[redis.git] / TODO

Redis TODO and Roadmap

VERSION 2.2 TODO
================

* BRPOPLPUSH
* Save dataset / fsync() on SIGTERM
* Change the implementation of ZCOUNT to use the augmented skiplist in order to be much faster.
* Write doc for ZCOUNT, and for open / closed intervals of sorted sets range operations.

Virtual Memory sub-TODO:
* Use multiple open FDs against the VM file, one for thread.
* vm-min-age <seconds> option
* Check what happens performance-wise if instead to create threads again and again the same threads are reused forever. Note: this requires a way to disable this clients in the child, but waiting for empty new jobs queue can be enough.

* Implement LEN, PEEK, POKE, SETBIT, GETBIT

VERSION 2.2 TODO (Fault tolerant sharding)
===========================================

* Redis-cluster, a fast intermediate layer (proxy) that implements consistent hashing and fault tollerant nodes handling.

Interesting readings about this:

    - http://ayende.com/Blog/archive/2009/04/06/designing-rhino-dht-a-fault-tolerant-dynamically-distributed-hash.aspx

VERSION 2.4 TODO (Optimizations and latency)
============================================

* Lower the CPU usage.
* Lower the RAM usage everywhere possible.
* Use epool and alike to rewrite ae.c for Linux and other platforms suppporting fater-than-select() mutiplexing APIs.
* Implement an UDP interface for low-latency GET/SET operations.

OTHER IMPORTANT THINGS THAT WILL BE ADDED BUT I'M NOT SURE WHEN
===============================================================

BIG ONES:

* Specially encoded memory-saving integer sets.
* A command to export a JSON dump (there should be mostly working patch needing major reworking).
* Specially encoded sets of integers (this includes a big refactoring providing an higher level layer for Sets manipulation)

SMALL ONES:

* If sizeof(double) == sizeof(void*) we could store the double value of sorted sets directly in place of the pointer instead of allocating it in the heap.
* Delete on writes against expire policy should only happen after argument parsing for commands doing their own arg parsing stuff.
* Give errors when incrementing a key that does not look like an integer, when providing as a sorted set score something can't be parsed as a double, and so forth.
* MSADD (n keys) (n values). See this thread in the Redis google group: http://groups.google.com/group/redis-db/browse_thread/thread/e766d84eb375cd41
* Don't save empty lists / sets / zsets on disk with snapshotting.
* Remove keys when a list / set / zset reaches length of 0.
* An option to exec a command slave-side if the master connection is lost: even cooler: if the script returns "0" the slave elects itself as master, otherwise continue trying to reconnect.
* PING the master from time to time to check if it's gone.

THE "MAYBE" TODO LIST: things that may or may not get implemented
=================================================================

Most of this can be seen just as proposals, the fact they are in this list
it's not a guarantee they'll ever get implemented ;)

