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src/zookeeper/README.md

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+# ZooKeeper
+
+[Apache ZooKeeper](https://zookeeper.apache.org/) is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services.
+
+## Features
+
+- Configuration Management: Centralized configuration management
+- Naming Service: Distributed naming service
+- Synchronization: Distributed synchronization primitives
+- Group Services: Group membership and leader election
+- High Availability: Built-in replication and failover
+
+## Quick Start
+
+Start ZooKeeper:
+
+```bash
+docker compose up -d
+```
+
+## Configuration
+
+### Environment Variables
+
+- `ZOOKEEPER_VERSION`: ZooKeeper version (default: `3.9.3`)
+- `ZOOKEEPER_CLIENT_PORT_OVERRIDE`: Client port (default: `2181`)
+- `ZOOKEEPER_ADMIN_PORT_OVERRIDE`: Admin server port (default: `8080`)
+- `ZOO_TICK_TIME`: Tick time in milliseconds (default: `2000`)
+- `ZOO_INIT_LIMIT`: Init limit (default: `10`)
+- `ZOO_SYNC_LIMIT`: Sync limit (default: `5`)
+- `ZOO_MAX_CLIENT_CNXNS`: Maximum client connections (default: `60`)
+- `ZOO_4LW_COMMANDS_WHITELIST`: Four letter words commands whitelist (default: `srvr,mntr,ruok`)
+
+## Access
+
+- Client Port: `localhost:2181`
+- Admin Server: <http://localhost:8080>
+
+## Usage
+
+### Connect to ZooKeeper
+
+```bash
+docker compose exec zookeeper zkCli.sh
+```
+
+### Check Status
+
+```bash
+echo ruok | nc localhost 2181
+```
+
+Response should be `imok` if ZooKeeper is running properly.
+
+### Get Server Stats
+
+```bash
+echo stat | nc localhost 2181
+```
+
+## Four Letter Words Commands
+
+ZooKeeper supports a set of commands that are exactly four letters:
+
+- `ruok`: Tests if server is running
+- `stat`: Lists server statistics and clients
+- `srvr`: Lists server information
+- `mntr`: Lists server metrics
+- `conf`: Shows server configuration
+
+## Data Storage
+
+ZooKeeper data is stored in three volumes:
+
+- `zookeeper_data`: Main data directory
+- `zookeeper_datalog`: Transaction logs
+- `zookeeper_logs`: Application logs
+
+## Resources
+
+- Resource Limits: 1 CPU, 1G RAM
+- Resource Reservations: 0.25 CPU, 512M RAM
+
+## Production Considerations
+
+For production deployments:
+
+1. Use an ensemble (cluster) of at least 3 nodes
+2. Configure proper disk I/O for transaction logs
+3. Monitor heap memory usage
+4. Set up proper backup strategies
+5. Configure firewall rules for all required ports