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什么是 andb ?

andb 是适用于 gdb/lldb 的 v8 离线调试工具，一般用于调试 v8 的 core 文件。

主要功能,

  1. c++ 调试能力

官方 node/alinode/aworker 均采用 Release 版本发布，缺乏调试信息无法进行调试。
andb 通过 "typ" 文件补全了非位置相关的调试信息，提供了c++调测能力，如结构体显示等。

  1. 检查 v8 堆内对象 (d8)

d8 或 node_g 可以提供 %DebugPrint 检查对象的详细信息， andb 可在 Release 版本上提供 %DebugPrint 的能力，无需应用重新编译 Debug 版本。

  1. 分析时能力 (Heap Snapshot)

Heap Snapshot 是 OOM 问题的主要定位手段，传统 Heap Snapshot 的获取则依赖于运行时开销较大， 通过 andb 则可以从 core 文件中离线导出 Heap Snapshot。

  1. 调试信息的自动匹配

通过 arthur 或者 kernel 产生 core 文件，其含有 node 二进制的 BuildId 信息， andb 可以从数据库中自动匹配 node 以及 alinode 官方 Release 的版本及配套的调试信息文件。 对于 gcore 产生的 core 文件，BuildId 信息未被保存，需要手工进行匹配调试。

支持的调试环境,

  • Linux + gdb 10.0+
  • Linux + lldb 8.0+
  • MacOS + lldb 11+ (catelina, bigsur, monterey)
  • MacOS + gdb 10.0+ (andb-gdb)

目前仅支持 x86_64 的 core 文件分析。

使用方法

  1. 克隆整个 andb 工程
  2. 使用 env.sh 设置环境变量
  3. 使用 "andb" 命令开始调试
# 设置环境变量, alias andb
git clone git@github.com:noslate-project/andb.git
cd andb
source env.sh

对于 Arthur 或者 kernel 产生的 core 文件，可选择 gdb/lldb 启动离线调试。

# 使用 lldb 启动调试
andb -l -c core

# 或 使用 gdb 启动调试
andb -g -c core

对于 gcore 产生的 core 文件，则需要准备二进制，配套的 node.typ 文件， 使用 lldb 启动调试, andb 会加载 node 二进制和当前目录下的 node.typ 文件

andb -l node -c core
# or
andb -g node -c core

isolate 的定位

andb 目前内置提供了两个快速找到 Isolate 的方法， 其一、通过 page 的控制字段 其二、通过当前堆栈上留存的 isolate 指针查找

# 通过 page 找 isolate
(gdb) isolate guess page
(class v8::internal::Isolate *) $isolate = 0x416ec60

# 通过 stack 找 isolate
(gdb) isolate guess stack
(class v8::internal::Isolate *) $isolate = 0x416ec60

C++ 调试

andb 通过 Convenience 变量关联重要对象，这类调试器变量均使用 ”$“ 前缀。 如 v8::internal::Isolate 在 isolate 定位后，就可使用 "$isolate" 访问结构体内容，类似的还是有 "$node" 等。

(gdb) p $isolate->heap_.old_space_
$1 = (class v8::internal::OldSpace *) 0x421de80

(gdb) p $isolate->heap_.gc_state_
$2 = v8::internal::Heap::NOT_IN_GC

命令行

andb 通过调试器的命令行接口提供统一的命令行。

命令行采用 "前缀 + 子命令 + 命令参数" 构成，不同的前缀，

  • isolate : isolate 核心结构命令
  • heap : v8 堆相关的命令
  • v8 : v8 相关调试命令
  • node : node 相关的调试命令

gdb 下可提供命令行补全，但受限于 lldb 的实现无法提供自动补全，子命令可使用 "?" 获取，

(gdb) heap ?
snapshot page dump space
(gdb) iso ?
guess

在没有冲突的情况下，可使用命令缩写，如

# gdb
(gdb) iso g p
(class v8::internal::Isolate *) $isolate = 0x416ec60
(gdb) iso g s
(class v8::internal::Isolate *) $isolate = 0x416ec60

# lldb
(lldb) iso g p
(v8::internal::Isolate *) $isolate = 0x416ec60L
(lldb) iso g s
(v8::internal::Isolate *) $isolate = 0x416ec60L

heap space [new|old|code|lo|...]

