From b01a50c59e62ca1d46c08c5e1815d6d9cbafa4fe Mon Sep 17 00:00:00 2001
From: Yusuke Tsutsumi <yusuke@tsutsumi.io>
Date: Thu, 26 Sep 2019 13:46:53 -0700
Subject: [PATCH 1/6] Implementing TraceContext (fixes #116)

This introduces a w3c TraceContext propagator, primarily inspired by opencensus.
---
 .../propagation/tracecontexthttptextformat.py | 122 +++++++++-
 .../src/opentelemetry/trace/__init__.py       |  33 ++-
 opentelemetry-api/tests/context/__init__.py   |   0
 .../tests/context/propagation/__init__.py     |   0
 .../test_tracecontexthttptextformat.py        | 208 ++++++++++++++++++
 5 files changed, 356 insertions(+), 7 deletions(-)
 create mode 100644 opentelemetry-api/tests/context/__init__.py
 create mode 100644 opentelemetry-api/tests/context/propagation/__init__.py
 create mode 100644 opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py

diff --git a/opentelemetry-api/src/opentelemetry/context/propagation/tracecontexthttptextformat.py b/opentelemetry-api/src/opentelemetry/context/propagation/tracecontexthttptextformat.py
index 575644a91f2..84fab18974e 100644
--- a/opentelemetry-api/src/opentelemetry/context/propagation/tracecontexthttptextformat.py
+++ b/opentelemetry-api/src/opentelemetry/context/propagation/tracecontexthttptextformat.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-
+import re
 import typing
 
 import opentelemetry.trace as trace
@@ -22,18 +22,128 @@
 
 
 class TraceContextHTTPTextFormat(httptextformat.HTTPTextFormat):
-    """TODO: extracts and injects using w3c TraceContext's headers.
+    """Extracts and injects using w3c TraceContext's headers.
     """
 
+    _TRACEPARENT_HEADER_NAME = "traceparent"
+    _TRACESTATE_HEADER_NAME = "tracestate"
+    _TRACEPARENT_HEADER_FORMAT = (
+        "^[ \t]*([0-9a-f]{2})-([0-9a-f]{32})-([0-9a-f]{16})-([0-9a-f]{2})"
+        + "(-.*)?[ \t]*$"
+    )
+    _TRACEPARENT_HEADER_FORMAT_RE = re.compile(_TRACEPARENT_HEADER_FORMAT)
+
+    @classmethod
     def extract(
-        self, _get_from_carrier: httptextformat.Getter[_T], _carrier: _T
+        cls, get_from_carrier: httptextformat.Getter[_T], carrier: _T
     ) -> trace.SpanContext:
-        return trace.INVALID_SPAN_CONTEXT
+        """Extracts a valid SpanContext from the carrier.
+
+        If a header
+        """
+        header = get_from_carrier(carrier, cls._TRACEPARENT_HEADER_NAME)
+
+        if not header:
+            return trace.INVALID_SPAN_CONTEXT
+
+        match = re.search(cls._TRACEPARENT_HEADER_FORMAT_RE, header[0])
+        if not match:
+            return trace.INVALID_SPAN_CONTEXT
+
+        version = match.group(1)
+        trace_id = match.group(2)
+        span_id = match.group(3)
+        trace_options = match.group(4)
 
