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Welcome to Hoist

Hoist is a web application development toolkit developed by Extremely Heavy.

Hoist is designed as a "full stack" UI development framework, meaning that it has both server and client components that work together to provide an integrated set of tools and utilities for quickly constructing sophisticated front-end interfaces - or entire applications - with a strong focus on building for the enterprise.

The core technologies used are Java and its more dynamic cousin Groovy - via the mature Grails framework - and JavaScript - via React and associated libraries.

This repository is hoist-core, which is the server-side implementation of Hoist. It is designed to be used with hoist-react, our latest front-end toolkit. Hoist's original front-end implementation. See that repository for detailed information on Hoist's client-side features and conventions.

About this Doc

This readme is intended to provide a general orientation to the features provided by Hoist, notes on specific features and implementation details of particular interest, and direct links into the most relevant and commonly used source code classes and routines. We have aimed to make the code itself as clear, readable, and well-commented as possible, and we are working to ensure a consistent level of in-code documentation - especially at the class level and for essential public methods.

When calling out particular source code files in the tables below, the following icons are used as the links to the containing repository: ๐Ÿ— for this repo and โš› for hoist-react.

This document does not provide an overview or introduction to Grails, Java, or other core technologies in general, and assumes a general familiarity with many concepts related to enterprise web application development.

Core Features - Overview

Hoist grew out of our ongoing practice developing applications for enterprise clients - primarily in finance - that required multiple interrelated yet distinct applications that were:

  • Data-dense - able to load and visualize large amounts of data, with a focus on grids and charts
  • Consistent - with shared UI controls, coding patterns, and styles
  • User friendly - efficient and enjoyable to operate, even for demanding users
  • Highly maintainable - stable, with strong tooling for deployment and operational support

While there are clearly many application development libraries and frameworks, we required a toolkit that could pre-select a set of libraries and bring together higher-level services such as:

  • Application configuration and administration
  • Activity tracking and auditing
  • User management and pluggable authentication
  • User preferences
  • Status monitoring and health checks
  • Error reporting and feedback
  • Customized / wrapped components, including grids, charts, and dashboards
  • Shared and consistent formatters (dates/numbers) and styles

With Hoist, these features work together and build on each other. A simple utility method to make an Ajax request to the server can automatically decode a JSON response, save a tracking record of who made the call and how long it took, and clearly alert the user and/or app administrators if there was an error. A customized grid component can offer a full-featured UI for column selection, support filtering column choices based on user roles, and persist the user's choice of visible columns and sorting options as a preference that is maintained across browsing sessions and workstations.

Role of the Server

The primary focus of Hoist is on building user interfaces that sit in front of and display data from a variety of back-end sources and services already deployed within an enterprise. As such, much of the developer's interaction with Hoist is in the form of client-side JavaScript development.

Given this emphasis on the front-end, the role of the Grails server provided by hoist-core can be limited almost exclusively to providing the built-in infrastructure expected by the client-side toolkits - serving up and storing configuration, preference, tracking, and other related data. These tasks require a server capable of persisting data to a database - Grails supports a wide variety - and of securely processing requests and serializing data.

When it comes to fetching business data specific to an application, a Hoist JS app can talk to independent back-end systems directly via CORS or proxy arrangements. Indeed once an initial project setup is complete, a developer might never touch Java / Groovy code.

That said, Grails does provide a feature rich server layer with the full power of the Java ecosystem available for use. Roles played by the Hoist server commonly include:

  • Authenticating users, via a username/password lookup or single-sign-on/NTLM auth.
  • Serving as an intermediate layer between the JS client app and other back-end systems, parsing and validating queries, relaying them, and then potentially transforming, caching, or combining results.
  • Directly proxying requests to other HTTP-based services, avoiding the need for CORS.
  • Querying a SQL database or alternative data store such as Redis.
  • Listening on or fetching data from a message queue such as Kafka or RabbitMQ.
  • Sending email or instant message notifications.
  • Managing its business objects directly, providing all services required for a full-stack app.

