Example of how to run nginx via ldp and vcl on top of vpp's host stack.

## VPP configuration
In addition to the typical vpp startup config parameters, the host stack requires the one lower for enabling the session layer socket api for app attachment. For a list of startup parameters see [here](https://fdio-vpp.readthedocs.io/en/latest/gettingstarted/users/configuring/startup.html#).

```
session { use-app-socket-api }
```

## Nginx
First start vpp and ensure that the network to the http client is working as expected. Then define the following environment variables with the appropriate paths

```
VCL_CFG=/path/to/vcl.conf
LDP_PATH=/path/to/vpp/build-root/build-vpp[_debug]-native/vpp/lib/libvcl_ldpreload.so
```

And create a minimal startup configuration in `/path/to/vcl.conf `like the one lower:

```
vcl {
  heapsize 64M
  segment-size 4000000000
  add-segment-size 4000000000
  rx-fifo-size 4000000
  tx-fifo-size 4000000
  app-socket-api /var/run/vpp/app_ns_sockets/default
}
```

The above configures vcl to request 4MB receive and transmit fifo sizes and it provides the path to vpp's session layer socket api.

To start nginx:

```
sudo LD_PRELOAD=$LDP_PATH VCL_CONFIG=$VCL_CFG nginx -c nginx.conf
```

A simple, known to work nginx.conf file includes:

```
worker_processes 4;
daemon off;
master_process on;
```

## Performance testing
For high scale loads testing make sure to properly configure fifo sizes and the number of nginx workers. Additionally, configurations known to improve RPS include:

```
worker_rlimit_nofile 10240;
events {
       use epoll;
       worker_connections  10240;
       accept_mutex       off;
       multi_accept       off;
}
http {
       keepalive_timeout 300s;
       keepalive_requests 1000000;
       access_log off;
}
```

Also, it's recommended to start nginx pinned to cores on the numa used by vpp's workers and the nic using taskset.