Merge ~didrocks/ubiquity:master-time-measurement-fix into ubiquity:master

[Didier Roche-Tolomelli]

Switch to use uptime instead of time.time() which is sensitive to BIOS time reset after NTP sync, leading to negative values. (LP: #1771966)

[Jean-Baptiste Lallement (jibel)]

Thanks for this patch. Reviewed and tested on Cosmic.

review: Approve

diff --git a/debian/changelog b/debian/changelog
index 2e9a915..52dfcc9 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,11 @@
+ubiquity (18.10.3) UNRELEASED; urgency=medium
+
+  * Switch to use uptime instead of time.time() which is sensitive to
+    BIOS time reset after NTP sync, leading to negative values.
+    (LP: #1771966)
+
+ -- Didier Roche <[e-mail]>  Mon, 28 May 2018 16:02:33 +0200
+
 ubiquity (18.10.2) cosmic; urgency=medium
 
   * Update Vcs-* for git migration
diff --git a/ubiquity/telemetry.py b/ubiquity/telemetry.py
index 7f68eac..e537160 100644
--- a/ubiquity/telemetry.py
+++ b/ubiquity/telemetry.py
@@ -24,7 +24,6 @@ import json
 import os
 import stat
 import syslog
-import time
 
 from ubiquity.misc import raise_privileges
 
@@ -45,7 +44,7 @@ class _Telemetry():
     def __init__(self):
         self._metrics = {}
         self._stages_hist = {}
-        self._start_time = time.time()
+        self._start_time = self._get_current_uptime()
         self.add_stage('start')
         self._dest_path = '/target/var/log/installer/telemetry'
         try:
@@ -54,9 +53,23 @@ class _Telemetry():
         except FileNotFoundError:
             self._metrics['Media'] = 'unknown'
 
+    def _get_current_uptime(self):
+        """Get current uptime info. None if we couldn't fetch it."""
+        uptime = None
+        try:
+            with open('/proc/uptime') as f:
+                uptime = float(f.read().split()[0])
+        except (FileNotFoundError, OSError, ValueError) as e:
+            syslog.syslog(syslog.LOG_ERR,
+                          "Exception while fetching current uptime: " + str(e))
+        return uptime
+
     def add_stage(self, stage_name):
         """Record installer stage with current time"""
-        self._stages_hist[int(time.time() - self._start_time)] = stage_name
+        now = self._get_current_uptime()
+        if self._start_time is None or now is None:
+            return
+        self._stages_hist[int(now - self._start_time)] = stage_name
 
     def set_installer_type(self, installer_type):
         """Record installer type"""