6 Managing Origin-Server Pools

An origin server is a back-end server to which Oracle Traffic Director forwards requests that it receives from clients, and from which it receives responses to client requests. The origin servers could, for example, be Oracle WebLogic Server instances or Oracle iPlanet Web Server instances. A group of origin servers providing the same service or serving the same content is called an origin-server pool. You can define several such origin-server pools in a configuration, and then configure each virtual server in an Oracle Traffic Director instance to route client requests to a specific pool.

This chapter describes how to create and manage origin-server pools. It contains the following sections:

Creating an Origin-Server Pool

You can create an origin-server pool by using either the administration console or the CLI.

Note:

  • When you create an origin-server pool, you are, in effect, modifying a configuration. So for the settings of the new origin-server pool to take effect in the Oracle Traffic Director instances, you should redeploy the configuration as described in Deploying a Configuration.

  • The CLI examples in this section are shown in shell mode (tadm>). For information about invoking the CLI shell, see Accessing the Command-Line Interface.

  • Oracle Java Cloud Service creates the initial origin server pool when you create an Oracle Java Cloud Service instance with a load balancer or add a load balancer to an Oracle Java Cloud Service instance. You need to create an origin server pool only if you require additional origin server pools.

Before You Begin

Before you begin creating an origin-server pool, decide the following:

  • A unique name for the origin-server pool. Choose the name carefully; after creating an origin-server pool, you cannot change its name.

  • host:port combinations for the servers in the origin-server pool.

    Note:

    If the origin servers for which you want to create a pool are Oracle WebLogic Server managed servers in a cluster, it is sufficient to create the pool with any one of the managed servers as the origin server. You can then configure Oracle Traffic Director to discover the other managed servers in the pool dynamically. For more information, see Configuring an Oracle WebLogic Server Cluster as an Origin-Server Pool.

  • The communication protocol—HTTP, HTTPS or TCP—of the servers in the pool.

  • The address family that the servers in the origin-server pool use to listen for requests.

    The supported address families are:

Creating an Origin-Server Pool Using the Administration Console

To create an origin-server pool by using the administration console, do the following:

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

    A list of the available configurations is displayed.

  3. Select the configuration for which you want to create a virtual server.
  4. In the Common Tasks pane, click New Origin-Server Pool.

    The New Origin-Server Pool wizard starts.

    Figure 6-1 New Origin-Server Pool Wizard

    Description of Figure 6-1 follows
    Description of "Figure 6-1 New Origin-Server Pool Wizard"
  5. Follow the on-screen prompts to complete creation of the origin-server pool by using the details—name, load balancing method, origin servers, and so on—that you decided earlier.

    After the origin-server pool is created, the Results screen of the New Origin-Server Pool wizard displays a message confirming successful creation of the origin-server pool.

  6. Click Close on the Results screen.

    • The details of the origin-server pool that you just created are displayed on the Origin-Server Pools page.

    • 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 Deploying a Configuration.

Creating an Origin-Server Pool Using the CLI

To create an origin-server pool, run the create-origin-server-pool command.

For example, the following command creates an origin-server pool osp-soa containing two origin servers http://soa.example.com:1901 and http://soa.example.com:1902 in the configuration soa.

tadm> create-origin-server-pool --config=soa --type=http --origin-server=soa.example.com:1901,soa.example.com:1902 osp-soa
OTD-70201 Command 'create-origin-server-pool' 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 create-origin-server-pool, see the Oracle Traffic Director Command-Line Reference or run the command with the --help option.

Viewing a List of Origin-Server Pools

You can view a list of origin-server pools by using either the administration console or the CLI.

Note:

The CLI examples in this section are shown in shell mode (tadm>). For information about invoking the CLI shell, see Accessing the Command-Line Interface.

Viewing a List of Origin-Server Pools Using the Administration Console

To view a list of origin-server pools by using the administration console, do the following:

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

    A list of the available configurations is displayed.

  3. Select the configuration for which you want to view origin-server pools.
  4. In the navigation pane, select Origin-Server Pools.

    The Origin-Server Pools page is displayed. It shows a list of the origin-server pools defined for the configuration.

