Implemented a json log formatter

flow/JsonTraceLogFormatter.cpp

@@ -0,0 +1,84 @@
+/*
+ * XmlTraceLogFormatter.h
+ *
+ * This source file is part of the FoundationDB open source project
+ *
+ * Copyright 2018 Apple Inc. and the FoundationDB project 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.
+ */
+
+#include "flow/flow.h"
+#include "JsonTraceLogFormatter.h"
+
+#include <sstream>
+
+void JsonTraceLogFormatter::addref()
+{
+    ReferenceCounted<JsonTraceLogFormatter>::addref();
+}
+
+void JsonTraceLogFormatter::delref()
+{
+    ReferenceCounted<JsonTraceLogFormatter>::delref();
+}
+
+const char* JsonTraceLogFormatter::getExtension()
+{
+    return "json";
+}
+
+const char* JsonTraceLogFormatter::getHeader()
+{
+    return "";
+}
+
+const char* JsonTraceLogFormatter::getFooter()
+{
+    return "";
+}
+
+namespace {
+
+void escapeString(std::stringstream& ss, const std::string source)
+{
+    for (auto c : source) {
+        if (c == '"') {
+            ss << "\"";
+        } else if (c == '\\') {
+            ss << "\\\\";
+        } else {
+            ss << c;
+        }
+    }
+}
+
+}
+
+std::string JsonTraceLogFormatter::formatEvent(const TraceEventFields& fields)
+{
+    std::stringstream ss;
+    ss << "{  ";
+    for (auto iter = fields.begin(); iter != fields.end(); ++iter) {
+        if (iter != fields.begin()) {
+            ss << ", ";
+        }
+        ss << "\"";
+        escapeString(ss, iter->first);
+        ss << "\": \"";
+        escapeString(ss, iter->second);
+        ss << "\"";
+    }
+    ss << " }\r\n";
+    return ss.str();
+}

flow/JsonTraceLogFormatter.h

@@ -0,0 +1,32 @@
+/*
+ * XmlTraceLogFormatter.h
+ *
+ * This source file is part of the FoundationDB open source project
+ *
+ * Copyright 2018 Apple Inc. and the FoundationDB project 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.
+ */
+
+#include "FastRef.h"
+#include "Trace.h"
+
+struct JsonTraceLogFormatter : public ITraceLogFormatter, ReferenceCounted<JsonTraceLogFormatter> {
+	const char* getExtension() override;
+	const char* getHeader() override; // Called when starting a new file
+	const char* getFooter() override; // Called when ending a file
+	std::string formatEvent(const TraceEventFields&) override; // Called for each event
+
+	void addref() override;
+	void delref() override;
+};

flow/Knobs.cpp

@@ -123,6 +123,7 @@ FlowKnobs::FlowKnobs(bool randomize, bool isSimulated) {
 	init( TRACE_EVENT_METRIC_UNITS_PER_SAMPLE,                 500 );
 	init( TRACE_EVENT_THROTTLER_SAMPLE_EXPIRY,              1800.0 ); // 30 mins
 	init( TRACE_EVENT_THROTTLER_MSG_LIMIT,                   20000 );
+	init( TRACE_FORMAT,                   			        "json" );
 
 	//TDMetrics
 	init( MAX_METRICS,                                         600 );

flow/Knobs.h

@@ -145,6 +145,7 @@ public:
 	int TRACE_EVENT_METRIC_UNITS_PER_SAMPLE;
 	int TRACE_EVENT_THROTTLER_SAMPLE_EXPIRY;
 	int TRACE_EVENT_THROTTLER_MSG_LIMIT;
+	std::string TRACE_FORMAT;
 
 	//TDMetrics
 	int64_t MAX_METRIC_SIZE;

flow/Trace.cpp

@@ -22,10 +22,12 @@
 #include "flow/Trace.h"
 #include "flow/FileTraceLogWriter.h"
 #include "flow/XmlTraceLogFormatter.h"
+#include "flow/JsonTraceLogFormatter.h"
 #include "flow/flow.h"
 #include "flow/DeterministicRandom.h"
 #include <stdlib.h>
 #include <stdarg.h>
+#include <cctype>
 #include <time.h>
 
 #include "flow/IThreadPool.h"
@@ -41,6 +43,19 @@
 #undef min
 #endif
 
+Reference<ITraceLogFormatter> createLogFormatter() {
+	auto f = FLOW_KNOBS->TRACE_FORMAT;
+	std::transform(f.begin(), f.end(), f.begin(), ::tolower);
+	if (f == "json") {
+		return Reference<ITraceLogFormatter>(new JsonTraceLogFormatter());
+	} else if (f == "xml") {
+		return Reference<ITraceLogFormatter>(new XmlTraceLogFormatter());
+	} else {
+		ASSERT(false);
+		return Reference<ITraceLogFormatter>(new XmlTraceLogFormatter());
+	}
+}
+
 class DummyThreadPool : public IThreadPool, ReferenceCounted<DummyThreadPool> {
 public:
 	~DummyThreadPool() {}
@@ -280,7 +295,14 @@ public:
 		}
 	};
 
-	TraceLog() : bufferLength(0), loggedLength(0), opened(false), preopenOverflowCount(0), barriers(new BarrierList), logTraceEventMetrics(false), formatter(new XmlTraceLogFormatter()) {}
+	TraceLog()
+		: bufferLength(0)
+		, loggedLength(0)
+		, opened(false)
+		, preopenOverflowCount(0)
+		, barriers(new BarrierList)
+		, logTraceEventMetrics(false)
+		, formatter(createLogFormatter()) {}
 
 	bool isOpen() const { return opened; }