* Move dict.c from hash table to skip list, in order to avoid the blocking resize operation needed for the hash table.
* FORK command (fork()s executing the commands received by the current
  client in the new process). Hint: large SORTs can use more cores,
  copy-on-write will avoid memory problems.
* DUP command? DUP srckey dstkey, creates an exact clone of srckey value in dstkey.
* SORT: Don't copy the list into a vector when BY argument is constant.
* Write the hash table size of every db in the dump, so that Redis can resize the hash table just one time when loading a big DB.
* LOCK / TRYLOCK / UNLOCK as described many times in the google group
* Replication automated tests
* Byte Array type (BA prefixed commands): BASETBIT BAGETBIT BASETU8 U16 U32 U64 S8 S16 S32 S64, ability to atomically INCRBY all the base types. BARANGE to get a range of bytes as a bulk value, BASETRANGE to set a range of bytes.
* zmalloc() should avoid to add a private header for archs where there is some other kind of libc-specific way to get the size of a malloced block. Already done for Mac OS X.
* Read-only mode.
* Pattern-matching replication.
* Add an option to relax the delete-expiring-keys-on-write semantic *denying* replication and AOF when this is on? Can be handy sometimes, when using Redis for non persistent state, but can create problems. For instance should rename and move also "move" the timeouts? How does this affect other commands?
* Multiple BY in SORT.
Commit	Line	Data
f284d963	1	Redis TODO and Roadmap
f284d963	2
32a66513	3	VERSION 2.2 TODO
6766f45e	4	================
23cff1a8	5
b177fd30	6	* BRPOPLPUSH
b177fd30	7	* Save dataset / fsync() on SIGTERM
32a66513	8	* Change the implementation of ZCOUNT to use the augmented skiplist in order to be much faster.
7c775e09	9	* Write doc for ZCOUNT, and for open / closed intervals of sorted sets range operations.
f6b141c5	10
f870935d	11	Virtual Memory sub-TODO:
7c775e09	12	* Use multiple open FDs against the VM file, one for thread.
b72f6a4b	13	* vm-min-age <seconds> option
478c2c6f	14	* Check what happens performance-wise if instead to create threads again and again the same threads are reused forever. Note: this requires a way to disable this clients in the child, but waiting for empty new jobs queue can be enough.
f870935d	15
a97b9060	16	* Implement LEN, PEEK, POKE, SETBIT, GETBIT
7d65b33d	17
b0d8747d	18	VERSION 2.2 TODO (Fault tolerant sharding)
c35f7d5b	19	===========================================
7d65b33d	20
c35f7d5b	21	* Redis-cluster, a fast intermediate layer (proxy) that implements consistent hashing and fault tollerant nodes handling.
7d65b33d	22
5b2a1c29	23	Interesting readings about this:
	24
	25	- http://ayende.com/Blog/archive/2009/04/06/designing-rhino-dht-a-fault-tolerant-dynamically-distributed-hash.aspx
	26
b0d8747d	27	VERSION 2.4 TODO (Optimizations and latency)
c35f7d5b	28	============================================
7d65b33d	29
	30	* Lower the CPU usage.
	31	* Lower the RAM usage everywhere possible.
	32	* Use epool and alike to rewrite ae.c for Linux and other platforms suppporting fater-than-select() mutiplexing APIs.
	33	* Implement an UDP interface for low-latency GET/SET operations.
	34
3f477979	35	OTHER IMPORTANT THINGS THAT WILL BE ADDED BUT I'M NOT SURE WHEN
	36	===============================================================
	37
	38	BIG ONES:
	39
	40	* Specially encoded memory-saving integer sets.
	41	* A command to export a JSON dump (there should be mostly working patch needing major reworking).
f0c138f6	42	* Specially encoded sets of integers (this includes a big refactoring providing an higher level layer for Sets manipulation)
3f477979	43
	44	SMALL ONES:
	45
ada386b2	46	* If sizeof(double) == sizeof(void*) we could store the double value of sorted sets directly in place of the pointer instead of allocating it in the heap.
978c2c94	47	* Delete on writes against expire policy should only happen after argument parsing for commands doing their own arg parsing stuff.
3f477979	48	* Give errors when incrementing a key that does not look like an integer, when providing as a sorted set score something can't be parsed as a double, and so forth.
25e52257	49	* MSADD (n keys) (n values). See this thread in the Redis google group: http://groups.google.com/group/redis-db/browse_thread/thread/e766d84eb375cd41
f0c138f6	50	* Don't save empty lists / sets / zsets on disk with snapshotting.
f0c138f6	51	* Remove keys when a list / set / zset reaches length of 0.
5921aa36	52	* An option to exec a command slave-side if the master connection is lost: even cooler: if the script returns "0" the slave elects itself as master, otherwise continue trying to reconnect.
3ea27d37	53	* PING the master from time to time to check if it's gone.
3f477979	54
f0c138f6	55	THE "MAYBE" TODO LIST: things that may or may not get implemented
f0c138f6	56	=================================================================
f6b141c5	57
0188805d	58	Most of this can be seen just as proposals, the fact they are in this list
	59	it's not a guarantee they'll ever get implemented ;)
	60
57033301	61	* Move dict.c from hash table to skip list, in order to avoid the blocking resize operation needed for the hash table.
682ac724	62	* FORK command (fork()s executing the commands received by the current
	63	client in the new process). Hint: large SORTs can use more cores,
	64	copy-on-write will avoid memory problems.
	65	* DUP command? DUP srckey dstkey, creates an exact clone of srckey value in dstkey.
	66	* SORT: Don't copy the list into a vector when BY argument is constant.
	67	* Write the hash table size of every db in the dump, so that Redis can resize the hash table just one time when loading a big DB.
	68	* LOCK / TRYLOCK / UNLOCK as described many times in the google group
	69	* Replication automated tests
	70	* Byte Array type (BA prefixed commands): BASETBIT BAGETBIT BASETU8 U16 U32 U64 S8 S16 S32 S64, ability to atomically INCRBY all the base types. BARANGE to get a range of bytes as a bulk value, BASETRANGE to set a range of bytes.
	71	* zmalloc() should avoid to add a private header for archs where there is some other kind of libc-specific way to get the size of a malloced block. Already done for Mac OS X.
	72	* Read-only mode.
	73	* Pattern-matching replication.
ac945e2d	74	* Add an option to relax the delete-expiring-keys-on-write semantic denying replication and AOF when this is on? Can be handy sometimes, when using Redis for non persistent state, but can create problems. For instance should rename and move also "move" the timeouts? How does this affect other commands?
f0c138f6	75	* Multiple BY in SORT.