# Clixon Restconf

  * [Evhtp](#evhtp)
  * [Nginx](#nginx)
  * [Streams](#streams)
  * [Nchan Streams](#nchan)
  * [Debugging](#debugging)	

There are two installation instructions: for libevhtp and nginx.

## Evhtp

Download, build and install libevhtp from source. Prereqs: libevent and cmake.
```
   git clone https://github.com/criticalstack/libevhtp.git
   cd libevhtp/build
   cmake -DEVHTP_DISABLE_REGEX=ON -DEVHTP_DISABLE_EVTHR=ON ..
   make
   sudo make install
```

Configure clixon with evhtp:
```
  ./configure --with-restconf=evhtp
```

Ensure www-data is member of the CLICON_SOCK_GROUP (default clicon). If not, add it:
```
  sudo usermod -a -G clicon www-data
```

## Nginx

Installation instruction for Nginx. Other reverse proxies should work but are not verified.

Ensure www-data is member of the CLICON_SOCK_GROUP (default clicon). If not, add it:
```
  sudo usermod -a -G clicon www-data
```

This implementation uses FastCGI, see http://www.mit.edu/~yandros/doc/specs/fcgi-spec.html.

Download and start nginx. For example on ubuntu:
```
  sudo apt install ngnix
```
on FreeBSD:
```
  sudo pkg install ngnix
```

Edit the nginx config file. (On Ubuntu: `/etc/nginx/sites-available/default`, on FreeBSD: `/usr/local/etc/nginx/sites-available/default`)
```
  server {
    ...
    location / {
      fastcgi_pass unix:/www-data/fastcgi_restconf.sock;
      include fastcgi_params;
    }
  }
```

Start nginx daemon
```
  sudo /etc/init.d nginx start
```
Alternatively, start it via systemd:
```
  sudo systemctl start nginx.service
```
Or on FreeBSD:
```
  sudo service nginx start
```

## Run

Start clixon backend daemon (if not already started)
```
  sudo clixon_backend -s init -f /usr/local/etc/example.xml
```

Start clixon restconf daemon
```
  sudo -u www-data -s /www-data/clixon_restconf -f /usr/local/etc/example.xml
```
On FreeBSD:
```
  sudo -u www -s /www/clixon_restconf -f /usr/local/etc/example.xml
```

Make restconf calls with curl (or other http client). Example of writing a new interface specification:
```
  curl -sX PUT http://localhost/restconf/data/ietf-interfaces:interfaces -H 'Content-Type: application/yang-data+json' -d '{"ietf-interfaces:interfaces":{"interface":{"name":"eth1","type":"clixon-example:eth","enabled":true}}}'
```

Get the data
```
  curl -X GET http://127.0.0.1/restconf/data/ietf-interfaces:interfaces
  {
    "ietf-interfaces:interfaces": {
      "interface": [
        {
          "name": "eth1",
          "type": "clixon-example:eth",
          "enabled": true
        }
      ]
    }
  }

```
Get the type of a specific interface:
```
  curl -X GET http://127.0.0.1/restconf/data/ietf-interfacesinterfaces/interface=eth1/type
  {
    "ietf-interfaces:type": "clixon-example:eth" 
  }
```

## Streams

Clixon have two experimental restconf event stream implementations following
RFC8040 Section 6 using SSE.  One native and one using Nginx
nchan. The Nchan alternaitve is described in the
next section.

The [example](../../example/main/README.md) creates an EXAMPLE stream.

Set the Clixon configuration options:
```
<CLICON_STREAM_PATH>streams</CLICON_STREAM_PATH>
<CLICON_STREAM_URL>https://example.com</CLICON_STREAM_URL>
<CLICON_STREAM_RETENTION>3600</CLICON_STREAM_RETENTION>
```
In this example, the stream EXAMPLE would be accessed with `https://example.com/streams/EXAMPLE`.

The retention is configured as 1 hour, i.e., the stream replay function will only save timeseries one hour.

Clixon defines an internal in-memory (not persistent) replay function
controlled by the configure option above.

You may access a restconf streams using curl.

