thias / couchbase-phosphor

High performance event tracing

Phosphor

Phosphor is a high-performance event tracing framework for C++11 applications designed for use in Couchbase Server - specifically KV Engine and ForestDB.

Event tracing is implemented in an application by instrumenting it as described in phosphor.h. You can then enable and manage tracing using the management API described in trace_log.h.

Example

The following is an example of hypothetical instrumentation in memcached:

void performSet(ENGINE_HANDLE* engine, const char* key, const char* value) {
    TRACE_EVENT_START1("Memcached:Operation", "performSet", "key", key);
    // Perform a set operation
    TRACE_EVENT_END0("Memcached:Operation", "performSet");
}

The following is an example of enabling tracing with a fixed-style 5MB buffer:

phosphor::TraceConfig config(phosphor::BufferMode::fixed, 5 * 1024 * 1024);
phosphor::TraceLog::getInstance().start(config);

Once the trace buffer becomes full you can retrieve it and iterate over it:

auto trace_buffer = phosphor::TraceLog::getInstance().getBuffer();
for(auto& event : *trace_buffer) {
    std::cout << event << '\n';
}

Build

Phosphor is written in C++17 and requires a mostly conforming compiler.

Phosphor is built as part of the full server build. See Build Couchbase server for more information.

Documentation

Documentation for Phosphor can be found on couchbase.github.io/phosphor. The documentation is generated by Doxygen and can be done using make docs with the top level Makefile.