From df9dc82de5129901b3c33e89121990b355ec7bbb Mon Sep 17 00:00:00 2001
From: Jon Chambers <jon@signal.org>
Date: Fri, 26 Feb 2021 16:59:12 -0500
Subject: [PATCH] Record days since last seen when somebody's "last seen" date
 changes.

---
 .../auth/BaseAccountAuthenticator.java              | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/auth/BaseAccountAuthenticator.java b/service/src/main/java/org/whispersystems/textsecuregcm/auth/BaseAccountAuthenticator.java
index 06f1b227a..c0359f44e 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/auth/BaseAccountAuthenticator.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/auth/BaseAccountAuthenticator.java
@@ -5,11 +5,14 @@
 
 package org.whispersystems.textsecuregcm.auth;
 
+import com.codahale.metrics.Histogram;
 import com.codahale.metrics.Meter;
 import com.codahale.metrics.MetricRegistry;
 import com.codahale.metrics.SharedMetricRegistries;
 import com.google.common.annotations.VisibleForTesting;
 import io.dropwizard.auth.basic.BasicCredentials;
+import io.micrometer.core.instrument.DistributionSummary;
+import io.micrometer.core.instrument.Metrics;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.whispersystems.textsecuregcm.storage.Account;
@@ -36,6 +39,10 @@ public class BaseAccountAuthenticator {
   private final Meter          deviceDisabledMeter          = metricRegistry.meter(name(getClass(), "authentication", "deviceDisabled" ));
   private final Meter          invalidAuthHeaderMeter       = metricRegistry.meter(name(getClass(), "authentication", "invalidHeader"  ));
 
+  private final String daysSinceLastSeenDistributionName = name(getClass(), "authentication", "daysSinceLastSeen");
+
+  private static final String IS_PRIMARY_DEVICE_TAG = "isPrimary";
+
   private final Logger logger = LoggerFactory.getLogger(AccountAuthenticator.class);
 
   private final AccountsManager accountsManager;
@@ -101,6 +108,12 @@ public class BaseAccountAuthenticator {
     final long todayInMillisWithOffset = Util.todayInMillisGivenOffsetFromNow(clock, Duration.ofSeconds(lastSeenOffsetSeconds).negated());
 
     if (device.getLastSeen() < todayInMillisWithOffset) {
+      DistributionSummary.builder(daysSinceLastSeenDistributionName)
+          .tags(IS_PRIMARY_DEVICE_TAG, String.valueOf(device.isMaster()))
+          .publishPercentileHistogram()
+          .register(Metrics.globalRegistry)
+          .record(Duration.ofMillis(todayInMillisWithOffset - device.getLastSeen()).toDays());
+
       device.setLastSeen(Util.todayInMillis(clock));
       accountsManager.update(account);
     }