context/tracing in the blockstore/datastore pipeline

[MichaelMure]

At Infura, we have to deal with the occasional performance issue. Even though we now have added tracing in the HTTP handler of go-ipfs-cmds (not upstreamed yet, it's opentracing and you are aiming for opencensus if I'm not mistaken?), the tracing essentially stop there.

The majority of the requests (and the perf issues) involve the data pipeline but it is essentially a black box. To resolve that problem, a proper tracing instrumentation there would be very helpful, but that imply adding a go context to most if not all blockstore and datastore functions.

Is that something you would be interested to pursue ?

cc @dirkmc maybe ?

[Stebalien]

We should be passing contexts through to the datastores but the refactor is going to be quite large and invasive and will affect multiple projects (ipfs, libp2p, filecoin, and probably quite a few more).

We should look into this next year but I don't have time right now to handle all the fallout of this refactor.