+        if trace_id == "0" * 32 or span_id == "0" * 16:
+            return trace.INVALID_SPAN_CONTEXT
+
+        if version == "00":
+            if match.group(5):
+                return trace.INVALID_SPAN_CONTEXT
+        if version == "ff":
+            return trace.INVALID_SPAN_CONTEXT
+
+        tracestate = trace.TraceState()
+        for tracestate_header in get_from_carrier(
+            carrier, cls._TRACESTATE_HEADER_NAME
+        ):
+            tracestate.update(_parse_tracestate(tracestate_header))
+
+        span_context = trace.SpanContext(
+            trace_id=int(trace_id, 16),
+            span_id=int(span_id, 16),
+            trace_options=trace.TraceOptions(trace_options),
+            trace_state=tracestate,
+        )
+
+        return span_context
+
+    @classmethod
     def inject(
-        self,
+        cls,
         context: trace.SpanContext,
         set_in_carrier: httptextformat.Setter[_T],
         carrier: _T,
     ) -> None:
-        pass
+        if context == trace.INVALID_SPAN_CONTEXT:
+            return
+        traceparent_string = "-".join(
+            [
+                "00",
+                format(context.trace_id, "032x"),
+                format(context.span_id, "016x"),
+                format(context.trace_options, "02x"),
+            ]
+        )
+        set_in_carrier(
+            carrier, cls._TRACEPARENT_HEADER_NAME, traceparent_string
+        )
+        if context.trace_state:
+            tracestate_string = _format_tracestate(context.trace_state)
+            set_in_carrier(
+                carrier, cls._TRACESTATE_HEADER_NAME, tracestate_string
+            )
+
+
+_DELIMITER_FORMAT = "[ \t]*,[ \t]*"
+_MEMBER_FORMAT = "(%s)(=)(%s)" % (
+    trace.TraceState.KEY_FORMAT,
+    trace.TraceState.VALUE_FORMAT,
+)
+
+_DELIMITER_FORMAT_RE = re.compile(_DELIMITER_FORMAT)
+_MEMBER_FORMAT_RE = re.compile(_MEMBER_FORMAT)
+
+
+def _parse_tracestate(string: str) -> trace.TraceState:
+    """Parse a w3c tracestate header into a TraceState.
+
+    Args:
+        string: the value of the tracestate header.
+
+    Returns:
+        A valid TraceState that contains values extracted from
+        the tracestate header.
+    """
+    tracestate = trace.TraceState()
+    for member in re.split(_DELIMITER_FORMAT_RE, string):
+        match = _MEMBER_FORMAT_RE.match(member)
+        if not match:
+            raise ValueError("illegal key-value format %r" % (member))
+        key, _eq, value = match.groups()
+        tracestate[key] = value
+    return tracestate
+
+
+def _format_tracestate(tracestate: trace.TraceState) -> str:
+    """Parse a w3c tracestate header into a TraceState.
+
+    Args:
+        tracestate: the tracestate header to write
+
+    Returns:
+        A string that adheres to the w3c tracestate
+        header format.
+    """
+    return ",".join(map(lambda key: key + "=" + tracestate[key], tracestate))
diff --git a/opentelemetry-api/src/opentelemetry/trace/__init__.py b/opentelemetry-api/src/opentelemetry/trace/__init__.py
index b79cdeb4df5..260a198d862 100644
--- a/opentelemetry-api/src/opentelemetry/trace/__init__.py
+++ b/opentelemetry-api/src/opentelemetry/trace/__init__.py
@@ -62,7 +62,9 @@
 """
 
 import enum
+import re
 import typing
+from collections import OrderedDict
 from contextlib import contextmanager
 
 from opentelemetry.util import loader, types
@@ -250,7 +252,7 @@ def get_default(cls) -> "TraceOptions":
 DEFAULT_TRACE_OPTIONS = TraceOptions.get_default()
 
 
-class TraceState(typing.Dict[str, str]):
+class TraceState(OrderedDict):
     """A list of key-value pairs representing vendor-specific trace info.
 
     Keys and values are strings of up to 256 printable US-ASCII characters.
@@ -261,10 +263,39 @@ class TraceState(typing.Dict[str, str]):
         https://www.w3.org/TR/trace-context/#tracestate-field
     """
 
+    MAX_TRACESTATE_VALUES = 32
+    KEY_WITHOUT_VENDOR_FORMAT = r"[a-z][_0-9a-z\-\*\/]{0,255}"
+    KEY_WITH_VENDOR_FORMAT = (
+        r"[a-z][_0-9a-z\-\*\/]{0,240}@[a-z][_0-9a-z\-\*\/]{0,13}"
+    )
+    KEY_FORMAT = KEY_WITHOUT_VENDOR_FORMAT + "|" + KEY_WITH_VENDOR_FORMAT
+    VALUE_FORMAT = (
+        r"[\x20-\x2b\x2d-\x3c\x3e-\x7e]{0,255}[\x21-\x2b\x2d-\x3c\x3e-\x7e]"
+    )
+
+    KEY_VALIDATION_RE = re.compile("^" + KEY_FORMAT + "$")
+    VALUE_VALIDATION_RE = re.compile("^" + VALUE_FORMAT + "$")
+
     @classmethod
     def get_default(cls) -> "TraceState":
         return cls()
 
+    def __setitem__(self, key: str, value: str) -> None:
+        # According to the w3c spec, we can only store 32 values
+        if len(self) >= self.MAX_TRACESTATE_VALUES:
+            return
+        # TODO: I believe the otel spec calls for no exceptions
+        # that interfere with execution in the API.
+        # if not isinstance(key, str):
+        #     raise ValueError("key must be an instance of str")
+        # if not re.match(self._KEY_VALIDATION_RE, key):
+        #     raise ValueError("illegal key provided")
+        # if not isinstance(value, str):
+        #     raise ValueError("value must be an instance of str")
+        # if not re.match(self._VALUE_VALIDATION_RE, value):
+        #     raise ValueError("illegal value provided")
+        super().__setitem__(key, value)
+
 
