From 8b45a157810eec24e846c1aed073ed836f11f4e7 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Wed, 13 Dec 2023 14:52:06 -0500
Subject: [PATCH 01/20] Add new session metrics to core glean metrics

---
 glean/src/metrics.yaml | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/glean/src/metrics.yaml b/glean/src/metrics.yaml
index fbe3a703d..1464ba7d5 100644
--- a/glean/src/metrics.yaml
+++ b/glean/src/metrics.yaml
@@ -122,6 +122,40 @@ glean.internal.metrics:
       - glean-team@mozilla.com
     expires: never
 
+  session_id:
+    type: uuid
+    description: |
+      A UUID uniquely identifying the client's current session.
+    send_in_pings:
+      - glean_client_info
+    lifetime: user
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1862955
+    data_reviews:
+      - TODO
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+
+  session_count:
+    type: counter
+    description: |
+      A running counter of the number of sessions for this client.
+    send_in_pings:
+      - glean_client_info
+    lifetime: user
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1862955
+    data_reviews:
+      - TODO
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+
   app_build:
     type: string
     lifetime: application

From e2d06139fe4aee539b7a11b277728f2fa93175a0 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Wed, 13 Dec 2023 15:46:29 -0500
Subject: [PATCH 02/20] Record session info metrics

Add checks in `internal_metrics` to determine when a session has expired
and we should create a new one. We use a timestamp in LocalStorage for
keeping track of the last active date.
---
 glean/src/core/internal_metrics.ts | 62 ++++++++++++++++++++++++++++++
 glean/src/core/sessions.ts         | 24 ++++++++++++
 2 files changed, 86 insertions(+)
 create mode 100644 glean/src/core/sessions.ts

diff --git a/glean/src/core/internal_metrics.ts b/glean/src/core/internal_metrics.ts
index 08dc4f341..9ec97b414 100644
--- a/glean/src/core/internal_metrics.ts
+++ b/glean/src/core/internal_metrics.ts
@@ -6,12 +6,14 @@ import { KNOWN_CLIENT_ID, CLIENT_INFO_STORAGE } from "./constants.js";
 import { InternalUUIDMetricType as UUIDMetricType } from "./metrics/types/uuid.js";
 import { InternalDatetimeMetricType as DatetimeMetricType } from "./metrics/types/datetime.js";
 import { InternalStringMetricType as StringMetricType } from "./metrics/types/string.js";
+import { InternalCounterMetricType as CounterMetricType } from "./metrics/types/counter.js";
 import { createMetric } from "./metrics/utils.js";
 import TimeUnit from "./metrics/time_unit.js";
 import { generateUUIDv4, isWindowObjectUnavailable } from "./utils.js";
 import { Lifetime } from "./metrics/lifetime.js";
 import log, { LoggingLevel } from "./log.js";
 import { Context } from "./context.js";
+import { hasSessionBeenInactiveForOverThirtyMinutes } from "./sessions.js";
 
 const LOG_TAG = "core.InternalMetrics";
 
@@ -28,6 +30,8 @@ export class CoreMetrics {
   readonly osVersion: StringMetricType;
   readonly architecture: StringMetricType;
   readonly locale: StringMetricType;
+  readonly sessionId: UUIDMetricType;
+  readonly sessionCount: CounterMetricType;
   // Provided by the user
   readonly appChannel: StringMetricType;
   readonly appBuild: StringMetricType;
@@ -120,6 +124,22 @@ export class CoreMetrics {
       },
       "second"
     );
+
+    this.sessionId = new UUIDMetricType({
+      name: "session_id",
+      category: "",
+      sendInPings: ["glean_client_info"],
+      lifetime: Lifetime.User,
+      disabled: false
+    });
+
+    this.sessionCount = new CounterMetricType({
+      name: "session_count",
+      category: "",
+      sendInPings: ["glean_client_info"],
+      lifetime: Lifetime.User,
+      disabled: false
+    });
   }
 
   initialize(migrateFromLegacyStorage?: boolean): void {
@@ -159,6 +179,42 @@ export class CoreMetrics {
     }
   }
 
