I am looking for suggestion before I could plan / design an open source flutter package which enable developers to introduce distributed consensus to their application (basically a blockchain within mobile phones) along with their existing backend stack.
This package would work along with existing backend to generate identity, participate in validation of transaction, and store a copy of chain within their device. Later I am planning to use pluggable encryption based on developer’s need for enhanced security.
Keeping in mind of the best consensus as Practical Byzantine Fault Tolerant but PBFT/BFT has resource intensive PoW to do consensus which phones can't be, I am planning to implement PBFT based on technique explained in “Elastico” paper (review/summary is attached here [1]).
This is just an initial idea rolling in my mind for few hours now. I need to realise the feasibility this technique inside a mobile phone to form a network.
[1] https://muratbuffalo.blogspot.com/2018/03/paper-review-secure-sharding-protocol.html
Why do you want to build this
This package would help devs to integrate features of blockchain to their centralised app stack without rebuilding their backend. Talking about application part, consider situations which involve decision making and forming opinions, supply chain management, data provenance (integrating with IPFS)
Development of the plugin will take some real effort and time.
Not having done any serious feasibility study on the project but I believe this plugin will be useful for a longer run.
If there are some suggestions based on your experience in plugin development, pl share it here.
Related
THE CONTEXT:
I should develop a software to calculate billing for a lot of customers
The software should be used by different local administrations, each one with its own rules to calculate the billing to its citizens.
At first i've thought to a workflow engine in order to "design" different calculation flows and apply then to the customers.
In the past i had a little experience with a workflow manager product (i worked a little with IBM BPM) and i had a lot of difficult to debug what happens when something went wrong and i found a lot of performance issue (respect to a simple OOP software).
Maybe these difficulties went caused by my poor knowledge of the tool, or maybe IBM BPM is not as good as IBM says.
Anyway, respect to my objective (produce a custom billing, and make it as flexible as possible in therm of configuration and process) is a workflow engine a suitable product?
Any suggestion about tools, frameworks and above all how to approach the problem.
My initial idea of the architecture is to develop a main software in c# (where i'm more confident) and using a workflow engine (like JBpm) as a black box, invoking previously configured flows into the bpm.
I would recommend using Cadence Workflow for your use case. It records all events that are related to your workflow in an execution history. It makes troubleshooting of production issues very straightforward.
As workflow is essentially a program in Java (or Go) you have unlimited flexibility on implementation. The performance is also not an issue as Cadence was built from ground up for high scalability. It was tested to over hundred million open workflows and tens of thousands of events per second.
See the presentation that goes over Cadence programming model.
We're an SME with SAP implemented. We're trying to use the transactional data in SAP to build another system in PHP for our trucking division for graphical reports, etc. This is because we don't have in-house expertise ABAP development and any SAP modifications are expensive.
Presently, I've managed to achieve our objectives with read-only access to our Quality DB2 server and any writes go to another DB2 server. We've found the CPU usage on the SELECT statements to be acceptable and the user is granted access only to specific tables/views.
SAP's Quality DB2 -> PHP -> Different DB2 client
Would like your opinion on whether it is safe to read from production the same way? Implementing all of this again via the RFC connector seems very painful. Master-Slave config is an option for us but again will involve external consultancy.
EDIT
Forgot to mention that our SAP guys don't want to build even reports for another 6-months - they want to leave the system intact. Which is why we're building this in PHP on the top.
If you don't have ABAP expertise, get it - it's not that hard, and you'll get a lot of stuff "for granted" (as in "provided by the platform") that you'll have to implement manually otherwise - like user authentication and authority management and software logistics (moving stuff from the development to the production repository). See these articles for a short (although biased) introduction. If you still need an external PHP application, fine - but you really should give ABAP a try first. For web applications, you might want to look into Web Dynpro ABAP. Using the IGS built'in chart engine with the BusinessGraphics element, you'll get a ton of the most custom chart types for free. You can also integrate PDF forms created with Adobe Livecycle Designer.