 DEFAULT_TRACE_STATE = TraceState.get_default()
 
diff --git a/opentelemetry-api/tests/context/__init__.py b/opentelemetry-api/tests/context/__init__.py
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/opentelemetry-api/tests/context/propagation/__init__.py b/opentelemetry-api/tests/context/propagation/__init__.py
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py b/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
new file mode 100644
index 00000000000..ec51582bcd0
--- /dev/null
+++ b/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
@@ -0,0 +1,208 @@
+# Copyright 2019, OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+
+from opentelemetry import trace
+from opentelemetry.context.propagation import tracecontexthttptextformat
+
+FORMAT = tracecontexthttptextformat.TraceContextHTTPTextFormat()
+
+
+def get_as_list(dict_object, key):
+    value = dict_object.get(key)
+    return [value] if value is not None else []
+
+
+class TestTraceContextFormat(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.trace_id = int("12345678901234567890123456789012", 16)
+        cls.span_id = int("1234567890123456", 16)
+
+    def test_no_traceparent_header(self):
+        """When tracecontext headers are not present, a new SpanContext
+        should be created.
+
+        RFC 4.2.2:
+
+        If no traceparent header is received, the vendor creates a new trace-id and parent-id that represents the current request.
+        """
+        span_context = FORMAT.extract(get_as_list, {})
+        self.assertTrue(isinstance(span_context, trace.SpanContext))
+
+    def test_from_headers_tracestate_entry_limit(self):
+        """If more than 32 entries are passed, do not propagate tracestate.
+
+        RFC 3.3.1.1
+
+        There can be a maximum of 32 list-members in a list.
+        """
+
+        span_context = FORMAT.extract(
+            get_as_list,
+            {
+                "traceparent": "00-12345678901234567890123456789012-1234567890123456-00",
+                "tracestate": ",".join(
+                    [
+                        "a00=0,a01=1,a02=2,a03=3,a04=4,a05=5,a06=6,a07=7,a08=8,a09=9",
+                        "b00=0,b01=1,b02=2,b03=3,b04=4,b05=5,b06=6,b07=7,b08=8,b09=9",
+                        "c00=0,c01=1,c02=2,c03=3,c04=4,c05=5,c06=6,c07=7,c08=8,c09=9",
+                        "d00=0,d01=1,d02=2",
+                    ]
+                ),
+            },
+        )
+        self.assertEqual(len(span_context.trace_state), 32)
+
+    def test_from_headers_tracestate_duplicated_keys(self):
+        """If a duplicate tracestate header is present, the most recent entry
+        is used.
+
+        RFC 3.3.1.4
+
+        Only one entry per key is allowed because the entry represents that last position in the trace.
+        Hence vendors must overwrite their entry upon reentry to their tracing system.
+
+        For example, if a vendor name is Congo and a trace started in their system and then went through
+        a system named Rojo and later returned to Congo, the tracestate value would not be:
+
+        congo=congosFirstPosition,rojo=rojosFirstPosition,congo=congosSecondPosition
+
+        Instead, the entry would be rewritten to only include the most recent position:
+
+        congo=congosSecondPosition,rojo=rojosFirstPosition
+        """
+        span_context = FORMAT.extract(
+            get_as_list,
+            {
+                "traceparent": "00-12345678901234567890123456789012-1234567890123456-00",
+                "tracestate": "foo=1,bar=2,foo=3",
+            },
+        )
+        self.assertEqual(span_context.trace_state, {"foo": "3", "bar": "2"})
+
+    def test_headers_with_tracestate(self):
+        """When there is a traceparent and tracestate header, data from
+        both should be addded to the SpanContext.
+        """
+        traceparent_value = "00-{trace_id}-{span_id}-00".format(
+            trace_id=format(self.trace_id, "032x"),
