Move to file_body in boost

As is, it reads the whole file into memory before sending it.  While
fairly fast for the user, this wastes ram, and makes bmcweb less useful
on less capable systems.

This patch enables using the boost::beast::http::file_body type, which
has more efficient serialization semantics than using a std::string.  To
do this, it adds a openFile() handler to http::Response, which can be
used to properly open a file.  Once the file is opened, the existing
string body is ignored, and the file payload is sent instead.
openFile() also returns success or failure, to allow users to properly
handle 404s and other errors.

To prove that it works, I moved over every instance of direct use of the
body() method over to using this, including the webasset handler.  The
webasset handler specifically should help with system load when doing an
initial page load of the webui.

Tested:
Redfish service validator passes.

Change-Id: Ic7ea9ffefdbc81eb985de7edc0fac114822994ad
Signed-off-by: Ed Tanous <ed@tanous.net>

5 files changed, 242 insertions, 133 deletions

diff --git a/http/complete_response_fields.hpp b/http/complete_response_fields.hpp
index 66a4bb79af..a5b3eec3d0 100644
--- a/http/complete_response_fields.hpp
+++ b/http/complete_response_fields.hpp
@@ -27,8 +27,7 @@ inline void completeResponseFields(const Request& req, Response& res)
     authentication::cleanupTempSession(req);
 
     res.setHashAndHandleNotModified();
-
-    if (res.body().empty() && res.jsonValue.is_structured())
+    if (res.jsonValue.is_structured())
     {
         using http_helpers::ContentType;
         std::array<ContentType, 3> allowed{ContentType::CBOR, ContentType::JSON,
@@ -44,7 +43,9 @@ inline void completeResponseFields(const Request& req, Response& res)
         {
             res.addHeader(boost::beast::http::field::content_type,
                           "application/cbor");
-            nlohmann::json::to_cbor(res.jsonValue, res.body());
+            std::string cbor;
+            nlohmann::json::to_cbor(res.jsonValue, cbor);
+            res.write(std::move(cbor));
         }
         else
         {
@@ -53,8 +54,8 @@ inline void completeResponseFields(const Request& req, Response& res)
             // backward compatibility.
             res.addHeader(boost::beast::http::field::content_type,
                           "application/json");
-            res.body() = res.jsonValue.dump(
-                2, ' ', true, nlohmann::json::error_handler_t::replace);
+            res.write(res.jsonValue.dump(
+                2, ' ', true, nlohmann::json::error_handler_t::replace));
         }
     }
 }
diff --git a/http/http2_connection.hpp b/http/http2_connection.hpp
index d815119e96..ee3a218807 100644
--- a/http/http2_connection.hpp
+++ b/http/http2_connection.hpp
@@ -106,19 +106,42 @@ class HTTP2Connection :
         BMCWEB_LOG_DEBUG("File read callback length: {}", length);
         crow::Response& res = stream.res;
 
-        BMCWEB_LOG_DEBUG("total: {} send_sofar: {}", res.body().size(),
-                         stream.sentSofar);
+        Response::string_response* body =
+            boost::variant2::get_if<Response::string_response>(&res.response);
+        Response::file_response* fbody =
+            boost::variant2::get_if<Response::file_response>(&res.response);
 
-        size_t toSend = std::min(res.body().size() - stream.sentSofar, length);
+        size_t size = res.size();
+        BMCWEB_LOG_DEBUG("total: {} send_sofar: {}", size, stream.sentSofar);
+
+        size_t toSend = std::min(size - stream.sentSofar, length);
         BMCWEB_LOG_DEBUG("Copying {} bytes to buf", toSend);
 
-        std::string::iterator bodyBegin = res.body().begin();
-        std::advance(bodyBegin, stream.sentSofar);
+        if (body != nullptr)
+        {
+            std::string::const_iterator bodyBegin = body->body().begin();
+            std::advance(bodyBegin, stream.sentSofar);
+
+            memcpy(buf, &*bodyBegin, toSend);
+        }
+        else if (fbody != nullptr)
+        {
+            boost::system::error_code ec;
+
+            size_t nread = fbody->body().file().read(buf, toSend, ec);
+            if (ec || nread != toSend)
+            {
+                return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
+            }
+        }
+        else
+        {
+            return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
+        }
 