+  /**
+   * If this is the first session, then we set a new session ID and a
+   * lastActive timestamp.
+   *
+   * If the lastActive time is under 30 minutes, then we only update
+   * the lastActive time.
+   *
+   * If the lastActive time is over 30 minutes, then we update the
+   * session ID, the session sequence number, and the lastActive time.
+   */
+  updateSessionInfo(): void {
+    const existingSessionId = Context.metricsDatabase.getMetric(
+      CLIENT_INFO_STORAGE,
+      this.sessionId
+    );
+
+    if (existingSessionId) {
+      try {
+        // If over 30 minutes has passed since last session interaction,
+        // then we create a new session.
+        if (hasSessionBeenInactiveForOverThirtyMinutes()) {
+          this.generateNewSession();
+        }
+      } catch (e) {
+        // Error parsing the last active timestamp, create a new session.
+        this.generateNewSession();
+      }
+    } else {
+      // There is no previous session information, create a new session.
+      this.generateNewSession();
+    }
+
+    // Set the session new session last active time in LocalStorage.
+    localStorage.setItem("glean_session_last_active", Date.now().toString());
+  }
+
   /**
    * Generates and sets the client_id if it is not set,
    * or if the current value is corrupted.
@@ -202,12 +258,18 @@ export class CoreMetrics {
     }
   }
 
+  private generateNewSession(): void {
+    this.sessionId.set(generateUUIDv4());
+    this.sessionCount.add();
+  }
+
   /**
    * Initializes the Glean internal user-lifetime metrics.
    */
   private initializeUserLifetimeMetrics(): void {
     this.initializeClientId();
     this.initializeFirstRunDate();
+    this.updateSessionInfo();
   }
 
   /**
diff --git a/glean/src/core/sessions.ts b/glean/src/core/sessions.ts
new file mode 100644
index 000000000..22af6e804
--- /dev/null
+++ b/glean/src/core/sessions.ts
@@ -0,0 +1,24 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Check if the current session has been inactive for over thirty minutes. If
+ * it has, then we create a new session.
+ *
+ * @returns {boolean} If the session has been inactive for over thirty minutes.
+ */
+export function hasSessionBeenInactiveForOverThirtyMinutes(): boolean {
+  const lastActive = localStorage.getItem("glean_session_last_active");
+  const lastActiveDate = new Date(Number(lastActive));
+
+  // Create a date 30 minutes ago to compare to our lastActiveDate.
+  //
+  // 60000 - number of milliseconds in a minute
+  // 30 - the number of minutes that can pass before a session is inactive
+  const thirtyMinutesAgo = new Date(Date.now() - (60000 * 30));
+
+  // If the date we created from 30 minutes ago is more recent than the last
+  // active date, then the current session has expired.
+  return thirtyMinutesAgo > lastActiveDate;
+}

From 0291c2bf584983d528599e52c09dec332b816942 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Fri, 15 Dec 2023 13:57:07 -0500
Subject: [PATCH 03/20] Add data review bugs

---
 glean/src/metrics.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/glean/src/metrics.yaml b/glean/src/metrics.yaml
index 1464ba7d5..3b1411d21 100644
--- a/glean/src/metrics.yaml
+++ b/glean/src/metrics.yaml
@@ -132,7 +132,7 @@ glean.internal.metrics:
     bugs:
       - https://bugzilla.mozilla.org/show_bug.cgi?id=1862955
     data_reviews:
-      - TODO
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1862955#c2
     data_sensitivity:
       - technical
     notification_emails:
@@ -149,7 +149,7 @@ glean.internal.metrics:
     bugs:
       - https://bugzilla.mozilla.org/show_bug.cgi?id=1862955
     data_reviews:
-      - TODO
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1862955#c2
     data_sensitivity:
       - technical
     notification_emails:

From 4aea218ac84e5cb5ca38b750e0fcd3b2ca8c9615 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Fri, 15 Dec 2023 14:40:13 -0500
Subject: [PATCH 04/20] Move updateSessionInfo call during init

changelog
- move updateSessionInfo call during init so it is always triggered
- add isWindowObjectUnavailable check to updateSessionInfo
---
 glean/src/core/internal_metrics.ts | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/glean/src/core/internal_metrics.ts b/glean/src/core/internal_metrics.ts
index 9ec97b414..55b1248ee 100644
--- a/glean/src/core/internal_metrics.ts
+++ b/glean/src/core/internal_metrics.ts
@@ -165,6 +165,8 @@ export class CoreMetrics {
       this.initializeUserLifetimeMetrics();
     }
 
+    this.updateSessionInfo();
+
     this.os.set(Context.platform.info.os());
     this.osVersion.set(Context.platform.info.osVersion());
     this.architecture.set(Context.platform.info.arch());
@@ -180,16 +182,28 @@ export class CoreMetrics {
   }
 