You can view the properties of an origin-server pool in detail by clicking on its name.

Viewing a List of Origin-Server Pools Using the CLI

To view a list of origin-server pools, run the list-origin-server-pools command, as shown in the following example:

tadm> list-origin-server-pools --config=soa --verbose --all
name            type            load-distribution
-------------------------------------------------
osp1            http            least-connection-count
osp2            http            round robin
osp3            https           least-connection-count

You can view the general properties and health-check settings of an origin-server pool by running the get-origin-server-pool-prop and get-health-check-prop command respectively.

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

Modifying an Origin-Server Pool

You can change the properties of an origin-server pool by using either the administration console or the CLI.

Note:

  • When you modify an origin-server pool, you are, in effect, modifying a configuration. So for the updated origin-server pool settings to take effect in the Oracle Traffic Director instances, you should redeploy the configuration as described in Deploying a Configuration.

  • The CLI examples in this section are shown in shell mode (tadm>). For information about invoking the CLI shell, see Accessing the Command-Line Interface.

Changing the Properties of an Origin-Server Pool Using the Administration Console

To change the properties of an origin-server pool by using the administration console, do the following:

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

    A list of the available configurations is displayed.

  3. Select the configuration for which you want to modify origin-server pools.
  4. In the navigation pane, select Server Pools.

    The Origin Server Pools page is displayed. It shows a list of the origin-server pools that are defined for the configuration.

  5. Click the name of the origin-server pool that you want to modify.

    The Origin Server Pool Settings page is displayed. On this page, you can do the following:

    • Change the network protocol—IPv4, IPv6, or SDP—for the servers in the pool.

    • Change the load-balancing method that Oracle Traffic Director should use to distribute client requests to the pool.

      • Least connection count (default): When processing a request, Oracle Traffic Director assesses the number of connections that are currently active for each origin server, and forwards the request to the origin server with the least number of active connections.

        The least connection count method works on the premise that origin servers that are faster have fewer active connections, and so can take on more load. To further adjust the load distribution based on the capacities of the origin servers, you can assign relative weights to the origin servers.

        Note:

        WebSocket connections affect the least connection count load balancing algorithm because WebSocket connections are potentially long lasting and will be counted as active connections until they are closed.

      • Least response time: Though least connection count works well on most workloads, there could be situations when the response time of origin servers in a given pool for the same amount of load could differ. For example:

        - When origin servers of a given pool are deployed on machines that differ in hardware specification.

        - When some origin server nodes are used for other services.

        - When network connectivity for different nodes is not uniform or some network interfaces are more loaded than others.

        Least response time is useful in such scenarios because it is a dynamic weighted least connection algorithm and it calculates weights based on the response time. These weights are continuously adjusted based on how the origin servers respond. Least response time helps you avoid manual tuning of weights in the least connection algorithm.

      • Round robin: Oracle Traffic Director forwards requests sequentially to the available origin servers—the first request to the first origin server in the pool, the second request to the next origin server, and so on. After it sends a request to the last origin server in the pool, it starts again with the first origin server.

        Though the round-robin method is simple, predictable, and low on processing overhead, it ignores differences in the origin servers' capabilities. So, over time, requests can accumulate at origin servers that are significantly slow. To overcome this problem, you can use a weighted round-robin method, by assigning relative weights to the origin servers.

      For more information about assigning weights to origin servers, see Modifying an Origin Server.

    • Configure health-check settings. For more information, see Configuring Health-Check Settings for Origin-Server Pools.

    • Specify whether Oracle Traffic Director should dynamically discover Oracle WebLogic Server managed servers in a cluster. For more information, see Configuring an Oracle WebLogic Server Cluster as an Origin-Server Pool.

    Note:

    You can add, modify, and remove origin servers in the pool, by selecting Origin Servers in the navigation pane. For more information, see Managing Origin Servers.

  6. 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.

  7. 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 Deploying a Configuration.

Changing the Properties of an Origin-Server Pool Using the CLI

  • To change the network protocol and load-balancing method for an origin-server pool, run the set-origin-server-pool-prop command.

