Add http reporter

[iilyak]

Overview

This PR adds support for http reporter for open tracing library. The http reporter is useful in following two cases:

• when you deployment doesn't include jaeger agents and you want to communicate directly to jaeger server
• when spans are greater than max udp packet size (65Kb).

Testing recommendations

1. update rel/overlay/etc/default.ini as follows

diff --git a/rel/overlay/etc/default.ini b/rel/overlay/etc/default.ini
index 592445c28..69091eab3 100644
--- a/rel/overlay/etc/default.ini
+++ b/rel/overlay/etc/default.ini
@@ -572,15 +572,15 @@ min_priority = 2.0
 ;   - jaeger.thrift over udp
 ;   - jaeger.thrift over http
 ; ## Common settings
-; enabled = false ; true | false
-; app_name = couchdb ; value to use for the `location.application` tag
-; protocol = udp ; udp | http - which reporter to use
+enabled = true ; true | false
+app_name = couchdb ; value to use for the `location.application` tag
+protocol = http ; udp | http - which reporter to use
 ; ## jaeger.thrift over udp reporter
 ; thrift_format = compact ; compact | binary
 ; agent_host = 127.0.0.1
 ; agent_port = 6831
 ; ## jaeger.thrift over udp reporter
-; endpoint = http://127.0.0.1:14268
+endpoint = http://127.0.0.1:14268
 [tracing.filters]
 ;
@@ -603,4 +603,4 @@ min_priority = 2.0
 ; corresponding operation name key configured. Thus, users can easily
 ; log every generated trace by including the following:
 ;
-; all = (#{}) -> true
+all = (#{}) -> true

2. start jaeger in docker container

docker run -d -p 6831:6831/udp -p 16686:16686 jaegertracing/all-in-one:1.14

3. Start couchdb dev/run --admin=adm:pass
4. Create database curl -X PUT -u adm:pass http://127.0.0.1:15984/test
5. Query database curl -X GET -u adm:pass http://127.0.0.1:15984/test -H 'X-B3-TraceId: 12345678901234567890123453782027'
6. Open http://localhost:16686/ in the browser and search for spans (you should find some traces)

Related Issues or Pull Requests

This PR depends on

• Use Apache CouchDB mirrors for dependencies couchdb-jaeger-passage#1

Checklist

• Code is written and works correctly
• Changes are covered by tests
• Any new configurable parameters are documented in rel/overlay/etc/default.ini
• A PR for documentation changes has been made in https://github.com/apache/couchdb-documentation

[iilyak]

This sha would be updated to {tag, "CouchDB-0.1.14-1"} when apache/couchdb-jaeger-passage#1 is merged and correspondent tag created.

[wohali]

Please merge that first, don't put shas into master.

[chewbranca]

Minor nit on asserting ok, but other than that looks good to me!

[chewbranca]

Minor nit, but the previous version of this function matched ok against jaeger_passage:start_tracer(...), whereas this version does not. Was that an intentional behavior change?

[iilyak]

Fixed in a5445d7

[jaydoane]

LGTM, although I highly recommend making that DRY change. If not, I'm happy to open a PR for it myself. Attached is a screenshot of my local jaeger after the test run:

[jaydoane]

s/reporter/reporters/

[iilyak]

fixed by f825540

[jaydoane]

I'd prefer a DRYer approach here, where the tracer is only started in one place:

    Options = [
        {default_service_name, ServiceName}
    ] ++ case config:get("tracing", "protocol", "udp") of
        "udp" ->
            [
                {protocol, udp},
                {thrift_format, list_to_atom(
                    config:get("tracing", "thrift_format", "compact"))},
                {agent_host,
                    config:get("tracing", "agent_host", "127.0.0.1")},
                {agent_port,
                    config:get_integer("tracing", "agent_port", 6831)}
            ];
        "http" ++ _ ->
            [
                {protocol, http},
                {endpoint,
                    config:get("tracing", "endpoint", "http://127.0.0.1:14268")},
                {http_client, fun http_client/5}
            ]
    end,
    ok = jaeger_passage:start_tracer(TracerId, Sampler, Options).

[iilyak]

DRYed in a5445d7