   /**
-   * If this is the first session, then we set a new session ID and a
+   * Update local stored session information for Glean. This is called whenever
+   * the app is initialized and on every read/write to storage.
+   *
+   * There are a few scenarios to handle depending on what we already have
+   * stored about the session and how long it has been since the last action.
+   *
+   * SCENARIOS:
+   *
+   * 1. If this is the first session, then we set a new session ID and a
    * lastActive timestamp.
    *
-   * If the lastActive time is under 30 minutes, then we only update
+   * 2. If the lastActive time is under 30 minutes, then we only update
    * the lastActive time.
    *
-   * If the lastActive time is over 30 minutes, then we update the
+   * 3. If the lastActive time is over 30 minutes, then we update the
    * session ID, the session sequence number, and the lastActive time.
    */
   updateSessionInfo(): void {
+    if (isWindowObjectUnavailable()) {
+      return;
+    }
+
     const existingSessionId = Context.metricsDatabase.getMetric(
       CLIENT_INFO_STORAGE,
       this.sessionId
@@ -269,7 +283,6 @@ export class CoreMetrics {
   private initializeUserLifetimeMetrics(): void {
     this.initializeClientId();
     this.initializeFirstRunDate();
-    this.updateSessionInfo();
   }
 
   /**

From 04951e0dd6fe9a2530a991ab70167e94aacc17d6 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Fri, 15 Dec 2023 19:23:23 -0500
Subject: [PATCH 05/20] Call updateSessionInfo when writing data to storage

---
 glean/src/platform/browser/web/storage.ts | 26 +++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/glean/src/platform/browser/web/storage.ts b/glean/src/platform/browser/web/storage.ts
index 2fcf4d592..9dabbd911 100644
--- a/glean/src/platform/browser/web/storage.ts
+++ b/glean/src/platform/browser/web/storage.ts
@@ -6,6 +6,7 @@ import type Store from "../../../core/storage.js";
 import type { StorageIndex } from "../../../core/storage.js";
 import type { JSONObject, JSONValue } from "../../../core/utils.js";
 
+import { Context } from "../../../core/context.js";
 import log, { LoggingLevel } from "../../../core/log.js";
 import {
   deleteKeyFromNestedObject,
@@ -44,6 +45,10 @@ class WebStore implements Store {
       log(LOG_TAG, ["Unable to fetch value from local storage.", err], LoggingLevel.Error);
     }
 
+    if (this.shouldUpdateSession(index)) {
+      Context.coreMetrics.updateSessionInfo();
+    }
+
     return result;
   }
 
@@ -61,6 +66,10 @@ class WebStore implements Store {
     } catch (err) {
       log(LOG_TAG, ["Unable to update value from local storage.", err], LoggingLevel.Error);
     }
+
+    if (this.shouldUpdateSession(index)) {
+      Context.coreMetrics.updateSessionInfo();
+    }
   }
 
   delete(index: StorageIndex): void {
@@ -89,6 +98,23 @@ class WebStore implements Store {
     } catch (err) {
       log(LOG_TAG, ["Unable to delete value from storage.", err], LoggingLevel.Error);
     }
+
+    if (this.shouldUpdateSession(index)) {
+      Context.coreMetrics.updateSessionInfo();
+    }
+  }
+
+  /**
+   * Check to see if the session information should be updated whenever
+   * interacting with storage. If we are updating the existing session metrics
+   * then running the `updateSessionInfo` function again would result in an
+   * infinite loop of updating the metrics and re-running this function.
+   *
+   * @param {StorageIndex} index Index to update in storage.
+   * @returns {boolean} Whether we should update session metrics.
+   */
+  private shouldUpdateSession(index: StorageIndex): boolean {
+    return !index.includes("session_id") && !index.includes("session_count");
   }
 }
 

From 73ee7fd1ec34ab1c8c5cfe7505d4d2e345f1d8d4 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Mon, 18 Dec 2023 15:35:09 -0500
Subject: [PATCH 06/20] #1850 changelog

---
 CHANGELOG.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f69c96677..53d3b7989 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,8 @@
 * [#1848](https://github.com/mozilla/glean.js/pull/1848): Support for automatically collecting element click events (first version)
 * [#1849](https://github.com/mozilla/glean.js/pull/1849): Truncate event extra strings to 500 bytes. This also updates other string-based metrics to truncate based on max bytes rather than a set number of characters.
 