-        memcpy(buf, &*bodyBegin, toSend);
         stream.sentSofar += toSend;
 
-        if (stream.sentSofar >= res.body().size())
+        if (stream.sentSofar >= size)
         {
             BMCWEB_LOG_DEBUG("Setting OEF flag");
             *dataFlags |= NGHTTP2_DATA_FLAG_EOF;
@@ -154,8 +177,8 @@ class HTTP2Connection :
         completeResponseFields(thisReq, thisRes);
         thisRes.addHeader(boost::beast::http::field::date, getCachedDateStr());
 
-        boost::beast::http::fields& fields = thisRes.stringResponse.base();
-        std::string code = std::to_string(thisRes.stringResponse.result_int());
+        boost::beast::http::fields& fields = thisRes.fields();
+        std::string code = std::to_string(thisRes.resultInt());
         hdr.emplace_back(headerFromStringViews(":status", code));
         for (const boost::beast::http::fields::value_type& header : fields)
         {
diff --git a/http/http_client.hpp b/http/http_client.hpp
index 046df2e0f0..8c27d6d61a 100644
--- a/http/http_client.hpp
+++ b/http/http_client.hpp
@@ -39,6 +39,8 @@
 #include <boost/beast/version.hpp>
 #include <boost/container/devector.hpp>
 #include <boost/system/error_code.hpp>
+#include <boost/url/format.hpp>
+#include <boost/url/url.hpp>
 #include <boost/url/url_view.hpp>
 
 #include <cstdlib>
@@ -50,9 +52,8 @@
 
 namespace crow
 {
-
-// With Redfish Aggregation it is assumed we will connect to another instance
-// of BMCWeb which can handle 100 simultaneous connections.
+// With Redfish Aggregation it is assumed we will connect to another
+// instance of BMCWeb which can handle 100 simultaneous connections.
 constexpr size_t maxPoolSize = 20;
 constexpr size_t maxRequestQueueSize = 500;
 constexpr unsigned int httpReadBodyLimit = 131072;
@@ -96,8 +97,8 @@ static inline boost::system::error_code
     return boost::system::errc::make_error_code(boost::system::errc::success);
 };
 
-// We need to allow retry information to be set before a message has been sent
-// and a connection pool has been created
+// We need to allow retry information to be set before a message has been
+// sent and a connection pool has been created
 struct ConnectionPolicy
 {
     uint32_t maxRetryAttempts = 5;
@@ -402,7 +403,7 @@ class ConnectionInfo : public std::enable_shared_from_this<ConnectionInfo>
 
         // Copy the response into a Response object so that it can be
         // processed by the callback function.
-        res.stringResponse = parser->release();
+        res.response = parser->release();
         callback(parser->keep_alive(), connId, res);
         res.clear();
     }
@@ -419,8 +420,8 @@ class ConnectionInfo : public std::enable_shared_from_this<ConnectionInfo>
         if (ec)
         {
             BMCWEB_LOG_ERROR("async_wait failed: {}", ec.message());
-            // If the timer fails, we need to close the socket anyway, same as
-            // if it expired.
+            // If the timer fails, we need to close the socket anyway, same
+            // as if it expired.
         }
         std::shared_ptr<ConnectionInfo> self = weakSelf.lock();
         if (self == nullptr)
@@ -454,8 +455,8 @@ class ConnectionInfo : public std::enable_shared_from_this<ConnectionInfo>
             callback(false, connId, res);
             res.clear();
 