显示 v8 堆内各 Space 的摘要，

(gdb) heap space
SPACE NAME          COMMIT        MAX
RO_SPACE      :     151552     262144
MAP_SPACE     :   22548480   38014976
CODE_SPACE    :    8749056   12681216
CODE_LO_SPACE :      49152      49152
OLD_SPACE     :  328626176  883847168
LO_SPACE      :  707457024 1462448128
NEW_LO_SPACE  :     299008  418394112
NEW_SPACE     :   33554432
 - from_space :   16777216
 - to_space   :   16777216
Total Committed 1101434880

显示指定 space 的所有 pages

(gdb) heap spa map
 0x30b45bd80000 : size(4096), sweep(1), start(0x30b45bd80120)
 0x2da021080000 : size(262144), sweep(1), start(0x2da021080120)
 ...
 0x1b609b100000 : size(262144), sweep(0), start(0x1b609b100120)
 0x3edd93fc0000 : size(262144), sweep(0), start(0x3edd93fc0120)
Total 32 pages.
(gdb)

heap page <page_address>

打印页内对象，

(gdb) heap page 0x3edd93fc0000
...
0x3edd93ffff30 : size(72), mapsize(72), MAP_TYPE
0x3edd93ffff78 : size(72), mapsize(72), MAP_TYPE
0x3edd93ffffc0 : size(64), mapsize(0), FREE_SPACE_TYPE

heap summary [old|code|lo|...]

摘要指定 Space 上对象的数量及占用字节数，

(gdb) heap sum old
...
0x3490b88c58c1:    42991      1375712 LOAD_HANDLER_TYPE
0x3490b88c0891:    43315      5587496 SCOPE_INFO_TYPE
0x3490b88c11e1:    45508     19311584 NAME_DICTIONARY_TYPE
0x14295ec40439:    47647      2668232 JS_OBJECT_TYPE
0x1f9e87f00439:    48833      3515976 JS_OBJECT_TYPE
0x3490b88c1bb9:    48926      1402440 INTERNALIZED_STRING_TYPE
0x3490b88c1781:    49847      1196328 UNCOMPILED_DATA_WITHOUT_PREPARSE_DATA_TYPE
0x3490b88c0241:    54119      7636728 DESCRIPTOR_ARRAY_TYPE
0x3490b88c02e1:    57338       458704 FILLER_TYPE
0x3490b88c12b9:    58272      1398528 FEEDBACK_CELL_TYPE
0x3490b88c1931:    58568     69492736 STRING_TYPE
0x14295ec403f1:    60238      3373328 JS_FUNCTION_TYPE
0x3490b88c08d9:    63642      3563952 SHARED_FUNCTION_INFO_TYPE
0x3490b88c04f9:    88135      1410160 HEAP_NUMBER_TYPE
0x3490b88c1979:    91588      2930816 CONS_ONE_BYTE_STRING_TYPE
0x3490b88c1421:    94980      4937800 PROPERTY_ARRAY_TYPE
0x14295ec40ca9:   131817      4218144 JS_ARRAY_TYPE
0x14295ec40751:   132339      8469696 JS_FUNCTION_TYPE
0x14295ec403a9:   171768     10993152 JS_FUNCTION_TYPE
0x14295ec40c61:   175716     10745528 FUNCTION_CONTEXT_TYPE
0x3490b88c0729:   176399     20811432 FIXED_ARRAY_TYPE
0x3490b88c0409:   184370     14378824 ONE_BYTE_INTERNALIZED_STRING_TYPE
0x3490b88c0849:   643297     52945368 ONE_BYTE_STRING_TYPE
ShowMapSummary() takes 166.896 second(s).
(gdb)

heap find [old|lo|...] <tag>

在指定堆上查找引用 tag 的对象。

(gdb) heap find old 0xda2d6b4f4e9
<FixedArray 0x1449d494b869>
<FixedArray 0x1449d494c9c9>
find 2
(gdb) heap find old 0x1449d494b869
<JsArray 0x1449d494f1f9>
find 1