Add the following to extend the nginx configuration file with the following statements (for example):
```
	location /streams {
	    fastcgi_pass unix:/www-data/fastcgi_restconf.sock;
	    include fastcgi_params;
 	    proxy_http_version 1.1;
	    proxy_set_header Connection "";
        }
```

An example of a stream access is as follows:
```
> curl -H "Accept: text/event-stream" -s -X GET http://localhost/streams/EXAMPLE
data: <notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"><eventTime>2018-11-04T14:47:11.373124</eventTime><event><event-class>fault</event-class><reportingEntity><card>Ethernet0</card></reportingEntity><severity>major</severity></event></notification>

data: <notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"><eventTime>2018-11-04T14:47:16.375265</eventTime><event><event-class>fault</event-class><reportingEntity><card>Ethernet0</card></reportingEntity><severity>major</severity></event></notification>
```

You can also specify start and stop time. Start-time enables replay of existing samples, while stop-time is used both for replay, but also for stopping a stream at some future time.
```
   curl -H "Accept: text/event-stream" -s -X GET http://localhost/streams/EXAMPLE?start-time=2014-10-25T10:02:00&stop-time=2014-10-25T12:31:00
```

See (stream tests)[../test/test_streams.sh] for more examples.

## Nchan

As an alternative streams implementation, Nginx/Nchan can be used. 
Nginx uses pub/sub channels and can be configured in a variety of
ways. The following uses a simple variant with one generic subscription
channel (streams) and one publication channel (pub).

The advantage with Nchan is the large eco-system around Nginx and Nchan.

Native mode and Nchan mode can co-exist, but the publish URL of Nchan should be different from the streams URL of the native streams.

Nchan mode does not use Clixon retention, since it uses its own replay mechanism.

Download and install nchan, see (https://nchan.io/#install).

Add the following to extend the Nginx configuration file with the following statements (example):
```
        location ~ /sub/(\w+)$ {
            nchan_subscriber;
            nchan_channel_id $1; #first capture of the location match
        }
        location ~ /pub/(\w+)$ {
            nchan_publisher;
            nchan_channel_id $1; #first capture of the location match
        }        
```

Configure clixon with `--enable-publish` which enables curl code for
publishing streams to nchan.

You also need to configure CLICON_STREAM_PUB to enable pushing notifications to Nginx/Nchan. Example:
```
<CLICON_STREAM_PUB>http://localhost/pub</CLICON_STREAM_PUB>
```
Clicon will then publish events from stream EXAMPLE to `http://localhost/pub/EXAMPLE

Access the event stream EXAMPLE using curl:
```
   curl -H "Accept: text/event-stream" -s -X GET http://localhost/streams/EXAMPLE
: hi

id: 1541344320:0
data: <notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"><eventTime>2018-11-04T15:12:00.435769</eventTime><event><event-class>fault</event-class><reportingEntity><card>Ethernet0</card></reportingEntity><severity>major</severity></event></notification>

id: 1541344325:0
data: <notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"><eventTime>2018-11-04T15:12:05.446425</eventTime><event><event-class>fault</event-class><reportingEntity><card>Ethernet0</card></reportingEntity><severity>major</severity></event></notification>

```
Note that the SSE stream output is different than for native streams, and that `Last-Event-Id` is used for replay:
```
curl -H "Accept: text/event-stream" -H "Last-Event-ID: 1539961709:0" -s -X GET http://localhost/streams/EXAMPLE
```

See (https://nchan.io/#eventsource) on more info on how to access an SSE sub endpoint.

## Debugging

Start the restconf fastcgi program with debug flag:
```
sudo su -c "/www-data/clixon_restconf -D 1 -f /usr/local/etc/example.xml" -s /bin/sh www-data
```
Look at syslog:
```
tail -f /var/log/syslog | grep clixon_restconf
```

Send command:
```
curl -G http://127.0.0.1/restconf/data/*
```

You can also run restconf in a debugger.
```
sudo gdb /www-data/clixon_restconf
(gdb) run -D 1 -f /usr/local/etc/example.xml
```
but you need to ensure /www-data/fastcgi_restconf.sock has the following access (may need to be done after restconf has started)
```
rwxr-xr-x 1 www-data www-data 0 sep 22 11:46 /www-data/fastcgi_restconf.sock
```

You can set debug level of the backend via restconf:
```
   curl -is -X POST -H "Content-Type: application/yang-data+json" -d '{"clixon-lib:input":{"level":1}}' http://localhost/restconf/operations/clixon-lib:debug
```