Application Structure and Deployment

A Hoist app is structured primarily as a Grails 3.x application, with a file and directory layout that follows the Grails conventions. The Grails project offers extensive and well maintained documentation on the framework's features and configuration. This library - hoist-core - is packaged as a Grails plugin, and should be specified as such within the Grails app's build.gradle file, e.g.:

dependencies {
  ...  // standard Grails dependencies / plugins / app-specific libraries
  compile "io.xh:hoist-core:$hoistCoreVersion"`
}

This will add server-side support for Hoist's core back-end services, including a set of endpoints expected by the client-side toolkit implementations. Versioned and snapshot builds of Hoist are pushed to XH's maven repository, which must also be configured within build.gradle.

Grails applications are built via Gradle, a highly flexible and popular build tool. The result is a single WAR file which can be deployed via Apache Tomcat.

All client-side code is commonly maintained within the same repository, but within its own dedicated folder tree. For hoist-react applications, JS apps are built independently by Webpack and deployed via nginx. We recommend and provide standardized Docker containers to ship both sides of the application and tie them together in an integrated whole, with very minimal infrastructure requirements or dependencies. See the Hoist React readme for a detailed outline on the build and deploy process for React-based applications, including information on building the Grails server-side components outlined here.

Custom plugins for enterprise deployments

While Hoist Core and its associated client-side libraries provide a good deal of functionality on their own, we realize that enterprise clients will have configurations, authentication requirements, dependencies, data source definitions, and other reusable code constructs that are unique to their environment.

To support these needs while still encouraging maximum consistency across multiple applications, we can assist in creating and maintaining a custom plugin layer between Hoist and business applications.

Hoist usage, licensing, and support

Hoist is currently developed exclusively by Extremely Heavy and intended for use by XH and our client partners to develop enterprise web applications with XH's guidance and direction. That said, we have released the toolkit under the permissive and open Apache 2.0 license. This allows other developers, regardless of whether they are current XH clients or not, to checkout, use, modify, and otherwise explore Hoist and its source code. See this project's license file for the full license.

We have selected an open source license as part of our ongoing commitment to openness, transparency, and ease-of-use, and to clarify and emphasize the suitability of Hoist for use within a wide variety of enterprise software projects. Note, however, that we cannot at this time commit to any particular support or contribution model outside of our consulting work. But if you are interested in Hoist and/or think it might be helpful for a project, please don't hesitate to contact us!

Core Features - Additional Details

While this document does not aim to provide a definitive or complete guide to the components of the Hoist framework or its usage, several key features are called out with additional details below.

User Authentication / Authorization

Class/File Note Link
BaseAuthenticationService.groovy Abstract service each app must implement ๐Ÿ—
HoistUser.groovy Trait/interface for core user data ๐Ÿ—
IdentityService.groovy Server-side source of current user info ๐Ÿ—
Access.groovy Annotation for endpoint security ๐Ÿ—
IdentityService.js Hoist-React source of current user info โš›๏ธ

๐Ÿ‘ซ As organizations and applications will have a wide variety of requirements for authenticating and authorizing users, Hoist has a deliberately minimal interface in this regard. A primary requirement for applications is that they implement a Grails Service named AuthenticationService that extends Hoist's BaseAuthenticationService and implement its completeAuthentication() method.

Implementations of this method must lookup and/or create a User class which implements the HoistUser trait/interface. This specifies the core information Hoist expects to access for any logged in user. Applications can choose to enhance their own user class with any additional details, managed via the app or sourced from systems such as Active Directory / LDAP.

While not included in Hoist directly, NTLM / SSO can be supported via integration with the Jespa library, commonly done via a custom plugin.

Once authentication is complete, IdentityService is the primary server-side Service for getting a reference to the current user. Hoist's client side code calls a dedicated endpoint to verify and fetch core user info, making it easily available to the JS app via a corresponding JS service.

Roles and Access

๐Ÿ”’ A minimal structure is provided for application roles. The HoistUser trait defines an abstract getRoles() method that returns a Set<String> of role names. It is up to the application to determine how roles are resolved and what meaning they have in the context of the app, although Hoist does have an expectation that a "HOIST_ADMIN" role will be assigned to any administrators of the app. (This role is required to access the built-in Admin console and make calls to admin-only endpoints.)

Server-side endpoints (Controllers) can be restricted to users with a given role or roles via the @Access annotation, e.g. a controller that should be accessible only to users with an "EDITOR" role could be decorated as such:

@Access(['EDITOR'])
class ReportController extends BaseController {
    def saveReport(params) { ... }
}

The @AccessAll annotation allows any user access. A controller endpoint must be decorated with one or the other of these annotations or an exception will be thrown.

