SummitDB is an in-memory, NoSQL key/value database. It persists to disk, uses the Raft consensus algorithm, is ACID compliant, and built on a transactional and strongly-consistent model. It supports custom indexes, geospatial data, JSON documents, and user-defined JS scripting.
Under the hood it utilizes Finn, Redcon, BuntDB, GJSON, and Otto.
Features
- In-memory with disk persistence
- Strong-consistency and durability
- High-availability
- Ordered key space
- Hot backups
- Simplified Redis-style APIs
- Indexing on values
- JSON documents
- Spatial indexing
- Fencing tokens
Getting started
Getting SummitDB
The easiest way to get SummitDB is to use one of the pre-built release binaries which are available for OSX, Linux, and Windows. Instructions for using these binaries are on the GitHub releases page.
If you want to try the latest version, you can build SummitDB from the master branch.
Building SummitDB
SummitDB can be compiled and used on Linux, OSX, Windows, FreeBSD, ARM (Raspberry PI) and probably others since the codebase is 100% Go. We support both 32 bit and 64 bit systems. Go must be installed on the build machine.
To build simply:
$ make
It's a good idea to install the redis-cli.
$ make redis-cli
To run tests:
$ make test
Docker
Check out the SummitDB images in Docker Hub.
Running
First start a single-member cluster:
$ ./summitdb-server
This will start the server listening on port 7481 for client and server-to-server communication.
Next, let's set a single key, and then retrieve it:
$ ./redis-cli -p 7481 SET mykey "my value"
OK
$ ./redis-cli -p 7481 GET mykey
"my value"
Adding members:
$ ./summitdb-server -p 7482 -dir data2 -join localhost:7481
$ ./summitdb-server -p 7483 -dir data3 -join localhost:7481
That's it. Now if node1 goes down, node2 and node3 will continue to operate.
Differences between SummitDB and Redis
It may be worth noting that while SummitDB supports many Redis features, it is not a strict Redis clone. Redis has a lot of commands and data types that are not available in SummitDB such as Sets, Hashes, Sorted Sets, and PubSub. SummitDB also has many features that are not available in Redis such as:
- Ordered key space - SummitDB provides one key space that is a large B-tree. An ordered key space allows for stable paging through keys using the KEYS command. Redis uses an unordered dictionary structure and provides a specialized SCAN command for iterating through keys.
- Everything a string - SummitDB stores only strings which are exact binary representations of what the user stores. Redis has many internal data types, such as strings, hashes, floats, sets, etc.
- Raft clusters - SummitDB uses the Raft consensus algorithm to provide high-availablity. Redis provides Master/Slave replication.
- Javascript - SummitDB uses Javascript for user-defined scripts. Redis uses Lua.
- Indexes - SummitDB provides an API for indexing the key space. Indexes allow for quickly querying and iterating on values. Redis has specialized data types like Sorted Sets and Hashes which can provide secondary indexing.
- Spatial indexes - SummitDB provides the ability to create spatial indexes. A spatial index uses an R-tree under the hood, and each index can be up to 20 dimensions. This is useful for geospatial, statistical, time, and range data. Redis has the GEO API which allows for using storing and querying geospatial data using the Geohashes.
- JSON documents - SummitDB allows for storing JSON documents and indexing fields directly. Redis has Hashes and a JSON parser via Lua.
In-memory with disk persistence
SummitDB store all data in memory. Yet each writable command is appended to a file that is used to rebuild the database if the database needs to be restarted.
This is similar to Redis AOF persistence.
JSON Documents
SummitDB provides the commands JSET, JGET, JDEL for working with json documents.
JSET and JDEL uses the
sjson path syntax
and JGET uses the
gjson path syntax.
Here are some examples:
> JSET user:101 name Tom
OK
> JSET user:101 age 46
OK
> GET user:101
"{\"age\":46,\"name\":\"Tom\"}"
> JGET user:101 age
"46"
> JSET user:101 name.first Tom
OK
> JSET user:101 name.last Anderson
OK
> GET user:101
"{\"age\":46,\"name\":{\"last\":\"Anderson\",\"first\":\"Tom\"}}"
> JDEL user:101 name.last
(integer) 1
> GET user:101
"{\"age\":46,\"name\":{\"first\":\"Tom\"}}"
> JSET user:101 friends.0 Carol
OK
> JSET user:101 friends.1 Andy
OK
> JSET user:101 friends.3 Frank
OK
> GET user:101
"{\"friends\":[\"Carol\",\"Andy\",null,\"Frank\"],\"age\":46,\"name\":{\"first\":\"Tom\"}}"
> JGET user:101 friends.1
"Andy"
JSON Indexes
Indexes can be created on individual fields inside JSON documents.
