DISCLAIMER: this is not an official Tweag I/O product.

Example deployment of Cloud Haskell app using NixOps

Install NixOps

You need the Nix package manager installed (see instructions here).

NixOps is installed with the following command:

nix-env -i nixops

Configure Virtualbox

For NixOps to work properly, Virtualbox needs to be configured to have a "host-only" network with a dhcp server. If this step is forgotten, NixOps will fail with a variety of terrifying error messages.

In Virtualbox go to File > Preferences > Network > Host-only Networks. Click the "Add" button. The "Host-only Networks" need to be named "vboxnet0" (if you already have a network named "vboxnet0" use it instead of creating a new one).

Click the "Edit" button, go to the DHCP Server tab. There enable the server. The default configuration works fine, but sometimes it isn't filled automatically. In that case here is said default

• Server address: 192.168.56.100 (in which case the IPv4 Address from the Adapter tab is 192.168.56.1).
• Server Mask: 255.255.255.0.
• Lower Address Bound: 192.168.56.101
• Upper Address Bound: 192.168.56.200

remark: there is also a command-line way, to be documented.

Deploy the cluster

Create the deployment with

nixops create config-nixops.nix -d test-dp

This does not build anything, it only creates a global name for the configuration file.

Build and deploy the VM cluster with:

nixops deploy -d test-dp

This command also makes an incremental update if the configuration or the source have changed.

Observe the trace

Log in to the helloworlder machine with

nixops ssh helloworlder -d test-dp

The traces are logged (with timestamps) in hwer.log in the home directory (of the helloworlder machine).

Turn the cluster off

The cluster can be turned off with

nixops stop -d test-dp

Alternatively, it can be torn down with

nixops destroy -d test-dp

After using nixops destroy the test-dp logical deployment still exists though every associated resource have been cleaned up. To completely remove it from NixOps memory use nixops delete -d test-dp.

Advanced

To hack around with GHCi:

nix-shell  # uses the shell.nix file
ghci

References

• Examples of https://nixos.org/nixops/manual and https://nixos.org/wiki/NixOS:extend_NixOS (for services config).