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meteor/v3-docs/docs/performance/websocket-compression.md
Leonardo Venturini af8e8ef317 add disclaimer
2024-12-04 11:03:29 -04:00

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# Websocket Compression in Meteor
::: warning
Modifying websocket compression settings without understanding your application's DDP messaging patterns can negatively impact performance. Before changing these settings, you should:
- Use [Meteor DevTools Evolved](https://chromewebstore.google.com/detail/meteor-devtools-evolved/ibniinmoafhgbifjojidlagmggecmpgf) or your browser's Network tab to monitor WebSocket traffic
- Analyze your DDP message frequency and payload sizes
- Test changes in a staging environment with realistic data and user load
:::
Meteor's stream server uses the permessage-deflate extension for websocket compression by default. While compression can help reduce bandwidth usage, it may impact performance in reactivity-intensive applications due to the computational overhead of compressing numerous DDP messages.
## Configuration
### Disabling Compression
You can disable websocket compression by setting the `SERVER_WEBSOCKET_COMPRESSION` environment variable to `false`:
```bash
SERVER_WEBSOCKET_COMPRESSION=false
```
### Custom Compression Settings
To customize compression settings, set `SERVER_WEBSOCKET_COMPRESSION` to a JSON string with your desired configuration:
```bash
# Example with custom settings
SERVER_WEBSOCKET_COMPRESSION='{"threshold": 2048, "level": 1}'
```
Available configuration options:
- `threshold`: Minimum message size (in bytes) before compression is applied (default: 1024)
- `level`: Compression level (0-9, where 0=none, 1=fastest, 9=best compression)
- `memLevel`: Memory level (1-9, lower uses less memory)
- `noContextTakeover`: When true, compressor resets for each message (default: true)
- `maxWindowBits`: Window size for compression (9-15, lower uses less memory)
## Configuration Examples
Here are recommended configurations for different types of applications:
### High-Frequency Updates / Real-Time Dashboard
For applications with frequent small updates (e.g., real-time dashboards, trading platforms):
```bash
# Disable compression for optimal performance with small, frequent updates
SERVER_WEBSOCKET_COMPRESSION=false
```
### Large Data Transfers
For applications transferring large datasets (e.g., file sharing, data visualization):
```bash
# Optimize for large data transfers
SERVER_WEBSOCKET_COMPRESSION='{"threshold": 1024, "level": 6, "memLevel": 8}'
```
### Memory-Constrained Environment
For deployments with limited memory resources:
```bash
# Minimize memory usage while maintaining compression
SERVER_WEBSOCKET_COMPRESSION='{"threshold": 2048, "level": 1, "memLevel": 1, "maxWindowBits": 9}'
```
### Balanced Configuration
For typical applications with mixed message sizes:
```bash
# Balance between compression and performance
SERVER_WEBSOCKET_COMPRESSION='{"threshold": 1536, "level": 3, "memLevel": 4}'
```
## Verifying Compression Status
You can check if compression is enabled through the Meteor shell:
```javascript
Meteor.server.stream_server.server.options.faye_server_options.extensions
```
Results interpretation:
- `[]` (empty array): Compression is disabled
- `[{}]` (array with object): Compression is enabled
## Performance Considerations
- For apps with high message throughput or frequent small updates, disabling compression may improve performance
- Large message payloads may benefit from compression, especially over slower network connections
- Consider monitoring CPU usage and response times when adjusting compression settings
## Default Configuration
When enabled, the default configuration uses:
- Compression threshold: 1024 bytes
- Compression level: Z_BEST_SPEED (fastest)
- Memory level: Z_MIN_MEMLEVEL (minimum memory usage)
- Context takeover: Disabled
- Window bits: Z_MIN_WINDOWBITS (minimum window size)