[trace view] Better visualization of inter-service calls

[yurishkuro]

In sharded storage implementations it's common for a request to one node to be forwarded to another node, e.g. Cassandra's coordinator node can talk to other nodes. The trace view currently colors spans by the service name only, so calls between different instances of the same service are colored the same, making it harder to understand without expanding the spans.

Some options to fix this:

1. take process hostname / ip into account when assigning the color
2. add an optional column Hostname to the grid
3. decorate service name to indicate different instances, e.g. cassandra[1], cassandra[2]
4. decorate service name with host name cassandra[host-001] if there are multiple nodes involved in the trace

[ringerc]

Strong +1 from me, I'm working with clustered systems where being able to see the node identity would be a huge help.

I'm hacking around it with service name decoration in my agent. But this makes it painful in the webui because there's no convenient way to find "all services starting with (prefix)" etc.

[yurishkuro]

I think option 3 is the easiest to implement.