Hi all, I'd like to introduce a change to an existing API that leads to a new function signature and add two new related convenience functions that enable plugins. This change enables control of buffer sizes and watermarks used with IOBuffers between the plugin and the core, which is implemented through the PluginVC interface. Tuning these parameters can have a marked improvement on plugin performance in some use cases due to more consistent flow of data and less pressure on the ATS event system in general.
The API changes are here: https://github.com/apache/trafficserver/pull/8088 Example of plugin modifications leveraging these changes: https://github.com/apache/trafficserver/pull/8089 Proposal: modify `TSHttpConnectWithPluginId()` to support IOBuffer sizes via indexes and watermarks. Existing signature: tsapi TSVConn TSHttpConnectWithPluginId(struct sockaddr const *addr, const char *tag, int64_t id) New/additional signature: tsapi TSVConn TSHttpConnectPlugin(struct sockaddr const *addr, const char *tag, int64_t id, int64_t buffer_index, int64_t buffer_water_mark) In order to provide backward compatibility for plugins that do not wish to specify these additional parameters or plugins that exist outside of the repository, I have modified the existing function to call the new function with values that match the current behavior. The `PluginVCCore::alloc()` and `PluginVCCore::init()` functions were modified to take these new arguments, and two new overridable `records.config` parameters were introduced to control the values on a default and per-remap basis. The defaults for these new parameters match the existing implicit values of a buffer index of 8 and no watermark. The new parameters are: proxy.config.plugin.vc.default_buffer_index proxy.config.plugin.vc.default_buffer_water_mark There are at least two ways that an intercept plugin can interact with IOBuffers through the PluginVC interface; what was just described, and when the intercept plugin calls `TSHttpTxnIntercept()`. The `TSHttpTxnIntercept()` function has also been modified to pass these two new parameters into the PluginVC alloc and init functions. Because the buffer index and watermark are required to call `TSHttpConnectPlugin()` and because `TSHttpTxnIntercept()` also needs these values, I introduced two self-explanatory convenience functions to quickly get these values: tsapi TSMgmtInt TSPluginVCGetIOBufferIndex(TSHttpTxn txnp) tsapi TSMgmtInt TSPluginVCGetIOBufferWaterMark(TSHttpTxn txnp) Because these settings can and will crash ATS when misconfigured, logic will cause defaults to be used when out of range values are detected, but error checking of watermarks is currently limited to non-negative values as the upper bound depends upon the buffer index. -- Thanks, Jeff
