feat: Add Session Aggregates as new Item

The new sessions item has pre-aggregated counts for different session
outcomes.

It is configurable if the aggregation should be exploded into individual
session updates, or rather sent as aggregates to the kafka topic.

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+**Features**:
+
+- Relay is now able to ingest pre-aggregated sessions, which will make it possible to efficiently handle applications that produce thousands of sessions per second. ([#815](https://github.com/getsentry/relay/pull/815))
+
 ## 20.11.1
 
 - No documented changes.

relay-config/src/config.rs

@@ -734,11 +734,18 @@ fn default_max_rate_limit() -> Option<u32> {
     Some(300) // 5 minutes
 }
 
+fn default_explode_session_aggregates() -> bool {
+    true
+}
+
 /// Controls Sentry-internal event processing.
 #[derive(Serialize, Deserialize, Debug)]
 pub struct Processing {
     /// True if the Relay should do processing. Defaults to `false`.
     pub enabled: bool,
+    /// Indicates if session aggregates should be exploded into individual session updates.
+    #[serde(default = "default_explode_session_aggregates")]
+    pub explode_session_aggregates: bool,
     /// GeoIp DB file source.
     #[serde(default)]
     pub geoip_path: Option<PathBuf>,
@@ -775,6 +782,7 @@ impl Default for Processing {
     fn default() -> Self {
         Self {
             enabled: false,
+            explode_session_aggregates: default_explode_session_aggregates(),
             geoip_path: None,
             max_secs_in_future: 0,
             max_secs_in_past: 0,
@@ -1434,6 +1442,11 @@ impl Config {
         self.values.processing.enabled
     }
 
+    /// Indicates if session aggregates should be exploded into individual session updates.
+    pub fn explode_session_aggregates(&self) -> bool {
+        self.values.processing.explode_session_aggregates
+    }
+
     /// The path to the GeoIp database required for event processing.
     pub fn geoip_path(&self) -> Option<&Path> {
         self.values.processing.geoip_path.as_deref()

relay-general/src/protocol/mod.rs

@@ -50,7 +50,9 @@ pub use self::request::{Cookies, HeaderName, HeaderValue, Headers, Query, Reques
 #[cfg(feature = "jsonschema")]
 pub use self::schema::event_json_schema;
 pub use self::security_report::{Csp, ExpectCt, ExpectStaple, Hpkp, SecurityReportType};
-pub use self::session::{ParseSessionStatusError, SessionAttributes, SessionStatus, SessionUpdate};
+pub use self::session::{
+    ParseSessionStatusError, SessionAggregates, SessionAttributes, SessionStatus, SessionUpdate,
+};
 pub use self::span::Span;
 pub use self::stacktrace::{Frame, FrameData, FrameVars, RawStacktrace, Stacktrace};
 pub use self::tags::{TagEntry, Tags};

relay-general/src/protocol/session.rs

@@ -21,6 +21,8 @@ pub enum SessionStatus {
     Crashed,
     /// The session had an unexpected abrupt termination (not crashing).
     Abnormal,
+    /// The session exited cleanly but experienced some errors during its run.
+    Errored,
 }
 
 impl Default for SessionStatus {
@@ -39,6 +41,7 @@ derive_fromstr_and_display!(SessionStatus, ParseSessionStatusError, {
     SessionStatus::Crashed => "crashed",
     SessionStatus::Abnormal => "abnormal",
     SessionStatus::Exited => "exited",
+    SessionStatus::Errored => "errored",
 });
 
 /// Additional attributes for Sessions.
@@ -117,6 +120,103 @@ impl SessionUpdate {
     }
 }
 
