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Prior concept Concept Module downloader updater 

Referenced implementation External module management support

Related concept Components in Magnolia  # Magnolia Startup and Shutdown sequence

Introduction

With the same philosophy as the prior concept, rationale and goals are not listed here but the design and implementation will be mentioned to align with Magnolia 5.6. Also over long time usage, customers having more and more demand on start / stop / install / uninstall a module, the needs has been increased while the technology has been updated. This allow us to easier achieve this goal in comparison to previous versions.

An overview of implementation looks like below:

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Most of the design and implementation focused in ModuleManager where Magnolia control its modules and components. Let's start with an easiest function uninstalling a module design.

...

The configuration point for this is within 'magnolia.properties' file with below default value:

Start / stop module

With traditional Mangolia Magnolia modules, we didn't really put our attentions to Module lifecycle management which means we didn't really implemented module 'start' and 'stop' function. However it is fully supported and in some cases, customers might want to implement them to support them persist of their critical information. Currently the start and stop just call corresponding functions of the modules.

Remember to store persistence config when module manager stop all modules before system shutdown.

Now let's go the difficult part - change module manager to support installing a new module on the fly.

Installing a module

Design

TO BE IMPROVED:

• consider whether not providing restart actions instead of start/stop. As stopping some module might mean that system will not work correctly and module "downtime" should be minimized.
• and last but not least consider that on restart (or stop) you should restart (or stop) all modules that have declared dependency on given module in a cascade.

Installing a module

Design

In order to support external module installationIn order to support external module installation, we need to refactor the whole Magnolia module installation, bootstrap, start and components loading process. This is so risky that we need to carefully test the solution before actually apply it. One of the most important requirement is backward compatibility when chaning this kind of thing. Just a note that previously we do the module installation in Magnolia startup process in bunch, which means the startup would take care of all modules installation at a time, now we broke it down into pieces to control, manage and also support installing external modules on the fly. This require us to have a mechanism to support loading external jars, persist those jars classpath and things like that for later start up. Also dependency checking has been by pass as an end user must control his / her external module dependency and install them sequentially.

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To implement this, we need to break out and refactor module manager in below detail. Example file for reference: ModuleManagerImplExt.java

External Jar file External Jar file loader support

This function get into consideration when we support dynamic loading of new jars file, instead of putting them within WEB-INF/lib so that any Application server such as Tomcat can load it automatically, we have to support dynamic jar file loading where-ever the file is located. Eventhough hacking directly to URLClassLoader is not recommended and will be deprecated soon, but this's the shortest path as of Magnolia 5.6 release.

    public void loadJar(File jar2load) {
        try (JarFile jarFile = new JarFile(jar2load)) {
            Enumeration<JarEntry> e = jarFile.entries();
            
            URL url = jar2load.toURI().toURL();
            
            URLClassLoader cl = (URLClassLoader) this.getClass().getClassLoader();
            
            Method method = URLClassLoader.class.getDeclaredMethod("addURL", new Class[]{URL.class});
            method.setAccessible(true); //
            method.invoke(cl, new Object[]{url});
            
            while (e.hasMoreElements()) {
                JarEntry je = e.nextElement();
                if (je.isDirectory() || !je.getName().endsWith(".class")) {
                    continue;
                }
                // -6 because of .class
                String className = je.getName().substring(0, je.getName().length() - 6);
                className = className.replace('/', '.');
                Class<?> c = cl.loadClass(className);
                log.debug("Class loaded: {}", c.getName());
            }
        } catch (Exception e) {
            log.error("Jar file failed to load.");
            log.error(e.getMessage(), e);
        }
    }

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After successfully loaded module jar file into classpath, we use our existing provided BetwixtModuleDefinitionReader to read it properly

public ModuleDefinition loadModule(String moduleName) throws ModuleManagementException {
        String moduleDescriptorFile = "/META-INF/magnolia/" + moduleName + ".xml";
        BetwixtModuleDefinitionReader moduleReader = new BetwixtModuleDefinitionReader();
        return moduleReader.readFromResource(moduleDescriptorFile);
    }

...