+* [#1850](https://github.com/mozilla/glean.js/pull/1850): Automatically record basic session information (`session_id` & `session_count`) for web properties.
+
 # v4.0.0-pre.2 (2023-12-06)
 
 [Full changelog](https://github.com/mozilla/glean.js/compare/v4.0.0-pre.1...v4.0.0-pre.2)

From 7ff5f62d400bf055d96582a4eab59c489e87d8cf Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Thu, 1 Feb 2024 16:58:06 -0500
Subject: [PATCH 07/20] Session scenarios clarifying comment

---
 glean/src/core/internal_metrics.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/glean/src/core/internal_metrics.ts b/glean/src/core/internal_metrics.ts
index 55b1248ee..f1df2ee27 100644
--- a/glean/src/core/internal_metrics.ts
+++ b/glean/src/core/internal_metrics.ts
@@ -190,8 +190,8 @@ export class CoreMetrics {
    *
    * SCENARIOS:
    *
-   * 1. If this is the first session, then we set a new session ID and a
-   * lastActive timestamp.
+   * 1. If this is the first session (there is no existing session ID),
+   * then we set a new session ID and a lastActive timestamp.
    *
    * 2. If the lastActive time is under 30 minutes, then we only update
    * the lastActive time.

From 4ce696e99d62cb2ffe52f613532a32ee338fcfaf Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Thu, 1 Feb 2024 23:43:06 -0500
Subject: [PATCH 08/20] Use uuid `.generateAndSet` function

---
 glean/src/core/internal_metrics.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/glean/src/core/internal_metrics.ts b/glean/src/core/internal_metrics.ts
index f1df2ee27..ec555d05c 100644
--- a/glean/src/core/internal_metrics.ts
+++ b/glean/src/core/internal_metrics.ts
@@ -273,7 +273,7 @@ export class CoreMetrics {
   }
 
   private generateNewSession(): void {
-    this.sessionId.set(generateUUIDv4());
+    this.sessionId.generateAndSet();
     this.sessionCount.add();
   }
 

From 891a49bc71f4b72bcac1bcd96d22066543daf4c0 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Fri, 2 Feb 2024 02:07:54 -0500
Subject: [PATCH 09/20] Make session expiry checking function more generic,
 allow custom timeout

---
 glean/src/core/internal_metrics.ts | 14 ++++++--------
 glean/src/core/sessions.ts         | 21 +++++++++------------
 2 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/glean/src/core/internal_metrics.ts b/glean/src/core/internal_metrics.ts
index ec555d05c..8f99e9213 100644
--- a/glean/src/core/internal_metrics.ts
+++ b/glean/src/core/internal_metrics.ts
@@ -13,7 +13,7 @@ import { generateUUIDv4, isWindowObjectUnavailable } from "./utils.js";
 import { Lifetime } from "./metrics/lifetime.js";
 import log, { LoggingLevel } from "./log.js";
 import { Context } from "./context.js";
-import { hasSessionBeenInactiveForOverThirtyMinutes } from "./sessions.js";
+import { isSessionInactive } from "./sessions.js";
 
 const LOG_TAG = "core.InternalMetrics";
 
@@ -193,11 +193,10 @@ export class CoreMetrics {
    * 1. If this is the first session (there is no existing session ID),
    * then we set a new session ID and a lastActive timestamp.
    *
-   * 2. If the lastActive time is under 30 minutes, then we only update
-   * the lastActive time.
+   * 2. If the session is not expired, then we only update the lastActive time.
    *
-   * 3. If the lastActive time is over 30 minutes, then we update the
-   * session ID, the session sequence number, and the lastActive time.
+   * 3. If the session is expired (inactive threshold is more recent than lastActive)
+   * then we update the session ID, the session sequence number, and the lastActive time.
    */
   updateSessionInfo(): void {
     if (isWindowObjectUnavailable()) {
@@ -211,9 +210,8 @@ export class CoreMetrics {
 
     if (existingSessionId) {
       try {
-        // If over 30 minutes has passed since last session interaction,
-        // then we create a new session.
-        if (hasSessionBeenInactiveForOverThirtyMinutes()) {
+        // If the session has timed out, then we create a new session.
+        if (isSessionInactive()) {
           this.generateNewSession();
         }
       } catch (e) {
diff --git a/glean/src/core/sessions.ts b/glean/src/core/sessions.ts
index 22af6e804..e6fd1b482 100644
--- a/glean/src/core/sessions.ts
+++ b/glean/src/core/sessions.ts
@@ -3,22 +3,19 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /**
- * Check if the current session has been inactive for over thirty minutes. If
- * it has, then we create a new session.
+ * Check if the current session is inactive - the default timeout is 30 minutes.
  *
- * @returns {boolean} If the session has been inactive for over thirty minutes.
+ * @param sessionLengthInMinutes Length of the session in minutes - defaults to 30.
+ * @returns {boolean} If the current session is inactive.
  */
-export function hasSessionBeenInactiveForOverThirtyMinutes(): boolean {
+export function isSessionInactive(sessionLengthInMinutes = 30): boolean {
   const lastActive = localStorage.getItem("glean_session_last_active");
   const lastActiveDate = new Date(Number(lastActive));
 