heap snapshot

从 core 中导出 core.heapsnapshot 文件，

(gdb) heap snap
Synchronize: (Strong roots)
Synchronize: (Bootstrapper)
Synchronize: (Relocatable)
Synchronize: (Debugger)
Synchronize: (Compilation cache)
Synchronize: (Builtins)
Synchronize: (Thread manager)
Synchronize: (Global handles)
Synchronize: (Stack roots)
Synchronize: (Handle scope)
Synchronize: (Eternal handles)
Synchronize: (Startup object cache)
Synchronize: (Internalized strings)
Synchronize: (External strings)
Iterated 0 RO Heap Objects
failed RO Heap Object: 0
(v8::internal::AllocationSpace) v8::internal::RO_SPACE
(v8::internal::AllocationSpace) v8::internal::MAP_SPACE
(v8::internal::AllocationSpace) v8::internal::CODE_SPACE
(v8::internal::AllocationSpace) v8::internal::CODE_LO_SPACE
(v8::internal::AllocationSpace) v8::internal::OLD_SPACE
18.6%: 999.9/sec, Object(10000), Entry(42830), Edge(119869)
(v8::internal::AllocationSpace) v8::internal::LO_SPACE
(v8::internal::AllocationSpace) v8::internal::NEW_LO_SPACE
(v8::internal::AllocationSpace) v8::internal::NEW_SPACE
Iterated 46355 Objects
failed HeapObject: 0
heap snapshot written to 'core.heapsnapshot'
Generate() takes 14.012 second(s).
(gdb)

之后使用 devtools 打开 core.heapsnapshot 文件。

v8 inspect <tag>

v8 inspect 命令 类似于 %DebugPrint 用于打印某个对象的详细信息。 v8 inspect 的输入是一个 <tag>，如果是非 HeapObject tag，则会显示为 Smi。

(gdb) v8 i 0xda2d6b4f4e9
[JSObject 0xda2d6b4f4e9]
- Properties:
 - originalColumn: <Smi 6 0x600000000>
 - name: <Oddball 0x3490b88c01b1>
 - generatedColumn: <Smi 161 0xa100000000>
 - source: <Smi 0 0x0>
 - originalLine: <Smi 81 0x5100000000>
 - generatedLine: <Smi 43 0x2b00000000>
- Elements: []
[Map 0x1f9e87f00439]
- InstanceSizeInWords: 9
- InobjectPropertiesStartOrConstructorFunctionIndex: 3
- UsedOrUnusedInstanceSizeInWords: 9
- VisitorId: 25
- InstanceType: JS_OBJECT_TYPE (1057)
- BitField: 0x0
[MapBitFields1 0x0]
- HasNonInstancePrototype: 0
- IsCallable: 0
- HasNamedInterceptor: 0
- HasIndexedInterceptor: 0
- IsUndetectable: 0
- IsAccessCheckNeeded: 0
- IsConstructor: 0
- HasPrototypeSlot: 0
- BitField2: 0x19
[MapBitFields2 0x19]
- NewTargetIsBase: 1
- IsImmutablePrototype: 0
- Unused: 0
- ElementsKind: HOLEY_ELEMENTS (3)
- BitField3: 0x8c01bff
[MapBitFields3 0x8c01bff]
- EnumLength: 1023
- NumberOfOwnDescriptors: 6
- IsPrototypeMap: 0
- IsDictionaryMap: 0
- OwnsDescriptors: 1
- IsInRetainedMapList: 1
- IsDeprecated: 0
- IsUnstable: 0
- IsMigrationTarget: 0
- IsExtensible: 1
- MayHaveIntrestingSymbols: 0
- ConstructionCounter: 0
- Prototype: <JsObject 0x2beeb7f52579>
- ConstructorOrBackPointerOrNativeContext: <Map 0x1f9e87f003f1>
- InstanceDescriptors: <DescriptorArray 0x2beeb7f525b1>
- DependentCode: <WeakFixedArray 0x21f08217e919>
- PrototypeValidityCell: <Cell 0x21f08217e411>
- TransitionsOrPrototypeInfo: <Smi 0 0x0>
[HeapObject]
 - MapWord: 0x1f9e87f00439
 - Size: 72
 - Page: 0xda2d6b40000
   - NextObject: 0xda2d6b4f531

