[docs] add CONTRIBUTING guidelines - #15
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jeremy-lq
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Apr 16, 2018
jcchavezs
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Apr 17, 2018
| # Contributing to dd-trace-php | ||
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| As an open source project we welcome contributions of many forms, but due to the experimental pre-beta nature | ||
| of this repository, you should reach out before starting work on any major code changes. |
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Maybe we should describe how to reach out. What the official means are.
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The "official" way for now it's filling a GitHub issue with the question. We don't want to open tickets in our support platform because the current state of the tracer is Alpha and so it's expected that it doesn't work properly. I'll follow-up via GitHub if someone wants to contribute and add integrations or updating the API after some changes in OpenTracing.
lejulie
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Apr 17, 2018
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AI summary of the mechanism: > The crash is a cross-thread use-after-free: > > 1. gRPC executes a PHP CallCredentials callback directly on a native > EventEngine worker thread. > 2. In PHP NTS, executor globals—including the profiler VM > interrupt—are process-wide. The gRPC thread can therefore consume a > pending wall-time profiling interrupt. > > 3. The profiler stack-walks that foreign thread and caches raw ThinStr > pointers in Zend’s function runtime cache. > 4. Those strings are actually owned by a Rust thread_local StringSet > belonging to that specific gRPC worker. > 5. After the worker remains idle, gRPC retires it. Its TLS destructor > frees/unmaps the string arena, but Zend’s runtime cache still contains > the pointers. > 6. A later callback/sample retrieves one of those dangling pointers > and crashes in: > ``` > ThinStr::len > StringSet::get_thin_str > collect_time > zend_call_function > plugin_get_metadata > ``` > The deterministic reproducer is one sufficiently long callback, a > 25-second idle interval allowing worker retirement, then another > callback. > > Forking, AppSec, tracing, payload stress, and allocation profiling are > not required. The profiler must avoid sampling threads that never ran > PHP request initialization and must not store thread-local arena > pointers in runtime-cache slots accessible from other threads. Stacktrace: ``` \#0 0x00007742bf3ee95c in ?? () from /lib/x86_64-linux-gnu/libc.so.6 \#1 0x00007742bf399cc2 in raise () from /lib/x86_64-linux-gnu/libc.so.6 \#2 0x00007742b87c94ec in libdd_crashtracker::collector::signal_handler_manager::chain_signal_handler () at libdatadog/libdd-crashtracker/src/collector/signal_handler_manager.rs:125 \#3 libdd_crashtracker::collector::crash_handler::handle_posix_sigaction () at libdatadog/libdd-crashtracker/src/collector/crash_handler.rs:235 \#4 <signal handler called> \#5 read<[u8; 8]> () at /rustc/17067e9ac6d7ecb70e50f92c1944e545188d2359/library/core/src/ptr/mod.rs:1380 \#6 read<[u8; 8]> () at /rustc/17067e9ac6d7ecb70e50f92c1944e545188d2359/library/core/src/ptr/mut_ptr.rs:1356 \#7 len<u8> () at /project/libdatadog/libdd-profiling/src/profiles/collections/thin_str.rs:213 \#8 inline_string_ptr () at /project/libdatadog/libdd-profiling/src/profiles/collections/thin_str.rs:235 \#9 borrow () at /project/libdatadog/libdd-profiling/src/profiles/collections/thin_str.rs:470 \#10 deref () at /project/libdatadog/libdd-profiling/src/profiles/collections/thin_str.rs:453 \#11 get_thin_str () at components-rs/../profiling/src/string_set.rs:117 \#12 get_or_insert<datadog_php::profiling::profiler::stack_walking::detail::handle_function_cache_slot::{closure_env#0}> () at components-rs/../profiling/src/profiler/stack_walking.rs:209 \#13 handle_function_cache_slot () at components-rs/../profiling/src/profiler/stack_walking.rs:466 \#14 collect_call_frame () at components-rs/../profiling/src/profiler/stack_walking.rs:417 \#15 collect_stack_sample_cached () at components-rs/../profiling/src/profiler/stack_walking.rs:362 \#16 0x00007742bea25a55 in {closure#0} () at components-rs/../profiling/src/profiler/stack_walking.rs:393 \#17 {closure#0}<datadog_php::profiling::string_set::StringSet, datadog_php::profiling::profiler::stack_walking::detail::collect_stack_sample::{closure_env#0}, core::result::Result<datadog_php::profiling::profiler::backtrace::Backtrace, datadog_php::profiling::profiler::stack_walking::CollectStackSampleError>> () at components-rs/../profiling/src/lib.rs:533 \#18 map<core::cell::RefMut<datadog_php::profiling::string_set::StringSet>, core::cell::BorrowMutError, core::result::Result<datadog_php::profiling::profiler::backtrace::Backtrace, datadog_php::profiling::profiler::stack_walking::CollectStackSampleError>, datadog_php::profiling::{impl#2}::try_with_borrow_mut::{closure#0}::{closure_env#0}<datadog_php::profiling::string_set::StringSet, datadog_php::profiling::profiler::stack_walking::detail::collect_stack_sample::{closure_env#0}, core::result::Result<datadog_php::profiling::profiler::backtrace::Backtrace, datadog_php::profiling::profiler::stack_walking::CollectStackSampleError>>> () at /rustc/17067e9ac6d7ecb70e50f92c1944e545188d2359/library/core/src/result.rs:773 \#19 {closure#0}<datadog_php::profiling::string_set::StringSet, datadog_php::profiling::profiler::stack_walking::detail::collect_stack_sample::{closure_env#0}, core::result::Result<datadog_php::profiling::profiler::backtrace::Backtrace, datadog_php::profiling::profiler::stack_walking::CollectStackSampleError>> () at components-rs/../profiling/src/lib.rs:533 \#20 try_with<core::cell::RefCell<datadog_php::profiling::string_set::StringSet>, datadog_php::profiling::{impl#2}::try_with_borrow_mut::{closure_env#0}<datadog_php::profiling::string_set::StringSet, datadog_php::profiling::profiler::stack_walking::detail::collect_stack_sample::{closure_env#0}, core::result::Result<datadog_php::profiling::profiler::backtrace::Backtrace, datadog_php::profiling::profiler::stack_walking::CollectStackSampleError>>, core::result::Result<core::result::Result<datadog_php::profiling::profiler::backtrace::Backtrace, datadog_php::profiling::profiler::stack_walking::CollectStackSampleError>, core::cell::BorrowMutError>> () at /rustc/17067e9ac6d7ecb70e50f92c1944e545188d2359/library/std/src/thread/local.rs:311 \#21 try_with_borrow_mut<datadog_php::profiling::string_set::StringSet, datadog_php::profiling::profiler::stack_walking::detail::collect_stack_sample::{closure_env#0}, core::result::Result<datadog_php::profiling::profiler::backtrace::Backtrace, datadog_php::profiling::profiler::stack_walking::CollectStackSampleError>> () at components-rs/../profiling/src/lib.rs:532 \#22 collect_stack_sample () at components-rs/../profiling/src/profiler/stack_walking.rs:393 \#23 0x00007742bea2cf55 in collect_stack_sample_timed () at components-rs/../profiling/src/profiler/mod.rs:1158 \#24 0x00007742bea2d087 in collect_time () at components-rs/../profiling/src/profiler/mod.rs:1182 \#25 0x00007742bea35d9a in ddog_php_prof_interrupt_function_wrapper () at components-rs/../profiling/src/wall_time.rs:308 \#26 0x00005b150b5ba079 in zend_interrupt_helper_SPEC () at /root/php/sources/8.5.0/Zend/zend_vm_execute.h:4027 \#27 0x00005b150b69fb6f in execute_ex (ex=0x7742bf013590) at /root/php/sources/8.5.0/Zend/zend_vm_execute.h:116152 \#28 0x00005b150b57cea5 in zend_call_function (fci=0x5b15381ade70, fci_cache=0x5b1538220230) at /root/php/sources/8.5.0/Zend/zend_execute_API.c:1010 \#29 0x00007742be4d7e7e in plugin_get_metadata (ptr=0x7742bf003190, context=..., cb=<optimized out>, user_data=<optimized out>, creds_md=0x77427a7fb0a0, num_creds_md=0x77427a7fb068, status=0x77427a7fb064, error_details=0x77427a7fb058) at /tmp/grpc-php-8.5-release.EUD4iV/src/php/ext/grpc/call_credentials.c:169 \#30 0x00007742be03098f in grpc_plugin_credentials::GetRequestMetadata (this=0x5b153821d660, initial_metadata=..., args=<optimized out>) at /tmp/grpc-php-8.5-release.EUD4iV/src/core/credentials/call/plugin/plugin_credentials.cc:162 \#31 0x00007742be19c295 in grpc_core::ClientAuthFilter::GetMetadataFromCreds (this=<optimized out>, creds=..., md=...) at ./src/core/filter/auth/auth_filters.h:61 \#32 grpc_core::ClientAuthFilter::GetCallCredsMetadata(std::__1::unique_ptr<grpc_metadata_batch, grpc_core::Arena::PooledDeleter>)::{lambda()#1}::operator()()::{lambda()#1}::operator()() const (this=<optimized out>) at ./src/core/filter/auth/auth_filters.h:80 \#33 grpc_core::promise_detail::PromiseLike<grpc_core::Map<grpc_core::ArenaPromise<absl::lts_20250512::StatusOr<std::__1::unique_ptr<grpc_metadata_batch, grpc_core::Arena::PooledDeleter> > >, grpc_core::ClientAuthFilter::GetMetadataFromCreds(grpc_core::RefCountedPtr<grpc_call_credentials>, std::__1::unique_ptr<grpc_metadata_batch, grpc_core::Arena::PooledDeleter>)::{lambda(absl::lts_20250512::StatusOr<std::__1::unique_ptr<grpc_metadata_batch, grpc_core::Arena::PooledDeleter> >)#1}>, void>::PromiseLike<grpc_core::ClientAuthFilter::GetCallCredsMetadata(std::__1::unique_ptr<grpc_metadata_batch, grpc_core::Arena::PooledDeleter>)::{lambda()#1}::operator()()::{lambda()#1}>(std::__1::in_place_t, grpc_core::ClientAuthFilter::GetCallCredsMetadata(std::__1::unique_ptr<grpc_metadata_batch, grpc_core::Arena::PooledDeleter>)::{lambda()#1}::operator()()::{lambda()#1}&&) (this=0x77427a7fb270, f=...) at ./src/core/lib/promise/detail/promise_like.h:219 \#34 grpc_core::promise_detail::PromiseFactoryImpl<grpc_core::promise_detail::OnceToken, grpc_core::ClientAuthFilter::GetCallCredsMetadata(std::__1::unique_ptr<grpc_metadata_batch, grpc_core::Arena::PooledDeleter>)::{lambda()#1}::operator()()::{lambda()#1}>(grpc_core::promise_detail::OnceToken, grpc_core::ClientAuthFilter::GetCallCredsMetadata(std::__1::unique_ptr<grpc_metadata_batch, grpc_core::Arena::PooledDeleter>)::{lambda()#1}::operator()()::{lambda()#1}&&) (f=...) at ./src/core/lib/promise/detail/promise_factory.h:221 ```
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Overview
Makes explicit the Work In-Progress state of the repository. Added
CONTRIBUTING.mdso that it's clear that discussions must be opened before implementing new functionalities.