src,cli: support compact (one-line) JSON reports

Multi-line JSON is more human readable, but harder for log aggregators
to consume, they usually require a log message per line, particularly
for JSON. Compact output will be consumable by aggregators such as EFK
(Elastic Search-Fluentd-Kibana), LogDNA, DataDog, etc.

PR-URL: #32254
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

doc/api/cli.md

@@ -615,6 +615,15 @@ file will be created if it does not exist, and will be appended to if it does.
 If an error occurs while attempting to write the warning to the file, the
 warning will be written to stderr instead.
 
+### `--report-compact`
+<!-- YAML
+added: REPLACEME
+-->
+
+Write reports in a compact format, single-line JSON, more easily consumable
+by log processing systems than the default multi-line format designed for
+human consumption.
+
 ### `--report-directory=directory`
 <!-- YAML
 added: v11.8.0
@@ -1160,6 +1169,7 @@ Node.js options that are allowed are:
 * `--preserve-symlinks`
 * `--prof-process`
 * `--redirect-warnings`
+* `--report-compact`
 * `--report-directory`
 * `--report-filename`
 * `--report-on-fatalerror`

doc/api/process.md

@@ -1767,6 +1767,21 @@ changes:
 reports for the current process. Additional documentation is available in the
 [report documentation][].
 
+### `process.report.compact`
+<!-- YAML
+added: REPLACEME
+-->
+
+* {boolean}
+
+Write reports in a compact format, single-line JSON, more easily consumable
+by log processing systems than the default multi-line format designed for
+human consumption.
+
+```js
+console.log(`Reports are compact? ${process.report.compact}`);
+```
+
 ### `process.report.directory`
 <!-- YAML
 added: v11.12.0

doc/api/report.md

@@ -420,6 +420,10 @@ that leads to termination of the application. Useful to inspect various
 diagnostic data elements such as heap, stack, event loop state, resource
 consumption etc. to reason about the fatal error.
 
+* `--report-compact` Write reports in a compact format, single-line JSON, more
+easily consumable by log processing systems than the default multi-line format
+designed for human consumption.
+
 * `--report-directory` Location at which the report will be
 generated.
 

doc/node.1

@@ -290,6 +290,11 @@ Write process warnings to the given
 .Ar file
 instead of printing to stderr.
 .
+.It Fl -report-compact
+Write
+.Sy diagnostic reports
+in a compact format, single-line JSON.
+.
 .It Fl -report-directory
 Location at which the
 .Sy diagnostic report

lib/internal/process/report.js

@@ -3,7 +3,11 @@ const {
   ERR_INVALID_ARG_TYPE,
   ERR_SYNTHETIC
 } = require('internal/errors').codes;
-const { validateSignalName, validateString } = require('internal/validators');
+const {
+  validateSignalName,
+  validateString,
+  validateBoolean,
+} = require('internal/validators');
 const nr = internalBinding('report');
 const {
   JSONParse,
@@ -45,6 +49,13 @@ const report = {
     validateString(name, 'filename');
     nr.setFilename(name);
   },
+  get compact() {
+    return nr.getCompact();
+  },
+  set compact(b) {
+    validateBoolean(b, 'compact');
+    nr.setCompact(b);
+  },
   get signal() {
     return nr.getSignal();
   },

lib/internal/validators.js

@@ -1,6 +1,7 @@
 'use strict';
 
 const {
+  ArrayIsArray,
   NumberIsInteger,
   NumberMAX_SAFE_INTEGER,
   NumberMIN_SAFE_INTEGER,
@@ -123,6 +124,30 @@ function validateNumber(value, name) {
     throw new ERR_INVALID_ARG_TYPE(name, 'number', value);
 }
 
+function validateBoolean(value, name) {
+  if (typeof value !== 'boolean')
+    throw new ERR_INVALID_ARG_TYPE(name, 'boolean', value);
+}
+
+const validateObject = hideStackFrames(
+  (value, name, { nullable = false } = {}) => {
+    if ((!nullable && value === null) ||
+        ArrayIsArray(value) ||
+        typeof value !== 'object') {
+      throw new ERR_INVALID_ARG_TYPE(name, 'Object', value);
+    }
+  });
+
+const validateArray = hideStackFrames((value, name, { minLength = 0 } = {}) => {
+  if (!ArrayIsArray(value)) {
+    throw new ERR_INVALID_ARG_TYPE(name, 'Array', value);
+  }
+  if (value.length < minLength) {
+    const reason = `must be longer than ${minLength}`;
+    throw new ERR_INVALID_ARG_VALUE(name, value, reason);
+  }
+});
+
 function validateSignalName(signal, name = 'signal') {
   if (typeof signal !== 'string')
     throw new ERR_INVALID_ARG_TYPE(name, 'string', signal);
@@ -162,10 +187,13 @@ module.exports = {
   isInt32,
   isUint32,
   parseMode,
+  validateArray,
+  validateBoolean,
   validateBuffer,
   validateInt32,
   validateInteger,
   validateNumber,
+  validateObject,
   validatePort,
   validateSignalName,
   validateString,

