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feat: add Nix Cache documentation to mkdocs and README
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‎nix/docs/README.md‎

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- **[Use direnv](./use-direnv.md)** - Development environment with direnv
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- **[Pre-commit Hooks](./pre-commit-hooks.md)** - Automatic formatting and code checks before commits
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- **[Nix Formatter](./nix-formatter.md)** - Code formatting with treefmt
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- **[Nix Cache](./nix-cache.md)** - Understanding and using the Nix binary cache system
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## Package Management
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‎nix/docs/nix-cache.md‎

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# Nix Cache Documentation
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This document explains the Nix binary cache system used in the Supabase PostgreSQL project to speed up builds and share pre-built artifacts.
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## What is the Nix Cache?
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The Nix cache is a binary cache that stores pre-built Nix packages, allowing developers to download pre-compiled artifacts instead of building them from source. This significantly speeds up development and CI builds.
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## Cache Configuration
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The project uses a custom Nix binary cache hosted on AWS S3:
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- **Cache URL**: `https://nix-postgres-artifacts.s3.amazonaws.com`
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- **Primary Cache**: `https://cache.nixos.org` (upstream Nix cache)
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- **Trusted Public Key**: `nix-postgres-artifacts:dGZlQOvKcNEjvT7QEAJbcV6b6uk7VF/hWMjhYleiaLI=%`
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## How It Works
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### 1. Cache Substituters
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The cache is configured with two substituters:
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```bash
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substituters = https://cache.nixos.org https://nix-postgres-artifacts.s3.amazonaws.com
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```
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This means Nix will:
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1. First check the upstream Nix cache (`cache.nixos.org`)
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2. Then check the Supabase-specific cache (`nix-postgres-artifacts.s3.amazonaws.com`)
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### 2. Trusted Public Keys
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```bash
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trusted-public-keys = nix-postgres-artifacts:dGZlQOvKcNEjvT7QEAJbcV6b6uk7VF/hWMjhYleiaLI=% cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
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```
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These keys ensure that only trusted, signed artifacts are downloaded from the caches.
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### 3. Post-Build Hook
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The cache includes a post-build hook that automatically uploads newly built packages to the cache:
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```bash
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post-build-hook = /etc/nix/upload-to-cache.sh
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```
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## Where Cache is Configured
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The cache configuration is duplicated across multiple files in the project:
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### CI/CD Workflows
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- `.github/workflows/nix-build.yml` - Main build workflow
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- `.github/workflows/ami-release-nix.yml` - AMI release workflow
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### Docker Images
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- `docker/nix/Dockerfile` - Nix Docker image
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- `Dockerfile-15`, `Dockerfile-17`, `Dockerfile-orioledb-17` - PostgreSQL Docker images
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### Provisioning Scripts
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- `scripts/nix-provision.sh` - Local provisioning
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- `ebssurrogate/scripts/qemu-bootstrap-nix.sh` - QEMU bootstrap
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- `ansible/files/admin_api_scripts/pg_upgrade_scripts/initiate.sh` - Upgrade scripts
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## Using the Cache Locally
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### Automatic Configuration
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The cache is automatically configured when you:
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1. **Enter the development shell**:
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```bash
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nix develop
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```
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2. **Run CI workflows** - Cache is configured automatically
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3. **Use Docker images** - Cache is pre-configured
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### Manual Configuration
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If you need to configure the cache manually, add these lines to your `~/.config/nix/nix.conf`:
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```bash
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substituters = https://cache.nixos.org https://nix-postgres-artifacts.s3.amazonaws.com
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trusted-public-keys = nix-postgres-artifacts:dGZlQOvKcNEjvT7QEAJbcV6b6uk7VF/hWMjhYleiaLI=% cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
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```
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### Verifying Cache Usage
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You can verify that the cache is working by checking the build logs:
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```bash
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# Look for cache hits in build output
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nix build .#psql_15/bin --verbose
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# Check cache status
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nix show-config | grep substituters
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```
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## Cache Benefits
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### For Developers
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- **Faster builds** - Pre-built packages download instead of compiling
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- **Consistent environments** - Same artifacts across different machines
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- **Reduced bandwidth** - Only download what's needed
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### For CI/CD
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- **Faster CI runs** - Builds complete in minutes instead of hours
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- **Reduced resource usage** - Less CPU and memory consumption
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- **Better reliability** - Fewer build failures due to compilation issues
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## Troubleshooting
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### Cache Not Working
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If you're not getting cache hits:
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1. **Check configuration**:
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```bash
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nix show-config | grep substituters
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```
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2. **Verify network access**:
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```bash
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curl -I https://nix-postgres-artifacts.s3.amazonaws.com
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```
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3. **Check trusted keys**:
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```bash
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nix show-config | grep trusted-public-keys
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```
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### Cache Misses
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If you're seeing cache misses for packages that should be cached:
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1. **Check if the package was recently built** - New packages may not be cached yet
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2. **Verify the package hash** - Different inputs produce different hashes
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3. **Check CI logs** - Ensure the post-build hook is working
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### Network Issues
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If you're having network issues with the cache:
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1. **Try the upstream cache only**:
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```bash
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nix build .#psql_15/bin --substituters https://cache.nixos.org
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```
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2. **Disable cache temporarily**:
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```bash
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nix build .#psql_15/bin --no-substituters
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```
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## Cache Management
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### Uploading to Cache
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The cache is automatically populated by:
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1. **CI builds** - GitHub Actions upload successful builds
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2. **Post-build hooks** - Automatic upload after local builds
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3. **Manual uploads** - Using `nix copy` command
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### Cache Contents
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The cache contains:
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- **PostgreSQL binaries** (15, 17, orioledb-17)
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- **Extension packages** (all 50+ extensions)
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- **Development tools** (build tools, test frameworks)
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- **Dependencies** (libraries, compilers, etc.)
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## Security
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The cache uses cryptographic signatures to ensure:
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- **Integrity** - Packages haven't been tampered with
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- **Authenticity** - Packages come from trusted sources
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- **Reproducibility** - Same inputs produce same outputs
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## Related Documentation
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- [Development Workflow](./development-workflow.md) - Complete development process
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- [Build PostgreSQL](./build-postgres.md) - Building PostgreSQL from source
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- [Nix Directory Structure](./nix-directory-structure.md) - Project structure overview
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## References
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- [Nix Binary Cache Documentation](https://nixos.org/manual/nix/stable/package-management/binary-cache.html)
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- [Nix Substituters](https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-substituters)
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- [Nix Trusted Public Keys](https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-trusted-public-keys)

‎nix/mkdocs.yml‎

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- Use direnv: use-direnv.md
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- Code Formatter: nix-formatter.md
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- Pre-commit Hooks: pre-commit-hooks.md
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- Nix Cache: nix-cache.md
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- Documentation: documentation.md
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- Package Management:
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- Adding New Packages: adding-new-package.md

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