- Assertion testing
- Asynchronous context tracking
- Async hooks
- Buffer
- C++ addons
- C/C++ addons with Node-API
- C++ embedder API
- Child processes
- Cluster
- Command-line options
- Console
- Corepack
- Crypto
- Debugger
- Deprecated APIs
- Diagnostics Channel
- DNS
- Domain
- Errors
- Events
- File system
- Globals
- HTTP
- HTTP/2
- HTTPS
- Inspector
- Internationalization
- Modules: CommonJS modules
- Modules: ECMAScript modules
- Modules:
node:module
API - Modules: Packages
- Net
- OS
- Path
- Performance hooks
- Permissions
- Process
- Punycode
- Query strings
- Readline
- REPL
- Report
- Single executable applications
- Stream
- String decoder
- Test runner
- Timers
- TLS/SSL
- Trace events
- TTY
- UDP/datagram
- URL
- Utilities
- V8
- VM
- WASI
- Web Crypto API
- Web Streams API
- Worker threads
- Zlib
Node.js v21.0.0-nightly202304192e0152ccf1 documentation
- Node.js v21.0.0-nightly202304192e0152ccf1
- ► Table of contents
-
►
Index
- Assertion testing
- Asynchronous context tracking
- Async hooks
- Buffer
- C++ addons
- C/C++ addons with Node-API
- C++ embedder API
- Child processes
- Cluster
- Command-line options
- Console
- Corepack
- Crypto
- Debugger
- Deprecated APIs
- Diagnostics Channel
- DNS
- Domain
- Errors
- Events
- File system
- Globals
- HTTP
- HTTP/2
- HTTPS
- Inspector
- Internationalization
- Modules: CommonJS modules
- Modules: ECMAScript modules
- Modules:
node:module
API - Modules: Packages
- Net
- OS
- Path
- Performance hooks
- Permissions
- Process
- Punycode
- Query strings
- Readline
- REPL
- Report
- Single executable applications
- Stream
- String decoder
- Test runner
- Timers
- TLS/SSL
- Trace events
- TTY
- UDP/datagram
- URL
- Utilities
- V8
- VM
- WASI
- Web Crypto API
- Web Streams API
- Worker threads
- Zlib
- ► Other versions
- ► Options
Table of contents
Diagnostic report#
Delivers a JSON-formatted diagnostic summary, written to a file.
The report is intended for development, test, and production use, to capture and preserve information for problem determination. It includes JavaScript and native stack traces, heap statistics, platform information, resource usage etc. With the report option enabled, diagnostic reports can be triggered on unhandled exceptions, fatal errors and user signals, in addition to triggering programmatically through API calls.
A complete example report that was generated on an uncaught exception is provided below for reference.
{
"header": {
"reportVersion": 3,
"event": "exception",
"trigger": "Exception",
"filename": "report.20181221.005011.8974.0.001.json",
"dumpEventTime": "2018-12-21T00:50:11Z",
"dumpEventTimeStamp": "1545371411331",
"processId": 8974,
"cwd": "/home/nodeuser/project/node",
"commandLine": [
"/home/nodeuser/project/node/out/Release/node",
"--report-uncaught-exception",
"/home/nodeuser/project/node/test/report/test-exception.js",
"child"
],
"nodejsVersion": "v12.0.0-pre",
"glibcVersionRuntime": "2.17",
"glibcVersionCompiler": "2.17",
"wordSize": "64 bit",
"arch": "x64",
"platform": "linux",
"componentVersions": {
"node": "12.0.0-pre",
"v8": "7.1.302.28-node.5",
"uv": "1.24.1",
"zlib": "1.2.11",
