| # SkyWalking Cross Process Correlation Headers Protocol |
| |
| * Version 1.0 |
| |
| SkyWalking Cross Process Correlation Headers Protocol is a new in-wire context propagation protocol which is |
| additional and optional. Please read SkyWalking language agents documentation to see whether it is supported. |
| |
| This is an optional and additional protocol for language tracer implementation. All tracer implementation could consider |
| implementing this. |
| Cross Process Correlation Header key is `sw8-correlation`. The value is the `encoded(key):encoded(value)` list with |
| elements splitted by `,` such as `base64(string key):base64(string value),base64(string key2):base64(string value2)`. |
| |
| ## Recommendations for language APIs |
| |
| The following implementation method is recommended for different language APIs. |
| |
| 1. `TraceContext#putCorrelation` and `TraceContext#getCorrelation` are recommended to write and read the correlation |
| context, with key/value string. |
| 1. The key should be added if it is absent. |
| 1. The latter writes should override the previous value. |
| 1. The total number of all keys should be less than 3, and the length of each value should be less than 128 bytes. |
| 1. The context should be propagated as well when tracing context is propagated across threads and processes. |
