# Netdata web server

Netdata supports 3 implementations of its internal web server:

- `static-threaded` is a web server with a fix (configured number of threads)
- `single-threaded` is a simple web server running with a single thread
- `multi-threaded` is a web server that spawns a thread for each client connection
- `none` to disable the web server

We suggest to use the `static-threaded` one. It is the most efficient.

All versions of the web servers use non-blocking I/O.

All web servers respect the `keep-alive` HTTP header to serve multiple HTTP requests via the same connection.

## Configuration

### Selecting the web server

You can select the web server implementation by editing `netdata.conf` and setting:

```
[web]
    mode = none | single-threaded | multi-threaded | static-threaded
```

The `static` web server supports also these settings:

```
[web]
    mode = static-threaded
    web server threads = 4
    web server max sockets = 512
```

The default number of processor threads is `min(cpu cores, 6)`.

The `web server max sockets` setting is automatically adjusted to 50% of the max number of open files netdata is allowed to use (via `/etc/security/limits.conf` or systemd), to allow enough file descriptors to be available for data collection.

### Binding netdata to multiple ports

Netdata can bind to multiple IPs and ports. Up to 100 sockets can be used (you can increase it at compile time with `CFLAGS="-DMAX_LISTEN_FDS=200" ./netdata-installer.sh ...`).

The ports to bind are controlled via `[web].bind to`, like this:

```
[web]
   default port = 19999
   bind to = 127.0.0.1 10.1.1.1:19998 hostname:19997 [::]:19996 localhost:19995 *:http unix:/tmp/netdata.sock
```

Using the above, netdata will bind to:

- IPv4 127.0.0.1 at port 19999 (port was used from `default port`)
- IPv4 10.1.1.1 at port 19998
- All the IPs `hostname` resolves to (both IPv4 and IPv6 depending on the resolved IPs) at port 19997
- All IPv6 IPs at port 19996
- All the IPs `localhost` resolves to (both IPv4 and IPv6 depending the resolved IPs) at port 19996
- All IPv4 and IPv6 IPs at port `http` as set in `/etc/services`
- Unix domain socket `/tmp/netdata.sock`

The option `[web].default port` is used when an entries in `[web].bind to` do not specify a port.

### Access lists

Netdata supports access lists in `netdata.conf`:

```
[web]
	allow connections from = localhost *
	allow dashboard from = localhost *
	allow badges from = *
	allow streaming from = *
	allow netdata.conf from = localhost fd* 10.* 192.168.* 172.16.* 172.17.* 172.18.* 172.19.* 172.20.* 172.21.* 172.22.* 172.23.* 172.24.* 172.25.* 172.26.* 172.27.* 172.28.* 172.29.* 172.30.* 172.31.*
```

`*` does string matches on the IPs of the clients.

- `allow connections from` matches anyone that connects on the netdata port(s).
   So, if someone is not allowed, it will be connected and disconnected immediately, without reading even
   a single byte from its connection. This is a global settings with higher priority to any of the ones below.

- `allow dashboard from` receives the request and examines if it is a static dashboard file or an API call the
   dashboards do.

- `allow badges from` checks if the API request is for a badge. Badges are not matched by `allow dashboard from`.

- `allow streaming from` checks if the slave willing to stream metrics to this netdata is allowed.
   This can be controlled per API KEY and MACHINE GUID in [stream.conf](../../streaming/stream.conf).
   The setting in `netdata.conf` is checked before the ones in [stream.conf](../../streaming/stream.conf).

- `allow netdata.conf from` checks the IP to allow `http://netdata.host:19999/netdata.conf`.
   By default it allows only private lans.

## DDoS protection

If you publish your netdata to the internet, you may want to apply some protection against DDoS:

1. Use the `static-threaded` web server (it is the default)
2. Use reasonable `[web].web server max sockets` (the default is)
3. Don't use all your cpu cores for netdata (lower `[web].web server threads`)
4. Run netdata with a low process scheduling priority (the default is the lowest)
5. If possible, proxy netdata via a full featured web server (nginx, apache, etc)