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Graceful shutdown of services

August 1, 2023
Contributed by: 
S

During scheduled network outages such as system upgrades or hardware maintenance, you may have to close or disable some services. You can later enable the service by using the “enable service <name> command.

To avoid disrupting established sessions, you can place a service in the Transition Out of Service (TROFS) state by doing one of the following:

  • Adding a TROFS code or string to the monitor—Configure the server to send a specific code or string in response to a monitor probe.
  • Explicitly disable the service and:
    • Set a delay (in seconds).
    • Enable graceful shutdown.

Adding a TROFS Code or String

If you bind only one monitor to a service, and the monitor is TROFS-enabled, it can place the service in the TROFS state on the basis of the server’s response to a monitor probe. This response is compared with the value in the trofsCode parameter for an HTTP monitor or the trofsString parameter for an HTTP-ECV or TCP-ECV monitor. If the code matches, the service is placed in the TROFS state. In this state, it continues to honor the persistent connections.

If multiple monitors are bound to a service, the effective state of the service is calculated on the basis of the state of all the monitors that are bound to the service. Upon receiving a TROFS response, the state of the TROFS-enabled monitor is considered as UP for the purpose of this calculation. For more information about how a NetScaler appliance designates a service as UP, see Setting a Threshold Value for the Monitors Bound to a Service.

Important:

  • You can bind multiple monitors to a service, but must not TROFS-enable more than one of them.
  • You can convert a TROFS-enabled monitor to a monitor that is not TROFS-enabled, but not vice versa.

To configure a TROFS code or string in a monitor by using the command line interface

At the command prompt, type one of the following commands:

add lb monitor <monitor-name> HTTP -trofsCode <respcode>

add lb monitor <monitor-name> HTTP-ECV  -trofsString <resp string>

add lb monitor <monitor-name> TCP-ECV  -trofsString <resp string>
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To modify the TROFS code or string by using the command line interface

At the command prompt, type one of the following commands:

set lb monitor <trofs monitorname> HTTP -trofscode <newcode>

set lb monitor <trofs monitorname> HTTP-ECV -trofsstring <new string>

set lb monitor <trofs monitorname> TCP-ECV -trofsstring <new string>
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Note: You can use the set command only if a TROFS-enabled monitor was added earlier. You cannot use this command to set the TROFS code or string for a monitor that is not TROFS-enabled.

To configure a TROFS code or string in a monitor by using the configuration utility

  1. Navigate to Traffic Management > Load Balancing > Monitors.
  2. On the Monitors pane, click Add, and do one of the following:
    • Select Type as HTTP, and specify a TROFS Code.
    • Select Type as HTTP-ECV or TCP-ECV, and specify a TROFS String.

Disabling a Service

Often, however, you cannot estimate the amount of time needed for all the connections to a service to complete the existing transactions. If a transaction is unfinished when the wait time expires, shutting down the service may result in data loss. In this case, you can specify graceful shutdown for the service, so that the service is disabled only when all the current active client connections are closed by either the server or the client. See the following table for behavior if you specify a wait time in addition to graceful shutdown.

Persistence is maintained according to the specified method even if you enable graceful shutdown. The system continues to serve all the persistent clients, including new connections from the clients, unless the service is marked DOWN during the graceful shutdown state as a result of the checks made by a monitor.

The following table describes the graceful shutdown options.

State Results
Graceful shutdown is enabled and a wait time is specified. Service is shut down after the last of the current active client connections is served, even if the wait time has not expired. The appliance checks the status of the connections once every second. If the wait time expires, any open sessions are closed.
Graceful shutdown is disabled and a wait time is specified. Service is shut down only after the wait time expires, even if all established connections are served before expiration.
Graceful shutdown is enabled and no wait time is specified. Service is shut down only after the last of the previously established connections is served, regardless of the time taken to serve the last connection.
Graceful shutdown is disabled and no wait time is specified. No graceful shutdown. Service is shut down immediately after the disable option is chosen or the disable command is issued. (The default wait time is zero seconds.)

To terminate existing connections when a service or a virtual server is marked DOWN, you can use the Down State Flush option. For more information, see Enabling Cleanup of Virtual Server Connections.

To configure graceful shutdown for a service by using the command line interface

At the command prompt, type the following commands to shut down a service gracefully and verify the configuration:

disable service <name> [<delay>] [-graceFul (YES|NO)]

show service <name>
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Example:

> disable service svc1 6000 -graceFul YES
Done
>show service svc1
svc1 (10.102.80.41:80) - HTTP
State: GOING OUT OF SERVICE (Graceful, Out Of Service in 5998 seconds)
Last state change was at Mon Nov 15 22:44:15 2010
Time since last state change: 0 days, 00:00:01.160
...
Down state flush: ENABLED

1 bound monitor:
1) Monitor Name: tcp-default
State: UP             Weight: 1
Probes: 13898    Failed [Total: 0 Current: 0]
Last response: Probe skipped - live traffic to service.
Response Time: N/A
Done

>show service svc1
svc1 (10.102.80.41:80) - HTTP
State: OUT OF SERVICE
Last state change was at Mon Nov 15 22:44:19 2010
Time since last state change: 0 days, 00:00:03.250
Down state flush: ENABLED

1 bound monitor:
1)  Monitor Name: tcp-default
State: UNKNOWN           Weight: 1
Probes: 13898    Failed [Total: 0 Current: 0]
Last response: Probe skipped - service state OFS.
Response Time: N/A
Done
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To configure graceful shutdown for a service by using the configuration utility

  1. Navigate to Traffic Management > Load Balancing > Services.
  2. Open the service, and from the Action list, click Disable. Enter a wait time, and select Graceful.
Graceful shutdown of services
August 1, 2023
Contributed by: 
S
August 1, 2023
Contributed by: 
S

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