Impersonation

๐Ÿ˜Ž Administrators have access to an impersonation mode where they can "act as" another user in the context of the application. This process is managed by IdentityService, which exposes several public methods for entering and exiting impersonation mode. When active, IdentityService.getUser() will return the user being impersonated, while IdentityService.getAuthUser() will return the actual admin.

The client toolkits provide built-in UIs for administrators to enter and exit impersonation mode. Services such as activity tracking are aware of impersonation and will log activity done while impersonation is active with both the impersonated and real user.

Configuration

Class/File Note Link
AppConfig.groovy Domain object for config entries ๐Ÿ—
ConfigService.groovy Server-side source for configs ๐Ÿ—
ConfigService.js Hoist-React source for configs โš›๏ธ

๐Ÿ”ง The ability to store simple typed configuration values (string|int|long|double|bool|json|pwd) and manage / adjust them in a running application has proven to be an extremely useful core feature. AppConfig entries are stored in the UI server's database and referenced via a simple string name.

Configs can also be made available to client applications (or not) via a dedicated flag, where they can be referenced by JS code. The built-in Admin console provides a full UI for reviewing, updating, and organizing these entries.

๐Ÿ™ˆ A special pwd type allows passwords and other sensitive info to be stored in an encrypted form for use on the server, avoiding the need to save these common types of configuration to the database in plaintext. Note however that any developer can deliberately print the output of an encrypted config by logging the (unencrypted) output of configService.getPwd().

Required Configs

Hoist requires certain configuration entries to be defined and present for the application to initialize. Apps themselves might also have hard dependencies on configs. To help ensure these entries are in place and to aid in the spinning up of a new app with an empty database, the ConfigService.ensureRequiredConfigsCreated() method is available to verify and auto-create required configs. See Bootstrap.groovy in hoist-core for configs required at the Hoist level.

Preferences

Class/File Note Link
Preference.groovy Domain object for preference definition ๐Ÿ—
UserPreference.groovy Domain object for user-specific value ๐Ÿ—
PrefService.groovy Server-side pref management ๐Ÿ—
PrefService.js Hoist-React pref management โš›๏ธ

โญ Preferences provide a lightweight way to persist user-specific options and settings. Similar to AppConfigs, preferences offer several predefined data types (string|int|long|double|boolean|json) and are referenced by a string name property. Preferences are assigned a default value that is returned if a user does not yet have a specific value set. When a user preference is assigned via PrefService.setPreference() (or one of the typed setters) a UserPreference object is created and saved. Both objects can be managed via the built-in Admin console.

Preferences may generally be accessed and used on the server and client, although they are primarily a client-side tool. Preferences with the local flag set to true, however, have their user-specific values stored on the client (in local storage) and are not accessible on the server. This flag is designed for preferences that store things like layout or sizing information that are most appropriate to save in the context of a particular device or workstation.

Applications are encouraged to provide end-users with controls to reset their preferences should they wish to restore their profile to a default state. Server and client APIs exist to do such a thing - see PrefService.clearPreferences().

Required Preferences

As with configs (above) the PrefService.ensureRequiredPrefsCreated() method is available to verify and auto-create required preferences. See Bootstrap.groovy in hoist-core for prefs required at the Hoist level.

Activity Tracking and Client Error Reporting

Class/File Note Link
TrackLog.groovy Domain object for track entries ๐Ÿ—
ClientError.groovy Domain object for error reports ๐Ÿ—
Feedback.groovy Domain object for user feedback ๐Ÿ—
TrackService.groovy Server-side API to log activity ๐Ÿ—
TrackService.js Hoist-React API to log activity โš›๏ธ
ExceptionHandler.js Hoist-React API to track errors โš›๏ธ

๐Ÿ‘€ Knowing which users are visiting an app and tracking specific actions of interest is another common need for apps. Hoist includes an API for easily tracking activity for the current user, and the Admin console provides a UI for searching and reviewing activity. Hoist services track some activities automatically (e.g. impersonation), but it is primarily up to app developers to determine which activities are of interest for tracking.

In its simplest form, a tracking record is a string - e.g. "Viewed chart". Tracks can also be given a category for easier organization in the UI and a JSON map of data for additional details (i.e. to note query parameters. The TrackLog object stores this record along with a timestamp, the current user, and browser/device info.