-  // Create a date 30 minutes ago to compare to our lastActiveDate.
-  //
-  // 60000 - number of milliseconds in a minute
-  // 30 - the number of minutes that can pass before a session is inactive
-  const thirtyMinutesAgo = new Date(Date.now() - (60000 * 30));
+  // Subtract the session length from the current date
+  const inactiveThreshold = new Date(Date.now() - (60000 * sessionLengthInMinutes));
 
-  // If the date we created from 30 minutes ago is more recent than the last
-  // active date, then the current session has expired.
-  return thirtyMinutesAgo > lastActiveDate;
+  // If the inactiveThreshold is more recent than the lastActiveDate, then the
+  // current session is expired.
+  return inactiveThreshold > lastActiveDate;
 }

From 28bb74ce2d539ce505b8ec76d410a7d79b05c142 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Fri, 2 Feb 2024 02:18:37 -0500
Subject: [PATCH 10/20] Simplify inactiveThreshold date math

---
 glean/src/core/sessions.ts | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/glean/src/core/sessions.ts b/glean/src/core/sessions.ts
index e6fd1b482..f0d127b1c 100644
--- a/glean/src/core/sessions.ts
+++ b/glean/src/core/sessions.ts
@@ -12,8 +12,9 @@ export function isSessionInactive(sessionLengthInMinutes = 30): boolean {
   const lastActive = localStorage.getItem("glean_session_last_active");
   const lastActiveDate = new Date(Number(lastActive));
 
-  // Subtract the session length from the current date
-  const inactiveThreshold = new Date(Date.now() - (60000 * sessionLengthInMinutes));
+  // Subtract the session length from the current date.
+  const inactiveThreshold = new Date();
+  inactiveThreshold.setMinutes(inactiveThreshold.getMinutes() - sessionLengthInMinutes);
 
   // If the inactiveThreshold is more recent than the lastActiveDate, then the
   // current session is expired.

From e2615cecbbc024ca406b56961cf43d7e51bdd05b Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Fri, 2 Feb 2024 16:12:19 -0500
Subject: [PATCH 11/20] Add session length to Glean config object

---
 glean/src/core/config.ts           | 4 ++++
 glean/src/core/internal_metrics.ts | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/glean/src/core/config.ts b/glean/src/core/config.ts
index daafe308e..2f28a033a 100644
--- a/glean/src/core/config.ts
+++ b/glean/src/core/config.ts
@@ -55,6 +55,8 @@ export interface ConfigurationInterface {
   readonly enableAutoElementClickEvents?: boolean,
   // Experimentation identifier to be set in all pings
   experimentationId?: string,
+  // Allow the client to explicitly define the length of a session in MINUTES.
+  readonly sessionLengthInMinutesOverride?: number,
 }
 
 // Important: the `Configuration` should only be used internally by the Glean singleton.
@@ -69,6 +71,7 @@ export class Configuration implements ConfigurationInterface {
   readonly enableAutoPageLoadEvents?: boolean;
   readonly enableAutoElementClickEvents?: boolean;
   experimentationId?: string;
+  readonly sessionLengthInMinutesOverride?: number;
 
   // Debug configuration.
   debug: DebugOptions;
@@ -85,6 +88,7 @@ export class Configuration implements ConfigurationInterface {
     this.enableAutoPageLoadEvents = config?.enableAutoPageLoadEvents;
     this.enableAutoElementClickEvents = config?.enableAutoElementClickEvents;
     this.experimentationId = config?.experimentationId;
+    this.sessionLengthInMinutesOverride = config?.sessionLengthInMinutesOverride;
 
     this.debug = {};
 
diff --git a/glean/src/core/internal_metrics.ts b/glean/src/core/internal_metrics.ts
index 8f99e9213..eec69dfd7 100644
--- a/glean/src/core/internal_metrics.ts
+++ b/glean/src/core/internal_metrics.ts
@@ -211,7 +211,7 @@ export class CoreMetrics {
     if (existingSessionId) {
       try {
         // If the session has timed out, then we create a new session.
-        if (isSessionInactive()) {
+        if (isSessionInactive(Context.config.sessionLengthInMinutesOverride)) {
           this.generateNewSession();
         }
       } catch (e) {

