feat(prof): add DD_TAGS support (#3121)

* build: update Cargo.lock

* feat(prof): add DD_TAGS support

"Fun" fact: the profiler once had DD_TAGS support, and this is why
there is tag parsing functions in libdatadog. I think it was lost when
the profiler adopted ZAI config, which was quite a long time ago.

Author: morrisonlevi

profiling/src/config.rs

@@ -12,6 +12,7 @@ use core::mem::{swap, transmute, MaybeUninit};
 use core::ptr;
 use core::str::FromStr;
 pub use datadog_profiling::exporter::Uri;
+use ddcommon::tag::{parse_tags, Tag};
 use libc::c_char;
 use log::{warn, LevelFilter};
 use std::borrow::Cow;
@@ -643,6 +644,16 @@ pub(crate) unsafe fn version() -> Option<String> {
     get_str(Version)
 }
 
+/// # Safety
+/// This function must only be called after config has been initialized in
+/// rinit, and before it is uninitialized in mshutdown.
+pub(crate) unsafe fn tags() -> (Vec<Tag>, Option<String>) {
+    match get_str(Tags) {
+        None => (Vec::new(), None),
+        Some(dd_tags) => parse_tags(&dd_tags),
+    }
+}
+
 /// # Safety
 /// This function must only be called after config has been initialized in
 /// first rinit, and before it is uninitialized in mshutdown.
@@ -978,7 +989,11 @@ pub(crate) fn minit(module_number: libc::c_int) {
                 zai_config_entry {
                     id: transmute::<ConfigId, u16>(Tags),
                     name: Tags.env_var_name(),
-                    type_: ZAI_CONFIG_TYPE_MAP,
+                    // Using a string here means we're going to parse the
+                    // string into tags over and over, but since it needs to
+                    // be a valid zval for destruction, we can't just use a
+                    // Box::leak of Vec<Tag> or something.
+                    type_: ZAI_CONFIG_TYPE_STRING,
                     default_encoded_value: ZaiStr::new(),
                     aliases: ptr::null_mut(),
                     aliases_count: 0,

profiling/src/lib.rs

@@ -380,6 +380,7 @@ pub struct RequestLocals {
     pub env: Option<String>,
     pub service: Option<String>,
     pub version: Option<String>,
+    pub tags: Vec<Tag>,
 
     /// SystemSettings are global. Note that if this is being read in fringe
     /// conditions such as in mshutdown when there were no requests served,
@@ -408,6 +409,7 @@ impl Default for RequestLocals {
             env: None,
             service: None,
             version: None,
+            tags: vec![],
             system_settings: ptr::NonNull::from(INITIAL_SYSTEM_SETTINGS.deref()),
             interrupt_count: AtomicU32::new(0),
             vm_interrupt_addr: ptr::null_mut(),
@@ -488,6 +490,15 @@ extern "C" fn rinit(_type: c_int, _module_number: c_int) -> ZendResult {
                 }
             });
             locals.version = config::version();
+
+            let (tags, maybe_err) = config::tags();
+            if let Some(err) = maybe_err {
+                // DD_TAGS can change on each request, so this warns on every
+                // request. Maybe we should cache the error string and only
+                // emit warnings for new ones?
+                warn!("{err}");
+            }
+            locals.tags = tags;
         }
         locals.system_settings = system_settings;
     });
@@ -581,6 +592,7 @@ extern "C" fn rinit(_type: c_int, _module_number: c_int) -> ZendResult {
                     "zend-nts-ndebug"
                 };
                 add_tag(&mut tags, "runtime_engine", runtime_engine);
+                tags.extend_from_slice(&locals.tags);
                 cell.replace(Arc::new(tags));
             });