Adding baggage implementation (#676)

api/include/opentelemetry/baggage/baggage.h

@@ -0,0 +1,304 @@
+// Copyright 2021, 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.
+
+#pragma once
+
+#include "opentelemetry/common/kv_properties.h"
+#include "opentelemetry/nostd/shared_ptr.h"
+#include "opentelemetry/nostd/string_view.h"
+#include "opentelemetry/version.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+
+namespace baggage
+{
+
+class Baggage
+{
+public:
+  static constexpr size_t kMaxKeyValuePairs = 180;
+  static constexpr size_t kMaxKeyValueSize  = 4096;
+  static constexpr size_t kMaxSize          = 8192;
+  static constexpr char kKeyValueSeparator  = '=';
+  static constexpr char kMembersSeparator   = ',';
+  static constexpr char kMetadataSeparator  = ';';
+
+  Baggage() : kv_properties_(new opentelemetry::common::KeyValueProperties()) {}
+  Baggage(size_t size) : kv_properties_(new opentelemetry::common::KeyValueProperties(size)){};
+
+  template <class T>
+  Baggage(const T &keys_and_values)
+      : kv_properties_(new opentelemetry::common::KeyValueProperties(keys_and_values))
+  {}
+
+  static nostd::shared_ptr<Baggage> GetDefault()
+  {
+    static nostd::shared_ptr<Baggage> baggage{new Baggage()};
+    return baggage;
+  }
+
+  /* Get value for key in the baggage
+     @returns true if key is found, false otherwise
+  */
+  bool GetValue(nostd::string_view key, std::string &value) const
+  {
+    return kv_properties_->GetValue(key, value);
+  }
+
+  /* Returns shared_ptr of new baggage object which contains new key-value pair. If key or value is
+     invalid, copy of current baggage is returned
+  */
+  nostd::shared_ptr<Baggage> Set(const nostd::string_view &key, const nostd::string_view &value)
+  {
+
+    nostd::shared_ptr<Baggage> baggage(new Baggage(kv_properties_->Size() + 1));
+    const bool valid_kv = IsValidKey(key) && IsValidValue(value);
+
+    if (valid_kv)
+    {
+      baggage->kv_properties_->AddEntry(key, value);
+    }
+
+    // add rest of the fields.
+    kv_properties_->GetAllEntries(
+        [&baggage, &key, &valid_kv](nostd::string_view e_key, nostd::string_view e_value) {
+          // if key or value was not valid, add all the entries. Add only remaining entries
+          // otherwise.
+          if (!valid_kv || key != e_key)
+          {
+            baggage->kv_properties_->AddEntry(e_key, e_value);
+          }
+
+          return true;
+        });
+
+    return baggage;
+  }
+
+  // @return all key-values entries by repeatedly invoking the function reference passed as argument
+  // for each entry
+  bool GetAllEntries(
+      nostd::function_ref<bool(nostd::string_view, nostd::string_view)> callback) const noexcept
+  {
+    return kv_properties_->GetAllEntries(callback);
+  }
+
+  // delete key from the baggage if it exists. Returns shared_ptr of new baggage object.
+  // if key does not exist, copy of current baggage is returned.
+  // Validity of key is not checked as invalid keys should never be populated in baggage in the
+  // first place.
+  nostd::shared_ptr<Baggage> Delete(nostd::string_view key)
+  {
+    // keeping size of baggage same as key might not be found in it
+    nostd::shared_ptr<Baggage> baggage(new Baggage(kv_properties_->Size()));
+    kv_properties_->GetAllEntries(
+        [&baggage, &key](nostd::string_view e_key, nostd::string_view e_value) {
+          if (key != e_key)
+            baggage->kv_properties_->AddEntry(e_key, e_value);
+          return true;
+        });
+    return baggage;
+  }
+
+  // Returns shared_ptr of baggage after extracting key-value pairs from header
+  static nostd::shared_ptr<Baggage> FromHeader(nostd::string_view header)
+  {
+    if (header.size() > kMaxSize)
+    {
+      // header size exceeds maximum threshold, return empty baggage
+      return GetDefault();
+    }
+
+    common::KeyValueStringTokenizer kv_str_tokenizer(header);
+    size_t cnt = kv_str_tokenizer.NumTokens();  // upper bound on number of kv pairs
+    if (cnt > kMaxKeyValuePairs)
+    {
+      cnt = kMaxKeyValuePairs;
+    }
+
+    nostd::shared_ptr<Baggage> baggage(new Baggage(cnt));
+    bool kv_valid;
+    nostd::string_view key, value;
+
+    while (kv_str_tokenizer.next(kv_valid, key, value) && baggage->kv_properties_->Size() < cnt)
+    {
+      if (!kv_valid || (key.size() + value.size() > kMaxKeyValueSize))
+      {
+        // if kv pair is not valid, skip it