"ares": "1.15.0",
"modules": "68",
"nghttp2": "1.34.0",
"napi": "3",
"llhttp": "1.0.1",
"openssl": "1.1.0j"
},
"release": {
"name": "node"
},
"osName": "Linux",
"osRelease": "3.10.0-862.el7.x86_64",
"osVersion": "#1 SMP Wed Mar 21 18:14:51 EDT 2018",
"osMachine": "x86_64",
"cpus": [
{
"model": "Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz",
"speed": 2700,
"user": 88902660,
"nice": 0,
"sys": 50902570,
"idle": 241732220,
"irq": 0
},
{
"model": "Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz",
"speed": 2700,
"user": 88902660,
"nice": 0,
"sys": 50902570,
"idle": 241732220,
"irq": 0
}
],
"networkInterfaces": [
{
"name": "en0",
"internal": false,
"mac": "13:10:de:ad:be:ef",
"address": "10.0.0.37",
"netmask": "255.255.255.0",
"family": "IPv4"
}
],
"host": "test_machine"
},
"javascriptStack": {
"message": "Error: *** test-exception.js: throwing uncaught Error",
"stack": [
"at myException (/home/nodeuser/project/node/test/report/test-exception.js:9:11)",
"at Object.<anonymous> (/home/nodeuser/project/node/test/report/test-exception.js:12:3)",
"at Module._compile (internal/modules/cjs/loader.js:718:30)",
"at Object.Module._extensions..js (internal/modules/cjs/loader.js:729:10)",
"at Module.load (internal/modules/cjs/loader.js:617:32)",
"at tryModuleLoad (internal/modules/cjs/loader.js:560:12)",
"at Function.Module._load (internal/modules/cjs/loader.js:552:3)",
"at Function.Module.runMain (internal/modules/cjs/loader.js:771:12)",
"at executeUserCode (internal/bootstrap/node.js:332:15)"
]
},
"nativeStack": [
{
"pc": "0x000055b57f07a9ef",
"symbol": "report::GetNodeReport(v8::Isolate*, node::Environment*, char const*, char const*, v8::Local<v8::String>, std::ostream&) [./node]"
},
{
"pc": "0x000055b57f07cf03",
"symbol": "report::GetReport(v8::FunctionCallbackInfo<v8::Value> const&) [./node]"
},
{
"pc": "0x000055b57f1bccfd",
"symbol": " [./node]"
},
{
"pc": "0x000055b57f1be048",
"symbol": "v8::internal::Builtin_HandleApiCall(int, v8::internal::Object**, v8::internal::Isolate*) [./node]"
},
{
"pc": "0x000055b57feeda0e",
"symbol": " [./node]"
}
],
"javascriptHeap": {
"totalMemory": 5660672,
"executableMemory": 524288,
"totalCommittedMemory": 5488640,
"availableMemory": 4341379928,
"totalGlobalHandlesMemory": 8192,
"usedGlobalHandlesMemory": 3136,
"usedMemory": 4816432,
"memoryLimit": 4345298944,
"mallocedMemory": 254128,
"externalMemory": 315644,
"peakMallocedMemory": 98752,
"nativeContextCount": 1,
"detachedContextCount": 0,
"doesZapGarbage": 0,
"heapSpaces": {
"read_only_space": {
"memorySize": 524288,
"committedMemory": 39208,
"capacity": 515584,
"used": 30504,
"available": 485080
},
"new_space": {
"memorySize": 2097152,
"committedMemory": 2019312,
"capacity": 1031168,
"used": 985496,
"available": 45672
},
"old_space": {
"memorySize": 2273280,
"committedMemory": 1769008,
"capacity": 1974640,
"used": 1725488,
"available": 249152
},
"code_space": {
"memorySize": 696320,
"committedMemory": 184896,
"capacity": 152128,
"used": 152128,
"available": 0
},
"map_space": {
"memorySize": 536576,
"committedMemory": 344928,
"capacity": 327520,
"used": 327520,
"available": 0
},
