Add support for sphinx as a documentation generator

api/docs/Doxyfile

@@ -790,8 +790,7 @@ WARN_LOGFILE           =
 # spaces. See also FILE_PATTERNS and EXTENSION_MAPPING
 # Note: If this tag is empty the current directory is searched.
 
-INPUT                  = ./Overview.md \
-                         ../include/opentelemetry/common \
+INPUT                  = ../include/opentelemetry/common \
                          ../include/opentelemetry/core \
                          ../include/opentelemetry/nostd/shared_ptr.h \
                          ../include/opentelemetry/nostd/span.h \
@@ -839,6 +838,8 @@ RECURSIVE              = YES
 # run.
 
 EXCLUDE                = ../include/opentelemetry/common/spin_lock_mutex.h \
+                         ../include/opentelemetry/common/key_value_iterable_view.h \
+                         ../include/opentelemetry/trace/span_context_kv_iterable_view.h \
                          ../include/opentelemetry/nostd/detail
 
 # The EXCLUDE_SYMLINKS tag can be used to select whether or not files or
@@ -1088,7 +1089,7 @@ IGNORE_PREFIX          =
 # If the GENERATE_HTML tag is set to YES, doxygen will generate HTML output
 # The default value is: YES.
 
-GENERATE_HTML          = YES
+GENERATE_HTML          = NO
 
 # The HTML_OUTPUT tag is used to specify where the HTML docs will be put. If a
 # relative path is entered the value of OUTPUT_DIRECTORY will be put in front of
@@ -1444,7 +1445,7 @@ DISABLE_INDEX          = NO
 # The default value is: NO.
 # This tag requires that the tag GENERATE_HTML is set to YES.
 
-GENERATE_TREEVIEW      = NO
+GENERATE_TREEVIEW      = YES
 
 # The ENUM_VALUES_PER_LINE tag can be used to set the number of enum values that
 # doxygen will group on one line in the generated HTML documentation.
@@ -1912,15 +1913,15 @@ MAN_LINKS              = NO
 # captures the structure of the code including all documentation.
 # The default value is: NO.
 
-GENERATE_XML           = NO
+GENERATE_XML           = YES
 
 # The XML_OUTPUT tag is used to specify where the XML pages will be put. If a
 # relative path is entered the value of OUTPUT_DIRECTORY will be put in front of
 # it.
 # The default directory is: xml.
 # This tag requires that the tag GENERATE_XML is set to YES.
 
-XML_OUTPUT             = xml
+XML_OUTPUT             = doxyoutput/xml
 
 # If the XML_PROGRAMLISTING tag is set to YES, doxygen will dump the program
 # listings (including syntax highlighting and cross-referencing information) to

api/docs/Makefile

@@ -0,0 +1,25 @@
+# Minimal makefile for Sphinx documentation
+#
+
+# You can set these variables from the command line, and also
+# from the environment for the first two.
+SPHINXOPTS    ?=
+SPHINXBUILD   ?= sphinx-build
+SOURCEDIR     = .
+BUILDDIR      = _build
+
+# Put it first so that "make" without argument is like "make help".
+help:
+	@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
+
+.PHONY: help Makefile clean
+
+# Catch-all target: route all unknown targets to Sphinx using the new
+# "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).
+%: Makefile
+	mkdir -p doxyoutput
+	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
+
+clean:
+	rm -rf doxyoutput
+	@$(SPHINXBUILD) -M clean "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)

api/docs/conf.py

@@ -0,0 +1,84 @@
+# Configuration file for the Sphinx documentation builder.
+#
+# This file only contains a selection of the most common options. For a full
+# list see the documentation:
+# https://www.sphinx-doc.org/en/master/usage/configuration.html
+
+# -- Path setup --------------------------------------------------------------
+
+# If extensions (or modules to document with autodoc) are in another directory,
+# add these directories to sys.path here. If the directory is relative to the
+# documentation root, use os.path.abspath to make it absolute, like shown here.
+#
+# import os
+# import sys
+# sys.path.insert(0, os.path.abspath('.'))
+
+
+# -- Project information -----------------------------------------------------
+
+project = 'OpenTelemetry C++ API'
+copyright = '2021, OpenTelemetry authors'
+author = 'OpenTelemetry authors'
+
+# Run doxygen
+# -----------
+# For the readthedocs builds, for some reason exhale doesn't find doxygen.
+# So we run it manually here.
+import subprocess
+import os
+if not os.path.isdir('doxyoutput'):
+    os.mkdir('doxyoutput')
+subprocess.call(['doxygen'])
+
+
+# -- General configuration ---------------------------------------------------
+
+# Add any Sphinx extension module names here, as strings. They can be
+# extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
+# ones.
+extensions = [
+        "breathe",
+        "exhale",
+]
+
+breathe_projects = {
+        "OpenTelemetry C++ API": "./doxyoutput/xml"
+}
+
+breathe_default_project = "OpenTelemetry C++ API"
+
+exhale_args = {
+        "containmentFolder": "otel_api",
+        "rootFileName": "otel_api.rst",
+        "rootFileTitle": "Reference documentation",
+        "doxygenStripFromPath": "..",
+        "exhaleUseDoxyfile": True,
+        "createTreeView": True,
+}
+
+primary_domain = "cpp"
+
+higlight_language = "cpp"
+
+
+# Add any paths that contain templates here, relative to this directory.
+templates_path = ['_templates']
+
+# List of patterns, relative to source directory, that match files and
+# directories to ignore when looking for source files.
+# This pattern also affects html_static_path and html_extra_path.
+exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']
+
+
+# -- Options for HTML output -------------------------------------------------
+
+# The theme to use for HTML and HTML Help pages.  See the documentation for
+# a list of builtin themes.
+#
+html_theme = "sphinx_rtd_theme"
+
+# Add any paths that contain custom static files (such as style sheets) here,
+# relative to this directory. They are copied after the builtin static files,
+# so a file named "default.css" will overwrite the builtin "default.css".
+html_static_path = ['_static']

api/docs/index.rst

@@ -0,0 +1,2 @@
+OpenTelemetry C++ API
+=====================

buildscripts/pre-commit

@@ -78,5 +78,5 @@ END
 git add "$(pwd)/sdk/src/version/version.cc"
 