+        continue;
+      }
+
+      // NOTE : metadata is kept as part of value only as it does not have any semantic meaning.
+      // but, we need to extract it (else Decode on value will return error)
+      nostd::string_view metadata;
+      auto metadata_separator = value.find(kMetadataSeparator);
+      if (metadata_separator != std::string::npos)
+      {
+        metadata = value.substr(metadata_separator);
+        value    = value.substr(0, metadata_separator);
+      }
+
+      bool err       = 0;
+      auto key_str   = UrlDecode(common::StringUtil::Trim(key), err);
+      auto value_str = UrlDecode(common::StringUtil::Trim(value), err);
+
+      if (err == false && IsValidKey(key_str) && IsValidValue(value_str))
+      {
+        if (!metadata.empty())
+        {
+          value_str.append(metadata.data(), metadata.size());
+        }
+        baggage->kv_properties_->AddEntry(key_str, value_str);
+      }
+    }
+
+    return baggage;
+  }
+
+  // Creates string from baggage object.
+  std::string ToHeader() const
+  {
+    std::string header_s;
+    bool first = true;
+    kv_properties_->GetAllEntries([&](nostd::string_view key, nostd::string_view value) {
+      if (!first)
+      {
+        header_s.push_back(kMembersSeparator);
+      }
+      else
+      {
+        first = false;
+      }
+      header_s.append(UrlEncode(key));
+      header_s.push_back(kKeyValueSeparator);
+
+      // extracting metadata from value. We do not encode metadata
+      auto metadata_separator = value.find(kMetadataSeparator);
+      if (metadata_separator != std::string::npos)
+      {
+        header_s.append(UrlEncode(value.substr(0, metadata_separator)));
+        auto metadata = value.substr(metadata_separator);
+        header_s.append(std::string(metadata.data(), metadata.size()));
+      }
+      else
+      {
+        header_s.append(UrlEncode(value));
+      }
+      return true;
+    });
+    return header_s;
+  }
+
+private:
+  static bool IsPrintableString(nostd::string_view str)
+  {
+    for (const auto ch : str)
+    {
+      if (ch < ' ' || ch > '~')
+      {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  static bool IsValidKey(nostd::string_view key) { return key.size() && IsPrintableString(key); }
+
+  static bool IsValidValue(nostd::string_view value) { return IsPrintableString(value); }
+
+  // Uri encode key value pairs before injecting into header
+  // Implementation inspired from : https://golang.org/src/net/url/url.go?s=7851:7884#L264
+  static std::string UrlEncode(nostd::string_view str)
+  {
+    auto to_hex = [](char c) -> char {
+      static const char *hex = "0123456789ABCDEF";
+      return hex[c & 15];
+    };
+
+    std::string ret;
+
+    for (auto c : str)
+    {
+      if (std::isalnum(c) || c == '-' || c == '_' || c == '.' || c == '~')
+      {
+        ret.push_back(c);
+      }
+      else if (c == ' ')
+      {
+        ret.push_back('+');
+      }
+      else
+      {
+        ret.push_back('%');
+        ret.push_back(to_hex(c >> 4));
+        ret.push_back(to_hex(c & 15));
+      }
+    }
+
+    return ret;
+  }
+
+  // Uri decode key value pairs after extracting from header
+  static std::string UrlDecode(nostd::string_view str, bool &err)
+  {
+    auto IsHex = [](char c) {
+      return std::isdigit(c) || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f');
+    };
+
+    auto from_hex = [](char c) -> char {
+      return std::isdigit(c) ? c - '0' : std::toupper(c) - 'A' + 10;
+    };
+
+    std::string ret;
+
+    for (size_t i = 0; i < str.size(); i++)
+    {
+      if (str[i] == '%')
+      {
+        if (i + 2 >= str.size() || !IsHex(str[i + 1]) || !IsHex(str[i + 2]))
+        {
+          err = 1;
+          return "";
+        }
+        ret.push_back(from_hex(str[i + 1]) << 4 | from_hex(str[i + 2]));
+        i += 2;
+      }
+      else if (str[i] == '+')
+      {
+        ret.push_back(' ');
+      }
+      else if (std::isalnum(str[i]) || str[i] == '-' || str[i] == '_' || str[i] == '.' ||
+               str[i] == '~')
+      {
+        ret.push_back(str[i]);
+      }
+      else
+      {
+        err = 1;
+        return "";
+      }
+    }
+
+    return ret;
+  }
+
+private:
+  // Store entries in a C-style array to avoid using std::array or std::vector.
+  nostd::unique_ptr<opentelemetry::common::KeyValueProperties> kv_properties_;
+};
+
+}  // namespace baggage
+
+OPENTELEMETRY_END_NAMESPACE