+            span_id=format(self.span_id, "016x"),
+        )
+        tracestate_value = "foo=1,bar=2,baz=3"
+        span_context = FORMAT.extract(
+            get_as_list,
+            {"traceparent": traceparent_value, "tracestate": tracestate_value},
+        )
+        self.assertEqual(span_context.trace_id, self.trace_id)
+        self.assertEqual(span_context.span_id, self.span_id)
+        self.assertEqual(
+            span_context.trace_state, {"foo": "1", "bar": "2", "baz": "3"}
+        )
+
+        output = {}
+        FORMAT.inject(span_context, dict.__setitem__, output)
+        self.assertEqual(output["traceparent"], traceparent_value)
+        self.assertEqual(output["tracestate"], tracestate_value)
+
+    def test_invalid_trace_id(self):
+        """If the trace id is invalid, we must ignore the full traceparent header.
+
+        Also ignore any tracestate.
+
+        RFC 3.2.2.3
+
+        If the trace-id value is invalid (for example if it contains non-allowed characters or all
+        zeros), vendors MUST ignore the traceparent.
+
+        RFC 3.3
+
+        If the vendor failed to parse traceparent, it MUST NOT attempt to parse tracestate.
+        Note that the opposite is not true: failure to parse tracestate MUST NOT affect the parsing of traceparent.
+        """
+        span_context = FORMAT.extract(
+            get_as_list,
+            {
+                "traceparent": "00-00000000000000000000000000000000-1234567890123456-00",
+                "tracestate": "foo=1,bar=2,foo=3",
+            },
+        )
+        self.assertEqual(span_context, trace.INVALID_SPAN_CONTEXT)
+
+    def test_invalid_parent_id(self):
+        """If the parent id is invalid, we must ignore the full traceparent header.
+
+        Also ignore any tracestate.
+
+        RFC 3.2.2.3
+
+        Vendors MUST ignore the traceparent when the parent-id is invalid (for example,
+        if it contains non-lowercase hex characters).
+
+        RFC 3.3
+
+        If the vendor failed to parse traceparent, it MUST NOT attempt to parse tracestate.
+        Note that the opposite is not true: failure to parse tracestate MUST NOT affect the parsing of traceparent.
+        """
+        span_context = FORMAT.extract(
+            get_as_list,
+            {
+                "traceparent": "00-00000000000000000000000000000000-0000000000000000-00",
+                "tracestate": "foo=1,bar=2,foo=3",
+            },
+        )
+        self.assertEqual(span_context, trace.INVALID_SPAN_CONTEXT)
+
+    def test_no_send_empty_tracestate(self):
+        """If the tracestate is empty, do not set the header.
+
+        RFC 3.3.1.1
+
+        Empty and whitespace-only list members are allowed. Vendors MUST accept empty
+        tracestate headers but SHOULD avoid sending them.
+        """
+        output = {}
+        FORMAT.inject(
+            trace.SpanContext(self.trace_id, self.span_id),
+            dict.__setitem__,
+            output,
+        )
+        self.assertTrue("traceparent" in output)
+        self.assertFalse("tracestate" in output)
+
+    def test_format_not_supported(self):
+        """If the traceparent does not adhere to the supported format, discard it and
+        create a new tracecontext.
+
+        RFC 4.3
+
+        If the version cannot be parsed, the vendor creates a new traceparent header and
+        deletes tracestate.
+        """
+        span_context = FORMAT.extract(
+            get_as_list,
+            {
+                "traceparent": "00-12345678901234567890123456789012-1234567890123456-00-residue",
+                "tracestate": "foo=1,bar=2,foo=3",
+            },
+        )
+        self.assertEqual(span_context, trace.INVALID_SPAN_CONTEXT)
+
+    def test_propagate_invalid_context(self):
+        """Do not propagate invalid trace context.
+        """
+        output = {}
+        FORMAT.inject(trace.INVALID_SPAN_CONTEXT, dict.__setitem__, output)
+        self.assertFalse("traceparent" in output)