 # Update documentation version
-sed -i "/^PROJECT_BRIEF/cPROJECT_BRIEF = \"Version ${short_version}\""  "$(pwd)/api/docs/Doxyfile"
-git add "$(pwd)/api/docs/Doxyfile"
+sed -i "/^release =/crelease = \"${short_version}\""  "$(pwd)/docs/public/conf.py"
+git add "$(pwd)/docs/public/conf.py"

docs/public/GettingHelp.rst

@@ -0,0 +1,17 @@
+Getting help
+------------
+
+-  Refer to `opentelemetry.io <https://opentelemetry.io/>`__ for general
+   information about OpenTelemetry.
+-  Refer to the `OpenTelemetry C++ GitHub
+   repository <https://github.com/open-telemetry/opentelemetry-cpp>`__
+   for further information and resources related to OpenTelemetry C++.
+-  For questions related to OpenTelemetry C++ that are not covered by
+   the existing documentation, please ask away in `GitHub
+   discussions <https://github.com/open-telemetry/opentelemetry-cpp/discussions>`__.
+-  Feel free to join the `CNCF OpenTelemetry C++ Slack
+   channel <https://cloud-native.slack.com/archives/C01N3AT62SJ>`__. If
+   you are new, you can create a CNCF Slack account
+   `here <http://slack.cncf.io/>`__.
+-  For bugs and feature requests, write a `GitHub
+   issue <https://github.com/open-telemetry/opentelemetry-cpp/issues>`__.

docs/public/GettingStarted.rst

@@ -0,0 +1,52 @@
+Getting started
+---------------
+
+Tracing
+~~~~~~~
+
+When instrumenting libraries and applications, the most simple approach
+requires three steps.
+
+Obtain a tracer
+^^^^^^^^^^^^^^^
+
+.. code:: cpp
+
+    auto provider = opentelemetry::trace::Provider::GetTracerProvider();
+    auto tracer = provider->GetTracer("foo_library", "1.0.0");
+
+The ``TracerProvider`` acquired in the first step is a singleton object
+that is usually provided by the OpenTelemetry C++ SDK. It is used to
+provide specific implementations for API interfaces. In case no SDK is
+used, the API provides a default no-op implementation of a
+``TracerProvider``.
+
+The ``Tracer`` acquired in the second step is needed to create and start
+``Span``\ s.
+
+Start a span
+^^^^^^^^^^^^
+
+.. code:: cpp
+
+    auto span = tracer->StartSpan("HandleRequest");
+
+This creates a span, sets its name to ``"HandleRequest"``, and sets its
+start time to the current time. Refer to the API documentation for other
+operations that are available to enrich spans with additional data.
+
+Mark a span as active
+^^^^^^^^^^^^^^^^^^^^^
+
+.. code:: cpp
+
+    auto scope = tracer->WithActiveSpan(span);
+
+This marks a span as active and returns a ``Scope`` object bound to the
+lifetime of the span. When the ``Scope`` object is destroyed, the
+related span is ended.
+
+The concept of an active span is important, as any span that is created
+without explicitly specifying a parent is parented to the currently
+active span.
+

docs/public/Makefile

@@ -0,0 +1,25 @@
+# Minimal makefile for Sphinx documentation
+#
+
+# You can set these variables from the command line, and also
+# from the environment for the first two.
+SPHINXOPTS    ?=
+SPHINXBUILD   ?= sphinx-build
+SOURCEDIR     = .
+BUILDDIR      = _build
+
+# Put it first so that "make" without argument is like "make help".
+help:
+	@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
+
+.PHONY: help Makefile clean
+
+# Catch-all target: route all unknown targets to Sphinx using the new
+# "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).
+%: Makefile
+	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
+
+clean:
+	rm -rf doxyoutput
+	@$(SPHINXBUILD) -M clean ../../api/docs "$(BUILDDIR)" $(SPHINXOPTS) $(O)
+	@$(SPHINXBUILD) -M clean "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)

docs/public/Overview.rst

@@ -0,0 +1,26 @@
+Overview
+========
+
+The OpenTelemetry C++ API enables developers to instrument their
+applications and libraries in order to make them ready to create and
+emit telemetry data. The OpenTelemetry C++ API exclusively focuses on
+instrumentation and does not address concerns like exporting, sampling,
+and aggregating telemetry data. Those concerns are addressed by the
+OpenTelemetry C++ SDK. This architecture enables developers to
+instrument applications and libraries with the OpenTelemetry C++ API
+while being completely agnostic of how telemetry data is exported and
+processed.
+
+Library design
+--------------
+
+The OpenTelemetry C++ API is provided as a header-only library and
+supports all recent versions of the C++ standard, down to C++11.
+
+A single application might dynamically or statically link to different
+libraries that were compiled with different compilers, while several of
+the linked libraries are instrumented with OpenTelemetry. OpenTelemetry
+C++ supports those scenarios by providing a stable ABI. This is achieved
+by a careful API design, and most notably by providing ABI stable
+versions of classes from the standard library. All those classes are
+provided in the ``opentelemetry::nostd`` namespace.