WebSocket Per-Message Compress Extension statistics calculator

ws-pmce-stats is a program that performs some basic calculations to determine the speed, memory usage, and compression effectiveness of various input data sets and compression settings.

In particular, it can be used to tune the negotiation parameters of WebSocket permessage compression extensions based on a set of input data that roughly matches the types of messages that will be sent by the application in question.

Build

ws-pmce-stats is written in C++. Its only dependencies are the C++11 standard library and the zlib headers and library. Build examples on several common platforms follow.

Mac OS X / XCode (clang/llvm) clang++ -std=c++0x -stdlib=libc++ -o ws-pmce-stats ws-pmce-stats.cpp -lz

Linux / GCC g++ -std=c++0x -o ws-pmce-stats ws-pmce-stats.cpp -lz

Usage

This information can also be printed by running ws-pmce-stats --help

Usage: ws-pmce-stats [parameter1=val1, [parameter2=val2]]

Pass data in via standard input. ws-pmce-stats will simulate a WebSocket connection using the parameters defined below. One line of input represents one websocket message. Stats about the speed, memory usage, and compression ratio will be printed at the end.

Optional parameters: (usage key=val, in any combination, in any order) server: [true,false]; Default true; Simulate a server (vs client). Affects frame overhead stats.

sending: [true,false]; Default true; Simulate sending (vs receiving). Affects memory usage stats.

context_takeover: [true,false]; Default true; Reuse compression context between messages. A value of false is equivilent to negotiating the permessage-deflate setting of *_no_context_takeover. If this value is true a separate compression context must be maintained for each connection.

speed_level: [0...9]; Default 6; A tuning parameter that trades compression quality vs CPU usage. A value of 0 indicates no compression at all. This value may be unilaterally set by a WebSocket endpoint without negotiation.

window_bits: [8-15]; Default 15; Base 2 logarithm of the size to use for the LZ77 sliding window. Higher values use more memory but provide better compression. This value must be negotiated. A stream compressed with n bits can be decompressed only by an endpoint that uses at least that many. Not all WebSocket endpoints will support negotiating this parameter.

memory_level: [1-9]; Default 8; A tuning parameter that trades compression quality vs memory usage. A value of 1 indicates lowest memory usage but worst compression. A value of 9 incidates most memory usage but best compression. This parameter may be set unilaterally without negotiation.

Examples

Run with default settings on JSON Chat example data set cat datasets/jsonchat.txt | ./ws-pmce-stats

Change one default setting cat datasets/jsonchat.txt | ./ws-pmce-stats context_takeover=false

Change all default settings cat datasets/jsonchat.txt | ./ws-pmce-stats server=false sending=false context_takeover=false windowbits=8 memory_level=1 speed_level=1

Author & License

Written by Peter Thorson ([email protected])

BSD Licensed (see source code for full license details)