Express plugin not working

[suhjohn]

I have an Express 4 app with dd-trace.

tracer.init is happening first thing in the code.

However, when I make an API request, top level request is http component not express, and everything is collapsed under the http method instead of the request path.

To override this, tried to add a hook:

tracer.use('http', {
  hooks: {
    request: (span, req, _) => {
      if (span !== undefined) {
        if (req instanceof IncomingMessage) {
          logger.info(
            `[tracer.ts] req instanceof IncomingMessage setting resource.name - Span: ${span} req: ${req.url}`,
          );
        } else if (req instanceof ClientRequest) {
          logger.info(
            `[tracer.ts] req instanceof ClientRequest setting resource.name - Span: ${span} req: ${req.path}`,
          );
        }
      }
      if (req instanceof IncomingMessage) {
        logger.info(
          `[tracer.ts] req instanceof IncomingMessage span is undefined - req: ${req.url}`,
        );
      } else if (req instanceof ClientRequest) {
        logger.info(
          `[tracer.ts] req instanceof ClientRequest span is undefined - req: ${req.path}`,
        );
      }
    },
  },
});

This caused the application to crash with the following issue:

2024-02-08 00:24:32 [server] error: TypeError: Cannot read properties of undefined (reading 'length')

at DatadogSpan.toString (/usr/src/app/node_modules/dd-trace/packages/dd-trace/src/opentracing/span.js:100:35)

at Object.request (file:///usr/src/app/server/build/src/config/tracer.js:27:109)

at Object.finishSpan (/usr/src/app/node_modules/dd-trace/packages/dd-trace/src/plugins/util/web.js:302:26)

at Object.finishAll (/usr/src/app/node_modules/dd-trace/packages/dd-trace/src/plugins/util/web.js:316:9)

at HttpServerPlugin.finish (/usr/src/app/node_modules/dd-trace/packages/datadog-plugin-http/src/server.js:66:9)

at /usr/src/app/node_modules/dd-trace/packages/dd-trace/src/plugins/tracing.js:73:22

at Subscription._handler (/usr/src/app/node_modules/dd-trace/packages/dd-trace/src/plugins/plugin.js:14:9)

at Channel.publish (node:diagnostics_channel:56:9)

at ServerResponse.emit (/usr/src/app/node_modules/dd-trace/packages/datadog-instrumentations/src/http/server.js:40:22)

at onFinish (node:_http_outgoing:1001:10)

Is that the right way to use hooks? How can I override the resource.name to something more sane?

Tried both ddtrace 4.26 and 5.2, and both don't work.

[suhjohn]

https://github.com/DataDog/dd-trace-js/issues/3595