"large_object_space": {
"memorySize": 0,
"committedMemory": 0,
"capacity": 1520590336,
"used": 0,
"available": 1520590336
},
"new_large_object_space": {
"memorySize": 0,
"committedMemory": 0,
"capacity": 0,
"used": 0,
"available": 0
}
}
},
"resourceUsage": {
"rss": "35766272",
"free_memory": "1598337024",
"total_memory": "17179869184",
"available_memory": "1598337024",
"maxRss": "36624662528",
"constrained_memory": "36624662528",
"userCpuSeconds": 0.040072,
"kernelCpuSeconds": 0.016029,
"cpuConsumptionPercent": 5.6101,
"userCpuConsumptionPercent": 4.0072,
"kernelCpuConsumptionPercent": 1.6029,
"pageFaults": {
"IORequired": 0,
"IONotRequired": 4610
},
"fsActivity": {
"reads": 0,
"writes": 0
}
},
"uvthreadResourceUsage": {
"userCpuSeconds": 0.039843,
"kernelCpuSeconds": 0.015937,
"cpuConsumptionPercent": 5.578,
"userCpuConsumptionPercent": 3.9843,
"kernelCpuConsumptionPercent": 1.5937,
"fsActivity": {
"reads": 0,
"writes": 0
}
},
"libuv": [
{
"type": "async",
"is_active": true,
"is_referenced": false,
"address": "0x0000000102910900",
"details": ""
},
{
"type": "timer",
"is_active": false,
"is_referenced": false,
"address": "0x00007fff5fbfeab0",
"repeat": 0,
"firesInMsFromNow": 94403548320796,
"expired": true
},
{
"type": "check",
"is_active": true,
"is_referenced": false,
"address": "0x00007fff5fbfeb48"
},
{
"type": "idle",
"is_active": false,
"is_referenced": true,
"address": "0x00007fff5fbfebc0"
},
{
"type": "prepare",
"is_active": false,
"is_referenced": false,
"address": "0x00007fff5fbfec38"
},
{
"type": "check",
"is_active": false,
"is_referenced": false,
"address": "0x00007fff5fbfecb0"
},
{
"type": "async",
"is_active": true,
"is_referenced": false,
"address": "0x000000010188f2e0"
},
{
"type": "tty",
"is_active": false,
"is_referenced": true,
"address": "0x000055b581db0e18",
"width": 204,
"height": 55,
"fd": 17,
"writeQueueSize": 0,
"readable": true,
"writable": true
},
{
"type": "signal",
"is_active": true,
"is_referenced": false,
"address": "0x000055b581d80010",
"signum": 28,
"signal": "SIGWINCH"
},
{
"type": "tty",
"is_active": true,
"is_referenced": true,
"address": "0x000055b581df59f8",
"width": 204,
"height": 55,
"fd": 19,
"writeQueueSize": 0,
"readable": true,
"writable": true
},
{
"type": "loop",
"is_active": true,
"address": "0x000055fc7b2cb180",
"loopIdleTimeSeconds": 22644.8
}
],
"workers": [],
"environmentVariables": {
"REMOTEHOST": "REMOVED",
"MANPATH": "/opt/rh/devtoolset-3/root/usr/share/man:",
"XDG_SESSION_ID": "66126",
"HOSTNAME": "test_machine",
"HOST": "test_machine",
"TERM": "xterm-256color",
"SHELL": "/bin/csh",
"SSH_CLIENT": "REMOVED",
"PERL5LIB": "/opt/rh/devtoolset-3/root//usr/lib64/perl5/vendor_perl:/opt/rh/devtoolset-3/root/usr/lib/perl5:/opt/rh/devtoolset-3/root//usr/share/perl5/vendor_perl",
"OLDPWD": "/home/nodeuser/project/node/src",
"JAVACONFDIRS": "/opt/rh/devtoolset-3/root/etc/java:/etc/java",
"SSH_TTY": "/dev/pts/0",
"PCP_DIR": "/opt/rh/devtoolset-3/root",
"GROUP": "normaluser",
"USER": "nodeuser",
"LD_LIBRARY_PATH": "/opt/rh/devtoolset-3/root/usr/lib64:/opt/rh/devtoolset-3/root/usr/lib",
"HOSTTYPE": "x86_64-linux",
"XDG_CONFIG_DIRS": "/opt/rh/devtoolset-3/root/etc/xdg:/etc/xdg",