From 9d462c7064bddfa32c9727799b63ff686036d343 Mon Sep 17 00:00:00 2001
From: Yusuke Tsutsumi <yusuke@tsutsumi.io>
Date: Fri, 27 Sep 2019 11:04:31 -0700
Subject: [PATCH 2/6] addressing feedback.

---
 .../propagation/tracecontexthttptextformat.py | 43 +++++++++++--------
 .../src/opentelemetry/trace/__init__.py       | 31 +------------
 .../test_tracecontexthttptextformat.py        |  7 ++-
 3 files changed, 32 insertions(+), 49 deletions(-)

diff --git a/opentelemetry-api/src/opentelemetry/context/propagation/tracecontexthttptextformat.py b/opentelemetry-api/src/opentelemetry/context/propagation/tracecontexthttptextformat.py
index 84fab18974e..6902d8e4f63 100644
--- a/opentelemetry-api/src/opentelemetry/context/propagation/tracecontexthttptextformat.py
+++ b/opentelemetry-api/src/opentelemetry/context/propagation/tracecontexthttptextformat.py
@@ -20,6 +20,30 @@
 
 _T = typing.TypeVar("_T")
 
+#    Keys and values are strings of up to 256 printable US-ASCII characters.
+#    Implementations should conform to the the `W3C Trace Context - Tracestate`_
+#    spec, which describes additional restrictions on valid field values.
+#
+#    .. _W3C Trace Context - Tracestate:
+#        https://www.w3.org/TR/trace-context/#tracestate-field
+
+
+_KEY_WITHOUT_VENDOR_FORMAT = r"[a-z][_0-9a-z\-\*\/]{0,255}"
+_KEY_WITH_VENDOR_FORMAT = (
+    r"[a-z][_0-9a-z\-\*\/]{0,240}@[a-z][_0-9a-z\-\*\/]{0,13}"
+)
+
+_KEY_FORMAT = _KEY_WITHOUT_VENDOR_FORMAT + "|" + _KEY_WITH_VENDOR_FORMAT
+_VALUE_FORMAT = (
+    r"[\x20-\x2b\x2d-\x3c\x3e-\x7e]{0,255}[\x21-\x2b\x2d-\x3c\x3e-\x7e]"
+)
+
+_DELIMITER_FORMAT = "[ \t]*,[ \t]*"
+_MEMBER_FORMAT = "({})(=)({})".format(_KEY_FORMAT, _VALUE_FORMAT)
+
+_DELIMITER_FORMAT_RE = re.compile(_DELIMITER_FORMAT)
+_MEMBER_FORMAT_RE = re.compile(_MEMBER_FORMAT)
+
 
 class TraceContextHTTPTextFormat(httptextformat.HTTPTextFormat):
     """Extracts and injects using w3c TraceContext's headers.
@@ -88,13 +112,8 @@ def inject(
     ) -> None:
         if context == trace.INVALID_SPAN_CONTEXT:
             return
-        traceparent_string = "-".join(
-            [
-                "00",
-                format(context.trace_id, "032x"),
-                format(context.span_id, "016x"),
-                format(context.trace_options, "02x"),
-            ]
+        traceparent_string = "00-{:032x}-{:016x}-{:02x}".format(
+            context.trace_id, context.span_id, context.trace_options
         )
         set_in_carrier(
             carrier, cls._TRACEPARENT_HEADER_NAME, traceparent_string
@@ -106,16 +125,6 @@ def inject(
             )
 
 
-_DELIMITER_FORMAT = "[ \t]*,[ \t]*"
-_MEMBER_FORMAT = "(%s)(=)(%s)" % (
-    trace.TraceState.KEY_FORMAT,
-    trace.TraceState.VALUE_FORMAT,
-)
-
-_DELIMITER_FORMAT_RE = re.compile(_DELIMITER_FORMAT)
-_MEMBER_FORMAT_RE = re.compile(_MEMBER_FORMAT)
-
-
 def _parse_tracestate(string: str) -> trace.TraceState:
     """Parse a w3c tracestate header into a TraceState.
 
diff --git a/opentelemetry-api/src/opentelemetry/trace/__init__.py b/opentelemetry-api/src/opentelemetry/trace/__init__.py
index 260a198d862..19cefa4e562 100644
--- a/opentelemetry-api/src/opentelemetry/trace/__init__.py
+++ b/opentelemetry-api/src/opentelemetry/trace/__init__.py
@@ -252,7 +252,7 @@ def get_default(cls) -> "TraceOptions":
 DEFAULT_TRACE_OPTIONS = TraceOptions.get_default()
 
 
-class TraceState(OrderedDict):
+class TraceState(typing.Dict[str, str]):
     """A list of key-value pairs representing vendor-specific trace info.
 
     Keys and values are strings of up to 256 printable US-ASCII characters.
@@ -263,39 +263,10 @@ class TraceState(OrderedDict):
         https://www.w3.org/TR/trace-context/#tracestate-field
     """
 
-    MAX_TRACESTATE_VALUES = 32
-    KEY_WITHOUT_VENDOR_FORMAT = r"[a-z][_0-9a-z\-\*\/]{0,255}"
-    KEY_WITH_VENDOR_FORMAT = (
-        r"[a-z][_0-9a-z\-\*\/]{0,240}@[a-z][_0-9a-z\-\*\/]{0,13}"
-    )
-    KEY_FORMAT = KEY_WITHOUT_VENDOR_FORMAT + "|" + KEY_WITH_VENDOR_FORMAT
-    VALUE_FORMAT = (
-        r"[\x20-\x2b\x2d-\x3c\x3e-\x7e]{0,255}[\x21-\x2b\x2d-\x3c\x3e-\x7e]"
-    )
-
-    KEY_VALIDATION_RE = re.compile("^" + KEY_FORMAT + "$")
-    VALUE_VALIDATION_RE = re.compile("^" + VALUE_FORMAT + "$")
-
     @classmethod
     def get_default(cls) -> "TraceState":
         return cls()
 