src/node_options.cc

@@ -617,6 +617,10 @@ PerIsolateOptionsParser::PerIsolateOptionsParser(
             "generate diagnostic report on uncaught exceptions",
             &PerIsolateOptions::report_uncaught_exception,
             kAllowedInEnvironment);
+  AddOption("--report-compact",
+            "output compact single-line JSON",
+            &PerIsolateOptions::report_compact,
+            kAllowedInEnvironment);
   AddOption("--report-on-signal",
             "generate diagnostic report upon receiving signals",
             &PerIsolateOptions::report_on_signal,

src/node_options.h

@@ -188,6 +188,7 @@ class PerIsolateOptions : public Options {
   bool report_uncaught_exception = false;
   bool report_on_signal = false;
   bool report_on_fatalerror = false;
+  bool report_compact = false;
   std::string report_signal = "SIGUSR2";
   std::string report_filename;
   std::string report_directory;

src/node_report.cc

@@ -52,7 +52,8 @@ static void WriteNodeReport(Isolate* isolate,
                             const char* trigger,
                             const std::string& filename,
                             std::ostream& out,
-                            Local<String> stackstr);
+                            Local<String> stackstr,
+                            bool compact);
 static void PrintVersionInformation(JSONWriter* writer);
 static void PrintJavaScriptStack(JSONWriter* writer,
                                  Isolate* isolate,
@@ -126,8 +127,9 @@ std::string TriggerNodeReport(Isolate* isolate,
     std::cerr << "\nWriting Node.js report to file: " << filename;
   }
 
+  bool compact = env != nullptr ? options->report_compact : true;
   WriteNodeReport(isolate, env, message, trigger, filename, *outstream,
-                  stackstr);
+                  stackstr, compact);
 
   // Do not close stdout/stderr, only close files we opened.
   if (outfile.is_open()) {
@@ -145,7 +147,7 @@ void GetNodeReport(Isolate* isolate,
                    const char* trigger,
                    Local<String> stackstr,
                    std::ostream& out) {
-  WriteNodeReport(isolate, env, message, trigger, "", out, stackstr);
+  WriteNodeReport(isolate, env, message, trigger, "", out, stackstr, false);
 }
 
 // Internal function to coordinate and write the various
@@ -156,7 +158,8 @@ static void WriteNodeReport(Isolate* isolate,
                             const char* trigger,
                             const std::string& filename,
                             std::ostream& out,
-                            Local<String> stackstr) {
+                            Local<String> stackstr,
+                            bool compact) {
   // Obtain the current time and the pid.
   TIME_TYPE tm_struct;
   DiagnosticFilename::LocalTime(&tm_struct);
@@ -169,7 +172,7 @@ static void WriteNodeReport(Isolate* isolate,
   // File stream opened OK, now start printing the report content:
   // the title and header information (event, filename, timestamp and pid)
 
-  JSONWriter writer(out);
+  JSONWriter writer(out, compact);
   writer.json_start();
   writer.json_objectstart("header");
   writer.json_keyvalue("reportVersion", NODE_REPORT_VERSION);

src/node_report.h

@@ -65,25 +65,37 @@ extern double prog_start_time;
 // JSON compiler definitions.
 class JSONWriter {
  public:
-  explicit JSONWriter(std::ostream& out) : out_(out) {}
+  JSONWriter(std::ostream& out, bool compact)
+    : out_(out), compact_(compact) {}
 
+ private:
   inline void indent() { indent_ += 2; }
   inline void deindent() { indent_ -= 2; }
   inline void advance() {
+    if (compact_) return;
     for (int i = 0; i < indent_; i++) out_ << ' ';
   }
+  inline void write_one_space() {
+    if (compact_) return;
+    out_ << ' ';
+  }
+  inline void write_new_line() {
+    if (compact_) return;
+    out_ << '\n';
+  }
 