Second, while "any SAP modifications are expensive" might be a good approach, what you're suggesting isn't a modification. That's add-on development, and it's neither expensive nor more complex than any other programming language and/or environment out there. If you can't or don't want to implement your own application entirely using the existing infrastructure, at least use a decent interface - web services, RFC, whatever. From an ABAP point of view, RFC is always the easiest option, but you can use SOAP or REST as well, although you'll have to implement the latter manually. It's not that hard either.
NEVER EVER access the SAP database directly. Just don't. You'll have to implement all the constraints like client dependency or checks for validity dates and cancellation flags for yourself - that's hardly less complex than writing a decent interface, and it's prone to break every time the structure is changed. And if at some point you need to read some of the more complex contents like long texts, you're screwed - period. Not to mention that most internal or external auditors (if that happens to be an issue with your company and/or legal requirements) don't like direct database access to a system as critical as this one, which again can cause lots of trouble from people you really don't want to mess with. It's just not worth it.
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We have written a software package for a particular niche industry. This package has been pretty successful, to the extent that we have signed up several different clients in the industry, who use us as a hosted solution provider, and many others are knocking on our doors. If we achieve the kind of success that we're aiming for, we will have literally hundreds of clients, each with their own web site hosted on our servers.
Trouble is, each client comes in with their own little customizations and tweaks that they need for their own local circumstances and conditions, often (but not always) based on local state or even county legislation or bureaucracy. So while probably 90-95% of the system is the same across all clients, we're going to have to build and support these little customizations.
Moreover, the system is still very much a work in progress. There are enhancements and bug fixes happening continually on the core system that need to be applied across all clients.
We are writing code in .NET (ASP, C#), MS-SQL 2005 is our DB server, and we're using SourceGear Vault as our source control system. I have worked with branching in Vault before, and it's great if you only need to keep 2 or 3 branches synchronized - but we're looking at maintaining hundreds of branches, which is just unthinkable.
My question is: How do you recommend we manage all this?
I expect answers will be addressing things like object architecture, web server architecture, source control management, developer teams etc. I have a few ideas of my own, but I have no real experience in managing something like this, and I'd really appreciate hearing from people who have done this sort of thing before.
Thanks!
I would recommend against maintaining separate code branches per customer. This is a nightmare to maintain working code against your Core.
I do recommend you do implement the Strategy Pattern and cover your "customer customizations" with automated tests (e.g. Unit & Functional) whenever you are changing your Core.
UPDATE:
I recommend that before you get too many customers, you need to establish a system of creating and updating each of their websites. How involved you get is going to be balanced by your current revenue stream of course, but you should have an end in mind.
For example, when you just signed up Customer X (hopefully all via the web), their website will be created in XX minutes and send the customer an email stating it's ready.
You definitely want to setup a Continuous Integration (CI) environment. TeamCity is a great tool, and free.
With this in place, you'll be able to check your updates in a staging environment and can then apply those patches across your production instances.
Bottom Line: Once you get over a handful of customers, you need to start thinking about automating your operations and your deployment as yet another application to itself.
UPDATE: This post highlights the negative effects of branching per customer.
Our software has very similar requirements and I've picked up a few things over the years.
First of all, such customizations will cost you both in the short and long-term. If you have control over it, place some checks and balances such that sales & marketing do not over-zealously sell customizations.
I agree with the other posters that say NOT to use source control to manage this. It should be built into the project architecture wherever possible. When I first began working for my current employer, source control was being used for this and it quickly became a nightmare.
We use a separate database for each client, mainly because for many of our clients, the law or the client themselves require it due to privacy concerns, etc...
