Add zipkin receiver to OTEL collector

[pavolloffay]

Add Zipkin receiver to OTEL collector.

The Zipkin receiver is disabled by default and it can be enabled by flags:

      --collector.zipkin.host-port string          The host:port (e.g. 127.0.0.1:5555 or :5555) of the collector's Zipkin server (default ":0")
      --collector.zipkin.http-port int             (deprecated, will be removed after 2020-06-30 or in release v1.20.0, whichever is later) see --collector.zipkin.host-port

Other notable changes:

• All collector flags are added to OTEL collector. Most of them are be noop exept zipkin. We could support other flags (grpc endpoint, HTTP endpoint) also but it will require changes in OTEL jaeger receiver.

      --collector.grpc-port int                    (deprecated, will be removed after 2020-06-30 or in release v1.20.0, whichever is later) see --collector.grpc-server.host-port
      --collector.grpc-server.host-port string     The host:port (e.g. 127.0.0.1:5555 or :5555) of the collector's GRPC server (default ":14250")
      --collector.grpc.tls                         (deprecated) see --collector.grpc.tls.enabled
      --collector.grpc.tls.cert string             Path to a TLS Certificate file, used to identify this server to clients
      --collector.grpc.tls.client-ca string        Path to a TLS CA (Certification Authority) file used to verify certificates presented by clients (if unset, all clients are permitted)
      --collector.grpc.tls.client.ca string        (deprecated) see --collector.grpc.tls.client-ca
      --collector.grpc.tls.enabled                 Enable TLS on the server
      --collector.grpc.tls.key string              Path to a TLS Private Key file, used to identify this server to clients
      --collector.http-port int                    (deprecated, will be removed after 2020-06-30 or in release v1.20.0, whichever is later) see --collector.http-server.host-port
      --collector.http-server.host-port string     The host:port (e.g. 127.0.0.1:5555 or :5555) of the collector's HTTP server (default ":14268")
      --collector.num-workers int                  The number of workers pulling items from the queue (default 50)
      --collector.queue-size int                   The queue size of the collector (default 2000)
      --collector.queue-size-memory uint           (experimental) The max memory size in MiB to use for the dynamic queue.
      --collector.tags string                      One or more tags to be added to the Process tags of all spans passing through this collector. Ex: key1=value1,key2=${envVar:defaultValue}
      --collector.zipkin.allowed-headers string    Comma separated list of allowed headers for the Zipkin collector service, default content-type (default "content-type")
      --collector.zipkin.allowed-origins string    Comma separated list of allowed origins for the Zipkin collector service, default accepts all (default "*")
      --collector.zipkin.host-port string          The host:port (e.g. 127.0.0.1:5555 or :5555) of the collector's Zipkin server (default ":0")
      --collector.zipkin.http-port int             (deprecated, will be removed after 2020-06-30 or in release v1.20.0, whichever is later) see --collector.zipkin.host-port

[objectiser]

@pavolloffay Wanted to clarify your comment:

We could support other flags (grpc endpoint, HTTP endpoint) also but it will require changes in OTEL jaeger receiver.

Wouldn't those flags just map their values onto the Jaeger receiver in the OTC config? e.g. https://github.com/open-telemetry/opentelemetry-collector/tree/master/receiver#communicating-over-tls - what changes would be required in OTEL jaeger receiver?

[pavolloffay]

Wouldn't those flags just map their values onto the Jaeger receiver in the OTC config? e.g.

Yes, that is my idea. I am not sure how it will be done. We need access to the receiver configuration object before it gets used by the factory. I will be looking into this shortly.

[rubenvp8510]

The tests on https://github.com/jaegertracing/jaeger/blob/master/cmd/opentelemetry-collector/app/defaults/default_config_test.go#L96 should be updated.

But this looks good so far

[pavolloffay]

This is ready for re-review. For the flags I have created #2182

[objectiser]

Rather than define a special port, would it be better to just have a pointer? So test against nil.

[pavolloffay]

We could do that too, although this uses the same approach as other parts of the codebase - zipkin is disabled if :0 is used. This value is also set as the default of the flag.

[pavolloffay]

I did a small change, I have removed the const and used a built-in func to return the value of disabled endpoint.

[objectiser]

Would it be better to use an interface so can just add extra flag fields if/when supported?

[pavolloffay]

Interface perhaps no but options/params struct could be used. I would wait and see until the number of parameters grows and then refactor. Three params still look good to me.

[codecov]

Codecov Report

Merging #2181 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2181   +/-   ##
=======================================
  Coverage   96.14%   96.14%           
=======================================
  Files         219      219           
  Lines       10585    10585           
=======================================
  Hits        10177    10177           
  Misses        352      352           
  Partials       56       56           

Impacted Files	Coverage Δ
cmd/query/app/server.go	91.78% <0.00%> (-2.74%)	⬇️
plugin/storage/badger/spanstore/reader.go	96.79% <0.00%> (+0.64%)	⬆️

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