Performance is not good enough to scale.

[ppepos]

Currently:

• Loading the homepage with under 10 players takes roughly 5 seconds.
• Loading a player page takes roughly 3 seconds

Increasing the amount of players to say 60 renders the application unusable.

We need to start worrying about performance and fix some bottlenecks. After some discussion, here are some possible paths:

• We tweaked the MongoDB connector to log each query and loading the homepage with 7 players triggers 821 queries to MongoDB. Most of which are pretty similar to each other.
• Looking at the time passed in user vs kernel space might yield interesting information.
• Profiling the app as it runs could also yield potential information.

Keep updating this issue with the information you gather so we can find appropriate fixes.

[Morriar]

Here's the bottleneck (and the source of all these queries): https://github.com/Morriar/Missions/blob/master/src/model/stats.nit#L33

[privat]

Here a callgrind of a single "/api/players" GET request on the web server:

callgrind.out.txt

conclusion: 2.57 GIr total
98.68% in Player::stats (7 calls)
63.03% in Repository:find (819 calls)
46% in BSON::to_json (1733 calls)

Code culprits:
48% in app
20% in boehm
15% in libbson (from mongo)
14% in libc (strlen and allocation)

[Morriar]

I will close #27 that is mostly about the same problem with less discussion in it.