I would say that the business logic differences have probably been the least difficult part of the experience for us (your mileage may vary depending on the nature of the customizations required). For us, most variations in business logic can be broken down into a set of configuration values which we store in an xml file that is modified upon deployment (if machine specific) or stored in a client-specific folder and kept in source control (explained below). The business logic obtains these values at runtime and adjusts its execution appropriately. You can use this in concert with various strategy and factory patterns as well -- config fields can contain names of strategies etc... . Also, unit testing can be used to verify that you haven't broken things for other clients when you make changes. Currently, adding most new clients to the system involves simply mixing/matching the appropriate config values (as far as business logic is concerned).
More of a problem for us is managing the content of the site itself including the pages/style sheets/text strings/images, all of which our clients often want customized. The current approach that I've taken for this is to create a folder tree for each client that mirrors the main site - this tree is rooted at a folder named "custom" that is located in the main site folder and deployed with the site. Content placed in the client-specific set of folders either overrides or merges with the default content (depending on file type). At runtime the correct file is chosen based on the current context (user, language, etc...). The site can be made to serve multiple clients this way. Efficiency may also be a concern - you can use caching, etc... to make it faster (I use a custom VirtualPathProvider). The largest problem we run into is the burden of visually testing all of these pages when we need to make changes. Basically, to be 100% sure you haven't broken something in a client's custom setup when you have changed a shared stylesheet, image, etc... you would have to visually inspect every single page after any significant design change. I've developed some "feel" over time as to what changes can be comfortably made without breaking things, but it's still not a foolproof system by any means.
In my case I also have no control other than offering my opinion over which visual/code customizations are sold so MANY more of them than I would like have been sold and implemented.
This is not something that you want to solve with source control management, but within the architecture of your application.
I would come up with some sort of plugin like architecture. Which plugins to use for which website would then become a configuration issue and not a source control issue.
This allows you to use branches, etc. for the stuff that they are intended for: parallel development of code between (or maybe even over) releases. Each plugin becomes a seperate project (or subproject) within your source code system. This also allows you to combine all plugins and your main application into one visual studio solution to help with dependency analisys etc.
Loosely coupling the various components in your application is the best way to go.
As mention before, source control does not sound like a good solution for your problem. To me it sounds that is better yo have a single code base using a multi-tenant architecture. This way you get a lot of benefits in terms of managing your application, load on the service, scalability, etc.
Our product using this approach and what we have is some (a lot) of core functionality that is the same for all clients, custom modules that are used by one or more clients and at the core a the "customization" is a simple workflow engine that uses different workflows for different clients, so each clients gets the core functionality, its own workflow(s) and some extended set of modules that are either client specific or generalized for more that one client.
Here's something to get you started on multi-tenancy architecture:
Multi-Tenant Data Architecture
SaaS database tenancy patterns
Without more info, such as types of client specific customization, one can only guess how deep or superficial the changes are. Some simple/standard approaches to consider:
If you can keep a central config specifying the uniqueness from client to client
If you can centralize the business rules to one class or group of classes
If you can store the business rules in the database and pull out based on client
If the business rules can all be DB/SQL based (each client having their own DB
Overall hard coding differences based on client name/id is very problematic, keeping different code bases per client is costly (think of the complete testing/retesting time required for the 90% that doesn't change)...I think more info is required to properly answer (give some specifics)
Layer the application. One of those layers contains customizations and should be able to be pulled out at any time without affect on the rest of the system. Application- and DB-level "triggers" (quoted because they may or many not employ actual DB triggers) that call customer-specific code or are parametrized with customer keys) are very helpful.
Core should never be customized, but you must layer it in somewhere, even if it is simplistic web filtering.
What we have is a a core datbase that has the functionality that all clients get. Then each client has a separate database that contains the customizations for that client. This is expensive in terms of maintenance. The other problem is that when two clients ask for a simliar functionality, it is often done differnetly by the two separate teams. There is currently little done to share custiomizations between clients and make common ones become part of the core application. Each client has their own application portal, so we don't have the worry about a change to one client affecting some other client.
Right now we are looking at changing to a process using a rules engine, but there is some concern that the perfomance won't be there for the number of records we need to be able to process. However, in your circumstances, this might be a viable alternative.