From 25933892e5d199d0a16ef8bddef4673d3756313f Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Tue, 6 Feb 2024 01:06:49 -0500
Subject: [PATCH 12/20] Browserstack tests for session ID

---
 automation/compat/index.html     |  3 ++-
 automation/compat/index.js       | 44 +++++++++++++++++++++++++-------
 automation/compat/tests/utils.js | 11 ++++++--
 3 files changed, 46 insertions(+), 12 deletions(-)

diff --git a/automation/compat/index.html b/automation/compat/index.html
index 3008fcc53..7d0ba3125 100644
--- a/automation/compat/index.html
+++ b/automation/compat/index.html
@@ -7,7 +7,8 @@
   <title>Glean Benchmarks Sample</title>
 </head>
 <body>
-  <p id="msg"></p>
+  <p id="ping_msg"></p>
+  <p id="session_msg"></p>
   <script src="./dist/index.js"></script>
 </body>
 </html>
diff --git a/automation/compat/index.js b/automation/compat/index.js
index f7e4f2894..0a606d716 100644
--- a/automation/compat/index.js
+++ b/automation/compat/index.js
@@ -8,19 +8,12 @@ import Glean from "@mozilla/glean/web";
 import { benchmark } from "./generated/pings.js";
 import * as metrics from "./generated/sample.js";
 
-Glean.setSourceTags(["automation"]);
-Glean.initialize("glean-compat-benchmark", true, {
-  enableAutoPageLoadEvents: true
-});
-
-metrics.pageLoaded.set();
-benchmark.submit();
-
 // !BIG HACK!
 //
 // Overwrite the console.info function in order to know when (and if) the benchmark ping was sent.
 // If a success ping message is logged we show that in the document.
 let pingSubmissionCount = 0;
+let sessionId = "";
 console.info = function () {
   var message = "";
   for (var i = 0; i < arguments.length; i++) {
@@ -30,6 +23,7 @@ console.info = function () {
       message += " ";
     }
   }
+
   console.log(message);
   if (/successfully sent 200.$/.test(message)) {
     pingSubmissionCount++;
@@ -38,8 +32,40 @@ console.info = function () {
     // 1. The built-in page_load event, which submits an events ping.
     // 2. The benchmark ping.
     if (pingSubmissionCount == 2) {
-      var elem = document.getElementById("msg");
+      var elem = document.getElementById("ping_msg");
       elem.innerHTML = "Pings submitted successfully.";
     }
   }
+
+  const sessionRegex = /"session_id": .+"/;
+  const sessionInfo = sessionRegex.exec(message);
+  if (!!sessionInfo) {
+    const currSessionId = sessionInfo?.[0].split(`"`)?.[3];
+    if (!!sessionId) {
+      if (currSessionId !== sessionId) {
+        var elem = document.getElementById("session_msg");
+        elem.innerHTML = "Session IDs updated successfully.";
+      } else {
+        console.log("Something went wrong...");
+      }
+    }
+
+    sessionId = currSessionId;
+  }
 }
+
+Glean.setSourceTags(["automation"]);
+
+// This needs to be set so we can pull the session ID from the log messages.
+Glean.setLogPings(true);
+
+Glean.initialize("glean-compat-benchmark", true, {
+  enableAutoPageLoadEvents: true,
+  // Setting the override to 0 means every action will trigger
+  // a new session. We use this to check that the session ID
+  // changes whenever a session has expired.
+  sessionLengthInMinutesOverride: 0
+});
+
+metrics.pageLoaded.set();
+benchmark.submit();
diff --git a/automation/compat/tests/utils.js b/automation/compat/tests/utils.js
index 2af9146da..929d31994 100644
--- a/automation/compat/tests/utils.js
+++ b/automation/compat/tests/utils.js
@@ -73,7 +73,7 @@ export async function runWebTest(driver) {
     // will receive the text "Ping submitted successfully."
     await driver.get(`http://localhost:${PORT}/`);
     // Give it time to send the ping request.
-    const successTextContainer = await driver.findElement(By.id("msg"));
+    const pingTextContainer = await driver.findElement(By.id("ping_msg"));
 
     const areGleanWindowVarsSet = await driver.executeScript(() => {
       // Verify that all Glean `window` vars are properly set.
@@ -100,10 +100,17 @@ export async function runWebTest(driver) {
 
     await driver.wait(
       until.elementTextIs(
-        successTextContainer,
+        pingTextContainer,
         "Pings submitted successfully."
       ), 11_000); // 1s more than the default upload timeout in Glean.
 
