[redis.git] / TODO

Redis TODO and Roadmap

VERSION 1.4 TODO (Hash type)
============================

* BRPOPLPUSH
* RPOPLPUSH should notify blocking POP operations
* List ops like L/RPUSH L/RPOP should return the new list length.
* Save dataset / fsync() on SIGTERM
* MULTI/EXEC should support the "EXEC FSYNC" form
* Synchronous Virtual Memory
* BLPOP & C. tests (write a non blocking Tcl client as first step)

Virtual Memory sub-TODO:
* Check if the page selection algorithm is working well.
* Divide swappability of objects by refcount
* vm-swap-file <filename>. The swap file should go where the user wants, and if it's already there and of the right size we can avoid to create it again.
* it should be possible to give the vm-max-memory option in megabyte, gigabyte, ..., just using 2GB, 100MB, and so forth.
* Make sure to wait all the IO threads are done before to fork() for BGSAVE and BGREWRITEAOF
* Enlarge the stack of threads, to problems when calling LZF lib.
* redis-cli vmstat, calling INFO every second and printing VM stats ala vmstat.

VERSION 1.6 TODO (Virtual memory)
=================================

* Asynchronous Virtual Memory
* Hashes (HSET, HGET, HEXISTS, HLEN, ...).

VERSION 1.8 TODO (Fault tollerant 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 2.0 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.

VERSION 2.2 TODO (Optimizations and latency)
============================================

* JSON command able to access data serialized in JSON format. For instance if I've a key foobar with a json object I can alter the "name" file using somthing like: "JSON SET foobar name Kevin". We should have GET and INCRBY as well.

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)
* ZRANK: http://docs.google.com/viewer?a=v&q=cache:tCQaP3ZeN4YJ:courses.csail.mit.edu/6.046/spring04/handouts/ps5-sol.pdf+skip+list+rank+operation+augmented&hl=en&pid=bl&srcid=ADGEEShXuNjTcZyXw_1cq9OaWpSXy3PprjXqVzmM-LE0ETFznLyrDXJKQ_mBPNT10R8ErkoiXD9JbMw_FaoHmOA4yoGVrA7tZWiy393JwfCwuewuP93sjbkzZ_gnEp83jYhPYjThaIzw&sig=AHIEtbRF0GkYCdYRFtTJBE69senXZwFY0w

SMALL ONES:

* 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.

