Category: software development

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APIs and applications

When I first started working on software applications nearly 2 decades ago, the norm was a user interface connecting to a db and presenting the end user with means to interact with the database. If I remember correctly the first application in the traditional client-server sense that I came across was Mailman. (Looks like the application is heavily rebranded and still around! ). The general idea was any software (desktop or web) can connect with a database using a database driver and work. Things have changed a lot and various API like techniques were introduced enabling faster development cycles and near infinite scalability.

Modern applications uses numerous methods to provide APIs. The shift from RPC, SOAP and even from REST is quite interesting. While RESTful APIs and techniques like OpenAPI specifications are still quite popular, we are moving away to more modern methods. Some ideas like using PostREST is around, GraphQL seems to be the most developer friendly mechanism available.

GraphQL

The GraphQL is a different approach and unlike a typical API, its more of a language that can query and end point. Behind the screens there can be a database and a service can run in-front of the db exposing a URL for querying various data points. Unlike traditional APIs provided by RESTful services etc, the GraphQL method needs just one end point and it can provide different types of responses based on the queries. In addition to this there are numerous advantage like the responses being typed.

Querying the Blockchain

The blockchain technology introduced by Bitcoin is now more than a decade old. But the blockchain implementations generally struggle with providing an easy way to query their blocks/data. Its quite normal to have traditional databases to hold much large amounts of data compared to blockchains but the databases always perform better when one attempt to query them.

Since its inherently difficult to query the blockchain (database), most projects provide means to stream data to a database. Applications often called as dApps essentially calls this “centralized” databases to understand the information on the blockchain. Modern blockchains like Ethereum, Polkadot etc has understood this problem and implemented interfaces to easily consume the data.


[ from: EIP-1767: GraphQL interface to Ethereum node data ]

Ethereum for example has introduced GraphQL support in addition to JSON RPC via EIP-1767. On Polkadot ecosystem there are multiple projects like Hydra, Subquery implementing indexing and exposing GraphQL end points.

In general the GraphQL solutions in the blockchain space looks as follows:

The Graph

The Graph Project, ie https://thegraph.com/en/ is attempt to build a SaaS product and attempt to bring in some level of decentralization via providing a method to run indexer nodes by multiple parties. They have a stacking system and people can run servers as indexers fetching and exposing GraphQL endpoints. While this might be interesting, I want to focus on the technical aspects.

The Graph project has implemented a “listener” to fetch data from various chains like Ethereum, Polkadot and others. This data is then pushed into a PostgreQL database. The team is using IPFS too, but just to store the schema and configuration files (looks like something done to justify the decentralization buzzword ?). The next step in the equation is a GraphQL server which exposes and end point for the external world.

The code for the indexer node is here https://github.com/graphprotocol/graph-node/tree/master/server/index-node

Browsing the code also gave insights to StreamingFast and firehose projects which used by the Graph Project. From a quick read, StreamingFast seems to be a protocol to read the blocks and pack them to into file like data structure and efficiently stream across the network. Looks like a fast and efficient method to stream the data from the chains to external databases.

Why use The Graph project ?

For aspiring blockchain projects to provide modern and easy methods for the dApp developers, getting associated with the project could be beneficial. Its definitely possible to self host a data ingestion tool to push the data into a database and then a software like Hansura to provide GraphQL. But being part of a project which aims at decentralizing the APIs can help in resilience and more visibility. There is some information here on on boarding https://thegraph.com/migration-incentive-program/ [Disclaimer: I am not a user or part of the graph project in anyway and this is not a recommendation to use the product, token or any of their programs ]

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I had https://pivpn.dev/ successfully running for a while withuot any issues. Then suddenly it stopped working. The configuration was never received on various devices. Unfortunately there was absolutely no information anywhere – no logs, search results returned big essays on OpenVPN.

There is a little handy command which can actually fix the issues in a moment.

Go to the VPN server and just run pivpn -d

Running the pivpn command with -d option fixes most of the issues.

Its diagnosis will be printed to the screen. 

=============================================
::::        Self check       ::::
:: [OK] IP forwarding is enabled
:: [OK] Ufw is enabled
:: [OK] Iptables MASQUERADE rule set
:: [OK] Ufw input rule set
:: [OK] Ufw forwarding rule set
:: [OK] OpenVPN is running
:: [OK] OpenVPN is enabled (it will automatically start on reboot)
:: [OK] OpenVPN is listening on port 1194/udp
=============================================
::::      Snippet of the server log      ::::
=============================================
::::        Debug complete       ::::
:::
::: Debug output completed above.
::: Copy saved to /tmp/debug.txt

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Code Reviews

Writing code is a tedious process as it involves many conditions. Often the programmers miss out scenarios which can result in bugs (rainy day scenarios). Another common scenario missed out is optimizing the code for space and time complexity (efficiency). The programmers will be busy trying to address the problem at hand and many a times they miss on optimizing.

When we have Peer code reviews, this can be improved. Having few issues with the code is fine but not having code reviews is not acceptable in any software development team.

Static Code Analysis

In simple terms this method is to assess the behavior of the code by performing lexical, syntax analysis as well as other advanced means. Control flow & Data flow analysis are also performed. Findbugs for Java is to a well established example.

Security considerations are one of the major aspects that static code analysis often targets. OWASP wiki entry on static code analysis is an excellent starting point to learn more.

Linting

Some of the basic static code analyzers are called Linters. Though there is no hard and fast rule to call a certain code analyzer as linting tool I think its safe to assume that the coding standard checkers can be called as a linting tool. The term is originated from a static code analyzer called “Lint”.

