dimgigov
4a83eb6783
- Add multi-database limitations to distributed docs - Fix backup commands and add multi-database backup guidance - Add SQL migration section to schema docs - Update storage examples to use per-database paths
113 lines
2.6 KiB
Markdown
113 lines
2.6 KiB
Markdown
# Distributed Systems
|
|
|
|
BaraDB supports distributed deployment with Raft consensus, sharding, and replication.
|
|
|
|
> ⚠️ **Multi-Database Limitation**
|
|
> The distributed modules (Raft, sharding, and replication) are currently wired to the **`default`** database only. If you use multiple databases (`CREATE DATABASE`, `USE DATABASE`), distributed features do not yet span across them. Each database would need its own cluster setup.
|
|
|
|
## Raft Consensus
|
|
|
|
Leader election and log replication:
|
|
|
|
```nim
|
|
import barabadb/core/raft
|
|
|
|
var cluster = newRaftCluster()
|
|
cluster.addNode("node1")
|
|
cluster.addNode("node2")
|
|
cluster.addNode("node3")
|
|
|
|
let n1 = cluster.nodes["n1"]
|
|
n1.becomeCandidate()
|
|
n1.becomeLeader()
|
|
let entry = n1.appendLog("SET key1 value1")
|
|
```
|
|
|
|
## Sharding
|
|
|
|
Distribute data across nodes:
|
|
|
|
```nim
|
|
import barabadb/core/sharding
|
|
|
|
var router = newShardRouter(ShardConfig(
|
|
numShards: 4,
|
|
replicas: 2,
|
|
strategy: ssHash
|
|
))
|
|
router.rebalance(@["node1", "node2", "node3"])
|
|
let shard = router.getShard("user_123")
|
|
```
|
|
|
|
### Sharding Strategies
|
|
|
|
| Strategy | Description |
|
|
|----------|-------------|
|
|
| `ssHash` | Hash-based sharding |
|
|
| `ssRange` | Range-based sharding |
|
|
| `ssConsistent` | Consistent hashing |
|
|
|
|
## Replication
|
|
|
|
```nim
|
|
import barabadb/core/replication
|
|
|
|
var rm = newReplicationManager(rmSync)
|
|
rm.addReplica(newReplica("r1", "10.0.0.1", 9472))
|
|
rm.connectReplica("r1")
|
|
let lsn = rm.writeLsn(@[1'u8, 2, 3])
|
|
rm.ackLsn("r1", lsn)
|
|
```
|
|
|
|
### Replication Modes
|
|
|
|
| Mode | Description |
|
|
|------|-------------|
|
|
| `rmSync` | Synchronous replication |
|
|
| `rmAsync` | Asynchronous replication |
|
|
| `rmSemiSync` | Semi-synchronous replication |
|
|
|
|
## Gossip Protocol
|
|
|
|
Membership and failure detection:
|
|
|
|
```nim
|
|
import barabadb/core/gossip
|
|
|
|
var g = newGossipManager()
|
|
g.addNode("node1")
|
|
g.addNode("node2")
|
|
g.tick() # Exchange membership info
|
|
```
|
|
|
|
## Distributed Transactions
|
|
|
|
Two-phase commit across nodes:
|
|
|
|
```nim
|
|
import barabadb/core/disttxn
|
|
|
|
var dt = newDistributedTxn()
|
|
dt.prepare(@["node1", "node2"])
|
|
dt.commit()
|
|
```
|
|
|
|
## Formal Verification
|
|
|
|
Core distributed algorithms are formally specified in TLA+ and model-checked:
|
|
|
|
- **Raft Consensus** — `formal-verification/raft.tla`
|
|
- Verified: ElectionSafety, StateMachineSafety
|
|
- **Two-Phase Commit** — `formal-verification/twopc.tla`
|
|
- Verified: Atomicity, NoOrphanBlocks
|
|
- **Replication** — `formal-verification/replication.tla`
|
|
- Verified: MonotonicLsn, AcksRemovePending
|
|
|
|
Run TLC locally:
|
|
|
|
```bash
|
|
cd formal-verification
|
|
java -cp tla2tools.jar tlc2.TLC -config models/raft.cfg raft.tla
|
|
java -cp tla2tools.jar tlc2.TLC -config models/twopc.cfg twopc.tla
|
|
java -cp tla2tools.jar tlc2.TLC -config models/replication.cfg replication.tla
|
|
``` |