clientContextImpl: Cap the number and age of beacons

Each beacon has an associated mutex. If we don't cap the beacon count,
IOCs running on resource limited platforms like RTEMS may eventually
run out of resources and crash.

Author: JJL772

src/remote/beaconHandler.cpp

@@ -23,7 +23,7 @@ BeaconHandler::BeaconHandler(Context::shared_pointer const & context,
     _serverChangeCount(-1),
     _first(true)
 {
-
+    _createdAt.getCurrent();
 }
 
 BeaconHandler::~BeaconHandler()

src/remote/pv/beaconHandler.h

@@ -61,6 +61,9 @@ class BeaconHandler
                       epics::pvData::int16 sequentalID,
                       epics::pvData::int16 changeCount,
                       const epics::pvData::PVFieldPtr& data);
+
+    epics::pvData::TimeStamp getCreationTime() const { return _createdAt; }
+
 private:
     /**
      * Context instance.
@@ -86,6 +89,8 @@ class BeaconHandler
      */
     bool _first;
 
+    epics::pvData::TimeStamp _createdAt;
+
     /**
      * Update beacon.
      * @param remoteTransportRevision encoded (major, minor) revision.

src/remoteClient/clientContextImpl.cpp

@@ -3957,7 +3957,7 @@ class InternalClientContextImpl :
     static size_t num_instances;
 
     InternalClientContextImpl(const Configuration::shared_pointer& conf) :
-        m_addressList(""), m_autoAddressList(true), m_connectionTimeout(30.0f), m_beaconPeriod(15.0f),
+        m_addressList(""), m_autoAddressList(true), m_connectionTimeout(30.0f), m_beaconPeriod(15.0f), m_maxBeacons(10), m_maxBeaconLifetime(15),
         m_broadcastPort(PVA_BROADCAST_PORT), m_receiveBufferSize(MAX_TCP_RECV),
         m_lastCID(0x10203040),
         m_lastIOID(0x80706050),
@@ -4021,6 +4021,8 @@ class InternalClientContextImpl :
         out << "AUTO_ADDR_LIST     : " << (m_autoAddressList ? "true" : "false") << std::endl;
         out << "CONNECTION_TIMEOUT : " << m_connectionTimeout << std::endl;
         out << "BEACON_PERIOD      : " << m_beaconPeriod << std::endl;
+        out << "BEACON_MAX         : " << m_maxBeacons << std::endl;
+        out << "BEACON_MAX_AGE     : " << m_maxBeaconLifetime << std::endl;
         out << "BROADCAST_PORT     : " << m_broadcastPort << std::endl;;
         out << "RCV_BUFFER_SIZE    : " << m_receiveBufferSize << std::endl;
         out << "STATE              : ";
@@ -4115,6 +4117,8 @@ class InternalClientContextImpl :
         m_beaconPeriod = m_configuration->getPropertyAsFloat("EPICS_PVA_BEACON_PERIOD", m_beaconPeriod);
         m_broadcastPort = m_configuration->getPropertyAsInteger("EPICS_PVA_BROADCAST_PORT", m_broadcastPort);
         m_receiveBufferSize = m_configuration->getPropertyAsInteger("EPICS_PVA_MAX_ARRAY_BYTES", m_receiveBufferSize);
+        m_maxBeacons = m_configuration->getPropertyAsInteger("EPICS_PVA_BEACON_MAX", m_maxBeacons);
+        m_maxBeaconLifetime = m_configuration->getPropertyAsFloat("EPICS_PVA_BEACON_LIFETIME", m_maxBeaconLifetime);
     }
 
     void internalInitialize() {
@@ -4351,6 +4355,38 @@ class InternalClientContextImpl :
         BeaconHandler::shared_pointer handler;
         if (it == m_beaconHandlers.end())
         {
+            TimeStamp now;
+            now.getCurrent();
+
+            double oldestAge = -1;
+            AddressBeaconHandlerMap::iterator oldestBeacon = m_beaconHandlers.end();
+
+            /* Before creating a new beacon, cleanup any old ones */
+            for (AddressBeaconHandlerMap::iterator it = m_beaconHandlers.begin(); it != m_beaconHandlers.end();)
+            {
+                double age = TimeStamp::diff(now, it->second->getCreationTime());
+                if (age >= m_maxBeaconLifetime)
+                {
+                    AddressBeaconHandlerMap::iterator toErase = it;
+                    ++it; /* Iterator to current is invalidated by erase, so do this before */
+                    m_beaconHandlers.erase(toErase);
+                    continue;
+                }
+
+                if (age > oldestAge)
+                {
+                    oldestAge = age;
+                    oldestBeacon = it;
+                }
+                ++it;
+            }
+
+            /* None were removed, axe the oldest we found to make room */
+            if (m_beaconHandlers.size() >= m_maxBeacons && oldestBeacon != m_beaconHandlers.end())
+            {
+                m_beaconHandlers.erase(oldestBeacon);
+            }
+
             // stores weak_ptr
             handler.reset(new BeaconHandler(internal_from_this(), responseFrom));
             m_beaconHandlers[*responseFrom] = handler;
@@ -4443,6 +4479,16 @@ class InternalClientContextImpl :
      */
     float m_beaconPeriod;
 
+    /**
+     * Max beacons allowed.
+     */
+    uint32_t m_maxBeacons;
+
+    /**
+     * Max beacon lifetime
+     */
+    float m_maxBeaconLifetime;
+
     /**
      * Broadcast (beacon, search) port number to listen to.
      */