Postgres, as an App! (Now with one-click deploys to AWS + Heroku!)

Table of Contents

Me saying “use Postgres as an app” is fine, but without shipping anything it doesn't do anyone much good. So let's ship!

First, the code

Here's the GitHub repository complementing this blog post. Clone the repository, set up the system requirements, and follow the instructions in the README.


Alternatively, here's a 3-step process to try out this stack:

  1. Deploy the database stack to AWS using AWS CloudFormation in descending order:

    Stack Component CloudFormation template
    VPC (network layer) launch vpc
    RDS (origin data source) launch rds
    EBS (custom database data layer) launch ebs
    ECS (custom database compute layer) launch db
  2. Run through the “AWS Modeling” steps listed in the README in order to set up your SQL tables. This involves connecting to your RDS origin database and ECS custom database.

  3. After you've done that, deploy PostgREST to Heroku:

    Deploy

    Punch in values for DB_ANON_ROLE as your custom database username, DB_SCHEMA for your custom database schema (should just be public), and DB_URI for the custom database URI. Change POSTGREST_VER from 7.0.1 to 0.5.0.0.

    Then, open up your Heroku app, and go to $YOUR_APP_NAME/$YOUR_TABLE_NAME to see your table!


Local Modeling

Follow the instructions listed in the local setup. This should model the stack on your local computer using docker-compose.

The difficulty of synchronizing foreign tables surprised me. Foreign table references can vary in many different ways, since they remain arbitrary table definitions, and something like JDBC-based database synchronization isn't possible or if it is, isn't cheap. This blog post references a stored procedure that can pull in multiple tables by regex at a time. I haven't tried it myself, but this would be one option I'd like to try in production should the need arise. Combine that with a job scheduler, and you can run a batched synchronization process. I've saved a copy of the stored procedure here.

Remote Modeling on AWS

Follow the instructions listed in the AWS setup. This should model the stack on AWS using AWS CloudFormation, a cloud-native infrastructure-as-code tool. Keep in mind that you do need a valid AWS account for this step, and running this stack may cost money / credits (may not fall within AWS Free Tier usage). This stack also assumes free access to the Internet for downloading package archives and for accessing AWS.

I broke up this stack into multiple CloudFormation templates, because then each stack's lifecycle can be managed separately from one another. This can be especially important for databases, because you can tear down the database without deleting the underlying files. Whether those files are useful in a recovery situation is a separate discussion, but I wanted to be able to mount a volume on AWS like you can locally with Docker volumes. It might also minimize the amount of copying and pasting you need to do to run templates in different regions, without resorting to something like Pulumi.

Defining an AWS IAM user

AWS supports a complete identity and access management platform. The collection of roles, policies, and permissions keeps unwarranted behavior to a minimum, which is nice from a security and legal perspective.

I read Docker on AWS by Justin Menga a few months back, and he walks you through how to set up an IAM user to force multi-factor authentication when accessing AWS resources. I liked it enough to structure it as an AWS CloudFormation template. In practice, MFA may be annoying to use at times, and it grants IAM admin access (everything except billing) after MFA login, but I think it's a great first step towards further refining IAM policies.

I found password scripting for IAM users fairly tricky. I've created my own passwords and IAM rejected them as they did not follow AWS's default password policy, so now I use awscli and the aws secretsmanager command instead. This Stack Overflow answer provided some good insight to me with respect to what's appropriate for AWS, as the password policy appeared opaque to me. Keep in mind you can always change your password in the AWS console later and get clearer errors. Store passwords in a password manager like Bitwarden for ease of access later on.

I've found this to be the only step I can't script, and / or don't feel comfortable scripting entirely, since you need to add some changes to your local system (i.e. it's not all changes to remote infrastructure), and since you need to use it in all other parts of your stack. You don't have to set up an IAM user, as long as you have access to the relevant AWS resources defined in these templates.

Configuring a VPC

AWS by default creates a VPC and two public subnets for your applications, and those are the ones used if you don't create your own VPC. If all services you're creating are accessible via Internet and need access to the Internet, this arrangement is perfectly fine.

I'm creating my own VPC here because in addition to learning how to do so, I'd like to add private subnets and a network address translation (NAT) gateway to this VPC, in order to secure the custom database while pulling down updates from package archives (i.e. running sudo apt-get -y update, which requires DNS resolution). I haven't done so, I acknowledge it's bad, but NAT gateways cost extra money to run and I'm pretty cost-constrained. Suffice to say a NAT would be the first thing on my todo list. Either that, or building a VM with no expectation of needing the Internet, and deploying said VM behind a private subnet without adding a NAT gateway.

I found this InfoQ article very useful on getting started with VPCs and CloudFormation.

Creating the RDS instance

It's a bit difficult to prototype using RDS because it takes some time for instances to start up and tear down, due to running backups and whatnot. That may be another reason why separating out various services into their own CloudFormation templates is a good idea, because faster deployment cycles means engineering is less of a bottleneck.

Since this is a proof of concept only, I templated this without usage of any private subnets, enabled access outside the VPC, and turned on global access to the instance via SSH. In production, you'd want to use private subnets and remove inbound rules except to allowlisted IPs.

