feat(stats_exporter)!: add process tags to CSS payloads (#1709)

# What does this PR do?

Add support for process tags in CSS payload. The process tags must be set at creation of the trace exporter and can't be updated without recreating the trace exporter

# Motivation

Process tags should be included in CSS payloads

# Additional Notes

This PR does not include setting the process tags on spans exporter by the stats exporter this can be done in the future but is out of the scope of this PR.

# How to test the change?

Added check for the process tags in unit tests. 


Co-authored-by: vianney.ruhlmann <vianney.ruhlmann@datadoghq.com>

Author: VianneyRuhlmann

libdd-data-pipeline-ffi/src/trace_exporter.rs

@@ -65,6 +65,7 @@ pub struct TraceExporterConfig {
     client_computed_stats: bool,
     telemetry_cfg: Option<TelemetryConfig>,
     health_metrics_enabled: bool,
+    process_tags: Option<String>,
     test_session_token: Option<String>,
     connection_timeout: Option<u64>,
 }
@@ -356,6 +357,26 @@ pub unsafe extern "C" fn ddog_trace_exporter_config_set_client_computed_stats(
     )
 }
 
+/// Sets the process tags to be included in the stats payload.
+#[no_mangle]
+pub unsafe extern "C" fn ddog_trace_exporter_config_set_process_tags(
+    config: Option<&mut TraceExporterConfig>,
+    process_tags: CharSlice,
+) -> Option<Box<ExporterError>> {
+    catch_panic!(
+        if let Option::Some(handle) = config {
+            handle.process_tags = match sanitize_string(process_tags) {
+                Ok(s) => Some(s),
+                Err(e) => return Some(e),
+            };
+            None
+        } else {
+            gen_error!(ErrorCode::InvalidArgument)
+        },
+        gen_error!(ErrorCode::Panic)
+    )
+}
+
 /// Sets the `X-Datadog-Test-Session-Token` header. Only used for testing with the test agent.
 #[no_mangle]
 pub unsafe extern "C" fn ddog_trace_exporter_config_set_test_session_token(
@@ -423,6 +444,7 @@ pub unsafe extern "C" fn ddog_trace_exporter_new(
                 .set_env(config.env.as_ref().unwrap_or(&"".to_string()))
                 .set_app_version(config.version.as_ref().unwrap_or(&"".to_string()))
                 .set_service(config.service.as_ref().unwrap_or(&"".to_string()))
+                .set_process_tags(config.process_tags.as_deref().unwrap_or(""))
                 .set_input_format(config.input_format)
                 .set_output_format(config.output_format)
                 .set_connection_timeout(config.connection_timeout);
@@ -537,6 +559,7 @@ mod tests {
             assert!(!cfg.compute_stats);
             assert!(cfg.telemetry_cfg.is_none());
             assert!(!cfg.health_metrics_enabled);
+            assert!(cfg.process_tags.is_none());
             assert!(cfg.test_session_token.is_none());
             assert!(cfg.connection_timeout.is_none());
 
@@ -726,6 +749,27 @@ mod tests {
         }
     }
 
+    #[test]
+    fn config_process_tags_test() {
+        unsafe {
+            let error = ddog_trace_exporter_config_set_process_tags(None, CharSlice::from("k:v"));
+            assert_eq!(error.as_ref().unwrap().code, ErrorCode::InvalidArgument);
+
+            ddog_trace_exporter_error_free(error);
+
+            let mut config = Some(TraceExporterConfig::default());
+            let error = ddog_trace_exporter_config_set_process_tags(
+                config.as_mut(),
+                CharSlice::from("key1:val1,key2:val2"),
+            );
+
+            assert_eq!(error, None);
+
+            let cfg = config.unwrap();
+            assert_eq!(cfg.process_tags.as_ref().unwrap(), "key1:val1,key2:val2");
+        }
+    }
+
     #[test]
     fn config_client_computed_stats_test() {
         unsafe {

libdd-data-pipeline/src/stats_exporter.rs

@@ -168,13 +168,13 @@ fn encode_stats_payload(
         sequence,
         stats: buckets,
         git_commit_sha: meta.git_commit_sha.clone(),
+        process_tags: meta.process_tags.clone(),
         // These fields are unused or will be set by the Agent
         service: String::new(),
         container_id: String::new(),
         tags: Vec::new(),
         agent_aggregation: String::new(),
         image_tag: String::new(),
-        process_tags: String::new(),
         process_tags_hash: 0,
     }
 }
@@ -217,6 +217,7 @@ mod tests {
             language: "rust".into(),
             tracer_version: "0.0.0".into(),
             runtime_id: "e39d6d12-0752-489f-b488-cf80006c0378".into(),
+            process_tags: "key1:value1,key2:value2".into(),
             ..Default::default()
         }
     }
@@ -257,7 +258,8 @@ mod tests {
                 when.method(POST)
                     .header("Content-type", "application/msgpack")
                     .path("/v0.6/stats")
-                    .body_includes("libdatadog-test");
+                    .body_includes("libdatadog-test")
+                    .body_includes("key1:value1,key2:value2");
                 then.status(200).body("");
             })
             .await;
@@ -318,7 +320,8 @@ mod tests {
                 when.method(POST)
                     .header("Content-type", "application/msgpack")
                     .path("/v0.6/stats")
-                    .body_includes("libdatadog-test");
+                    .body_includes("libdatadog-test")
+                    .body_includes("key1:value1,key2:value2");
                 then.status(200).body("");
             })
             .await;
@@ -356,7 +359,8 @@ mod tests {
                 when.method(POST)
                     .header("Content-type", "application/msgpack")
                     .path("/v0.6/stats")
-                    .body_includes("libdatadog-test");
+                    .body_includes("libdatadog-test")
+                    .body_includes("key1:value1,key2:value2");
                 then.status(200).body("");
             })
             .await;

libdd-data-pipeline/src/trace_exporter/builder.rs

@@ -34,6 +34,7 @@ pub struct TraceExporterBuilder {
     language_interpreter: String,
     language_interpreter_vendor: String,
     git_commit_sha: String,
+    process_tags: String,
     input_format: TraceExporterInputFormat,
     output_format: TraceExporterOutputFormat,
     dogstatsd_url: Option<String>,
@@ -111,6 +112,11 @@ impl TraceExporterBuilder {
         self
     }
 
+    pub fn set_process_tags(&mut self, process_tags: &str) -> &mut Self {
+        process_tags.clone_into(&mut self.process_tags);
+        self
+    }
+
     /// Set the `Datadog-Meta-Tracer-Version` header
     pub fn set_tracer_version(&mut self, tracer_version: &str) -> &mut Self {
         tracer_version.clone_into(&mut self.tracer_version);
@@ -309,6 +315,7 @@ impl TraceExporterBuilder {
                 language_interpreter_vendor: self.language_interpreter_vendor,
                 language: self.language,
                 git_commit_sha: self.git_commit_sha,
+                process_tags: self.process_tags,
                 client_computed_stats: self.client_computed_stats,
                 client_computed_top_level: self.client_computed_top_level,
                 hostname: self.hostname,

libdd-data-pipeline/src/trace_exporter/mod.rs

@@ -128,6 +128,7 @@ pub struct TracerMetadata {
     pub language_interpreter: String,
     pub language_interpreter_vendor: String,
     pub git_commit_sha: String,
+    pub process_tags: String,
     pub client_computed_stats: bool,
     pub client_computed_top_level: bool,
 }