Implement statistics to support Connection Management

[hacdias]

In order to implement stats/bw on js-ipfs, we need to have some way to measure the bandwidth that comes in and out of js-ipfs. It should also support peer and protocol basis metrics.

Some refs:

• per-peer stats ipfs/js-ipfs-bitswap#165
• feat: stats API (stats.bitswap and stats.repo) ipfs/js-ipfs#1198

/cc @pgte @diasdavid

[pgte]

It turns out I also need global stats to implement this connection manager API: https://github.com/libp2p/js-libp2p-connection-manager/tree/master#api

[pgte]

@diasdavid what would be, in your opinion, the best place in the libp2p stack to monitor total traffic (if that's even possible)?

[daviddias]

It can be a module that implements that functionality and gets plugged into js-libp2p.

[pgte]

@diasdavid and how would it hook itself into watching the traffic?

[pgte]

@diasdavid ping :)

[daviddias]

@pgte wanna make a suggestion for that one?

[pgte]

OK, took me a bit to figure out how switch is handling all the outgoing and incoming connections, but here goes:

Some requirements: we need to observe unencrypted traffic in protocol-specific streams so we can compute total (unencrypted) traffic by peer, protocol, direction (upload / download) and the combinations of these ({ peer, protocol }, {peer, direction}, {peer, protocol, direction}).

In my guess, we need the following hooks on js-libp2p-switch:

On self-initiated connections:

• We have the multiplexed protocol-specific connection in this line. We must attach an observer to this stream.

On incoming connections:

• I guess this is a bit more tricky. I think we must wrap each protocol handler function, and one place to do this is before this line: https://github.com/libp2p/js-libp2p-switch/blob/75ba1c156d24c2a4814ef48b1ebdab71f6eaf3d9/src/protocol-muxer.js#L13

@diasdavid thoughts?