# Transaction Manager

The Transaction Manager handles buffering transactions to Redis, managing state, implementing retry logic, and coordinating with the background processor.

```{contents} Table of Contents
:depth: 2
:local: true
```

## Core Implementation

Key code from `transaction_manager.py`:

```{literalinclude} ../../../ccat_ops_db_api/transaction_buffering/transaction_manager.py
:emphasize-lines: 20-28
:language: python
:lines: 23-78
```

## Key Responsibilities

1. **Buffer transactions** to Redis queue (LPUSH)
2. **Track transaction status** with TTL
3. **Implement write-through cache** for generated IDs
4. **Cache buffered data** for smart queries
5. **Manage retry logic** with exponential backoff
6. **Handle failed transactions** (dead-letter queue)

## Buffering Flow

```python
# Buffer a transaction
async def buffer_transaction(transaction):
    # 1. Add to queue
    await redis.lpush(buffer_key, transaction.model_dump_json())

    # 2. Store status
    await redis.setex(status_key, 3600, transaction.model_dump_json())

    # 3. Write-through cache
    await _cache_generated_ids(transaction)

    # 4. Cache buffered data
    await _cache_buffered_data(transaction)

    return transaction.transaction_id
```

## Redis Key Structure

**Transaction Buffer** (List):

```text
Key: site:{site_name}:transaction_buffer
Operations: LPUSH (add), RPOP (process)
```

**Transaction Status** (String):

```text
Key: site:{site_name}:transaction:{transaction_id}
TTL: 3600 seconds
Value: JSON transaction
```

**Write-Through Cache** (String):

```text
Key: site:{site_name}:cache:ids:{model}:{id}
TTL: Extended until replicated
Value: JSON record data
```

**Buffered Data Cache** (String):

```text
Key: site:{site_name}:buffered:{model}:{id}
TTL: Extended until replicated
Value: JSON record data
```

See {doc}`../../development/redis-inspection` for debugging commands.

## Next Steps

- {doc}`background-processor` - Processing buffered transactions
- {doc}`lsn-tracking` - Replication confirmation