I've used some applications that offered the following customizations:
Web pages were configurable - we could drag fields out of view, position them where we wanted with our own name for the field label.
Add our own views or stored procedures and use them in: data grids (along with an update proc) and reports. Each client would need their own database.
Custom mapping of Excel files to import data into system.
Add our own calculated fields.
Ability to run custom scripts on forms during various events.
Identify our own custom fields.
If you clients are larger companies, you're almost going to need your own SDK, API's, etc.
What is the most typical structure of business where you want to develop several web services? Should one establish a company for each of them or keep under one? I would like to hear your experiences maintaining such situation, keeping in mind the global focus.
By far the two most critical sets of issues determining the answer to this question are legal and financial (including, but not mainly, accounting). So it's hard to see how this question fits with the intent of this site.
It is advised to provide more background information on the topic. Business plans for SaaS companies can range from large cloud computing service vendors (with integrated solutions) and up to business analytics providers targeting specific market niche.
Business is a bit like programming: Keep It Simple (Stupid). Do not create multiple companies, unless there is a good reason to do it.
If You Planning to use python, you can use Django to build saas application,
this video Build SaaS application in Python django will explain about getting started with Sass.
Thanks
Most of the work I do is with what could be considered enterprise Web applications. These projects have large budgets, longer timelines (from 3-12 months), and heavy customizations. Because as developers we have been touting the idea of the Web as the next desktop OS, customers are coming to expect the software running on this "new OS" to react the same as on the desktop. That includes easy to manage automatic upgrades. In other words, "An update is available. Do you want to upgrade?" Is this even a realistic expectation? Can anyone speak from experience on trying to implement this feature?
At my company we have enterprise installations ranging into the thousands of seats. If we implemented an auto-upgrade, our customers would mutiny!
Large installations have peculiar issues that don't apply to small ones. For example, with 2000 users (not all of whom are, let us say, the most sophisticated of tool users), tool-training is a big deal: training time, internal demos, internal process documents, etc.. They cannot unleash a new feature or UI change without a chance to understand how it fits in their process and therefore what their internal best practices are and how to communicate that to their users.
Also when applications fail, it's the internal IT team who are responsible. Therefore, they want time to install a new version in a test area, beat it up, and deploy on a Saturday only when they're good and ready.
I can see the value in making minor patches more easy to install, particularly when the patch is just for a bug-fix and not for anything that would require retraining, and if the admins still get final say over when it's installed. But even then, I don't believe anyone has ever asked for this! Whether because they don't want it or they are trained to not expect it, it doesn't seem worth it.
Well, it really depends on your business model but for a lot of applications the SaaS model can end up biting you. It's great for a lot of things but for some larger applications the users are not investing as significant amount up front and could possibly move to something else before you've made any money.
See
http://news.zdnet.com/2424-9595_22-218408.html
and here
http://www.25hoursaday.com/weblog/2008/07/21/SoftwareAsAServiceWhenYourBusinessModelBecomesAParadox.aspx
for more information
One of the primary reasons to implement an application as a web application is that you get automatic upgrades for free. Why would users be getting prompted for upgrades on a web app?
For Windows applications, the "update is available, do you want to upgrade?" functionality is provided by Microsoft using ClickOnce, which I have used in an enterprise environment successfully -- there are a few gotchas but for the most part it is a good way to manage automatic deployment and upgrade of Windows apps.
For mobile apps, you can also implement auto-upgrades, although it is a little trickier.
In any case, to answer your question in a broad sense, I don't know if it is expected that all enterprise apps should make upgrading easy, but it certainly is worth the money from an IT support standpoint to architect them to allow for easy upgrading.
If you're providing a hosted solution, I wouldn't bother. Let the upgrade happen silently (perhaps with a notice that you did it). If you're selling an application that's hosted on their servers, let the upgrade decision be made by a single owner, not every user of the app.