+    const sessionTextContainer = await driver.findElement(By.id("session_msg"));
+    await driver.wait(
+      until.elementTextIs(
+        sessionTextContainer,
+        "Session IDs updated successfully."
+      ), 1000);
+
     console.log("Test passed.");
   } catch(e) {
     console.log("Test failed.", e);

From 7ce3caa0c7e459937835737cd26374fc7c50ce23 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Wed, 7 Feb 2024 12:24:20 -0500
Subject: [PATCH 13/20] Add session description in metrics.yaml

---
 glean/src/metrics.yaml | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/glean/src/metrics.yaml b/glean/src/metrics.yaml
index 3b1411d21..91fa17aa4 100644
--- a/glean/src/metrics.yaml
+++ b/glean/src/metrics.yaml
@@ -125,7 +125,11 @@ glean.internal.metrics:
   session_id:
     type: uuid
     description: |
-      A UUID uniquely identifying the client's current session.
+      A UUID uniquely identifying the client's current session. A session is
+      the period of time in which a user interacts with the application. After
+      a period of inactivity (default being 30 minutes) a new session will be
+      created the next time the user interacts with the application. On each
+      new session, the session_id will be updated.
     send_in_pings:
       - glean_client_info
     lifetime: user
@@ -142,7 +146,11 @@ glean.internal.metrics:
   session_count:
     type: counter
     description: |
-      A running counter of the number of sessions for this client.
+      A running counter of the number of sessions for this client. A session is
+      the period of time in which a user interacts with the application. After
+      a period of inactivity (default being 30 minutes) a new session will be
+      created the next time the user interacts with the application. On each
+      new session, the session_count will be incremented.
     send_in_pings:
       - glean_client_info
     lifetime: user

From 5056d0ddf4e466a653817570aa19b75cf4719062 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Wed, 7 Feb 2024 16:21:29 -0500
Subject: [PATCH 14/20] Update innerHTML to innerText

---
 automation/compat/index.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/automation/compat/index.js b/automation/compat/index.js
index 0a606d716..0ff4bb4d6 100644
--- a/automation/compat/index.js
+++ b/automation/compat/index.js
@@ -33,7 +33,7 @@ console.info = function () {
     // 2. The benchmark ping.
     if (pingSubmissionCount == 2) {
       var elem = document.getElementById("ping_msg");
-      elem.innerHTML = "Pings submitted successfully.";
+      elem.innerText = "Pings submitted successfully.";
     }
   }
 
@@ -44,7 +44,7 @@ console.info = function () {
     if (!!sessionId) {
       if (currSessionId !== sessionId) {
         var elem = document.getElementById("session_msg");
-        elem.innerHTML = "Session IDs updated successfully.";
+        elem.innerText = "Session IDs updated successfully.";
       } else {
         console.log("Something went wrong...");
       }

From 9f89f0acf6e11a76be0571df25a3eb92fecaccc1 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Wed, 7 Feb 2024 16:43:57 -0500
Subject: [PATCH 15/20] Fix clarifying comment

---
 glean/src/core/internal_metrics.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/glean/src/core/internal_metrics.ts b/glean/src/core/internal_metrics.ts
index eec69dfd7..e5164f323 100644
--- a/glean/src/core/internal_metrics.ts
+++ b/glean/src/core/internal_metrics.ts
@@ -223,7 +223,7 @@ export class CoreMetrics {
       this.generateNewSession();
     }
 
-    // Set the session new session last active time in LocalStorage.
+    // Update the last-active timestamp in LocalStorage to the current time.
     localStorage.setItem("glean_session_last_active", Date.now().toString());
   }
 

From 7f977aad5c08022a5bb454e4141e7547a2da7c90 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Thu, 8 Feb 2024 00:35:27 -0500
Subject: [PATCH 16/20] Update session override clarifying comment