-            // Reset the retrycount to zero so that client can try connecting
-            // again if needed
+            // Reset the retrycount to zero so that client can try
+            // connecting again if needed
             retryCount = 0;
             return;
         }
@@ -604,10 +605,11 @@ class ConnectionInfo : public std::enable_shared_from_this<ConnectionInfo>
                 BMCWEB_LOG_ERROR("prepareSSLContext failed - {}, id: {}", host,
                                  connId);
                 // Don't retry if failure occurs while preparing SSL context
-                // such as certificate is invalid or set cipher failure or set
-                // host name failure etc... Setting conn state to sslInitFailed
-                // and connection state will be transitioned to next state
-                // depending on retry policy set by subscription.
+                // such as certificate is invalid or set cipher failure or
+                // set host name failure etc... Setting conn state to
+                // sslInitFailed and connection state will be transitioned
+                // to next state depending on retry policy set by
+                // subscription.
                 state = ConnState::sslInitFailed;
                 waitAndRetry();
                 return;
@@ -742,8 +744,8 @@ class ConnectionPool : public std::enable_shared_from_this<ConnectionPool>
             }
         }
 
-        // All connections in use so create a new connection or add request to
-        // the queue
+        // All connections in use so create a new connection or add request
+        // to the queue
         if (connections.size() < connPolicy->maxConnections)
         {
             BMCWEB_LOG_DEBUG("Adding new connection to pool {}", id);
@@ -760,8 +762,8 @@ class ConnectionPool : public std::enable_shared_from_this<ConnectionPool>
         }
         else
         {
-            // If we can't buffer the request then we should let the callback
-            // handle a 429 Too Many Requests dummy response
+            // If we can't buffer the request then we should let the
+            // callback handle a 429 Too Many Requests dummy response
             BMCWEB_LOG_ERROR("{}:{} request queue full.  Dropping request.",
                              id);
             Response dummyRes;
@@ -875,8 +877,8 @@ class HttpClient
             pool.first->second = std::make_shared<ConnectionPool>(
                 ioc, clientKey, connPolicy, destUrl);
         }
-        // Send the data using either the existing connection pool or the newly
-        // created connection pool
+        // Send the data using either the existing connection pool or the
+        // newly created connection pool
         pool.first->second->sendData(std::move(data), destUrl, httpHeader, verb,
                                      resHandler);
     }
diff --git a/http/http_connection.hpp b/http/http_connection.hpp
index 86cc49a2f7..1ec80ae77a 100644
--- a/http/http_connection.hpp
+++ b/http/http_connection.hpp
@@ -17,11 +17,11 @@
 #include <boost/asio/ip/tcp.hpp>
 #include <boost/asio/ssl/stream.hpp>
 #include <boost/asio/steady_timer.hpp>
+#include <boost/beast/core/buffers_generator.hpp>
 #include <boost/beast/core/flat_static_buffer.hpp>
 #include <boost/beast/http/error.hpp>
 #include <boost/beast/http/parser.hpp>
 #include <boost/beast/http/read.hpp>
-#include <boost/beast/http/serializer.hpp>
 #include <boost/beast/http/write.hpp>
 #include <boost/beast/ssl/ssl_stream.hpp>
 #include <boost/beast/websocket.hpp>
@@ -532,47 +532,50 @@ class Connection :
         });
     }
 
-    void doWrite(crow::Response& thisRes)
+    void afterDoWrite(const std::shared_ptr<self_type>& /*self*/,
+                      const boost::system::error_code& ec,
+                      std::size_t bytesTransferred)
     {
-        BMCWEB_LOG_DEBUG("{} doWrite", logPtr(this));
-        thisRes.preparePayload();
-        serializer.emplace(thisRes.stringResponse);
-        startDeadline();
-        boost::beast::http::async_write(adaptor, *serializer,
-                                        [this, self(shared_from_this())](
-                                            const boost::system::error_code& ec,
-                                            std::size_t bytesTransferred) {
-            BMCWEB_LOG_DEBUG("{} async_write {} bytes", logPtr(this),
-                             bytesTransferred);
+        BMCWEB_LOG_DEBUG("{} async_write {} bytes", logPtr(this),
+                         bytesTransferred);
 
-            cancelDeadlineTimer();
+        cancelDeadlineTimer();
 