    For example, the following command changes the load-balancing method for the origin-server pool osp1 in the configuration soa to the round-robin method.

    tadm> set-origin-server-pool-prop --config=soa --origin-server-pool=osp1 load-distribution=round-robin
OTD-70201 Command 'set-origin-server-pool-prop' ran successfully.

  • To change the health-check parameters for an origin-server pool, run the set-health-check-prop command.

    For example, the following command changes the health-check ping interval for servers in the origin-server pool osp1 of the configuration soa to 60 seconds.

    tadm> set-health-check-prop --config=soa --origin-server-pool=osp1 interval=60
OTD-70201 Command 'set-origin-server-pool-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 a list of the properties that you can set or change by using the set-origin-server-pool-prop and set-health-check-prop commands, see the Oracle Traffic Director Command-Line Reference or run the command with the --help option.

Deleting an Origin-Server Pool

You can delete an origin-server pool by using either the administration console or the CLI.

Note:

  • You cannot delete an origin-server pool that is associated with one or more routes in virtual servers.

    To delete an origin-server pool that is associated with routes, you must first delete the referring routes, as described in Configuring Routes.

  • When you delete 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 Deploying a Configuration.

  • The CLI examples in this section are shown in shell mode (tadm>). For information about invoking the CLI shell, see Accessing the Command-Line Interface.

Deleting an Origin-Server Pool Using the Administration Console

To delete an origin-server pool by using the administration console, do the following:

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

    A list of the available configurations is displayed.

  3. Select the configuration for which you want to delete origin-server pools.
  4. In the navigation pane, select Origin-Server Pools.

    The Origin-Server Pools page is displayed.

  5. Click the Delete icon for the origin-server pool that you want to delete.

    • If the origin-server pool is associated with one or more routes in virtual servers, a message is displayed indicating that you cannot delete the pool.

    • If the origin-server pool is not associated with any virtual server, a prompt to confirm the deletion is displayed.

  6. Click OK.

    A message is displayed in the Console Message pane confirming that the origin-server pool was deleted.

    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 Deploying a Configuration.

Deleting an Origin-Server Pool Using the CLI

To delete an origin-server pool, run the delete-origin-server-pool command, as shown in the following example:

tadm> delete-origin-server-pool --config=soa osp1
OTD-70201 Command 'delete-origin-server-pool' ran successfully.

Note:

If the specified origin-server pool is associated with one or more routes in virtual servers, the following error message is displayed:

OTD-67108 Cannot delete the origin-server pool. It is referred by virtual server(s): vs1_name,vs1_name,[...]

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 delete-origin-server-pool, see the Oracle Traffic Director Command-Line Reference or run the command with the --help option.

Configuring an Oracle WebLogic Server Cluster as an Origin-Server Pool

Note:

Oracle Traffic Director has built-in support for some common functionality offered by the WebLogic Server plug-in. Hence Oracle Traffic Director does not require any other plug-in to inter-operate with WebLogic Server.

If you want to create an origin-server pool that represents a cluster of Oracle WebLogic Server managed servers, you need not specify each managed server in the cluster as an origin server. It is sufficient to specify any one of the managed servers as the sole origin server in the pool. You can configure Oracle Traffic Director to discover the presence of other Oracle WebLogic Server instances in the cluster dynamically, and distribute client requests to the managed server that is configured as an origin server and to the dynamically discovered managed servers in the same cluster.

So when dynamic discovery is enabled, if any of the managed servers in the cluster is stopped, added, or removed, you need not update the definition of the origin-server pool. However, for detecting changes in the Oracle WebLogic Server cluster, Oracle Traffic Director sends health-check requests at a specified interval, which causes some overhead.

How Dynamic Discovery Works

When dynamic discovery is enabled for an origin-server pool, Oracle Traffic Director discovers the remaining Oracle WebLogic Server managed servers in the cluster, by doing the following:

  1. When an Oracle Traffic Director instance starts, it checks whether the origin servers specified in the pool are Oracle WebLogic Server managed servers and whether the servers belong to a cluster, by sending an HTTP health-check request to each configured origin server.

    The origin server's response indicates whether the server is an Oracle WebLogic Server managed server. If the origin server is an Oracle WebLogic Server managed server that belongs to a cluster, the response also includes a list of the managed servers in the cluster.

