Could not get binary context for sub requests

[ichaozai]

Get failed to expand opentracing_context_ for request 000055D4589C9190: get_binary_context failed: could not find request trace when invoking subrequest by ngx lua.

$ curl 127.0.0.1:8080
2020/07/02 10:22:11 [error] 308#308: *22 failed to expand opentracing_context_ for request 000055D4589C9190: get_binary_context failed: could not find request trace, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", subrequest: "/sub", host: "127.0.0.1:8080"
terminate called without an active exception
2020/07/02 10:22:11 [alert] 154#154: worker process 308 exited on signal 6
curl: (52) Empty reply from server

How to trace sub requests?

nginx.conf:

load_module modules/ngx_http_opentracing_module.so;
worker_processes  1;

events {
    worker_connections  1024;
}

http {
    include       mime.types;
    default_type  application/octet-stream;
    opentracing on;
    opentracing_load_tracer /usr/local/lib/libjaegertracing_plugin.so jaeger-config.json;
    opentracing_propagate_context;

    server {
        listen 8080;
        location / {
            default_type text/html;
            content_by_lua '
                local bridge_tracer = require("opentracing_bridge_tracer")
                local tracer = bridge_tracer.new_from_global()
                local parent_context = tracer:binary_extract(ngx.var.opentracing_binary_context)
                local span = tracer:start_span("lua-hello", {["references"] = {{"child_of", parent_context}}})
                local res = ngx.location.capture("/sub")
                ngx.say(res.body)
                span:finish()
            ';
        }

        location /sub {
            default_type text/html;
            content_by_lua '
                local bridge_tracer = require("opentracing_bridge_tracer")
                local tracer = bridge_tracer.new_from_global()
                local parent_context = tracer:binary_extract(ngx.var.opentracing_binary_context)
                local span = tracer:start_span("sub-lua-hello", {["references"] = {{"child_of", parent_context}}})
                ngx.say("<p>hello, world</p>")
                span:finish()
            ';
        }
    }
}

jaeger-config.json:

{
  "service_name": "nginx",
  "diabled": false,
  "reporter": {
    "logSpans": true,
    "localAgentHostPort": "127.0.0.1:6831"
  },
  "sampler": {
    "type": "const",
    "param": "1"
  }
}

[ichaozai]

After debugging from the source code, I need to set log_subrequest on; to enable sub request tracing.

But I got a new problem, the sub request's span is not a child of the caller request.
Here is the nginx.conf:

load_module modules/ngx_http_opentracing_module.so;

worker_processes  1;

events {
    worker_connections  1024;
}

http {
    include       mime.types;
    default_type  application/octet-stream;
    opentracing on;
    opentracing_load_tracer /usr/local/lib/libjaegertracing_plugin.so jaeger-config.json;
    opentracing_propagate_context;
    log_subrequest on;

    server {
        listen 8080;
        location / {
            default_type text/html;
            content_by_lua '
                local res = ngx.location.capture("/sub")
                ngx.say(res.body)
            ';
        }

        location /sub {
            default_type text/html;
            content_by_lua '
                ngx.say("<p>hello, world</p>")
            ';
        }
    }
}