+ public:
   inline void json_start() {
     if (state_ == kAfterValue) out_ << ',';
-    out_ << '\n';
+    write_new_line();
     advance();
     out_ << '{';
     indent();
     state_ = kObjectStart;
   }
 
   inline void json_end() {
-    out_ << '\n';
+    write_new_line();
     deindent();
     advance();
     out_ << '}';
@@ -92,34 +104,42 @@ class JSONWriter {
   template <typename T>
   inline void json_objectstart(T key) {
     if (state_ == kAfterValue) out_ << ',';
-    out_ << '\n';
+    write_new_line();
     advance();
     write_string(key);
-    out_ << ": {";
+    out_ << ':';
+    write_one_space();
+    out_ << '{';
     indent();
     state_ = kObjectStart;
   }
 
   template <typename T>
   inline void json_arraystart(T key) {
     if (state_ == kAfterValue) out_ << ',';
-    out_ << '\n';
+    write_new_line();
     advance();
     write_string(key);
-    out_ << ": [";
+    out_ << ':';
+    write_one_space();
+    out_ << '[';
     indent();
     state_ = kObjectStart;
   }
   inline void json_objectend() {
-    out_ << '\n';
+    write_new_line();
     deindent();
     advance();
     out_ << '}';
+    if (indent_ == 0) {
+      // Top-level object is complete, so end the line.
+      out_ << '\n';
+    }
     state_ = kAfterValue;
   }
 
   inline void json_arrayend() {
-    out_ << '\n';
+    write_new_line();
     deindent();
     advance();
     out_ << ']';
@@ -128,18 +148,19 @@ class JSONWriter {
   template <typename T, typename U>
   inline void json_keyvalue(const T& key, const U& value) {
     if (state_ == kAfterValue) out_ << ',';
-    out_ << '\n';
+    write_new_line();
     advance();
     write_string(key);
-    out_ << ": ";
+    out_ << ':';
+    write_one_space();
     write_value(value);
     state_ = kAfterValue;
   }
 
   template <typename U>
   inline void json_element(const U& value) {
     if (state_ == kAfterValue) out_ << ',';
-    out_ << '\n';
+    write_new_line();
     advance();
     write_value(value);
     state_ = kAfterValue;
@@ -177,6 +198,7 @@ class JSONWriter {
 
   enum JSONState { kObjectStart, kAfterValue };
   std::ostream& out_;
+  bool compact_;
   int indent_ = 0;
   int state_ = kObjectStart;
 };

src/node_report_module.cc

@@ -68,6 +68,18 @@ void GetReport(const FunctionCallbackInfo<Value>& info) {
                                 .ToLocalChecked());
 }
 
+static void GetCompact(const FunctionCallbackInfo<Value>& info) {
+  Environment* env = Environment::GetCurrent(info);
+  info.GetReturnValue().Set(env->isolate_data()->options()->report_compact);
+}
+
+static void SetCompact(const FunctionCallbackInfo<Value>& info) {
+  Environment* env = Environment::GetCurrent(info);
+  Isolate* isolate = env->isolate();
+  bool compact = info[0]->ToBoolean(isolate)->Value();
+  env->isolate_data()->options()->report_compact = compact;
+}
+
 static void GetDirectory(const FunctionCallbackInfo<Value>& info) {
   Environment* env = Environment::GetCurrent(info);
   std::string directory = env->isolate_data()->options()->report_directory;
@@ -161,6 +173,8 @@ static void Initialize(Local<Object> exports,
 
   env->SetMethod(exports, "writeReport", WriteReport);
   env->SetMethod(exports, "getReport", GetReport);
+  env->SetMethod(exports, "getCompact", GetCompact);
+  env->SetMethod(exports, "setCompact", SetCompact);
   env->SetMethod(exports, "getDirectory", GetDirectory);
   env->SetMethod(exports, "setDirectory", SetDirectory);
   env->SetMethod(exports, "getFilename", GetFilename);

test/common/report.js

@@ -25,7 +25,12 @@ function findReports(pid, dir) {
 }
 
 function validate(filepath) {
-  validateContent(JSON.parse(fs.readFileSync(filepath, 'utf8')));
+  const report = fs.readFileSync(filepath, 'utf8');
+  if (process.report.compact) {
+    const end = report.indexOf('\n');
+    assert.strictEqual(end, report.length - 1);
+  }
+  validateContent(JSON.parse(report));
 }
 
 function validateContent(report) {