-    def __setitem__(self, key: str, value: str) -> None:
-        # According to the w3c spec, we can only store 32 values
-        if len(self) >= self.MAX_TRACESTATE_VALUES:
-            return
-        # TODO: I believe the otel spec calls for no exceptions
-        # that interfere with execution in the API.
-        # if not isinstance(key, str):
-        #     raise ValueError("key must be an instance of str")
-        # if not re.match(self._KEY_VALIDATION_RE, key):
-        #     raise ValueError("illegal key provided")
-        # if not isinstance(value, str):
-        #     raise ValueError("value must be an instance of str")
-        # if not re.match(self._VALUE_VALIDATION_RE, value):
-        #     raise ValueError("illegal value provided")
-        super().__setitem__(key, value)
-
 
 DEFAULT_TRACE_STATE = TraceState.get_default()
 
diff --git a/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py b/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
index ec51582bcd0..86ca166f2a0 100644
--- a/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
+++ b/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
@@ -43,7 +43,10 @@ def test_no_traceparent_header(self):
         self.assertTrue(isinstance(span_context, trace.SpanContext))
 
     def test_from_headers_tracestate_entry_limit(self):
-        """If more than 32 entries are passed, do not propagate tracestate.
+        """If more than 33 entries are passed, allow them.
+
+        We are explicitly choosing not to limit the list members
+        as outlined in RFC 3.3.1.1
 
         RFC 3.3.1.1
 
@@ -64,7 +67,7 @@ def test_from_headers_tracestate_entry_limit(self):
                 ),
             },
         )
-        self.assertEqual(len(span_context.trace_state), 32)
+        self.assertEqual(len(span_context.trace_state), 33)
 
     def test_from_headers_tracestate_duplicated_keys(self):
         """If a duplicate tracestate header is present, the most recent entry

From 4d5b7167e16d4b57d7db9d5e2defd0ca1cab0a9b Mon Sep 17 00:00:00 2001
From: Yusuke Tsutsumi <yusuke@tsutsumi.io>
Date: Fri, 27 Sep 2019 12:01:48 -0700
Subject: [PATCH 3/6] Addressing feedback, fixing build.

---
 .../context/propagation/httptextformat.py     |  4 +--
 .../propagation/tracecontexthttptextformat.py | 14 +++++----
 .../src/opentelemetry/trace/__init__.py       |  2 --
 .../test_tracecontexthttptextformat.py        | 30 ++++++++++---------
 4 files changed, 27 insertions(+), 23 deletions(-)

diff --git a/opentelemetry-api/src/opentelemetry/context/propagation/httptextformat.py b/opentelemetry-api/src/opentelemetry/context/propagation/httptextformat.py
index 35bdfbb3fe8..9b6098a9a42 100644
--- a/opentelemetry-api/src/opentelemetry/context/propagation/httptextformat.py
+++ b/opentelemetry-api/src/opentelemetry/context/propagation/httptextformat.py
@@ -19,8 +19,8 @@
 
 _T = typing.TypeVar("_T")
 
-Setter = typing.Callable[[typing.Type[_T], str, str], None]
-Getter = typing.Callable[[typing.Type[_T], str], typing.List[str]]
+Setter = typing.Callable[[_T, str, str], None]
+Getter = typing.Callable[[_T, str], typing.List[str]]
 
 
 class HTTPTextFormat(abc.ABC):
diff --git a/opentelemetry-api/src/opentelemetry/context/propagation/tracecontexthttptextformat.py b/opentelemetry-api/src/opentelemetry/context/propagation/tracecontexthttptextformat.py
index 6902d8e4f63..abe778db953 100644
--- a/opentelemetry-api/src/opentelemetry/context/propagation/tracecontexthttptextformat.py
+++ b/opentelemetry-api/src/opentelemetry/context/propagation/tracecontexthttptextformat.py
@@ -62,8 +62,6 @@ def extract(
         cls, get_from_carrier: httptextformat.Getter[_T], carrier: _T
     ) -> trace.SpanContext:
         """Extracts a valid SpanContext from the carrier.
-
-        If a header
         """
         header = get_from_carrier(carrier, cls._TRACEPARENT_HEADER_NAME)
 
