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Envoy Discovery service 'hello world'

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Envoy EDS "hello world"

A simple app demonstrating a small part of Envoy's Endpoint Discovery Service. THis is a sample walkthough of a trivial envoy config that sets up:

  • Envoy with SDS bootstrap (both envoy v1 and v2 APIs)
  • SDS Server to provide service discovery info for upstream back to Envoy
  • N upstream instances envoy will proxy back.

Some of the configurations are hardcoded in the envoy_config.yaml file just as a demonstration. Specifically, the service, cluster and bootstrap endpoint to get discovery information.

References

Prerequsites

arch.png

Start Envoy with SDS

Bootstraping SDS within Envoy is relatively simple:

  - name: listener_0
    address:
      socket_address: { address: 0.0.0.0, port_value: 10000 }
    filter_chains:
    - filters:
      - name: envoy.http_connection_manager
        config:
          stat_prefix: ingress_http
        ...
        ...
              - match: { prefix: "/" }
                route: { cluster: service_backend }
          http_filters:
          - name: envoy.router
  clusters:
  - name: service_backend
    type: EDS  
    connect_timeout: 0.25s
    eds_cluster_config:
      service_name: myservice
      eds_config:
        api_config_source:
          #api_type: REST_LEGACY # GET /v1/registration/myservice
          #api_type: REST # POST /v2/discovery:endpoints
          api_type: REST
          cluster_names: [eds_cluster]
          refresh_delay: 5s
  - name: eds_cluster
    type: STATIC
    connect_timeout: 0.25s
    hosts: [{ socket_address: { address: 127.0.0.1, port_value: 8080 }}]

Note the api_type: is set to v2 REST endpoint. If you want to swtich to v1 simply use api_type: REST_LEGACY

You can basically 'copy out an envoy binary from docker if you're using a linux flavor

$ mkdir /tmp/envoybin
$ docker run -v /tmp/envoybin/:/tmp/envoybin -ti envoyproxy/envoy /bin/bash

copy the envoy binary out and exit container

root@45e96404eb8a:/# cp /usr/local/bin/envoy /tmp/envoybin/
root@45e96404eb8a:/# exit
exit

find envoy outside now

$ ls /tmp/envoybin/envoy 
/tmp/envoybin/envoy

So start envoy with debug enabled:

envoy -c envoy_config.yaml -l debug

At this point, envoy attempts to connect to the upstream EDS cluster at 127.0.0.1:8080 but since your SDS isn't running yet, nothing additional config takes place.

Start Upstream services

Now in a new window, start the upstream service on a given the default port for the script (:8081)

cd upstream/

virtualenv env --python=python2.7
source env/bin/activate
pip install -r requirements.txt

$ python server.py -p 8081

Right now envoy doens't know aboutt his endpoint:

Start SDS

Now start SDS without any bootstrapped config:

cd eds_server/

virtualenv env --python=python2.7
source env/bin/activate
pip install -r requirements.txt

# ImportError: No module named enum
# pip install enum34

python main.py

You should see the following output on SDS stdout indicating an inbound Envoy discovery request:

Inbound v2 request for discovery.  POST payload: {u'node': {u'build_version': u'fd44fd6051f5d1de3b020d0e03685c24075ba388/1.6.0-dev/Clean/RELEASE', u'cluster': u'mycluster', u'id': u'test-id'}, u'resource_names': [u'myservice']}
127.0.0.1 - - [29/Apr/2018 22:59:04] "POST /v2/discovery:endpoints HTTP/1.1" 200 -

then on the envoy proxy stdout, something like:

[2018-04-29 22:59:10.323][157796][debug][config] bazel-out/k8-opt/bin/source/common/config/_virtual_includes/http_subscription_lib/common/config/http_subscription_impl.h:67] Sending REST request for /v2/discovery:endpoints
[2018-04-29 22:59:10.323][157796][debug][router] source/common/router/router.cc:250] [C0][S636378528925215024] cluster 'eds_cluster' match for URL '/v2/discovery:endpoints'
[2018-04-29 22:59:10.323][157796][debug][router] source/common/router/router.cc:298] [C0][S636378528925215024]   ':method':'POST'
[2018-04-29 22:59:10.323][157796][debug][router] source/common/router/router.cc:298] [C0][S636378528925215024]   ':path':'/v2/discovery:endpoints'
[2018-04-29 22:59:10.323][157796][debug][router] source/common/router/router.cc:298] [C0][S636378528925215024]   ':authority':'eds_cluster'
...
[2018-04-29 22:59:10.324][157796][debug][client] source/common/http/codec_client.cc:52] [C2] connected
[2018-04-29 22:59:10.324][157796][debug][pool] source/common/http/http1/conn_pool.cc:225] [C2] attaching to next request
...
[2018-04-29 22:59:10.330][157796][debug][client] source/common/http/codec_client.cc:81] [C2] response complete
[2018-04-29 22:59:10.330][157796][debug][pool] source/common/http/http1/conn_pool.cc:200] [C2] response complete
...
[2018-04-29 22:59:10.331][157796][debug][pool] source/common/http/http1/conn_pool.cc:115] [C2] client disconnected

