Agent target selection.
The Client loads the current data source configurations into the new target Agent.
All data collection sessions that were active at the time of the shutdown fail, and new commands and collections are routed to the new target Agent.
If no active and initialized Agent is available, the Client marks the data center as unconnected and uninitialized. All command traffic that is sent to the data center receives an immediate no agent available error response.
If a non-target Agent instance is shut down, whether intentionally or not, the Client simply removes it from the list of active Agent instances.
OpenText Cloud Bridge uses initialization vectors (IVs) and keys to encrypt and decrypt data for protection of customer data and data source connection passwords stored in the Agent instances. For more information about initialization vectors, see TechTarget and Wikipedia.
Each Agent instance in your high availability environment must use the same encryption IV and Key values. Using the same values on all Agent instances ensures that no disruptions will occur during failovers.
If you create new encryption IV and Key values for the Agent configurations, the set of credentials for the Agents (which were encrypted using the older keys) become invalid. At that point you must reset the password values. The Agent console indicates which credential sets are invalid.
For information about how to set the same encryption IV and Key values on secondary and backup Agent instances after you have installed your primary Agent instances, see Installing Secondary and Backup Agent Instances.
The following are critical elements of successful configuration of the Agent high availability components:
Each Agent instance must have a unique Instance Id.
Each instance of the Agent configuration must use the same encryption IV and Key values. For more information, see Understanding Encryption IV and Key Values.
The set of data source credentials that are stored in the high availability Agent instances must be correct and consistent. After you have set up credentials for your first Agent, you can export and import credentials for the remaining Agents.
Each Agent instance must be configured with the appropriate instance and site priority so that failover occurs as expected. For more information, see Understanding High Availability in OpenText Cloud Bridge.
Before you begin preparing servers to install the OpenText Cloud Bridge Agent, you should determine the following:
If you have more than one data center, which one will be the primary site, and which ones will serve as secondary and backup sites in the event of catastrophic site failure
The number of Agent servers you plan to install in each data center
The priority (primary, secondary, or backup) of each Agent server you plan to install
The naming convention you will use to identify each Agent instance
As a best practice, create a spreadsheet similar to the following example to record your decisions. Ensure that you keep this document up to date as you make changes in your environment.
Table 2-3 High Availability Planning Spreadsheet
|
Data Center Site Name |
Site Priority |
Instance Id |
Instance Priority |
|---|---|---|---|
|
Houston data center |
Primary |
Hou_Instance_1 |
Primary |
|
|
Hou_Instance_2 |
Secondary |
|
|
Hou_Instance_3 |
Backup |
|
Provo data center |
Secondary |
Pro_Instance_1 |
Primary |
|
|
Pro_Instance_2 |
Secondary |
|
|
Pro_Instance_3 |
Backup |
|
Cambridge data center |
Backup |
Cam_Instance_1 |
Primary |
|
|
Cam_Instance_2 |
Secondary |
|
|
Cam_Instance_3 |
Backup |
If you plan to install multiple Agent instances for high availability, the most efficient method for you to set up your environment is as follows:
Install your first Agent instance, saving your encryption key and IV for reuse.
Install all subsequent Agent instances using the encryption key and IV that you copied from your first Agent instance.
Configure your first Agent instance with the credentials for all data sources you plan to use, then export those credentials to a file for reuse.
NOTE:OpenText recommends that you verify all data source credentials are correct before you export them for reuse.
Import the data source credentials to each secondary and backup instance one at a time.
For more information, see Section 3.0, Installing the OpenText Cloud Bridge Agent.