Code Review tools

The process of code review is quite tedious and as the complexity of the project increases, this gets tougher. There are numerous tools that helps developers to conduct effective code reviews. With the advent of Continuous Integration, its lot more easier to incorporate code review in an automated fashion. Once the automatic code review is done, its essential to report the issues in a easily addressable way.

New generation Project management and Source Control Management Software like Gitlab integrates automation of the review, CI and CD in an innovative manner.

A Gitlab repository which is a CI + CD back end for a Github project.

In addition to the modern all-in-one platforms, there are obviously tools like Reviewboard and others which is focused on the code review alone.

Review Board an excellent, dedicated code review tool.

Phabricator

Meet Phabricator – an excellent project management & source code management platform. The platform has a powerful CLI interface which makes it the swiss army knife of Software Development Process.

Well, I have not heard about it, who uses it ?

Honestly this is the most frequent comment I have heard about Phabricator. So here is a list of users:

  • Wikimedia Foundation – yea, that small website guys!
  • Facebook
  • Asana.com
  • Blender (https://developer.blender.org/)
  • KDE
  • then of-course, yours faithfully!

I rest my case.

In my opinion, Phabricator is the best project management and source hosting platform existing with its unique code review features, CLI tools etc. When it comes to CI and CD, phabricator is not the best and with tools like Gitlab and we just have to mirror Phabricator hosted repository and take care of the CI and CD. Needless to say, Phabricator also supports Subversion and Mercurial. Since they provide a powerful programmable API, it may be even possible to integrate with other code management solutions like Preforce.

Arcanist

This section is about arcanist & is intended for users who are new to it or know about it but haven’t set it up anytime.

Arcanist aka arc is the command line tool which is provided by Phabricator to help with code reviews, merging etc. In a nutshell, we can raise a code review, with pre-defined static code analysis and rules using this powerful tool.


There are four sections of this article:

  • What is it?
  • Which features can we use?
  • Why should we bother?
  • Quick start guide

What is it ?
Arcanist basically works on top of tools like Git, Differential, Linter etc and provides command line interface to them. It is a code review and revision management utility.

Which features can we use ?

  • lint
  • diff
  • land
  • anoid

Why Should we bother ?

Lint: Wouldn’t it be nice if someone could look into your code and point out syntax errors, wrong use of constructs, use of undeclared variable and many more ? It turns out that there are tools which do this exact work and are referred to as Lint. It also simplifies code review process for the reviewer as well as the author

Diff: Working on a project and not sure whether the changes made are ready to be pushed? This is where diff comes into play. If using Git, arc diff sends all commits in a range for review. By default, this range is 

git merge-base origin/master HEAD..HEAD

Land: If the review raised through gets accepted, then we use arc land to publish the changes.

Quick Start Guide

Supported on: Linux, Mac OS X, Windows, FreeBSD & there is a quick way to setup anywhere with NixOS.

The one liner install on macOS and Linuxes using the awesome Nix package manager :

sudo mkdir /nix ; sudo chown -R  $LOGNAME /nix; bash <(curl https://nixos.org/nix/install) ; nix-shell -p arcanist

The manual, old school, Installation:

  1. mkdir ~/phabricator && cd ~/phabricator
  2. git clone https://github.com/phacility/libphutil.git
  3. git clone https://github.com/phacility/arcanist.git
  4. Add ~/phabricator/arcanist/bin to your PATH environment variable

Example:
export PATH=”/home/user/phabricator/arcanist/bin:$PATH”

  1. Try typing ‘arc’, if it shows usage exception, then we are good so far.
  2. To set up tab completion add the following to you PATH environment variable source /path/to/arcanist/resources/shell/bash-completion
    Example:-
    source /home/user/phabricator/arcanist/resources/shell/bash-completion

Configuring arc for a project :

This section assumes that you have a Phabricator installation at https://phabricator.steem.io

  1. Goto project directory
  2. Create a file with name ‘.arcconfig’ (without quotes)
  3. Paste the following in the file.
    {"phabricator.uri" : "https://phabricator.steem.io"}
  4. Run
    arc install-certificate and follow the instructions.

The commands could be used in this sequence:


arc lint –> arc diff –> arc land

arc lint

Setting up lint :


1. Create a file with name ‘.arclint’ in project directory
2. Detailed documentation for setting up .arclint can be found here.

Example of .arclint file:-
{
“linters”: {
“lint”: {
“type”: “pep8”,
“include”: “(\.py$)”
}
}
}
“lint” –> this is a custom name given by you, it doesn’t affect anything.
“type” –> to specify the linter we would like to use.
“include” –> regex for the format of files to lint.
“exclude” –> can be used to exclude files matching include tag in specific directories.

arc diff

  • First time while using this command, it will ask for access token which can be obtained by following the instructions.
  • Specify Test plan, reviewers and proceed.
  • A review request can be updated any number of times before it has been reviewed or separate reviews can be raised using
    arc diff –create arc land
    Once a review gets accepted, the changes can be published using this command. It is the last step in the standard Differential pre-publish code review workflow. arc anoid

Extended read: arc tasks, arc browse.

Encouragement

The Phabricator command line tooling sounds little weird when we first read the documentation. But once you setup, which is very fast if you follow the documentation as it is, its very powerful. The tools are written in PHP7.X and don’t be concerned, its blazing fast. I have been extensively using it, even to review documents. ie, instead of Google Doc, Tracking via Mircorsoft word’s tracking etc.

A sample document under review.

Summary

As already mentioned, test-driven, peer-reviewed code is the only acceptable way to develop software. Code review tools like Phabricator’s inbuilt tools are highly recommended irrespective of the tooling, language that a developer is using.