Basically, this shows no updates were recieved from the endpoint

You can verify that envoy doesn't know anything about this endpoint by attempting to connect through to it:

curl -v http://localhost:10000/
$ curl -v  http://localhost:10000/
... 
< HTTP/1.1 503 Service Unavailable
< content-length: 19
< content-type: text/plain
< date: Mon, 30 Apr 2018 06:06:20 GMT
< server: envoy
< 
* Connection #0 to host localhost left intact
no healthy upstreams

Add endpoint to SDS

Now we're ready to add an upstream service configuration to the SDS server. This sample uses Flask-RESTplus framework which delivers a convenient API console (you can, ofcourse, use curl)

connect to SDS servers UI console at:

http://localhost:8080/

images/api_console.png

curl -X GET "http://localhost:8080/edsservice/myservice" -H "accept: application/json"

{
  "hosts": [
    {
      "ip_address": "127.0.0.1",
      "port": 8081,
      "tags": {
        "az": "us-central1-a",
        "canary": false,
        "load_balancing_weight": 50
      }
    }
  ]
}

From there, you can register a service endpoint by selecting POST and the default payload.

Create Endpoint

Since we defined the service as myservice in the envoy_config.yaml, we can need to register an endpoint against it:

curl -X POST --header 'Content-Type: application/json' --header 'Accept: application/json' -d '{
  "hosts": [
    {
      "ip_address": "127.0.0.1",
      "port": 8081,
      "tags": {
        "az": "us-central1-a",
        "canary": false,
        "load_balancing_weight": 50
      }
    }
  ]
}' http://localhost:8080/edsservice/myservice

What this will do is set some endpoints for myservice. Now, envoy will query SDS for membership so on the next poll, you'll see some lines like:

[2018-04-29 23:18:02.360][159226][debug][upstream] source/common/upstream/eds.cc:105] EDS hosts changed for cluster: service_backend (0) priority 0
[2018-04-29 23:18:02.360][159231][debug][upstream] source/common/upstream/cluster_manager_impl.cc:642] membership update for TLS cluster service_backend
[2018-04-29 23:18:02.360][159226][debug][upstream] source/common/upstream/cluster_manager_impl.cc:642] membership update for TLS cluster service_backend
[2018-04-29 23:18:02.360][159233][debug][upstream] source/common/upstream/cluster_manager_impl.cc:642] membership update for TLS cluster service_backend
[2018-04-29 23:18:02.360][159234][debug][upstream] source/common/upstream/cluster_manager_impl.cc:642] membership update for TLS cluster service_backend
[2018-04-29 23:18:02.360][159232][debug][upstream] source/common/upstream/cluster_manager_impl.cc:642] membership update for TLS cluster service_backend
[2018-04-29 23:18:02.360][159226][debug][pool] source/common/http/http1/conn_pool.cc:200] [C7] response complete
[2018-04-29 23:18:02.360][159226][debug][pool] source/common/http/http1/conn_pool.cc:220] [C7] moving to ready

Check client connectivity via envoy

Since we already started the upstream service above, you can connect to it via envoy:

$ curl -v  http://localhost:10000/
 
< HTTP/1.1 200 OK
< content-type: text/html; charset=utf-8
< content-length: 36
< server: envoy
< date: Mon, 30 Apr 2018 06:21:43 GMT
< x-envoy-upstream-service-time: 3
< 
* Connection #0 to host localhost left intact
40b9bc6f-77b8-49b7-b939-1871507b0fcc

(note the server: envoy part in the header)

Delete Endpoint

Ok, so now we've dynamically added in an endpoint...lets remove it by the SDS server's custom API and emptying out its hosts: []

curl -X PUT --header 'Content-Type: application/json' --header 'Accept: application/json' -d '{
  "hosts": [  ]
}' http://localhost:8080/edsservice/myservice

Now try the endpoint, you should see no healthy upstream message from envoy

$ curl -v  http://localhost:10000/
< HTTP/1.1 503 Service Unavailable
< content-length: 19
< content-type: text/plain
< date: Mon, 30 Apr 2018 06:23:40 GMT
< server: envoy
< 
* Connection #0 to host localhost left intact
no healthy upstream

Rinse and repeat

Ok, you can continue to play with the endpoints by adding and removing new upstream services on differnet ports:

eg:

$ python server.py -p 8082
$ python server.py -p 8083

and then using the API to add hosts to the SDS server (use the PUT endpoint to do that)

curl -X PUT "http://localhost:8080/edsservice/myservice" -H "accept: application/json" -H "Content-Type: application/json" -d "{ \"hosts\": [ { \"ip_address\": \"127.0.0.1\", \"port\": 8081, \"tags\": { \"az\": \"us-central1-a\", \"canary\": false, \"load_balancing_weight\": 50 } }, { \"ip_address\": \"127.0.0.1\", \"port\": 8082, \"tags\": { \"az\": \"us-central1-a\", \"canary\": false, \"load_balancing_weight\": 50 } } ]}"

Conclusion

I wrote this up just in an effort to play around with envoy i'm pretty much new to this so i likely have numerous misunderstanding on what i just did here...if you see something amiss, please do let me know.

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Envoy Discovery service 'hello world'

License:Apache License 2.0

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