@@ -92,7 +90,11 @@ def extract(
         for tracestate_header in get_from_carrier(
             carrier, cls._TRACESTATE_HEADER_NAME
         ):
-            tracestate.update(_parse_tracestate(tracestate_header))
+            # typing.Dict's update is not recognized by pylint:
+            # https://github.com/PyCQA/pylint/issues/2420
+            tracestate.update(  # pylint:disable=E1101
+                _parse_tracestate(tracestate_header)
+            )
 
         span_context = trace.SpanContext(
             trace_id=int(trace_id, 16),
@@ -141,7 +143,9 @@ def _parse_tracestate(string: str) -> trace.TraceState:
         if not match:
             raise ValueError("illegal key-value format %r" % (member))
         key, _eq, value = match.groups()
-        tracestate[key] = value
+        # typing.Dict's update is not recognized by pylint:
+        # https://github.com/PyCQA/pylint/issues/2420
+        tracestate[key] = value  # pylint:disable=E1137
     return tracestate
 
 
@@ -155,4 +159,4 @@ def _format_tracestate(tracestate: trace.TraceState) -> str:
         A string that adheres to the w3c tracestate
         header format.
     """
-    return ",".join(map(lambda key: key + "=" + tracestate[key], tracestate))
+    return ",".join(key + "=" + value for key, value in tracestate.items())
diff --git a/opentelemetry-api/src/opentelemetry/trace/__init__.py b/opentelemetry-api/src/opentelemetry/trace/__init__.py
index 19cefa4e562..b79cdeb4df5 100644
--- a/opentelemetry-api/src/opentelemetry/trace/__init__.py
+++ b/opentelemetry-api/src/opentelemetry/trace/__init__.py
@@ -62,9 +62,7 @@
 """
 
 import enum
-import re
 import typing
-from collections import OrderedDict
 from contextlib import contextmanager
 
 from opentelemetry.util import loader, types
diff --git a/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py b/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
index 86ca166f2a0..581466e0e52 100644
--- a/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
+++ b/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import typing
 import unittest
 
 from opentelemetry import trace
@@ -20,16 +21,16 @@
 FORMAT = tracecontexthttptextformat.TraceContextHTTPTextFormat()
 
 
-def get_as_list(dict_object, key):
+def get_as_list(
+    dict_object: typing.Dict[str, str], key: str
+) -> typing.List[str]:
     value = dict_object.get(key)
     return [value] if value is not None else []
 
 
 class TestTraceContextFormat(unittest.TestCase):
-    @classmethod
-    def setUpClass(cls):
-        cls.trace_id = int("12345678901234567890123456789012", 16)
-        cls.span_id = int("1234567890123456", 16)
+    TRACE_ID = int("12345678901234567890123456789012", 16)  # type:int
+    SPAN_ID = int("1234567890123456", 16)  # type:int
 
     def test_no_traceparent_header(self):
         """When tracecontext headers are not present, a new SpanContext
@@ -39,7 +40,8 @@ def test_no_traceparent_header(self):
 
         If no traceparent header is received, the vendor creates a new trace-id and parent-id that represents the current request.
         """
-        span_context = FORMAT.extract(get_as_list, {})
+        output: typing.Dict[str, str] = {}
+        span_context = FORMAT.extract(get_as_list, output)
         self.assertTrue(isinstance(span_context, trace.SpanContext))
 
     def test_from_headers_tracestate_entry_limit(self):
@@ -101,21 +103,21 @@ def test_headers_with_tracestate(self):
         both should be addded to the SpanContext.
         """
         traceparent_value = "00-{trace_id}-{span_id}-00".format(
-            trace_id=format(self.trace_id, "032x"),
-            span_id=format(self.span_id, "016x"),
+            trace_id=format(self.TRACE_ID, "032x"),
+            span_id=format(self.SPAN_ID, "016x"),
         )
         tracestate_value = "foo=1,bar=2,baz=3"
         span_context = FORMAT.extract(
             get_as_list,
             {"traceparent": traceparent_value, "tracestate": tracestate_value},
         )
-        self.assertEqual(span_context.trace_id, self.trace_id)
-        self.assertEqual(span_context.span_id, self.span_id)
+        self.assertEqual(span_context.trace_id, self.TRACE_ID)
+        self.assertEqual(span_context.span_id, self.SPAN_ID)
         self.assertEqual(
             span_context.trace_state, {"foo": "1", "bar": "2", "baz": "3"}
         )
 
