14.3 Configuring Health-Check Settings for Origin-Server Pools

To ensure that requests are distributed to only those origin servers that are available and can receive requests, Oracle Traffic Director monitors the availability and health of origin servers by sending health-check requests to all of the origin servers in a pool.

You can configure health-check parameters for an origin-server pool by using either the administration console or the CLI.

Note:

When you configure health-check settings for an origin-server pool, you are, in effect, modifying a configuration. So for the updated configuration to take effect in the Oracle Traffic Director instances, you should redeploy the configuration as described in Section 4.3, "Deploying a Configuration."
The CLI examples in this section are shown in shell mode (tadm>). For information about invoking the CLI shell, see Section 2.3.1, "Accessing the Command-Line Interface."

When Does Oracle Traffic Director Send Health-Check Requests?

When an Oracle Traffic Director instance starts, it performs an initial health check for all the origin servers in all of the configured origin-server pools.

If the initial health check indicates that an origin server is healthy, Oracle Traffic Director sends further health-check requests to an origin server only in the following situations:

The server has not served any request successfully for the entire duration of the previous health-check interval.
Dynamic discovery is enabled for this origin server pool. For more information, see Section 6.5, "Configuring an Oracle WebLogic Server Cluster as an Origin-Server Pool."

If a health check—either initial or subsequent—indicates that an origin server is not available, Oracle Traffic Director repeats the health check at the specified health-check interval.

Configurable Health-Check Settings

Table 14-1 lists the health-check settings that you can configure for each origin-server pool in a configuration.

Table 14-1 Health-Check Parameters

Parameter	Default Value
The type of connection—HTTP or TCP—that Oracle Traffic Director should attempt with the origin server to determine its health. TCP connection: Oracle Traffic Director attempts to open a TCP connection to each origin server. HTTP request: Oracle Traffic Director sends an HTTP GET or OPTIONS request to each origin server in the pool, and checks the response to determine the availability and health of the origin server. Note: If you want to enable dynamic discovery of Oracle WebLogic Server managed servers in a cluster, then the health-check connection type must be set to HTTP.	HTTP
The frequency at which health-check requests should be sent.	30 seconds
The duration after which a health-check request should be timed out if no response is received from the origin server.	5 seconds
The number of times that Oracle Traffic Director should attempt to connect to an origin server in the pool, before marking it as unavailable.	5
The HTTP request method—GET or OPTIONS—that should be sent.	OPTIONS
The URI that should be sent for HTTP requests.	/
The HTTP response codes that Oracle Traffic Director can accept as indicators of a healthy origin server. By default, Oracle Traffic Director accepts response codes from `1xx` to `4xx` as indicators of a healthy origin server.
For HTTP GET health-check requests, a regular expression for the response body that Oracle Traffic Director can accept as the indicator of a healthy origin server
For HTTP GET health-check requests, the maximum number of bytes in the response body that Oracle Traffic Director should consider when comparing the response body with the specified acceptable response body.	2048

When Is an Origin Server Considered Available and Healthy?

If the configured health-check connection type is TCP, an origin server is considered available if the connection is successfully established, indicating that the server is actively listening on its service port.

If the configured health-check connection type is HTTP, an origin server is considered available and health when all of the following conditions are fulfilled:

There is no error while sending the HTTP request.
The response is received before timeout period is reached.
The status code in the response matches any of the acceptable response codes, if specified.

By default, Oracle Traffic Director accepts response codes from 1xx to 4xx as indicators of a healthy origin server.
The response body matches the acceptable response body, if specified.

Configuring Health-Check Settings for Origin Servers Using the Administration Console

To view and change health-check settings origin servers in a pool by using the administration console, do the following:

Log in to the administration console, as described in Section 2.3.2, "Accessing the Administration Console."
Click the Configurations button that is situated at the upper left corner of the page.

A list of the available configurations is displayed.
Select the configuration for which you want to view or change origin-server health-check settings.
In the navigation pane, expand Origin-Server Pools, and select the origin-server pool for which you want to view or change health-check settings.

The Origin-Server Pools page is displayed. It shows a list of the origin-server pools that are defined for the configuration.
Click the name of the origin-server pool that you want to modify.

The Server Pool Settings page is displayed.
Go to the Advanced Settings section of the page.
Specify the parameters that you want to change.

On-screen help and prompts are provided for all of the parameters.

When you change the value in a field or tab out of a text field that you changed, the Save button near the upper right corner of the page is enabled.

At any time, you can discard the changes by clicking the Reset button.
After making the required changes, click Save.
- A message, confirming that the updated configuration was saved, is displayed in the Console Messages pane.
- In addition, the Deployment Pending message is displayed at the top of the main pane. You can either deploy the updated configuration immediately by clicking Deploy Changes, or you can do so later after making further changes as described in Section 4.3, "Deploying a Configuration."

Configuring Health-Check Settings for Origin Servers Using the CLI

To view the current health-check settings for an origin-server pool in a configuration, run the get-health-check-prop command, as shown in the following example:

tadm> get-health-check-prop --config=soa --origin-server-pool=osp1
response-body-match-size=2048
protocol=HTTP
interval=30
request-method=OPTIONS
failover-threshold=3
request-uri=/
dynamic-server-discovery=false
timeout=5

To change the health-check settings for an origin-server pool in a configuration, run the set-health-check-prop command.

For example, the following command changes the health-check interval to 60 seconds and the health-check timeout period to 10 seconds for the origin-server pool osp1 in the configuration soa.
```
tadm> set-health-check-prop --config=soa --origin-server-pool=osp1 interval=60 timeout=10
OTD-70201 Command 'set-health-check-prop' ran successfully.
```
For the updated configuration to take effect, you should deploy it to the Oracle Traffic Director instances by using the deploy-config command.

For more information about the commands mentioned in this section, see the Oracle Traffic Director Command-Line Reference or run the commands with the --help option.