-            if (ec)
-            {
-                BMCWEB_LOG_DEBUG("{} from write(2)", logPtr(this));
-                return;
-            }
-            if (!keepAlive)
-            {
-                close();
-                BMCWEB_LOG_DEBUG("{} from write(1)", logPtr(this));
-                return;
-            }
+        if (ec)
+        {
+            BMCWEB_LOG_DEBUG("{} from write(2)", logPtr(this));
+            return;
+        }
+        if (!keepAlive)
+        {
+            close();
+            BMCWEB_LOG_DEBUG("{} from write(1)", logPtr(this));
+            return;
+        }
 
-            serializer.reset();
-            BMCWEB_LOG_DEBUG("{} Clearing response", logPtr(this));
-            res.clear();
-            parser.emplace(std::piecewise_construct, std::make_tuple());
-            parser->body_limit(httpReqBodyLimit); // reset body limit for
-                                                  // newly created parser
-            buffer.consume(buffer.size());
+        BMCWEB_LOG_DEBUG("{} Clearing response", logPtr(this));
+        res.clear();
+        parser.emplace(std::piecewise_construct, std::make_tuple());
+        parser->body_limit(httpReqBodyLimit); // reset body limit for
+                                              // newly created parser
+        buffer.consume(buffer.size());
 
-            userSession = nullptr;
+        userSession = nullptr;
 
-            // Destroy the Request via the std::optional
-            req.reset();
-            doReadHeaders();
-        });
+        // Destroy the Request via the std::optional
+        req.reset();
+        doReadHeaders();
+    }
+
+    void doWrite(crow::Response& thisRes)
+    {
+        BMCWEB_LOG_DEBUG("{} doWrite", logPtr(this));
+        thisRes.preparePayload();
+
+        startDeadline();
+        boost::beast::async_write(adaptor, thisRes.generator(),
+                                  std::bind_front(&self_type::afterDoWrite,
+                                                  this, shared_from_this()));
     }
 
     void cancelDeadlineTimer()
@@ -637,10 +640,6 @@ class Connection :
 
     boost::beast::flat_static_buffer<8192> buffer;
 
-    std::optional<boost::beast::http::response_serializer<
-        boost::beast::http::string_body>>
-        serializer;
-
     std::optional<crow::Request> req;
     crow::Response res;
 
diff --git a/http/http_response.hpp b/http/http_response.hpp
index cb07a83635..a5f95a90b2 100644
--- a/http/http_response.hpp
+++ b/http/http_response.hpp
@@ -2,8 +2,11 @@
 #include "logging.hpp"
 #include "utils/hex_utils.hpp"
 
+#include <boost/beast/http/file_body.hpp>
 #include <boost/beast/http/message.hpp>
+#include <boost/beast/http/message_generator.hpp>
 #include <boost/beast/http/string_body.hpp>
+#include <boost/variant2/variant.hpp>
 #include <nlohmann/json.hpp>
 
 #include <optional>
@@ -16,37 +19,52 @@ namespace crow
 template <typename Adaptor, typename Handler>
 class Connection;
 
+namespace http = boost::beast::http;
+
 struct Response
 {
     template <typename Adaptor, typename Handler>
     friend class crow::Connection;
-    using response_type =
-        boost::beast::http::response<boost::beast::http::string_body>;
 
-    response_type stringResponse;
+    using string_response = http::response<http::string_body>;
+    using file_response = http::response<http::file_body>;
+
+    // Use boost variant2 because it doesn't have valueless by exception
+    boost::variant2::variant<string_response, file_response> response;
 
     nlohmann::json jsonValue;
+    using fields_type = http::header<false, http::fields>;
+    fields_type& fields()
+    {
+        return boost::variant2::visit(
+            [](auto&& r) -> fields_type& { return r.base(); }, response);
+    }
 
-    void addHeader(std::string_view key, std::string_view value)
+    const fields_type& fields() const
     {
-        stringResponse.insert(key, value);
+        return boost::variant2::visit(
+            [](auto&& r) -> const fields_type& { return r.base(); }, response);
     }
 
-    void addHeader(boost::beast::http::field key, std::string_view value)
+    void addHeader(std::string_view key, std::string_view value)
     {
-        stringResponse.insert(key, value);
+        fields().insert(key, value);
     }
 
-    void clearHeader(boost::beast::http::field key)
+    void addHeader(http::field key, std::string_view value)
     {
-        stringResponse.erase(key);
+        fields().insert(key, value);
     }
 