api/include/opentelemetry/common/kv_properties.h

@@ -47,6 +47,12 @@ class KeyValueStringTokenizer
       : str_(str), opts_(opts), index_(0)
   {}
 
+  static nostd::string_view GetDefaultKeyOrValue()
+  {
+    static std::string default_str = "";
+    return default_str;
+  }
+
   // Returns next key value in the string header
   // @param valid_kv : if the found kv pair is valid or not
   // @param key : key in kv pair
@@ -57,29 +63,34 @@ class KeyValueStringTokenizer
     valid_kv = true;
     while (index_ < str_.size())
     {
-      size_t end = str_.find(opts_.member_separator, index_);
+      bool is_empty_pair = false;
+      size_t end         = str_.find(opts_.member_separator, index_);
       if (end == std::string::npos)
       {
         end = str_.size() - 1;
       }
+      else if (end == index_)  // empty pair. do not update end
+      {
+        is_empty_pair = true;
+      }
       else
       {
         end--;
       }
 
       auto list_member = StringUtil::Trim(str_, index_, end);
-      if (list_member.size() == 0)
+      if (list_member.size() == 0 || is_empty_pair)
       {
         // empty list member
-        index_ = end + 2;
+        index_ = end + 2 - is_empty_pair;
         if (opts_.ignore_empty_members)
         {
           continue;
         }
 
         valid_kv = true;
-        key      = "";
-        value    = "";
+        key      = GetDefaultKeyOrValue();
+        value    = GetDefaultKeyOrValue();
         return true;
       }
 
@@ -226,7 +237,7 @@ class KeyValueProperties
   }
 
   // Adds new kv pair into kv properties
-  void AddEntry(const nostd::string_view &key, const nostd::string_view &value)
+  void AddEntry(nostd::string_view key, nostd::string_view value)
   {
     if (num_entries_ < max_num_entries_)
     {
@@ -251,7 +262,7 @@ class KeyValueProperties
   }
 
   // Return value for key if exists, return false otherwise
-  bool GetValue(const nostd::string_view key, std::string &value) const
+  bool GetValue(nostd::string_view key, std::string &value) const
   {
     for (size_t i = 0; i < num_entries_; i++)
     {

api/include/opentelemetry/common/string_util.h

@@ -35,6 +35,16 @@ class StringUtil
     }
     return str.substr(left, 1 + right - left);
   }
+
+  static nostd::string_view Trim(nostd::string_view str)
+  {
+    if (str.empty())
+    {
+      return str;
+    }
+
+    return Trim(str, 0, str.size() - 1);
+  }
 };
 
 }  // namespace common

api/test/CMakeLists.txt

@@ -6,3 +6,4 @@ add_subdirectory(trace)
 add_subdirectory(metrics)
 add_subdirectory(logs)
 add_subdirectory(common)
+add_subdirectory(baggage)