Terminal Connection Pool

In many cases, using a connection pool in a Terminal-based project gives a big improvement in performance, as opening a session and, in many cases, logging into the Terminal is a time-consuming operation. For this reason, OpenLegacy allows the use of Connection Pools when creating such Terminal-based projects.

To achieve this functionality, the user will need to do the following:

First, we need to enable the pool in the project's configuration, this is done by adding the following properties to the YAML file located in the resource folder:

ol:
  h3270:
    project:
      h3270Pool:
        {sdk name}:        
          pool:
            enable: true
            maxSize: 5
            minSize: 1
            keepAliveInterval: 1000

Let’s take a minute to explain these properties:

enable - boolean - by default, the pool is not enabled. To enable it, we need to set the Enable flag to true
maxSize - int - the maximum number of allowed open sessions to the legacy
minSize - int - the minimum number of allowed open sessions to the legacy
keepAliveInterval - long - the amount of time between each keep-alive action

To meet the conditions above, every project must implement three methods:

Init Action- The actions taken once a new session is created, such as log in to the terminal.
Clean Up Action- The actions taken once the application returns a session into the pool, for example navigating back to the main menu screen.
Keep Alive Action - An action that keeps the session alive when the session is stored in the pool. This action is usually is very quick. If the application takes a session from the pool, the applicative action will wait for the Keep Alive Action to complete due to synchronization.

Following is a code snippet we created to show a basic implementation of such pool configurations:


@Setter
@Getter
@Slf4j
public class MfTerminalSessionActionsImpl implements TerminalPoolActions {
	TerminalAction initAction = (TerminalAction) (new MfTerminalSessionActionsImpl.InitDummyAction());
	TerminalAction cleanUpAction = (TerminalAction) (new CleanupDummyAction());
	TerminalAction keepAliveAction = (TerminalAction) (new MfTerminalSessionActionsImpl.KeepAliveDummyAction());

	static class CleanupDummyAction implements TerminalAction {
		@Override
		public void perform(TerminalSession session, Object entity, Object... keys) {
			log.info("performing clean up action");
			ScreenEntity screen = session.doAction(TerminalActions.escape());
			while (!(screen instanceof EmptyScreen)) {
				screen = session.doAction(TerminalActions.escape());
			}
			screen = session.doAction(TerminalActions.escape());
			EmptyScreen emptyScreen = (EmptyScreen) screen;
			
			emptyScreen.setInput("INQ1");
			session.doAction(TerminalActions.enter(), emptyScreen, LoansInquiry.class);
		}

		@Override
		public boolean isMacro() {
			return false;
		}

		@Override
		public String getAdditionalCommand() {
			return "";
		}
	}

	class InitDummyAction implements TerminalAction {
		@Override
		public void perform(TerminalSession session, Object entity, Object... keys) {
			log.info("performing init action");
			try {
				EmptyScreen emptyScreen = session.getEntity(EmptyScreen.class);
				emptyScreen.setInput("INQ1");
				session.doAction(TerminalActions.enter(), emptyScreen, LoansInquiry.class);
			} catch (Exception e) {
				ScreenEntity screen = session.doAction(TerminalActions.escape());
				while (!(screen instanceof EmptyScreen)) {
					screen = session.doAction(TerminalActions.escape());
				}
			}
		}

		@Override
		public boolean isMacro() {
			return false;
		}

		@Override
		public String getAdditionalCommand() {
			return "";
		}
	}

	class KeepAliveDummyAction implements TerminalAction {
		
		@Override
		public void perform(TerminalSession session, Object entity, Object... keys) {
			log.info("performing keep alive action");
			ScreenEntity screen = session.doAction(TerminalActions.escape());
			while (!(screen instanceof EmptyScreen)) {
				screen = session.doAction(TerminalActions.escape());
			}
			EmptyScreen emptyScreen = (EmptyScreen) screen;
			
			emptyScreen.setInput("INQ1");
			session.doAction(TerminalActions.enter(), emptyScreen, LoansInquiry.class);
		}

		@Override
		public boolean isMacro() {
			return false;
		}

		@Override
		public String getAdditionalCommand() {
			return "";
		}
	}
}

For Spring to load the pool implementation, you will need to register it as a Bean to your projects configuration class located at:

package com.h3270_pool.openlegacy.config;

named - {SDK Project name}Configuration.java

For example, in the attached project we called the pool implementation class MfTerminalSessionActionsImpl, and the SDK name h3270Pool, this resulted with:

Attached below are sample API and SDK projects implementing the pool

To test them, you run the API* and execute one call, then you will be able to see in the logs that the pool actions are being executed as expected

*To run the API please add your OpenLegacy License string to the API YAML.