-    Response() = default;
+    void clearHeader(http::field key)
+    {
+        fields().erase(key);
+    }
 
+    Response() : response(string_response()) {}
     Response(Response&& res) noexcept :
-        stringResponse(std::move(res.stringResponse)),
-        jsonValue(std::move(res.jsonValue)), completed(res.completed)
+        response(std::move(res.response)), jsonValue(std::move(res.jsonValue)),
+        completed(res.completed)
     {
         // See note in operator= move handler for why this is needed.
         if (!res.completed)
@@ -61,7 +79,6 @@ struct Response
     ~Response() = default;
 
     Response(const Response&) = delete;
-
     Response& operator=(const Response& r) = delete;
 
     Response& operator=(Response&& r) noexcept
@@ -72,8 +89,7 @@ struct Response
         {
             return *this;
         }
-        stringResponse = std::move(r.stringResponse);
-        r.stringResponse.clear();
+        response = std::move(r.response);
         jsonValue = std::move(r.jsonValue);
 
         // Only need to move completion handler if not already completed
@@ -98,27 +114,45 @@ struct Response
 
     void result(unsigned v)
     {
-        stringResponse.result(v);
+        fields().result(v);
     }
 
-    void result(boost::beast::http::status v)
+    void result(http::status v)
     {
-        stringResponse.result(v);
+        fields().result(v);
     }
 
-    boost::beast::http::status result() const
+    void copyBody(const Response& res)
     {
-        return stringResponse.result();
+        const string_response* s =
+            boost::variant2::get_if<string_response>(&(res.response));
+        if (s == nullptr)
+        {
+            BMCWEB_LOG_ERROR("Unable to copy a file");
+            return;
+        }
+        string_response* myString =
+            boost::variant2::get_if<string_response>(&response);
+        if (myString == nullptr)
+        {
+            myString = &response.emplace<string_response>();
+        }
+        myString->body() = s->body();
+    }
+
+    http::status result() const
+    {
+        return fields().result();
     }
 
     unsigned resultInt() const
     {
-        return stringResponse.result_int();
+        return fields().result_int();
     }
 
     std::string_view reason() const
     {
-        return stringResponse.reason();
+        return fields().reason();
     }
 
     bool isCompleted() const noexcept
@@ -126,75 +160,87 @@ struct Response
         return completed;
     }
 
-    std::string& body()
+    const std::string* body()
     {
-        return stringResponse.body();
+        string_response* body =
+            boost::variant2::get_if<string_response>(&response);
+        if (body == nullptr)
+        {
+            return nullptr;
+        }
+        return &body->body();
     }
 
     std::string_view getHeaderValue(std::string_view key) const
     {
-        return stringResponse.base()[key];
+        return fields()[key];
     }
 
     void keepAlive(bool k)
     {
-        stringResponse.keep_alive(k);
+        return boost::variant2::visit([k](auto&& r) { r.keep_alive(k); },
+                                      response);
     }
 
     bool keepAlive() const
     {
-        return stringResponse.keep_alive();
+        return boost::variant2::visit([](auto&& r) { return r.keep_alive(); },
+                                      response);
     }
 