---
 glean/src/core/config.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/glean/src/core/config.ts b/glean/src/core/config.ts
index 2f28a033a..98e41587d 100644
--- a/glean/src/core/config.ts
+++ b/glean/src/core/config.ts
@@ -55,7 +55,7 @@ export interface ConfigurationInterface {
   readonly enableAutoElementClickEvents?: boolean,
   // Experimentation identifier to be set in all pings
   experimentationId?: string,
-  // Allow the client to explicitly define the length of a session in MINUTES.
+  // Allows custom session length, in minutes. The default value is 30 minutes.
   readonly sessionLengthInMinutesOverride?: number,
 }
 

From 87514257d94e6c68d470acc04e3585be9428f4a9 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Thu, 8 Feb 2024 00:38:00 -0500
Subject: [PATCH 17/20] updateSessionInfo jsdoc correction

---
 glean/src/core/internal_metrics.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/glean/src/core/internal_metrics.ts b/glean/src/core/internal_metrics.ts
index e5164f323..62791777d 100644
--- a/glean/src/core/internal_metrics.ts
+++ b/glean/src/core/internal_metrics.ts
@@ -183,7 +183,8 @@ export class CoreMetrics {
 
   /**
    * Update local stored session information for Glean. This is called whenever
-   * the app is initialized and on every read/write to storage.
+   * the app on initialization and just after every read/write/delete to/from
+   * storage.
    *
    * There are a few scenarios to handle depending on what we already have
    * stored about the session and how long it has been since the last action.

From 3289a2e63ce22fd811f9a21e2ea48bddb8ee1950 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Thu, 8 Feb 2024 00:42:27 -0500
Subject: [PATCH 18/20] Update session_count description

---
 glean/src/metrics.yaml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/glean/src/metrics.yaml b/glean/src/metrics.yaml
index 91fa17aa4..0df9230e8 100644
--- a/glean/src/metrics.yaml
+++ b/glean/src/metrics.yaml
@@ -151,6 +151,7 @@ glean.internal.metrics:
       a period of inactivity (default being 30 minutes) a new session will be
       created the next time the user interacts with the application. On each
       new session, the session_count will be incremented.
+      This count will ONLY be reset on opt-out or whenever storage is deleted.
     send_in_pings:
       - glean_client_info
     lifetime: user

From ed6be6704b133dbf2b031f445066611efa998d70 Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Wed, 21 Feb 2024 11:40:06 -0500
Subject: [PATCH 19/20] Exclude session_id if ping has no client_id

---
 glean/src/core/pings/maker.ts        | 3 +++
 glean/src/core/pings/ping_payload.ts | 4 +++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/glean/src/core/pings/maker.ts b/glean/src/core/pings/maker.ts
index 506c5ac47..ae22d194b 100644
--- a/glean/src/core/pings/maker.ts
+++ b/glean/src/core/pings/maker.ts
@@ -216,6 +216,9 @@ export function buildClientInfoSection(ping: CommonPingData): ClientInfo {
 
   if (!ping.includeClientId) {
     delete finalClientInfo["client_id"];
+
+    // If the ping doesn't include the client_id, we also should exclude session_id.
+    delete finalClientInfo["session_id"];
   }
 
   return finalClientInfo;
diff --git a/glean/src/core/pings/ping_payload.ts b/glean/src/core/pings/ping_payload.ts
index 54a8f3637..20bd2f392 100644
--- a/glean/src/core/pings/ping_payload.ts
+++ b/glean/src/core/pings/ping_payload.ts
@@ -27,7 +27,9 @@ export interface ClientInfo extends JSONObject {
   first_run_date?: string,
   os?: string,
   os_version?: string,
-  telemetry_sdk_build: string
+  telemetry_sdk_build: string,
+  session_id?: string,
+  session_count?: number
 }
 
 /**

From 04ccc1f5194c842a0b7a210e5ba03652213d397e Mon Sep 17 00:00:00 2001
From: Bruno Rosa <rosahbruno@gmail.com>
Date: Thu, 22 Feb 2024 16:50:26 -0500
Subject: [PATCH 20/20] Update session_id description for include_client_id

---
 glean/src/metrics.yaml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/glean/src/metrics.yaml b/glean/src/metrics.yaml
index 0df9230e8..f8df19e60 100644
--- a/glean/src/metrics.yaml
+++ b/glean/src/metrics.yaml
@@ -130,6 +130,8 @@ glean.internal.metrics:
       a period of inactivity (default being 30 minutes) a new session will be
       created the next time the user interacts with the application. On each
       new session, the session_id will be updated.
+
+      This metric WILL NOT be included for pings where `include_client_id` is `false`.
     send_in_pings:
       - glean_client_info
     lifetime: user