  2. Oracle Traffic Director uses the information in the response from the origin server to update the configuration with the discovered managed servers.

    The dynamically discovered origin servers inherit all of the properties—weight, maximum connections, and so on—that are specified for the configured origin server.

  3. Subsequently, at each health-check interval (default: 30 seconds) configured for the origin-server pool, Oracle Traffic Director attempts to detect changes in the cluster, by sending dynamic-discovery health-check requests to the Oracle WebLogic Server instances that are configured as origin servers in the pool.

    If the response indicates a change—removal or addition of a managed server—in the cluster since the previous health check, Oracle Traffic Director updates the configuration with the new set of dynamically discovered origin servers.

Note:

  • Dynamically discovered origin servers are not stored permanently in the origin-server pool definition of the instance's configuration. So when you restart an Oracle Traffic Director instance, the process of dynamic discovery starts afresh.

  • The HTTP request type that Oracle Traffic Director sends for dynamic discovery is the health-check request type that is currently configured for the origin-server pool—OPTIONS (default) or GET. For more information, see Configuring Health-Check Settings for Origin-Server Pools.

Enabling Dynamic Discovery

Oracle Java Cloud Service enables dynamic discovery for the initial origin server pool when you create an Oracle Java Cloud Service instance with a load balancer or add a load balancer to an Oracle Java Cloud Service instance.

If you create additional origin server pools, you must enable dynamic discovery for these origin server pools yourself. Dynamic discovery of Oracle WebLogic Server managed servers in a cluster is not enabled by default for any origin server pools that you add yourself. You can enable dynamic discovery by using either the administration console or the CLI.

Note:

  • When you modify an origin-server pool, you are, in effect, modifying a configuration. So for the updated origin-server pool settings to take effect in the Oracle Traffic Director instances, you should redeploy the configuration as described in Deploying a Configuration.

  • The CLI examples in this section are shown in shell mode (tadm>). For information about invoking the CLI shell, see Accessing the Command-Line Interface.

Enabling Dynamic Discovery Using the Administration Console

To enable dynamic discovery of WebLogic Server managed servers in a cluster by using the administration console, do the following:

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

    A list of the available configurations is displayed.

  3. Select the configuration for which you want to enable dynamic discovery.
  4. In the navigation pane, expand Server Pools and select the origin-server pool for which you want to enable dynamic discovery.

    The Server Pool Settings page is displayed.

  5. Go to the Advanced Settings section of the page.
  6. Under the Health Check subsection, make sure that the Protocol is HTTP, select the Dynamic Discovery check box.
  7. Click Save.

    Note:

    If the current health-check protocol is TCP, an error message is displayed indicating that the protocol must be changed to HTTP in order to enable dynamic discovery.

    A message is displayed in the Console Message pane confirming that the updated health-check settings were saved.

    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 Deploying a Configuration.

Enabling Dynamic Discovery Using the CLI

To enable dynamic discovery of Oracle WebLogic Server managed servers in a cluster, run the set-health-check-prop command.

For example, the following command enables dynamic discovery of managed servers in the Oracle WebLogic Server cluster that the wls-1 origin-server pool represents.

tadm> set-health-check-prop --config=soa.example.com --origin-server-pool=wls-1 dynamic-server-discovery=true
OTD-70201 Command 'set-health-check-prop' ran successfully.

Note:

If the current health-check protocol is TCP, an error message is displayed indicating that the protocol must be changed to HTTP in order to enable dynamic discovery.

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 set-health-check-prop, see the Oracle Traffic Director Command-Line Reference or run the command with the --help option.

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 Deploying a Configuration.

  • The CLI examples in this section are shown in shell mode (tadm>). For information about invoking the CLI shell, see 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:

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 6-1 lists the health-check settings that you can configure for each origin-server pool in a configuration.

Table 6-1 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:

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

    A list of the available configurations is displayed.

  3. Select the configuration for which you want to view or change origin-server health-check settings.
  4. 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.

  5. Click the name of the origin-server pool that you want to modify.

    The Server Pool Settings page is displayed.

  6. Go to the Advanced Settings section of the page.
  7. 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.

  8. 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 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.