-    void preparePayload()
+    uint64_t getContentLength(boost::optional<uint64_t> pSize)
     {
         // This code is a throw-free equivalent to
         // beast::http::message::prepare_payload
-        boost::optional<uint64_t> pSize = stringResponse.payload_size();
-        using boost::beast::http::status;
-        using boost::beast::http::status_class;
-        using boost::beast::http::to_status_class;
+        using http::status;
+        using http::status_class;
+        using http::to_status_class;
         if (!pSize)
         {
-            pSize = 0;
+            return 0;
         }
-        else
+        bool is1XXReturn = to_status_class(result()) ==
+                           status_class::informational;
+        if (*pSize > 0 && (is1XXReturn || result() == status::no_content ||
+                           result() == status::not_modified))
         {
-            bool is1XXReturn = to_status_class(stringResponse.result()) ==
-                               status_class::informational;
-            if (*pSize > 0 &&
-                (is1XXReturn || stringResponse.result() == status::no_content ||
-                 stringResponse.result() == status::not_modified))
-            {
-                BMCWEB_LOG_CRITICAL(
-                    "{} Response content provided but code was no-content or not_modified, which aren't allowed to have a body",
-                    logPtr(this));
-                pSize = 0;
-                body().clear();
-            }
+            BMCWEB_LOG_CRITICAL("{} Response content provided but code was "
+                                "no-content or not_modified, which aren't "
+                                "allowed to have a body",
+                                logPtr(this));
+            return 0;
         }
-        stringResponse.content_length(*pSize);
+        return *pSize;
+    }
+
+    uint64_t size()
+    {
+        return boost::variant2::visit(
+            [](auto&& res) -> uint64_t { return res.body().size(); }, response);
+    }
+
+    void preparePayload()
+    {
+        boost::variant2::visit(
+            [this](auto&& r) {
+            r.content_length(getContentLength(r.payload_size()));
+        },
+            response);
     }
 
     void clear()
     {
         BMCWEB_LOG_DEBUG("{} Clearing response containers", logPtr(this));
-        stringResponse.clear();
-        stringResponse.body().shrink_to_fit();
+        response.emplace<string_response>();
         jsonValue = nullptr;
         completed = false;
         expectedHash = std::nullopt;
     }
 
-    void write(std::string_view bodyPart)
-    {
-        stringResponse.body() += std::string(bodyPart);
-    }
-
     std::string computeEtag() const
     {
         // Only set etag if this request succeeded
-        if (result() != boost::beast::http::status::ok)
+        if (result() != http::status::ok)
         {
             return "";
         }
@@ -207,12 +253,24 @@ struct Response
         return "\"" + intToHexString(hashval, 8) + "\"";
     }
 
+    void write(std::string&& bodyPart)
+    {
+        string_response* str =
+            boost::variant2::get_if<string_response>(&response);
+        if (str != nullptr)
+        {
+            str->body() += bodyPart;
+            return;
+        }
+        response.emplace<string_response>(result(), 11, std::move(bodyPart));
+    }
+
     void end()
     {
         std::string etag = computeEtag();
         if (!etag.empty())
         {
-            addHeader(boost::beast::http::field::etag, etag);
+            addHeader(http::field::etag, etag);
         }
         if (completed)
         {
@@ -268,17 +326,17 @@ struct Response
     void setHashAndHandleNotModified()
     {
         // Can only hash if we have content that's valid
-        if (jsonValue.empty() || result() != boost::beast::http::status::ok)
+        if (jsonValue.empty() || result() != http::status::ok)
         {
             return;
         }
         size_t hashval = std::hash<nlohmann::json>{}(jsonValue);
         std::string hexVal = "\"" + intToHexString(hashval, 8) + "\"";
-        addHeader(boost::beast::http::field::etag, hexVal);
+        addHeader(http::field::etag, hexVal);
         if (expectedHash && hexVal == *expectedHash)
         {
             jsonValue = nullptr;
-            result(boost::beast::http::status::not_modified);
+            result(http::status::not_modified);
         }
     }
 
@@ -287,6 +345,32 @@ struct Response
         expectedHash = hash;
     }
 
+    using message_generator = http::message_generator;
+    message_generator generator()
+    {
+        return boost::variant2::visit(
+            [](auto& r) -> message_generator { return std::move(r); },
+            response);
+    }
+
+    bool openFile(const std::filesystem::path& path)
+    {
+        http::file_body::value_type file;
+        boost::beast::error_code ec;
+        file.open(path.c_str(), boost::beast::file_mode::read, ec);
+        if (ec)
+        {
+            return false;
+        }
+        // store the headers on stack temporarily so we can reconstruct the new
+        // base with the old headers copied in.
+        http::header<false> headTemp = std::move(fields());
+        file_response& fileResponse =
+            response.emplace<file_response>(std::move(headTemp));
+        fileResponse.body() = std::move(file);
+        return true;
+    }
+
   private:
     std::optional<std::string> expectedHash;
     bool completed = false;