clixon/apps/restconf

Clixon Restconf

• Evhtp
• Nginx
• Streams
• Nchan Streams
• Debugging

There are two installation instructions: for libevhtp and nginx.

Evhtp

Download, build and install libevhtp from source. Prereqs: libevent and cmake.

   sudo git clone https://github.com/clicon/clixon-libevhtp.git
   cd clixon-libevhtp
   ./configure --libdir=/usr/lib
   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 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