Traffic Server Projects

These are my personal projects for Traffic Server. These vary from very personal ones to collaborative work. A large diagram of the projects and their dependencies is here.


Less Detailed Projects

Most these should be in separate pages but I have not yet had time to properly document them.

Layer 7 Routing

Select upstream target based on the HTTP header information.


Need to consider the ability to bypass upstream selection for non-caching objects (e.g., skip a second caching layer for requests that will always end up at the origin anyway).

Logging tags from plugins

This has been a desire for a long time but the implementation is a bit tricky with regard to timing, due to logging being done as the transaction is being terminated and data may have already disappeared. I have some ideas but those would require some additional infrastructure such as better arenas.

C++ ABI to Core

There is currently a C++ API for plugins but this is really a wrapper on the C API. It would be good to be able to have actual C++ APIs in to the core. There are a number of core features that should be made available to plugins, such as the network address handling code and the string view classes. The primary problem is the fragility of the C++ ABI, some mechanism would be needed to deal with this.

Plugin C++ API

The plugin C++ API needs a lot of polishing and updating.


Bijection is a class I wrote for my own product software long ago, but it depends on some sophisticated Boost library support and so could not be easily ported to Traffic Server. It was a very useful class, particularly for configuration work and enumeration support. It is a goal of mine because building will create a good amount of powerful infrastructure which will be useful in other situations.

Replace TCL hash maps

There is currently a templated hash map table but it requires externally allocated memory. This has its benefits in complex situations but is simply annoying for basic hash table use. Adding the compacting arena to the current TSHashTable would yield an easily usable hash table with the desired memory allocation properties.


Given the compacting arena and TSHashTable buidling the bijection class is straightforward. Two hash tables (or a hash table an arra) can easily be constructed on the same elements which is the essential technique.


There are a number of utility classes that would be useful, particularly in replacing old and increasingly inadequate containers.


This would have an API very similar to std::vector but would take a template size parameter and statically allocate that many elements. This is a pattern used in several places in Traffic Server frequently in an ad hoc way. The DynArray class does this but has other defects. SplitVector would replace all of these uses.

Traffic Server Core

Restructure the overridable configs to remove cyclic dependencies. Already discussed with community and I have a design.

Potentially the “proxy-protocol” extension.

Internal version of the C++17 filesystem library.

Fix TSNetConnect to have options instead of a multiplying set of API calls.

Make remap rules be pure first match (long term).

The crypto hash support needs to be cleaned up.

Add log tags to dump transaction headers in full. This would be useful for the operations teams. The idea is a custom log is setup that logs the full headers but is filtered by error return codes. The result is a log of full headers only for failed transactions. We had originally looked at doing this with a plugin but Dan Xu discovered that it would be easier to add these tags and use the existing logging mechanisms.

Use std::chrono.

Prevent restart on cache failure (bad disks).

Transaction arenas for plugin use.

Pending event counting at base event loop / continuation.

Look at allocating SDK Handles from the transaction arena instead of a global allocator, to avoid cleanup issues.

TLS Extensions

It would be interesting in terms of L4 routing to be enable TLS clients to send a Traffic Server specialized TLS extension to provide addition L4 routing information or other control data. This needs to be design carefully to avoid security issues but I think it could be very powerful.

Cache API Toolkit

This is a restructuring of how the cache to enable fine grained control by plugins. Put in a reference to the summit presentation on this.

Live Restart

A long running request is to be able to do a live restart of Traffic Server. The mechanism would be

  • Start new Traffic Server process.

  • New process starts accepting connections.

  • Old process stops accepting connections.

  • Old process shuts down.

    • When all inbound connections have terminated.

    • When there are less than a specified number of inbound connections.

    • After a specific amount of time.

    • When explicitly requested by the administrator.

The main difficulty for this is handling the cache. To some extent the cache would need to be multi-process. To make this more feasible the access would be single writer and the control of writing would pass from the old process to the new process. This may mean terminating cache writes in the old process.