v8 bt

显示 v8 调用帧信息，JS函数、this、参数等

(gdb) v8 bt
#0  0x00000e5ce6f04010 home(this=<JsObject 0x620f5fe24e9>) at /disks/banana/zlei/alibaba/andb/test/backtrace/deadloop/dist/controller/home.controller.js:0
#1  0x0000000001462119 <arguments_adaptor>()
#2  0x00000000014681e2 (anonymous)(this=<Oddball 0x5d12f880471>, arg0=<JsObject 0x620f5fc8421>, arg1=<JsBoundFunction 0x620f5fe1c39>) at /disks/banana/zlei/alibaba/andb/test/backtrace/deadloop/node_modules/@midwayjs/core/dist/common/webGenerator.js:0
#3  0x0000000001494db0 (anonymous)(this=<JsGlobalProxy 0x12b3e36823e1>, arg0=<JsObject 0x620f5fe24e9>) at undefined:1489
#4  0x00000000015110ee <stub>()
#5  0x0000000001487eda <stub>()
#6  0x0000000001465e58 <entry>()
#7  0x0000000000d2863b v8::internal::(anonymous namespace)::Invoke(v8::internal::Isolate*, v8::internal::(anonymous namespace)::InvokeParams const&)()
#8  0x0000000000d29553 v8::internal::Execution::TryRunMicrotasks(v8::internal::Isolate*, v8::internal::MicrotaskQueue*, v8::internal::MaybeHandle<v8::internal::Object>*)()
#9  0x0000000000d52be1 v8::internal::MicrotaskQueue::RunMicrotasks(v8::internal::Isolate*)()
#10 0x0000000000d52fc1 v8::internal::MicrotaskQueue::PerformCheckpoint(v8::Isolate*)()
#11 0x0000000000c38261 v8::internal::MaybeHandle<v8::internal::Object> v8::internal::(anonymous namespace)::HandleApiCallHelper<false>(v8::internal::Isolate*, v8::internal::Handle<v8::internal::HeapObject>, v8::internal::Handle<v8::internal::HeapObject>, v8::internal::Handle<v8::internal::FunctionTemplateInfo>, v8::internal::Handle<v8::internal::Object>, v8::internal::BuiltinArguments)()
#12 0x0000000000c39eff v8::internal::Builtin_HandleApiCall(int, unsigned long*, v8::internal::Isolate*)()
#13 0x00000000014cf459 <builtin_exit>()
#14 0x00000000014681e2 processTicksAndRejections(this=<JsApiObject 0x12b3e3681d81>) at internal/process/task_queues.js:0
#15 0x0000000001465efa <internal>()
#16 0x0000000001465cd8 <entry>()
#17 0x0000000000d281e1 v8::internal::(anonymous namespace)::Invoke(v8::internal::Isolate*, v8::internal::(anonymous namespace)::InvokeParams const&)()
#18 0x0000000000d2900f v8::internal::Execution::Call(v8::internal::Isolate*, v8::internal::Handle<v8::internal::Object>, v8::internal::Handle<v8::internal::Object>, int, v8::internal::Handle<v8::internal::Object>*)()
#19 0x0000000000bd4879 v8::Function::Call(v8::Local<v8::Context>, v8::Local<v8::Value>, int, v8::Local<v8::Value>*)()
#20 0x000000000098af6e node::InternalCallbackScope::Close()()
#21 0x000000000098c172 node::InternalMakeCallback(node::Environment*, v8::Local<v8::Object>, v8::Local<v8::Object>, v8::Local<v8::Function>, int, v8::Local<v8::Value>*, node::async_context)()
#22 0x000000000099ae06 node::AsyncWrap::MakeCallback(v8::Local<v8::Function>, int, v8::Local<v8::Value>*)()
#23 0x0000000000a473cd non-virtual thunk to node::(anonymous namespace)::Parser::OnStreamRead(long, uv_buf_t const&)()
#24 0x0000000000b0fcbc node::LibuvStreamWrap::ReadStart()::{lambda(uv_stream_s*, long, uv_buf_t const*)#2}::_FUN(uv_stream_s*, long, uv_buf_t const*)()
#25 0x00000000014551d2 uv__read(stream=<optimized out>) at ../deps/uv/src/unix/stream.c:1259
#26 0x00000000014558d8 uv__stream_io(loop=<optimized out>, w=<optimized out>, events=<optimized out>) at ../deps/uv/src/unix/stream.c:1326
#27 0x000000000145c2e5 uv__io_poll(loop=<optimized out>, timeout=<optimized out>) at ../deps/uv/src/unix/linux-core.c:472
#28 0x0000000001449595 uv_run(loop=<optimized out>, mode=<optimized out>) at ../deps/uv/src/unix/core.c:394
#29 0x0000000000a6fef5 node::NodeMainInstance::Run()()
#30 0x00000000009f7c41 node::Start(int, char**)()
#31 0x00007f71ae0fe445 __libc_start_main(main=0x9885b0 <main>, argc=2, argv=0x7fff155e5378, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff155e5368) at ../csu/libc-start.c:266
#32 0x0000000000989c5d _start()

更多信息请访问 Noslate 官网。

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v8 corefile debugger for gdb/lldb.

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