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
2014c437	3	VERSION 1.4 TODO (Hash type)
c35f7d5b	4	============================
23cff1a8	5
b177fd30	6	* BRPOPLPUSH
b177fd30	7	* RPOPLPUSH should notify blocking POP operations
09f6f702	8	* List ops like L/RPUSH L/RPOP should return the new list length.
b177fd30	9	* Save dataset / fsync() on SIGTERM
	10	* MULTI/EXEC should support the "EXEC FSYNC" form
	11	* Synchronous Virtual Memory
	12	* BLPOP & C. tests (write a non blocking Tcl client as first step)
f6b141c5	13
f870935d	14	Virtual Memory sub-TODO:
f870935d	15	* Check if the page selection algorithm is working well.
f870935d	16	* Divide swappability of objects by refcount
0d7170a4	17	* vm-swap-file <filename>. The swap file should go where the user wants, and if it's already there and of the right size we can avoid to create it again.
ec6c7a1d	18	* it should be possible to give the vm-max-memory option in megabyte, gigabyte, ..., just using 2GB, 100MB, and so forth.
72e9fd40	19	* Make sure to wait all the IO threads are done before to fork() for BGSAVE and BGREWRITEAOF
b74880b4	20	* Enlarge the stack of threads, to problems when calling LZF lib.
2e111efe	21	* redis-cli vmstat, calling INFO every second and printing VM stats ala vmstat.
f870935d	22
2014c437	23	VERSION 1.6 TODO (Virtual memory)
c35f7d5b	24	=================================
7d65b33d	25
b177fd30	26	* Asynchronous Virtual Memory
b177fd30	27	* Hashes (HSET, HGET, HEXISTS, HLEN, ...).
7d65b33d	28
2014c437	29	VERSION 1.8 TODO (Fault tollerant sharding)
c35f7d5b	30	===========================================
7d65b33d	31
c35f7d5b	32	* Redis-cluster, a fast intermediate layer (proxy) that implements consistent hashing and fault tollerant nodes handling.
7d65b33d	33
5b2a1c29	34	Interesting readings about this:
	35
	36	- http://ayende.com/Blog/archive/2009/04/06/designing-rhino-dht-a-fault-tolerant-dynamically-distributed-hash.aspx
	37
2014c437	38	VERSION 2.0 TODO (Optimizations and latency)
c35f7d5b	39	============================================
7d65b33d	40
	41	* Lower the CPU usage.
	42	* Lower the RAM usage everywhere possible.
	43	* Use epool and alike to rewrite ae.c for Linux and other platforms suppporting fater-than-select() mutiplexing APIs.
	44	* Implement an UDP interface for low-latency GET/SET operations.
	45
2014c437	46	VERSION 2.2 TODO (Optimizations and latency)
	47	============================================
	48
	49	* JSON command able to access data serialized in JSON format. For instance if I've a key foobar with a json object I can alter the "name" file using somthing like: "JSON SET foobar name Kevin". We should have GET and INCRBY as well.
	50
3f477979	51	OTHER IMPORTANT THINGS THAT WILL BE ADDED BUT I'M NOT SURE WHEN
	52	===============================================================
	53
	54	BIG ONES:
	55
	56	* Specially encoded memory-saving integer sets.
	57	* A command to export a JSON dump (there should be mostly working patch needing major reworking).
f0c138f6	58	* Specially encoded sets of integers (this includes a big refactoring providing an higher level layer for Sets manipulation)
322fc7d8	59	* ZRANK: http://docs.google.com/viewer?a=v&q=cache:tCQaP3ZeN4YJ:courses.csail.mit.edu/6.046/spring04/handouts/ps5-sol.pdf+skip+list+rank+operation+augmented&hl=en&pid=bl&srcid=ADGEEShXuNjTcZyXw_1cq9OaWpSXy3PprjXqVzmM-LE0ETFznLyrDXJKQ_mBPNT10R8ErkoiXD9JbMw_FaoHmOA4yoGVrA7tZWiy393JwfCwuewuP93sjbkzZ_gnEp83jYhPYjThaIzw&sig=AHIEtbRF0GkYCdYRFtTJBE69senXZwFY0w
3f477979	60
	61	SMALL ONES:
	62
	63	* 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	64	* 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	65	* Don't save empty lists / sets / zsets on disk with snapshotting.
f0c138f6	66	* Remove keys when a list / set / zset reaches length of 0.
3f477979	67
f0c138f6	68	THE "MAYBE" TODO LIST: things that may or may not get implemented
f0c138f6	69	=================================================================
f6b141c5	70
0188805d	71	Most of this can be seen just as proposals, the fact they are in this list
	72	it's not a guarantee they'll ever get implemented ;)
	73
57033301	74	* Move dict.c from hash table to skip list, in order to avoid the blocking resize operation needed for the hash table.
682ac724	75	* FORK command (fork()s executing the commands received by the current
	76	client in the new process). Hint: large SORTs can use more cores,
	77	copy-on-write will avoid memory problems.
	78	* DUP command? DUP srckey dstkey, creates an exact clone of srckey value in dstkey.
	79	* SORT: Don't copy the list into a vector when BY argument is constant.
	80	* 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.
	81	* LOCK / TRYLOCK / UNLOCK as described many times in the google group
	82	* Replication automated tests
	83	* 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.
	84	* 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.
	85	* Read-only mode.
	86	* Pattern-matching replication.
ac945e2d	87	* 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	88	* Multiple BY in SORT.