Previously we supported this function as a batch runner which affect all every modules at a time, now we need to split it to run at each module level composition. Here are steps involved:

1. Get and register module version handler
2. Process version tasks

Load module repository

We also support refactor this batch effect operator to work on module level. Quite easy, looks like below:

    public void loadModuleRepository(ModuleDefinition def) {
        for (final RepositoryDefinition repDef : def.getRepositories()) {
            final String repositoryName = repDef.getName();
            final String nodetypeFile = repDef.getNodeTypeFile();
            final List<String> wsList = repDef.getWorkspaces();
            String[] workSpaces = wsList.toArray(new String[wsList.size()]);
            loadRepository(repositoryName, nodetypeFile, workSpaces);
        }
    }

...

MavenModuleDefinitionReader.java

A note on load repository on the fly

First we will need RepositoryDefinition from existing repository mapping

private info.magnolia.repository.definition.RepositoryDefinition getRepositoryMapping(String repositoryOrLogicalWorkspace) {

        if (!repositoryManager.hasRepository(repositoryOrLogicalWorkspace)) {

            WorkspaceMappingDefinition mapping = repositoryManager.getWorkspaceMapping(repositoryOrLogicalWorkspace);

            repositoryOrLogicalWorkspace = mapping != null ? mapping.getRepositoryName() : repositoryOrLogicalWorkspace;

        }

        return repositoryManager.getRepositoryDefinition(repositoryOrLogicalWorkspace);

    }

If it is null (doesn't exist before) then we'll create a new one.

Create a new repository definition on the fly

    final info.magnolia.repository.definition.RepositoryDefinition defaultRepositoryMapping = getRepositoryMapping(DEFAULT_REPOSITORY_NAME);
    final Map<String, String> defaultParameters = defaultRepositoryMapping.getParameters();

    rm = new info.magnolia.repository.definition.RepositoryDefinition();
    rm.setName(repositoryName);
    rm.setProvider(defaultRepositoryMapping.getProvider());
    rm.setLoadOnStartup(true);

    final Map<String, String> parameters = new HashMap<>();
    parameters.putAll(defaultParameters);

    // override changed parameters
    final String bindName = repositoryName + StringUtils.replace(defaultParameters.get("bindName"), "magnolia", "");
    final String repositoryHome = StringUtils.substringBeforeLast(defaultParameters.get("configFile"), "/") + "/" + repositoryName;

    parameters.put("repositoryHome", repositoryHome);
    parameters.put("bindName", bindName);
    parameters.put("customNodeTypes", nodeTypeFile);

    rm.setParameters(parameters);

    try {
        repositoryManager.loadRepository(rm);
    } catch (Exception e) {
        log.error(e.getMessage(), e);
    }

Then register nodetype

void registerNodeTypeFile(String repositoryName, String nodeTypeFile) {

        Provider provider = repositoryManager.getRepositoryProvider(repositoryName);

        try {

            provider.registerNodeTypes(nodeTypeFile);

        } catch (RepositoryException e) {

            log.error(e.getMessage(), e);

        }

    }

Load workspace

As simple as calling repositoryManager.loadWorkspace(repositoryName, workspace);

Module installation notes

Current status

Previously Magnolia crashed when failed to install any module. This has a reason and could not be easily fixed. However by refactoring module installation and startup now we can handle this. A note on module installation and startup is that if we failed on installing a root module which has few dependent modules, all dependent modules will be affected. In this context when we support end user to install their custom modules, this should not heavily affect Magnolia platform provided ones.

Implementation

Just prevent exception propagation by catch it here and by it pass to continue running:

    protected void installOrUpdateModule(ModuleAndDeltas moduleAndDeltas, InstallContextImpl ctx) {
        final ModuleDefinition moduleDef = moduleAndDeltas.getModule();
        final List<Delta> deltas = moduleAndDeltas.getDeltas();
        ctx.setCurrentModule(moduleDef);
        log.debug("Install/update for {} is starting: {}", moduleDef, moduleAndDeltas);
        // viet fix continue running after fail install
        try {
            applyDeltas(moduleDef, deltas, ctx);
        } catch (Exception e) {
            log.error("Install module {} failed {}.", moduleDef.getName(), e.getMessage(), e);
        }
        log.debug("Install/update for {} has finished", moduleDef, moduleAndDeltas);
    }

Verify the result

As a result you'll find this, which not block Magnolia from continue running (I've tried with Contacts module like below):

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