distributor/docs/config.md

# Configuration Reference

## Config File Location

`distributor run --config <path>` loads the YAML config at the provided path.

If `--config` is omitted, `run` uses:

```text
/usr/local/etc/distributor/config.yml
```

Config parsing rejects unknown YAML fields. The executable backends are `local`, `ssh`, and `s3`.

## Minimal Local Config

```yaml
pipelines:
  - id: reports
    source:
      backend: local
      path: /var/spool/distributor/reports
    destinations:
      - id: archive
        backend: local
        path: /srv/reports/archive
```

This publishes source files only. It uses the default validation and transfer policies.

## Production-Oriented Local Config

```yaml
pipelines:
  - id: reports
    source:
      backend: local
      path: /var/spool/distributor/reports
    validation:
      on_digest_mismatch: fail
    destinations:
      - id: archive
        backend: local
        path: /srv/reports/archive
        publish:
          source: true
          html: false
        transfer:
          on_destination_same: skip
          on_destination_older: replace
          on_destination_newer: skip
          on_conflict: fail
```

## HTML Publication

To publish generated HTML from Markdown files:

```yaml
publish:
  source: false
  html: true
transform:
  markdown_to_html:
    enabled: true
    mode: sidecar
```

Sidecar generation writes `report.html` for `report.md`. It does not mutate the source bundle.

## Reference

Top level:

- `secrets.directory`: optional credential secrets directory.
- `pipelines`: required non-empty list.

Pipeline:

- `id`: required unique slug-like identifier.
- `source`: required backend config.
- `validation.on_digest_mismatch`: optional; defaults to `fail`; only `fail` is supported.
- `destinations`: required non-empty destination list.

Source backend:

- `backend`: required.
- `path`: required for `local` and `ssh`.
- `host`: required for `ssh`.
- `user`: optional for `ssh`; defaults to the current OS user when available.
- `port`: optional for `ssh`; defaults to `22`.
- `ssh_key_file`: optional for `ssh`.
- `known_hosts`: optional for `ssh`; defaults to the service user's OpenSSH `known_hosts` path when available.
- `host_key_policy`: optional for `ssh`; defaults to `accept-new`.
- `endpoint`: required for `s3`.
- `bucket`: required for `s3`.
- `prefix`: optional for `s3`; leading and trailing slashes are trimmed.
- `region`: optional for `s3`; defaults to `us-east-1`.
- `force_path_style`: optional for `s3`; defaults to `true`. Set `false` only for services that require virtual-host addressing.
- `credentials.access_key_id_env`: optional S3 credential environment variable name.
- `credentials.secret_access_key_env`: optional S3 credential environment variable name.

Destination:

- `id`: required unique slug-like identifier within the pipeline.
- Backend fields: same accepted shape as source backends, with destination fields at the destination level.
- `publish`: optional; defaults to source-only publication.
- `transform`: required only for generated HTML publication.
- `transfer`: optional; defaults described below.

Accepted backend names:

- `local`: executable; requires `path`.
- `ssh`: executable; requires `host` and `path`.
- `s3`: executable; requires `endpoint` and `bucket`.

## SSH Backend

SSH uses native SFTP. It can be used for sources, destinations, or both:

```yaml
backend: ssh
host: example.com
user: distributor
port: 2222
path: /remote/root
ssh_key_file: /home/distributor/.ssh/id_ed25519
known_hosts: /home/distributor/.ssh/known_hosts
host_key_policy: accept-new
```

Authentication uses SSH agent identities first when `SSH_AUTH_SOCK` is set, then `ssh_key_file` if configured. Password authentication in YAML is not supported.

Host key policies:

- `strict`, `true`, and `"true"` require a matching known host key.
- `accept-new` accepts and persists a new host key, but fails if an existing key changed. During `run --dry-run`, new host keys are accepted only for the current connection and are not persisted.
- `off`, `false`, and `"false"` disable host key checking and are insecure.