If you log into the RDS instance, and try to create an unsupported extension, you can see how RDS locks down your data:

pgdb=> CREATE EXTENSION pg_cron;
ERROR:  Extension "pg_cron" is not supported by Amazon RDS
DETAIL:  Installing the extension "pg_cron" failed, because it is not on the list of extensions supported by Amazon RDS.
HINT:  Amazon RDS allows users with rds_superuser role to install supported extensions. See: SHOW rds.extensions;

If you didn't want to create the table by hand, you can also create an AWS Lambda custom resource in order to run a SQL file or script after RDS signals CloudFormation that the database is stood up. I didn't create the custom resource for this tutorial due to time and resource constraints.

Creating the EBS data layer

We can back our custom database deployment using AWS Elastic Block Store (EBS). I found this AWS article on deploying databases with ECS and EBS to be very useful when templating out this feature.

Creating the ECS compute node for custom Postgres / PostgREST

Now, we can stick on our compute node for our custom database, and our PostgREST proxy.

I'm using Docker and AWS ECS to deploy this stack. If you don't want to use Docker, you can define your own “automated machine image” using a tool like Packer, and deploy that AMI directly onto a VM, cutting Docker out of the process. That's honestly a safer way of doing things, since containers are meant to be created and terminated without notice, which may not be appropriate for databases. Might also be faster, as well, as ECS API calls are on top of EC2 API calls.

I'm using an EC2 autoscaling group, which from my understanding means the Docker containers for a given ECS cluster run on that EC2 node, and if additional load is detected, a new EC2 instance is created with that cluster replicated. If that is the case, it's kind of like a Kubernetes pod, without having to install Kubernetes.

I'm using Docker Hub for this example. Usually, I use AWS Elastic Container Registry (ECR) an alternative to Docker Hub. I typically use ECR over Docker Hub because of the unlimited private repositories you can create, and because you can template it easily with CloudFormation. I'm not using ECR for this tutorial because it isn't possible to fetch public Docker images from a private repository unless you add things like API Gateway + Lambda, which may be prone to breaking, and because building and uploading Docker images may work well with one-click deploys.

I wanted to integrate PostgREST with AWS ECS, but I ran into the problem of service discovery between interconnected containers. Apparently, containers from different task definitions have a hard time communicating with each other. There's ways around it, like AWS has a Route 53 DNS-based service discovery tool integrated with AWS Cloud Map, but that involves standing up your own DNS servers and that's where I drew the line in terms of scoping out this proof of concept.

What comes next?

  • Synchronize to Office 365 or Google Sheets: It's a lot easier to solve a technical problem than a cultural one (if a problem exists in the first place!), and so it is with people using Excel. You like your VBA macros, you keep your VBA macros. No need to learn SQL, no need to switch computers or operating systems or change your workflow in any way, because if it ain't broke fixing it costs money and might break more things. This company called Layer 2 creates codeless data integration tools between Microsoft products and SQL, and released a connector for SharePoint and Office 365 with Postgres. This other company called Seekwell does much the same thing (their pricing looks tantalizing for an indie SaaS company).

    I'm sure somebody would be able to build an executable to create a local server that does pretty much the same thing for on-prem Excel. Biggest problem might be something like navigating corporate firewalls.

  • Create your own Airtable: Slap on something like Grid.js or DataTables or Handsontable or PostGUI or really any of these plugins as a client, combine it with something like SQitch for a running log of framework-agonstic SQL migrations per table, and you have your own self-deployable version of Airtable, with open-source APIs at every layer (GUI, API, DB).

    Type the API response from each table on a per-column basis, in order to dispatch the correct React.js view component (Image, DatePicker, etc.) to render your data, and use a separate webapp backend in order to orchestrate file / object handling (e.g. image and file uploads go to S3, while storing the URI within Postgres). It should be reasonably easy to execute on; but as always, the hard part is doing it.

    I think this might be something I'd be interested in building out. I have this sleep log on Google Sheets where the y-axis range is bisected at midnight and upside down from what I want, and it's quite annoying. I wanted to get into Airtable a few years ago, but I didn't like the GUI…and the data lock-in is glaringly evident. In any case, it'd be great to offboard from Google. Apparently they do shenanigans like inserting a line break on carriage return based on the user agent of the browser.

  • Create your own Firebase: You can use your data management auth flow as a pass-through entity for cheap mobile and web clients, without needing any SDKs, if you don't need full-duplex realtime streaming protocols like WebSockets. You can also connect a webapp framework like Django to a specific Postgres schema, as per this Stack Overflow answer, and have apps within your master admin app, without the need to create / destroy individual Postgres databases. Sharding data onto new compute nodes, and scaling admin-related tasks such as data import/export, still remain unknowns to me.

    This is what I think Supabase aspires to be. It's also what TinyDev aspires to be, on a tiny scale.

  • Data-driven testing framework: I've mentioned data-driven testing before, but a platform like this one might just wrap everything in one go. Create your state tables, deduplicate inputs using an Alloy model or some other kind of formal reasoning metric, and then couple together input sets using a directed acyclic graph. I'm not sure if this is possible still, Postgres would have to expose its relational algebra as an API, but I think it's worth taking a stab at. If it is possible, this means you can integration test ETL tools like Airflow.

I'm sure there's other ideas I haven't thought of. The app possibilities are quite endless, as they are with anything. But this with kernel as the core of your stack, you can effectively communicate your work and results with non-technical stakeholders in a much more transparent manner.

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