observe methods from attribute (#146)

Add the capability to observe/hook methods and functions via WithSpan and SpanAttribute
attributes. This capability is disabled by default (it has some runtime overhead), and can be enabled via php.ini

WithSpan is a signal that a function or method should be auto-instrumented. SpanAttribute enables arguments to be passed through to pre hook as attributes to be added to a span.
The attributes are provided by the API, as OpenTelemetry\API\Instumentation\WithSpan and OpenTelemetry\API\Instrumentation\SpanAttribute
Two extra parameters are passed to pre hooks:
1. span name + span kind (from WithSpan's arguments, if provided)
2. attributes (from WithSpan's 3rd argument, and from SpanAttribute)

WithSpan and SpanAttribute can be applied to a methods, functions, or interface methods.

The default pre/post hook callbacks for WithSpan are provided by the API, as OpenTelemetry\API\Instrumentation\WithSpanHandler. They can be changed via php.ini

There is a restriction that WithSpan hooks can only be added to functions/methods that
are not already hooked by something else (because the hooks are added at runtime: when
a method is executed and has no hooks, we then check for attribute and add hooks.

DEVELOPMENT.md

@@ -180,4 +180,4 @@ A more advanced example: https://github.com/open-telemetry/opentelemetry-php-con
 
 # Further reading
 
-* https://www.phpinternalsbook.com/php7/build_system/building_extensions.html
+* https://www.phpinternalsbook.com/php7/build_system/building_extensions.html

Makefile

@@ -1,4 +1,4 @@
-PHP_VERSION ?= 8.3.0
+PHP_VERSION ?= 8.3.10
 DISTRO ?= debian
 
 .DEFAULT_GOAL : help
@@ -21,4 +21,6 @@ build: ## Build extension
 	docker compose run $(DISTRO) ./build.sh
 test: ## Run tests
 	docker compose run $(DISTRO) make test
+remove-orphans: ## Remove orphaned containers
+	docker compose down --remove-orphans
 .PHONY: clean build test git-clean

README.md

@@ -13,7 +13,10 @@ Issues have been disabled for this repo in order to help maintain consistency be
 This is a PHP extension for OpenTelemetry, to enable auto-instrumentation.
 It is based on [zend_observer](https://www.datadoghq.com/blog/engineering/php-8-observability-baked-right-in/) and requires php8+
 
-The extension allows creating `pre` and `post` hook functions to arbitrary PHP functions and methods, which allows those methods to be wrapped with telemetry.
+The extension allows:
+
+- creating `pre` and `post` hook functions to arbitrary PHP functions and methods, which allows those methods to be wrapped with telemetry
+- adding attributes to functions and methods to enable observers at runtime
 
 In PHP 8.2+, internal/built-in PHP functions can also be observed.
 