For example, let's say you have the following documents:
{"name":{"first":"Tom","last":"Johnson"},"age":38}
{"name":{"first":"Janet","last":"Prichard"},"age":47}
{"name":{"first":"Carol","last":"Anderson"},"age":52}
{"name":{"first":"Alan","last":"Cooper"},"age":28}Create an index:
> SETINDEX last_name user:* JSON name.last
Then add some JSON:
> SET user:1 '{"name":{"first":"Tom","last":"Johnson"},"age":38}'
> SET user:2 '{"name":{"first":"Janet","last":"Prichard"},"age":47}'
> SET user:3 '{"name":{"first":"Carol","last":"Anderson"},"age":52}'
> SET user:4 '{"name":{"first":"Alan","last":"Cooper"},"age":28}'
Query with the ITER command:
> ITER last_name
1) "user:3"
2) "{\"name\":{\"first\":\"Carol\",\"last\":\"Anderson\"},\"age\":52}"
3) "user:4"
4) "{\"name\":{\"first\":\"Alan\",\"last\":\"Cooper\"},\"age\":28}"
5) "user:1"
6) "{\"name\":{\"first\":\"Tom\",\"last\":\"Johnson\"},\"age\":38}"
7) "user:2"
8) "{\"name\":{\"first\":\"Janet\",\"last\":\"Prichard\"},\"age\":47}"
Or perhaps you want to index on age:
> SETINDEX age user:* JSON age
> ITER age
1) "user:4"
2) "{\"name\":{\"first\":\"Alan\",\"last\":\"Cooper\"},\"age\":28}"
3) "user:1"
4) "{\"name\":{\"first\":\"Tom\",\"last\":\"Johnson\"},\"age\":38}"
5) "user:2"
6) "{\"name\":{\"first\":\"Janet\",\"last\":\"Prichard\"},\"age\":47}"
7) "user:3"
8) "{\"name\":{\"first\":\"Carol\",\"last\":\"Anderson\"},\"age\":52}"
It's also possible to multi-index on two fields:
> SETINDEX last_name_age user:* JSON name.last JSON age
For full JSON indexing syntax check out the SETINDEX and ITER commands.
Fencing Tokens
A fencing token is simply a number that increases. It's guaranteed to be consistent across the cluster and can never be deleted or decreased. The value is a 64-bit unsigned integer. The first FENCE call will return "1". This can be useful in applications that need things like distributed locking and preventing race conditions. FENCEGET will read the token without incrementing it.
> FENCE mytoken
"1"
> FENCE mytoken
"2"
> FENCE mytoken
"3"
> FENCEGET mytoken
"3"
> FENCE mytoken
"4"
Built-in Raft Commands
Here are a few commands for monitoring and managing the cluster:
- RAFTADDPEER addr
Adds a new member to the Raft cluster - RAFTREMOVEPEER addr
Removes an existing member - RAFTPEERS
Lists known peers and their status - RAFTLEADER
Returns the Raft leader, if known - RAFTSNAPSHOT
Triggers a snapshot operation - RAFTSTATE
Returns the state of the node - RAFTSTATS
Returns information and statistics for the node and cluster
Consistency and Durability
SummitDB is tuned by design for strong consistency and durability. A server shutdown, power event, or kill -9 will not corrupt the state of the cluster or lose data.
All data persists to disk. SummitDB uses an append-only file format that stores for each command in exact order of execution. Each command consists of a one write and one fsync. This provides excellent durability.
Read Consistency
The --consistency param has the following options:
low- all nodes accept reads, small risk of stale datamedium- only the leader accepts reads, itty-bitty risk of stale data during a leadership changehigh- only the leader accepts reads, the raft log index is incremented to guarantee no stale data. this is the default
For example, setting the following options:
$ summitdb --consistency high
Provides the highest level of consistency. The default is high.
Leadership Changes
In a Raft cluster only the leader can apply commands. If a command is attempted on a follower you will be presented with the response:
> SET x y
-TRY 127.0.0.1:7481
This means you should try the same command at the specified address.
Hot Backups
SummitDB supports hot-backing up a node. You can retrieve and restore a snapshot of the database to a file using the BACKUP command.
> BACKUP
BULK REPLY OF DATA
Or using an HTTP connection like such:
curl localhost:7481/backup -o backup.db
The backup file format is a series of commands which are stored as RESP Arrays. The command:
SET mykey 123
Is stored on disk as:
"*3\r\n$3\r\nSET\r\n$5\r\nmykey\r\n$3\r\n123\r\n"To restore a system from a backup, issue each command to the leader. For example, using the nc command you could execute:
$ cat backup.db | nc localhost 7481Commands
Below is the complete list of commands.
Keys and values
APPEND,
BITCOUNT,
BITOP,
BITPOS,
DBSIZE,
DECR,
DECRBY,
DEL,
EXISTS,
EXPIRE,
EXPIREAT,
FENCE,
FENCEGET,
FLUSHDB,
GET,
GETBIT,
GETRANGE,
GETSET,
INCR,
INCRBY,
INCRBYFLOAT,
KEYS,
MGET,
MSET,
MSETNX,
PDEL,
PERSIST,
PEXPIRE,
PEXPIREAT,
PTTL,
RENAME,
RENAMENX,
SET,
SETBIT,
SETRANGE,
STRLEN,
TTL
Indexes and iteration
DELINDEX,
INDEXES,
ITER,
RECT,
SETINDEX
Transactions
MULTI,
EXEC,
DISCARD
Scripts
EVAL,
EVALRO,
EVALSHA,
EVALSHARO,
SCRIPT LOAD,
SCRIPT FLUSH
Raft management
RAFTADDPEER,
RAFTREMOVEPEER,
RAFTLEADER,
RAFTSNAPSHOT,
RAFTSTATE,
RAFTSTATS
Server
BACKUP
Contact
Josh Baker @tidwall
License
SummitDB source code is available under the MIT License.