Dokku uses nginx as its server for routing requests to specific applications. By default, access and error logs are written for each app to `/var/log/nginx/${APP}-access.log` and `/var/log/nginx/${APP}-error.log` respectively
You may check nginx access logs via the `nginx:access-logs` command. This assumes that app access logs are being stored in `/var/log/nginx/$APP-access.log`, as is the default in the generated `nginx.conf`.
```shell
dokku nginx:access-logs node-js-app
```
You may also follow the logs by specifying the `-t` flag.
```shell
dokku nginx:access-logs node-js-app -t
```
## Checking error logs
You may check nginx error logs via the `nginx:access-logs` command. This assumes that app error logs are being stored in `/var/log/nginx/$APP-error.log`, as is the default in the generated `nginx.conf`.
```shell
dokku nginx:error-logs node-js-app
```
You may also follow the logs by specifying the `-t` flag.
```shell
dokku nginx:error-logs node-js-app -t
```
## Regenerating nginx config
In certain cases, your app nginx configs may drift from the correct config for your app. You may regenerate the config at any point via the `nginx:build-config` command. This may fail if there are no current web listeners for your app.
It may be desired to validate an nginx config outside of the deployment process. To do so, run the `nginx:validate` command. With no arguments, this will validate all app nginx configs, one at a time. A minimal wrapper nginx config is generated for each app's nginx config, upon which `nginx -t` will be run.
```shell
dokku nginx:validate
```
As app nginx configs are actually executed within a shared context, it is possible for an individual config to be invalid when being validated standalone but _also_ be valid within the global server context. As such, the exit code for the `nginx:validate` command is the exit code of `nginx -t` against the server's real nginx config.
The `nginx:validate` command also takes an optional `--clean` flag. If specified, invalid nginx configs will be removed.
> Warning: Invalid app nginx config's will be removed _even if_ the config is valid in the global server context.
```shell
dokku nginx:validate --clean
```
The `--clean` flag may also be specified for a given app:
Dokku uses a templating library by the name of [sigil](https://github.com/gliderlabs/sigil) to generate nginx configuration for each app. You may also provide a custom template for your application as follows:
> When using a custom `nginx.conf.sigil` file, depending upon your application configuration, you *may* be exposing the file externally. As this file is extracted before the container is run, you can, safely delete it in a custom `entrypoint.sh` configured in a Dockerfile `ENTRYPOINT`.
> The default template is available [here](https://github.com/dokku/dokku/blob/master/plugins/nginx-vhosts/templates/nginx.conf.sigil), and can be used as a guide for your own, custom `nginx.conf.sigil` file. Please refer to the appropriate template file version for your Dokku version.
### Available template variables
```
{{ .APP }} Application name
{{ .APP_SSL_PATH }} Path to SSL certificate and key
{{ .DOKKU_ROOT }} Global Dokku root directory (ex: app dir would be `{{ .DOKKU_ROOT }}/{{ .APP }}`)
{{ .DOKKU_APP_LISTENERS }} List of IP:PORT pairs of app containers
{{ .PROXY_PORT_MAP }} List of port mappings (same as `DOKKU_PROXY_PORT_MAP` config var)
{{ .PROXY_UPSTREAM_PORTS }} List of configured upstream ports (derived from `DOKKU_PROXY_PORT_MAP` config var)
{{ .RAW_TCP_PORTS }} List of exposed tcp ports as defined by Dockerfile `EXPOSE` directive (**Dockerfile apps only**)
{{ .SSL_INUSE }} Boolean set when an app is SSL-enabled
{{ .SSL_SERVER_NAME }} List of SSL VHOSTS
```
> Note: Application config variables are available for use in custom templates. To do so, use the form of `{{ var "FOO" }}` to access a variable named `FOO`.
The example above uses additional configuration files directly on the Dokku host. Unlike the `nginx.conf.sigil` file, these additional files will not be copied over from your application repo, and thus need to be placed in the `/home/dokku/node-js-app/nginx.conf.d/` directory manually.
For PHP Buildpack users, you will also need to provide a `Procfile` and an accompanying `nginx.conf` file to customize the nginx config *within* the container. The following are example contents for your `Procfile`
By default, Dokku provides custom error pages for the following three categories of errors:
- 4xx: For all non-404 errors with a 4xx response code.
- 404: For "404 Not Found" errors.
- 5xx: For all 5xx error responses
These are provided as an alternative to the generic Nginx error page, are shared for _all_ applications, and their contents are located on disk at `/var/lib/dokku/data/nginx-vhosts/dokku-errors`. To customize them for a specific app, create a custom `nginx.conf.sigil` as described above and change the paths to point elsewhere.
