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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 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)