"MAIL": "/var/spool/mail/nodeuser",
"PATH": "/home/nodeuser/project/node:/opt/rh/devtoolset-3/root/usr/bin:/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin",
"PWD": "/home/nodeuser/project/node",
"LANG": "en_US.UTF-8",
"PS1": "\\u@\\h : \\[\\e[31m\\]\\w\\[\\e[m\\] > ",
"SHLVL": "2",
"HOME": "/home/nodeuser",
"OSTYPE": "linux",
"VENDOR": "unknown",
"PYTHONPATH": "/opt/rh/devtoolset-3/root/usr/lib64/python2.7/site-packages:/opt/rh/devtoolset-3/root/usr/lib/python2.7/site-packages",
"MACHTYPE": "x86_64",
"LOGNAME": "nodeuser",
"XDG_DATA_DIRS": "/opt/rh/devtoolset-3/root/usr/share:/usr/local/share:/usr/share",
"LESSOPEN": "||/usr/bin/lesspipe.sh %s",
"INFOPATH": "/opt/rh/devtoolset-3/root/usr/share/info",
"XDG_RUNTIME_DIR": "/run/user/50141",
"_": "./node"
},
"userLimits": {
"core_file_size_blocks": {
"soft": "",
"hard": "unlimited"
},
"data_seg_size_kbytes": {
"soft": "unlimited",
"hard": "unlimited"
},
"file_size_blocks": {
"soft": "unlimited",
"hard": "unlimited"
},
"max_locked_memory_bytes": {
"soft": "unlimited",
"hard": 65536
},
"max_memory_size_kbytes": {
"soft": "unlimited",
"hard": "unlimited"
},
"open_files": {
"soft": "unlimited",
"hard": 4096
},
"stack_size_bytes": {
"soft": "unlimited",
"hard": "unlimited"
},
"cpu_time_seconds": {
"soft": "unlimited",
"hard": "unlimited"
},
"max_user_processes": {
"soft": "unlimited",
"hard": 4127290
},
"virtual_memory_kbytes": {
"soft": "unlimited",
"hard": "unlimited"
}
},
"sharedObjects": [
"/lib64/libdl.so.2",
"/lib64/librt.so.1",
"/lib64/libstdc++.so.6",
"/lib64/libm.so.6",
"/lib64/libgcc_s.so.1",
"/lib64/libpthread.so.0",
"/lib64/libc.so.6",
"/lib64/ld-linux-x86-64.so.2"
]
}
Usage#
node --report-uncaught-exception --report-on-signal \
--report-on-fatalerror app.js
-
--report-uncaught-exception
Enables report to be generated on un-caught exceptions. Useful when inspecting JavaScript stack in conjunction with native stack and other runtime environment data. -
--report-on-signal
Enables report to be generated upon receiving the specified (or predefined) signal to the running Node.js process. (See below on how to modify the signal that triggers the report.) Default signal isSIGUSR2
. Useful when a report needs to be triggered from another program. Application monitors may leverage this feature to collect report at regular intervals and plot rich set of internal runtime data to their views.
Signal based report generation is not supported in Windows.
Under normal circumstances, there is no need to modify the report triggering
signal. However, if SIGUSR2
is already used for other purposes, then this
flag helps to change the signal for report generation and preserve the original
meaning of SIGUSR2
for the said purposes.
-
--report-on-fatalerror
Enables the report to be triggered on fatal errors (internal errors within the Node.js runtime, such as out of memory) 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. -
--report-filename
Name of the file to which the report will be written. -
--report-signal
Sets or resets the signal for report generation (not supported on Windows). Default signal isSIGUSR2
.