+#[allow(clippy::trivially_copy_pass_by_ref)]
+fn is_zero(val: &u32) -> bool {
+    *val == 0
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct SessionAggregateItem {
+    /// The timestamp of when the session itself started.
+    pub started: DateTime<Utc>,
+    /// The distinct identifier.
+    #[serde(rename = "did", default, skip_serializing_if = "Option::is_none")]
+    pub distinct_id: Option<String>,
+    /// The number of exited sessions that ocurred.
+    #[serde(default, skip_serializing_if = "is_zero")]
+    pub exited: u32,
+    /// The number of errored sessions that ocurred, not including the abnormal and crashed ones.
+    #[serde(default, skip_serializing_if = "is_zero")]
+    pub errored: u32,
+    /// The number of abnormal sessions that ocurred.
+    #[serde(default, skip_serializing_if = "is_zero")]
+    pub abnormal: u32,
+    /// The number of crashed sessions that ocurred.
+    #[serde(default, skip_serializing_if = "is_zero")]
+    pub crashed: u32,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct SessionAggregates {
+    /// A batch of sessions that were started.
+    #[serde(default)]
+    pub aggregates: Vec<SessionAggregateItem>,
+    /// The shared session event attributes.
+    #[serde(rename = "attrs")]
+    pub attributes: SessionAttributes,
+}
+
+impl SessionAggregates {
+    /// Parses a session batch from JSON.
+    pub fn parse(payload: &[u8]) -> Result<Self, serde_json::Error> {
+        serde_json::from_slice(payload)
+    }
+
+    /// Serializes a session batch back into JSON.
+    pub fn serialize(&self) -> Result<Vec<u8>, serde_json::Error> {
+        serde_json::to_vec(self)
+    }
+
+    /// The total number of sessions in this aggregate.
+    pub fn num_sessions(&self) -> u32 {
+        self.aggregates
+            .iter()
+            .map(|i| i.exited + i.errored + i.abnormal + i.crashed)
+            .sum()
+    }
+
+    /// Creates individual session updates from the aggregates.
+    pub fn into_updates_iter(self) -> impl Iterator<Item = SessionUpdate> {
+        let attributes = self.attributes;
+        let mut items = self.aggregates;
+        let mut item_opt = items.pop();
+        std::iter::from_fn(move || loop {
+            let item = item_opt.as_mut()?;
+
+            let (status, errors) = if item.exited > 0 {
+                item.exited -= 1;
+                (SessionStatus::Exited, 0)
+            } else if item.errored > 0 {
+                item.errored -= 1;
+                // when exploding, we create "legacy" session updates that have no `errored` state
+                (SessionStatus::Exited, 1)
+            } else if item.abnormal > 0 {
+                item.abnormal -= 1;
+                (SessionStatus::Abnormal, 1)
+            } else if item.crashed > 0 {
+                item.crashed -= 1;
+                (SessionStatus::Crashed, 1)
+            } else {
+                item_opt = items.pop();
+                continue;
+            };
+            let attributes = attributes.clone();
+            return Some(SessionUpdate {
+                session_id: Uuid::new_v4(),
+                distinct_id: item.distinct_id.clone(),
+                sequence: 0,
+                init: true,
+                timestamp: Utc::now(),
+                started: item.started,
+                duration: None,
+                status,
+                errors,
+                attributes,
+            });
+        })
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -241,4 +341,99 @@ mod tests {
         let update = SessionUpdate::parse(json.as_bytes()).unwrap();
         assert_eq_dbg!(update.attributes.ip_address, Some(IpAddr::auto()));
     }
+
+    #[test]
+    fn test_session_aggregates() {
+        let json = r#"{
+  "aggregates": [{
+    "started": "2020-02-07T14:16:00Z",
+    "exited": 2,
+    "abnormal": 1
+  },{
+    "started": "2020-02-07T14:17:00Z",
+    "did": "some-user",
+    "errored": 1
+  }],
+  "attrs": {
+    "release": "sentry-test@1.0.0",
+    "environment": "production",
+    "ip_address": "::1",
+    "user_agent": "Firefox/72.0"
+  }
+}"#;
+        let aggregates = SessionAggregates::parse(json.as_bytes()).unwrap();
+        let mut iter = aggregates.into_updates_iter();
+
+        let mut settings = insta::Settings::new();
+        settings.add_redaction(".timestamp", "[TS]");
+        settings.add_redaction(".sid", "[SID]");
+        settings.bind(|| {
+            insta::assert_yaml_snapshot!(iter.next().unwrap(), @r###"
+            ---
+            sid: "[SID]"
+            did: some-user
+            seq: 0
+            init: true
+            timestamp: "[TS]"
+            started: "2020-02-07T14:17:00Z"
+            status: exited
+            errors: 1
+            attrs:
+              release: sentry-test@1.0.0
+              environment: production
+              ip_address: "::1"
+              user_agent: Firefox/72.0
+            "###);
+            insta::assert_yaml_snapshot!(iter.next().unwrap(), @r###"
+            ---
+            sid: "[SID]"
+            did: ~
+            seq: 0
+            init: true
+            timestamp: "[TS]"
+            started: "2020-02-07T14:16:00Z"
+            status: exited
+            errors: 0
+            attrs:
+              release: sentry-test@1.0.0
+              environment: production
+              ip_address: "::1"
+              user_agent: Firefox/72.0
+            "###);
+            insta::assert_yaml_snapshot!(iter.next().unwrap(), @r###"
+            ---
+            sid: "[SID]"
+            did: ~
+            seq: 0
+            init: true
+            timestamp: "[TS]"
+            started: "2020-02-07T14:16:00Z"
+            status: exited
+            errors: 0
+            attrs:
+              release: sentry-test@1.0.0
+              environment: production
+              ip_address: "::1"
+              user_agent: Firefox/72.0
+            "###);
+            insta::assert_yaml_snapshot!(iter.next().unwrap(), @r###"
+            ---
+            sid: "[SID]"
+            did: ~
+            seq: 0
+            init: true
+            timestamp: "[TS]"
+            started: "2020-02-07T14:16:00Z"
+            status: abnormal
+            errors: 1
+            attrs:
+              release: sentry-test@1.0.0
+              environment: production
+              ip_address: "::1"
+              user_agent: Firefox/72.0
+            "###);
+        });
+
+        assert_eq!(iter.next(), None);
+    }
 }

relay-server/src/actors/events.rs

@@ -681,6 +681,7 @@ impl EventProcessor {
 
             // session data is never considered as part of deduplication
             ItemType::Session => false,
+            ItemType::Sessions => false,
         }
     }