@@ -241,5 +244,90 @@ string(3) "new"
 string(8) "original"
 ```
 
+## Attribute-based hooking
+
+By applying attributes to source code, the OpenTelemetry extension can add hooks at runtime.
+
+Default pre and post hook methods are provided by the OpenTelemetry API: `OpenTelemetry\API\Instrumentation\Handler::pre`
+and `::post`.
+
+This feature is disabled by default, but can be enabled by setting `opentelemetry.attr_hooks_enabled = On` in php.ini
+
+## Restrictions
+
+Attribute-based hooks can only be applied to a function/method that does not already have
+hooks applied.
+Only one hook can be applied to a function/method, including via interfaces.
+
+Since the attributes are evaluated at runtime, the extension checks whether a hook already
+exists to decide whether it should apply a new runtime hook.
+
+## Configuration
+
+This feature can be configured via `.ini` by modifying the following entries:
+
+- `opentelemetry.attr_hooks_enabled` - boolean, default Off
+- `opentelemetry.attr_pre_handler_function` - FQN of pre method/function
+- `opentelemetry.attr_post_handler_function` - FQN of post method/function
+
+## `OpenTelemetry\API\Instrumentation\WithSpan` attribute
+
+This attribute is provided by the OpenTelemetry API can be applied to a function or class method.
+
+You can also provide optional parameters to the attribute, which control:
+- span name
+- span kind
+- attributes
+
+```php
+use OpenTelemetry\API\Instrumentation\WithSpan
+
+class MyClass
+{
+    #[WithSpan]
+    public function trace_me(): void
+    {
+        /* ... */
+    }
+
+    #[WithSpan('custom_span_name', SpanKind::KIND_INTERNAL, ['my-attr' => 'value'])]
+    public function trace_me_with_customization(): void
+    {
+        /* ... */
+    }
+}
+
+#[WithSpan]
+function my_function(): void
+{
+    /* ... */
+}
+```
+
+## `OpenTelemetry\API\Instrumentation\SpanAttribute` attribute
+
+This attribute should be used in conjunction with `WithSpan`. It is applied to function/method
+parameters, and causes those parameters and values to be passed through to the `pre` hook function
+where they can be added as trace attributes.
+There is one optional parameter, which controls the attribute key. If not set, the parameter name
+is used.
+
+```php
+use OpenTelemetry\API\Instrumentation\WithSpan
+use OpenTelemetry\API\Instrumentation\SpanAttribute
+
+class MyClass
+{
+    #[WithSpan]
+    public function add_user(
+        #[SpanAttribute] string $username,
+        string $password,
+        #[SpanAttribute('a_better_attribute_name')] string $foo_bar_baz,
+    ): void
+    {
+        /* ... */
+    }
+```
+
 ## Contributing
 See [DEVELOPMENT.md](DEVELOPMENT.md) and https://github.com/open-telemetry/opentelemetry-php/blob/main/CONTRIBUTING.md

docker-compose.yaml

@@ -1,11 +1,10 @@
-version: '3.7'
 services:
   debian:
     build:
       context: docker
       dockerfile: Dockerfile.debian
       args:
-        PHP_VERSION: ${PHP_VERSION:-8.3.0}
+        PHP_VERSION: ${PHP_VERSION:-8.3.10}
     volumes:
       - ./ext:/usr/src/myapp
     environment:
@@ -15,7 +14,7 @@ services:
       context: docker
       dockerfile: Dockerfile.alpine
       args:
-        PHP_VERSION: ${PHP_VERSION:-8.3.0}
+        PHP_VERSION: ${PHP_VERSION:-8.3.10}
     volumes:
       - ./ext:/usr/src/myapp
     environment:

ext/.gitignore

@@ -37,6 +37,7 @@ run-tests.php
 tests/**/*.diff
 tests/**/*.out
 tests/**/*.php
+!tests/mocks/*.php
 tests/**/*.exp
 tests/**/*.log
 tests/**/*.sh

ext/opentelemetry.c

@@ -10,6 +10,7 @@
 #include "otel_observer.h"
 #include "stdlib.h"
 #include "string.h"
+#include "zend_attributes.h"
 #include "zend_closures.h"
 
 static int check_conflict(HashTable *registry, const char *extension_name) {
@@ -86,9 +87,21 @@ STD_PHP_INI_ENTRY_EX("opentelemetry.allow_stack_extension", "Off", PHP_INI_ALL,
                      OnUpdateBool, allow_stack_extension,
                      zend_opentelemetry_globals, opentelemetry_globals,
                      zend_ini_boolean_displayer_cb)
+STD_PHP_INI_ENTRY_EX("opentelemetry.attr_hooks_enabled", "Off", PHP_INI_ALL,
+                     OnUpdateBool, attr_hooks_enabled,
+                     zend_opentelemetry_globals, opentelemetry_globals,
+                     zend_ini_boolean_displayer_cb)
+STD_PHP_INI_ENTRY("opentelemetry.attr_pre_handler_function",
+                  "Opentelemetry\\API\\Instrumentation\\WithSpanHandler::pre",
+                  PHP_INI_ALL, OnUpdateString, pre_handler_function_fqn,
+                  zend_opentelemetry_globals, opentelemetry_globals)
+STD_PHP_INI_ENTRY("opentelemetry.attr_post_handler_function",
+                  "Opentelemetry\\API\\Instrumentation\\WithSpanHandler::post",
+                  PHP_INI_ALL, OnUpdateString, post_handler_function_fqn,
+                  zend_opentelemetry_globals, opentelemetry_globals)
 PHP_INI_END()
 
-PHP_FUNCTION(hook) {
+PHP_FUNCTION(OpenTelemetry_Instrumentation_hook) {
     zend_string *class_name;
     zend_string *function_name;
     zval *pre = NULL;

ext/opentelemetry.stub.php

@@ -7,7 +7,7 @@
 /**
  * @param string|null $class The (optional) hooked function's class. Null for a global/built-in function.
  * @param string $function The hooked function's name.
- * @param \Closure|null $pre function($class, array $params, string $class, string $function, ?string $filename, ?int $lineno): $params
+ * @param \Closure|null $pre function($class, array $params, string $class, string $function, ?string $filename, ?int $lineno, ?array $span_args, ?array $span_attributes): $params
  *        You may optionally return modified parameters.
  * @param \Closure|null $post function($class, array $params, $returnValue, ?Throwable $exception): $returnValue
  *        You may optionally return modified return value.
@@ -20,4 +20,4 @@ function hook(
     string $function,
     ?\Closure $pre = null,
     ?\Closure $post = null,
-): bool {}
+): bool {}

ext/opentelemetry_arginfo.h

@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 98cf39fd2bbea1a60b5978923e7d83e3954afb6e */
+ * Stub hash: aa29142596154400c530f1194a7f29fbb9036929 */
 
 ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(
     arginfo_OpenTelemetry_Instrumentation_hook, 0, 2, _IS_BOOL, 0)
@@ -9,8 +9,8 @@ ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(
     ZEND_ARG_OBJ_INFO_WITH_DEFAULT_VALUE(0, post, Closure, 1, "null")
 ZEND_END_ARG_INFO()
 
-ZEND_FUNCTION(hook);
+ZEND_FUNCTION(OpenTelemetry_Instrumentation_hook);
 
-static const zend_function_entry ext_functions[] = {
-    ZEND_NS_FE("OpenTelemetry\\Instrumentation", hook,
-               arginfo_OpenTelemetry_Instrumentation_hook) ZEND_FE_END};
+static const zend_function_entry ext_functions[] = {ZEND_NS_FALIAS(
+    "OpenTelemetry\\Instrumentation", hook, OpenTelemetry_Instrumentation_hook,
+    arginfo_OpenTelemetry_Instrumentation_hook) ZEND_FE_END};