H2O: Version upgrade and other changes (#3253)

* Update H2O to version 2.2.4.
* Document some performance issues.
* Clean up some informational messages.

frameworks/C/h2o/README.md

@@ -6,6 +6,16 @@ This is a framework implementation using the [H2O](https://h2o.examp1e.net/) HTT
 
 CMake, H2O, libpq, mustache-c, OpenSSL, YAJL
 
+## Performance issues
+
+### Plaintext
+
+H2O performs at least one system call per pipelined response.
+
+### Cached queries
+
+The in-memory caching mechanism provided by libh2o uses mutexes even for read-only access, so when the application is running multithreaded, cache usage is serialized.
+
 ## Contact
 
 Anton Kirilov <[email protected]>

frameworks/C/h2o/setup.sh

@@ -70,12 +70,12 @@ rm -rf "$BUILD_DIR"
 echo "Maximum database connections per thread: $DB_CONN"
 
 if "$USE_PROCESSES"; then
-	echo "Running $NUM_WORKERS h2o_app processes..."
+	echo "h2o_app processes: $NUM_WORKERS"
 
 	for ((i = 0; i < NUM_WORKERS; i++)); do
 		run_h2o_app "$i" "${H2O_APP_HOME}/bin" "${H2O_APP_HOME}/share/h2o_app" -t1
 	done
 else
-	echo "Running h2o_app multithreaded..."
+	echo "Running h2o_app multithreaded."
 	run_h2o_app 0 "${H2O_APP_HOME}/bin" "${H2O_APP_HOME}/share/h2o_app"
 fi

toolset/setup/linux/webservers/h2o.sh

@@ -5,7 +5,7 @@ fw_depends ruby-2.4
 fw_installed h2o && return 0
 
 H2O_HOME="${IROOT}/h2o"
-VERSION="2.2.2"
+VERSION="2.2.4"
 ARCHIVE="v${VERSION}.tar.gz"
 BUILD_DIR="h2o-${VERSION}"