-        output = {}
+        output: typing.Dict[str, str] = {}
         FORMAT.inject(span_context, dict.__setitem__, output)
         self.assertEqual(output["traceparent"], traceparent_value)
         self.assertEqual(output["tracestate"], tracestate_value)
@@ -176,9 +178,9 @@ def test_no_send_empty_tracestate(self):
         Empty and whitespace-only list members are allowed. Vendors MUST accept empty
         tracestate headers but SHOULD avoid sending them.
         """
-        output = {}
+        output: typing.Dict[str, str] = {}
         FORMAT.inject(
-            trace.SpanContext(self.trace_id, self.span_id),
+            trace.SpanContext(self.TRACE_ID, self.SPAN_ID),
             dict.__setitem__,
             output,
         )
@@ -206,6 +208,6 @@ def test_format_not_supported(self):
     def test_propagate_invalid_context(self):
         """Do not propagate invalid trace context.
         """
-        output = {}
+        output: typing.Dict[str, str] = {}
         FORMAT.inject(trace.INVALID_SPAN_CONTEXT, dict.__setitem__, output)
         self.assertFalse("traceparent" in output)

From b2b8807c7d9fb61f6f5ad742fe1e4f5b5a28940e Mon Sep 17 00:00:00 2001
From: Yusuke Tsutsumi <yusuke@tsutsumi.io>
Date: Fri, 27 Sep 2019 12:14:17 -0700
Subject: [PATCH 4/6] fixing build for python versions older than 3.7

---
 .../context/propagation/test_tracecontexthttptextformat.py  | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py b/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
index 581466e0e52..909db6e86df 100644
--- a/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
+++ b/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
@@ -40,7 +40,7 @@ def test_no_traceparent_header(self):
 
         If no traceparent header is received, the vendor creates a new trace-id and parent-id that represents the current request.
         """
-        output: typing.Dict[str, str] = {}
+        output = {}  # type:typing.Dict[str, str]
         span_context = FORMAT.extract(get_as_list, output)
         self.assertTrue(isinstance(span_context, trace.SpanContext))
 
@@ -117,7 +117,7 @@ def test_headers_with_tracestate(self):
             span_context.trace_state, {"foo": "1", "bar": "2", "baz": "3"}
         )
 
-        output: typing.Dict[str, str] = {}
+        output = {}  # type:typing.Dict[str, str]
         FORMAT.inject(span_context, dict.__setitem__, output)
         self.assertEqual(output["traceparent"], traceparent_value)
         self.assertEqual(output["tracestate"], tracestate_value)
@@ -178,7 +178,7 @@ def test_no_send_empty_tracestate(self):
         Empty and whitespace-only list members are allowed. Vendors MUST accept empty
         tracestate headers but SHOULD avoid sending them.
         """
-        output: typing.Dict[str, str] = {}
+        output = {}  # type:typing.Dict[str, str]
         FORMAT.inject(
             trace.SpanContext(self.TRACE_ID, self.SPAN_ID),
             dict.__setitem__,

From a9f939e60f3dfb802b5918011aa0e41016764ae1 Mon Sep 17 00:00:00 2001
From: Yusuke Tsutsumi <yusuke@tsutsumi.io>
Date: Fri, 27 Sep 2019 12:17:57 -0700
Subject: [PATCH 5/6] missed one output

---
 .../context/propagation/test_tracecontexthttptextformat.py      | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py b/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
index 909db6e86df..fb5b8b8eff1 100644
--- a/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
+++ b/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
@@ -208,6 +208,6 @@ def test_format_not_supported(self):
     def test_propagate_invalid_context(self):
         """Do not propagate invalid trace context.
         """
-        output: typing.Dict[str, str] = {}
+        output = {}  # type:typing.Dict[str, str]
         FORMAT.inject(trace.INVALID_SPAN_CONTEXT, dict.__setitem__, output)
         self.assertFalse("traceparent" in output)

From 21b46817078831882e1a89e5f4e19aada798bfa2 Mon Sep 17 00:00:00 2001
From: Yusuke Tsutsumi <yusuke@tsutsumi.io>
Date: Fri, 27 Sep 2019 12:30:12 -0700
Subject: [PATCH 6/6] making tests python3.4 compatible.

insertion order as iteration order is not a guarantee in older version of python.
---
 .../context/propagation/test_tracecontexthttptextformat.py    | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py b/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
index fb5b8b8eff1..aaf392be248 100644
--- a/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
+++ b/opentelemetry-api/tests/context/propagation/test_tracecontexthttptextformat.py
@@ -120,7 +120,9 @@ def test_headers_with_tracestate(self):
         output = {}  # type:typing.Dict[str, str]
         FORMAT.inject(span_context, dict.__setitem__, output)
         self.assertEqual(output["traceparent"], traceparent_value)
-        self.assertEqual(output["tracestate"], tracestate_value)
+        for pair in ["foo=1", "bar=2", "baz=3"]:
+            self.assertIn(pair, output["tracestate"])
+        self.assertEqual(output["tracestate"].count(","), 2)
 
     def test_invalid_trace_id(self):
         """If the trace id is invalid, we must ignore the full traceparent header.