`accept-new` and `strict` use `known_hosts` when configured. If omitted, distributor uses the current service user's default OpenSSH `known_hosts` path where practical. `accept-new` fails when it needs to persist a new host key and no writable `known_hosts` path is available. It does not create a missing parent `.ssh` directory.

## S3 Backend

S3 uses the AWS SDK for Go v2 and supports S3-compatible endpoints:

```yaml
backend: s3
endpoint: https://s3.example.com
bucket: reports
prefix: archive
region: us-east-1
force_path_style: true
credentials:
  access_key_id_env: DISTRIBUTOR_S3_ACCESS_KEY_ID
  secret_access_key_env: DISTRIBUTOR_S3_SECRET_ACCESS_KEY
```

`endpoint` and `bucket` are required. `prefix` is an optional backend root; it is treated as an object-key prefix, not a real directory. Prefixes must be clean slash-separated paths after trimming leading and trailing slashes. `http://` endpoints are allowed for explicitly configured local development or local S3-compatible test services.

If either credential environment variable name is configured, both must be configured and both referenced variables must resolve to non-empty values through the real process environment or `secrets.directory`. Explicit credentials take precedence over the AWS SDK default credential chain. If credential environment variable names are omitted, the SDK default credential chain is used and `secrets.directory` values are not injected into the process environment.

Publish policy:

- `publish.source`: publish source artifacts.
- `publish.html`: publish generated HTML artifacts from Markdown source files.

At least one output type must be enabled. When `publish.html` is true, `transform.markdown_to_html.enabled` must be `true` and `transform.markdown_to_html.mode` must be `sidecar`.

Transfer policy:

- `transfer.on_destination_same`: `skip` or `fail`; defaults to `skip`.
- `transfer.on_destination_older`: `replace` or `fail`; defaults to `replace`.
- `transfer.on_destination_newer`: `skip`, `replace`, or `fail`; defaults to `skip`.
- `transfer.on_conflict`: `fail` or `replace`; defaults to `fail`.

`replace` for `on_destination_newer` and `on_conflict` is honored only when `run --force` is used for that invocation. Force is CLI-only; there is no persistent config field that enables forced replacement by default.

## Defaults

Defaults are applied after YAML decoding and before validation:

- `validation.on_digest_mismatch: fail`
- SSH `port: 22`
- SSH `host_key_policy: accept-new`
- S3 `region: us-east-1`
- S3 `force_path_style: true`
- `publish.source: true`
- `publish.html: false`
- `transfer.on_destination_same: skip`
- `transfer.on_destination_older: replace`
- `transfer.on_destination_newer: skip`
- `transfer.on_conflict: fail`

## Secrets

Do not put literal secrets in config files. `secrets.directory` lets deployments provide credential values as files:

```yaml
secrets:
  directory: /run/secrets/distributor
```

Each regular file in the directory becomes an internal credential environment value named by the filename. Valid filenames must match `[A-Za-z_][A-Za-z0-9_]*`. Directories are ignored, and symlinks to regular files are followed. Exactly one trailing LF or CRLF is trimmed from each file; other whitespace is preserved.

The resolver checks the real process environment first, then the secrets directory. If both define the same variable with different values, `run` prints a warning with the variable name and uses the real environment value. Secret values are not printed. The process environment is not modified, so SDK default credential chains see only real environment variables.

S3 credentials may name environment variables:

- `credentials.access_key_id_env`
- `credentials.secret_access_key_env`

## Examples

Maintained examples live under [examples](../examples/):

- `local-to-local.yml`: minimal local config.
- `local-publish.yml`: runnable local source publication.
- `local-html.yml`: runnable local HTML publication.
- `fan-out.yml`: runnable local fan-out publication to source and HTML destinations.
- `ssh-destination.yml`: environment-gated local-to-SSH publication example.
- `s3-destination.yml`: environment-gated local-to-S3 publication example.