On the client-side, a track() method is added to the Promise prototype to provide convenient tracking for asynchronous requests - e.g. tracking a particular API call. This method provides built-in timing of the call and saves as 'TrackLog.elapsed'.

Client Errors

๐Ÿ’ฅ The ClientError object provides a special variation on tracking to handle exception reports posted by the client applications. See ExceptionHandler.js for the hoist-react entry point to this service. Note that the ClientErrorService on the server fires an xhClientErrorReceived event, which is listened to be the related ClientErrorEmailService to automatically send error reports to the configured xhEmailSupport email address. Custom services can also listen to these events to e.g. send other notifications via instant message, or raise an issue in a ticketing system.

Feedback

๐Ÿ’ฌ A simple model is also included for collecting and storing feedback (in the form of simple messages) submitted by end-users directly from the application. A FeedbackService fires a similar event and is listened to by a built-in service that will email out report notifications.

Emailing

Class/File Note Link
EmailService.groovy Managed service for sending email ๐Ÿ—

๐Ÿ“ซ Hoist core provides EmailService to send mail from the server. This relies on the Grails mail plugin which must be configured with a suitable SMTP server within an app's application.groovy configuration file.

Several default AppConfigs are available to default the sender and provide filtering and override options for email, especially useful in dev/test scenarios where careful control of what emails are sent to which users is required.

Status Monitoring

Class/File Note Link
Monitor.groovy Domain object for monitor definitions ๐Ÿ—
MonitorResult.groovy In-memory object for monitor outcomes ๐Ÿ—
MonitoringService.groovy Service that coordinates monitor runs ๐Ÿ—

๐Ÿ‘๐Ÿ‘Ž Hoist provides an API and services for runtime monitoring of the application, with a deliberate focus on running application-specific checks that relate to the business logic and data sources specific to the app (as opposed to e.g. system or OS level monitoring of metrics like CPU or memory usage).

To use monitoring, applications must implement a MonitorDefinitionService (i.e. a standard Grails service with that name) that implements one or more monitoring methods of the form:

// Method signature
def customCheckName(MonitorResult result) {
    // Run any custom business logic here, setting properties on MonitorResult to record outcomes
}

// For example...
def activeTradeCount(MonitorResult result) {
    def trades = tradeReportingService.getActiveTrades()
    result.metric = trades.size()
}

def inventorAgeMs(MonitorResult result) {
    def rptDate = inventoryWatcher.getReport().asOfDate
    result.metric = System.currentTimeMillis() - rptDate.time
    result.message = "Latest inventory update: ${asOfDate}"
}

The names of these methods should match the code property of Monitor objects created and managed via the Admin console. These definition objects hold data-driven parameters to determine how monitor results are evaluated. The MonitorResult.status property is the outcome of a given monitor. While the app's MonitorDefinitionService can set this status directly on results within its methods, a more flexible and common pattern is to have the service set a metric instead - e.g. the number of rows returned by a query, or the age in seconds of a particular result set.

This metric can then be evaluated against data-driven parameters on the Monitor object to determine the status dynamically, allowing for runtime adjustments and tuning of the checks. The Hoist monitor runner will time all checks (and enforce a timeout) and catch any exceptions that might get thrown (marking the check as having failed and noting the exception on the result).

Monitor results can be viewed via the Admin console. The xhMonitorConfig and xhMonitorEmailRecipients configs control option for email-based alerting on monitor failures, including support for debouncing alerts. MonitoringService fires a server-side xhMonitorStatusReport event that can be picked up by other custom services for additional notifications.

๐Ÿ”ฎ Note an XH project is underway to provide a more general and cross-application implementation of this monitoring API for both Hoist and non-Hoist based applications.

Readme TODOs

๐Ÿšง The sections below are planned near-term additions to this readme, covering additional features and services provided by the framework.

  • Instance configuration
  • Environments (Grails vs. Hoist)
  • Base/Super classes
  • Development setup
  • Additional deployment info
  • Proxy Service
  • Logging levels and management

๐Ÿ™ Thanks for your patience, and for reading this far!


๐Ÿ“ซโ˜Ž๏ธ๐ŸŒŽ info@xh.io | https://xh.io/contact

Copyright ยฉ 2022 Extremely Heavy Industries Inc.