inject session UUID into root context

[btc]

There's a context.Context created at the top of main.go.

ctx := context.Background()

What would we gain if we were to inject a UUID into it using the eventlog library?

ctx := eventlog.ContextWithLoggable(context.Background(), eventlog.UUID("session"))

With this in place, perhaps...

1. it would be possible to tie together all events that occur during program execution.
2. contexts created midway through execution would be revealed (The session UUID will be missing when events are logged)

To make this a reality, it would be necessary to...

• remove all extraneous context.TODOs and context.Backgrounds
• pass contexts through all function calls

Eventlog output would look like this...

{"event":"updatePeer","remotePeer":{"id":"QmSoLueR4xBeUbY9WZ9xGUUxunbKWcrNFTDAadQJmocnWm","latency":89949944},"session":"893c8d83-dfdf-400c-bf9f-b0541fd2597b","system":"dht","time":"2014-12-09T14:50:29.920815354Z"}

[jbenet]

@maybebtc sgtm. may also be good to make a session object, which could include our metrics object

# yml for easy typing
id: <uuid>
timeStart: <ISO datetime>   # gives us uptime
metrics:
  bandwidth: { "in": <num>, "out": <num bytes> }
  protocolMessages: # per-protocol msg counts
    total: { "in": <num>, "out": <num bytes> }
    handshakes: { "in": <num>, "out": <num bytes> }
    bitswap: { "in": <num>, "out": <num bytes> }
    dht: { "in": <num>, "out": <num bytes> }
    ...
  clientRequests: # per-command counts
    total: <num>
    add: <num>
    ls: <num>
    ...

and so on.

[jbenet]

hm, that might be too much data to dump out on every request... maybe these are two separate things.:

# the session (logged with everything)
<uuid>

# the metrics, logged periodically (minute?)
uptime:
  timeStart: <ISO datetime>
  timeOnline: <now - uptime.timeStart>
bandwidth: { "in": <num>, "out": <num bytes> }
protocolMessages: # per-protocol msg counts
  total: { "in": <num>, "out": <num bytes> }
  handshakes: { "in": <num>, "out": <num bytes> }
  bitswap: { "in": <num>, "out": <num bytes> }
  dht: { "in": <num>, "out": <num bytes> }
  ...
clientRequests: # per-command counts
  total: <num>
  add: <num>
  ls: <num>
  ...

[btc]

added in #436

further work:

• more metadata
• remove all extraneous context.TODOs and context.Backgrounds
• pass contexts through all function calls