Brad Fitzpatrick (brad) wrote,
Brad Fitzpatrick
brad

MogileFS and FotoBilder

xb95 is a machine. I outlined how I wanted MogileFS's HTTP transport support to work and he chugged through it all week and it's pretty much complete.

Check out these paths for different actions:

First, some definitions:

Client: web browser or fotobilder client
Perlbal: front-end reverse proxy load balancer & web server
mod_perl: application server
Mogile Tracker: daemons that handles MogileFS "where is this file?" or "where can I put this file?" requests
Mogile Database: the database cluster that holds the Mogile Tracker info (will be MySQL Cluster in production)
mogstored: MogileFS's HTTP interface to the actual files. this is actually just a tiny, tiny wrapper around Perlbal. So it's actually Perlbal, with a static configuration (web server mode, allows GET, HEAD, PUT, and DELETE requests).

Uploading a file:

1: client sends to perlbal
2: perlbal sends to a mod_perl
3: mod_perl to app database
4: app database to mod_perl
5: mod_perl asks tracker where to put it
6: tracker contacts database cluster
7: database cluster responds
8: tracker replies to mod_perl
9: mod_perl does a streaming PUT to mogstored, while streaming read from perlbal (while that does a streaming read from client, sans 250k buffer or so)
10: mogstored replies HTTP OK once file is safely on disk
11: mod_perl sends fotobilder protocol OK or HTTP html okay to perlbal
12: perlbal to client

Downloading a file: (Picture)

1: client to perlbal
2: perlbal to mod_perl
3: mod_perl to app database
4: app database to mod_perl
5: mod_perl to tracker
6: tracker to database
7: database to tracker
8: tracker to mod_perl (with 1-3 internal URLs to the resource)
9: mod_perl to perlbal (with 1-3 internal URLs to resource)
10: perlbal tries 1-3 internal URLs (mogstored) until it finds somebody alive.
11: mogstored streaming to perlbal
12: perlbal streaming to client

Everything is redundant, and we never lock up mod_perls which are memory-heavy and need to do hard work. Wasting their time pushing bytes around is useless.
Tags: img, mysql, tech
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