|author||Christian Grothoff <firstname.lastname@example.org>||2010-07-18 20:18:17 +0000|
|committer||Christian Grothoff <email@example.com>||2010-07-18 20:18:17 +0000|
Diffstat (limited to 'RATIONALE')
1 files changed, 24 insertions, 21 deletions
@@ -1,12 +1,13 @@
-This document is a summary of why we're moving to GNUnet NG and what
-this major redesign tries to address.
+This document is a summary of the changes made to GNUnet for version
+0.9.x (from 0.8.x) and what this major redesign tries to address.
First of all, the redesign does not (intentionally) change anything
fundamental about the application-level protocols or how files are
encoded and shared. However, it is not protocol-compatible due to
other changes that do not relate to the essence of the application
+protocols. This choice was made since productive development and
+readable code were considered more important than compatibility at
The redesign tries to address the following major problem groups
describing isssues that apply more or less to all GNUnet versions
@@ -26,10 +27,10 @@ PROBLEM GROUP 1 (scalability):
mutexes and almost 1000 lines of lock/unlock operations.
It is challenging for even good programmers to program or
maintain good multi-threaded code with this complexity.
- The excessive locking essentially prevents GNUnet from
+ The excessive locking essentially prevents GNUnet 0.8 from
actually doing much in parallel on multicores.
* Despite efforts like Freeway, it was virtually
- impossible to contribute code to GNUnet that was not
+ impossible to contribute code to GNUnet 0.8 that was not
writen in C/C++.
* Changes to the configuration almost always required restarts
of gnunetd; the existence of change-notifications does not
@@ -44,11 +45,11 @@ PROBLEM GROUP 1 (scalability):
days, result in really nasty and hard-to-find crashes.
* structs of function pointers in service APIs were
needlessly adding complexity, especially since in
- most cases there was no polymorphism
+ most cases there was no actual polymorphism
* Use multiple, lously-coupled processes and one big select
- loop in each (supported by a powerful library to eliminate
+ loop in each (supported by a powerful util library to eliminate
code duplication for each process).
* Eliminate all threads, manage the processes with a
master-process (gnunet-arm, for automatic restart manager)
@@ -65,13 +66,15 @@ SOLUTION:
=> Process priorities can be used to schedule the CPU better
Note that we can not just use one process with a big
select loop because we have blocking operations (and the
- blocking is outside of our control, thanks MySQL,
+ blocking is outside of our control, thanks to MySQL,
sqlite, gethostbyaddr, etc.). So in order to perform
reasonably well, we need some construct for parallel
RULE: If your service contains blocking functions, it
- MUST be a process by itself.
+ MUST be a process by itself. If your service
+ is sufficiently complex, you MAY choose to make
+ it a separate process.
* Eliminate structs with function pointers for service APIs;
instead, provide a library (still ending in _service.h) API
that transmits the requests nicely to the respective
@@ -121,6 +124,8 @@ SOLUTION:
thing given the potential for bugs.
* There is no more TIME API function to do anything
with 32-bit seconds
+* There is now a bandwidth API to handle
+ non-trivial bandwidth utilization calculations
PROBLEM GROUP 3 (statistics):
@@ -237,18 +242,15 @@ PROBLEM GROUP 6 (FS-APIs):
* FILENAME metadata is killed by ECRS/FSUI to avoid
exposing HOME, but what if the user set it manually?
-SOLUTION (draft, not done yet, details missing...):
* Eliminate threads from FS-APIs
- => Open question: how to best write the APIs to
- allow integration with diverse event loops
- of GUI libraries?
-* Store FS-state always also on disk
- => Open question: how to do this without
- compromising state/scalability?
+* Incrementally store FS-state always also on disk using many
+ small files instead of one big file
* Have API to manipulate sharing tree before
upload; have auto-construction modify FILENAME
but allow user-modifications afterwards
PROBLEM GROUP 7 (User experience):
* Searches often do not return a sufficient / significant number of
@@ -281,11 +283,12 @@ SUMMARY:
- network traffic monitors (goal: eliminate)
- IPC semaphores (goal: d-bus? / eliminate?)
- second timers
- - DNS lookup (goal: have async service; issue: still need synchronous
- resolution in places, current code may not be portable)
- => code shrunk from 61 files to 34, 22k LOC to 15k LOC, 470k to 330k (with symbols)
* New features in util:
- service and program boot-strap code
+ - bandwidth and time APIs
+ - buffered IO API
+ - HKDF implementation (crypto)
* Major changes in util:
- more expressive server (replaces selector)
+ - DNS lookup replaced by async service