# Containerized Squid on Container Optimized OS
This module manages a `cloud-config` configuration that starts a containerized [Squid](http://www.squid-cache.org/) proxy on Container Optimized OS. The default configuration creates a filtering proxy that only allows connection to a whitelisted set of domains.
The resulting `cloud-config` can be customized in a number of ways:
- a custom squid.conf configuration can be set using the `squid_config` variable
- additional files (e.g. additional acls) can be passed in via the `files` variable
- a completely custom `cloud-config` can be passed in via the `cloud_config` variable, and additional template variables can be passed in via `config_variables`
The default instance configuration inserts iptables rules to allow traffic on TCP port 3128. With the default `squid.conf`, deny rules take precedence over allow rules.
Logging and monitoring are enabled via the [Google Cloud Logging driver](https://docs.docker.com/config/containers/logging/gcplogs/) configured for the Squid container, and the [Node Problem Detector](https://cloud.google.com/container-optimized-os/docs/how-to/monitoring) service started by default on boot.
The module renders the generated cloud config in the `cloud_config` output, to be used in instances or instance templates via the `user-data` metadata.
For convenience during development or for simple use cases, the module can optionally manage a single instance via the `test_instance` variable. If the instance is not needed the `instance*tf` files can be safely removed. Refer to the [top-level README](../README.md) for more details on the included instance.
## Examples
### Default Squid configuration
This example will create a `cloud-config` that allows any client in the 10.0.0.0/8 CIDR to use the proxy to connect github.com or any subdomain of github.com.
```hcl
module "cos-squid" {
source = "./modules/cloud-config-container/squid"
whitelist = [".github.com"]
clients = ["10.0.0.0/8"]
}
# use it as metadata in a compute instance or template
resource "google_compute_instance" "default" {
metadata = {
user-data = module.cos-squid.cloud_config
}
```
### Test Squid instance
This example shows how to create the single instance optionally managed by the module, providing all required attributes in the `test_instance` variable. The instance is purposefully kept simple and should only be used in development, or when designing infrastructures.
```hcl
module "cos-squid" {
source = "./modules/cloud-config-container/squid"
whitelist = ["github.com"]
clients = ["10.0.0.0/8"]
test_instance = {
project_id = "my-project"
zone = "europe-west1-b"
name = "cos-squid"
type = "f1-micro"
network = "default"
subnetwork = "https://www.googleapis.com/compute/v1/projects/my-project/regions/europe-west1/subnetworks/my-subnet"
}
}
```
## Variables
| name | description | type | required | default |
|---|---|:---: |:---:|:---:|
| *allow* | List of domains Squid will allow connections to. | list(string)
| | []
|
| *clients* | List of CIDR ranges from which Squid will allow connections. | list(string)
| | []
|
| *cloud_config* | Cloud config template path. If null default will be used. | string
| | null
|
| *config_variables* | Additional variables used to render the cloud-config and Squid templates. | map(any)
| | {}
|
| *default_action* | Default action for domains not matching neither the allow or deny lists | string
| | ...
|
| *deny* | List of domains Squid will deny connections to. | list(string)
| | []
|
| *file_defaults* | Default owner and permissions for files. | object({...})
| | ...
|
| *files* | Map of extra files to create on the instance, path as key. Owner and permissions will use defaults if null. | map(object({...}))
| | {}
|
| *squid_config* | Squid configuration path, if null default will be used. | string
| | null
|
| *test_instance* | Test/development instance attributes, leave null to skip creation. | object({...})
| | null
|
| *test_instance_defaults* | Test/development instance defaults used for optional configuration. If image is null, COS stable will be used. | object({...})
| | ...
|
## Outputs
| name | description | sensitive |
|---|---|:---:|
| cloud_config | Rendered cloud-config file to be passed as user-data instance metadata. | |
| test_instance | Optional test instance name and address | |