A report can also be triggered via an API call from a JavaScript application:
process.report.writeReport();
This function takes an optional additional argument filename
, which is
the name of a file into which the report is written.
process.report.writeReport('./foo.json');
This function takes an optional additional argument err
which is an Error
object that will be used as the context for the JavaScript stack printed in the
report. When using report to handle errors in a callback or an exception
handler, this allows the report to include the location of the original error as
well as where it was handled.
try {
process.chdir('/non-existent-path');
} catch (err) {
process.report.writeReport(err);
}
// Any other code
If both filename and error object are passed to writeReport()
the
error object must be the second parameter.
try {
process.chdir('/non-existent-path');
} catch (err) {
process.report.writeReport(filename, err);
}
// Any other code
The content of the diagnostic report can be returned as a JavaScript Object via an API call from a JavaScript application:
const report = process.report.getReport();
console.log(typeof report === 'object'); // true
// Similar to process.report.writeReport() output
console.log(JSON.stringify(report, null, 2));
This function takes an optional additional argument err
, which is an Error
object that will be used as the context for the JavaScript stack printed in the
report.
const report = process.report.getReport(new Error('custom error'));
console.log(typeof report === 'object'); // true
The API versions are useful when inspecting the runtime state from within the application, in expectation of self-adjusting the resource consumption, load balancing, monitoring etc.
The content of the report consists of a header section containing the event
type, date, time, PID, and Node.js version, sections containing JavaScript and
native stack traces, a section containing V8 heap information, a section
containing libuv
handle information, and an OS platform information section
showing CPU and memory usage and system limits. An example report can be
triggered using the Node.js REPL:
$ node
> process.report.writeReport();
Writing Node.js report to file: report.20181126.091102.8480.0.001.json
Node.js report completed
>
When a report is written, start and end messages are issued to stderr and the filename of the report is returned to the caller. The default filename includes the date, time, PID, and a sequence number. The sequence number helps in associating the report dump with the runtime state if generated multiple times for the same Node.js process.
Diagnostic report has an associated single-digit version number (report.header.reportVersion
),
uniquely representing the report format. The version number is bumped
when new key is added or removed, or the data type of a value is changed.
Report version definitions are consistent across LTS releases.
Configuration#
Additional runtime configuration of report generation is available via
the following properties of process.report
:
reportOnFatalError
triggers diagnostic reporting on fatal errors when true
.
Defaults to false
.
reportOnSignal
triggers diagnostic reporting on signal when true
. This is
not supported on Windows. Defaults to false
.
reportOnUncaughtException
triggers diagnostic reporting on uncaught exception
when true
. Defaults to false
.
signal
specifies the POSIX signal identifier that will be used
to intercept external triggers for report generation. Defaults to
'SIGUSR2'
.
filename
specifies the name of the output file in the file system.
Special meaning is attached to stdout
and stderr
. Usage of these
will result in report being written to the associated standard streams.
In cases where standard streams are used, the value in directory
is ignored.
URLs are not supported. Defaults to a composite filename that contains
timestamp, PID, and sequence number.
directory
specifies the file system directory where the report will be
written. URLs are not supported. Defaults to the current working directory of
the Node.js process.
// Trigger report only on uncaught exceptions.
process.report.reportOnFatalError = false;
process.report.reportOnSignal = false;
process.report.reportOnUncaughtException = true;
// Trigger report for both internal errors as well as external signal.
process.report.reportOnFatalError = true;
process.report.reportOnSignal = true;
process.report.reportOnUncaughtException = false;
// Change the default signal to 'SIGQUIT' and enable it.
process.report.reportOnFatalError = false;
process.report.reportOnUncaughtException = false;
process.report.reportOnSignal = true;
process.report.signal = 'SIGQUIT';
Configuration on module initialization is also available via environment variables:
NODE_OPTIONS="--report-uncaught-exception \
--report-on-fatalerror --report-on-signal \
--report-signal=SIGUSR2 --report-filename=./report.json \
--report-directory=/home/nodeuser"
Specific API documentation can be found under
process API documentation
section.
Interaction with workers#
Worker
threads can create reports in the same way that the main thread
does.
Reports will include information on any Workers that are children of the current
thread as part of the workers
section, with each Worker generating a report
in the standard report format.
The thread which is generating the report will wait for the reports from Worker threads to finish. However, the latency for this will usually be low, as both running JavaScript and the event loop are interrupted to generate the report.