monitor: Allow missing sensors

Don't count sensors that don't exist as nonfunctional.  Let some
other application decide if missing sensors are a problem or not.

Change-Id: Ie3d438c92df16bfd86ddc86db8a9dd143bf2cfb0
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>

3 files changed, 37 insertions, 12 deletions

diff --git a/monitor/fan.cpp b/monitor/fan.cpp
index f3937c2..6d88d2a 100644
--- a/monitor/fan.cpp
+++ b/monitor/fan.cpp
@@ -49,13 +49,21 @@ Fan::Fan(sdbusplus::bus::bus& bus,
 
     for (auto& s : sensors)
     {
-        _sensors.emplace_back(
-            std::make_unique<TachSensor>(bus,
-                                         *this,
-                                         std::get<sensorNameField>(s),
-                                         std::get<hasTargetField>(s),
-                                         std::get<timeoutField>(def),
-                                         events));
+        try
+        {
+            _sensors.emplace_back(
+                    std::make_unique<TachSensor>(
+                            bus,
+                            *this,
+                            std::get<sensorNameField>(s),
+                            std::get<hasTargetField>(s),
+                            std::get<timeoutField>(def),
+                            events));
+        }
+        catch (InvalidSensorError& e)
+        {
+
+        }
     }
 
     //Start from a known state of functional
diff --git a/monitor/fan.hpp b/monitor/fan.hpp
index 8e7f86f..0004353 100644
--- a/monitor/fan.hpp
+++ b/monitor/fan.hpp
@@ -14,6 +14,13 @@ namespace fan
 namespace monitor
 {
 
+/**
+ * @class InvalidSensorError
+ *
+ * An exception type for sensors that don't exist or
+ * are otherwise inaccessible.
+ */
+class InvalidSensorError : public std::exception {};
 
 /**
  * @class Fan
diff --git a/monitor/tach_sensor.cpp b/monitor/tach_sensor.cpp
index 0ec52ba..a4ebcd9 100644
--- a/monitor/tach_sensor.cpp
+++ b/monitor/tach_sensor.cpp
@@ -77,11 +77,21 @@ TachSensor::TachSensor(sdbusplus::bus::bus& bus,
     _timer(events, [this, &fan](){ fan.timerExpired(*this); })
 {
     //Load in starting Target and Input values
-    readProperty(FAN_SENSOR_VALUE_INTF,
-                 FAN_VALUE_PROPERTY,
-                 _name,
-                 _bus,
-                 _tachInput);
+
+    try
+    {
+        // Use getProperty directly to allow a missing sensor object
+        // to abort construction.
+        _tachInput = util::SDBusPlus::getProperty<decltype(_tachInput)>(
+                _bus,
+                _name,
+                FAN_SENSOR_VALUE_INTF,
+                FAN_VALUE_PROPERTY);
+    }
+    catch (std::exception& e)
+    {
+        throw InvalidSensorError();
+    }
 
     if (_hasTarget)
     {