wsd: configurable idle document timeout

When a document is idle (no activity from
any views) for this timeout duration, the
document is saved and unloaded to minimize
resource consumption.

Change-Id: If6f09136ae40c7e84180fc8c8adbf6db8396d292
Reviewed-on: https://gerrit.libreoffice.org/37374
Reviewed-by: Ashod Nakashian <ashnakash@gmail.com>
Tested-by: Ashod Nakashian <ashnakash@gmail.com>

loolwsd.xml.in

@@ -14,6 +14,7 @@
     <num_prespawn_children desc="Number of child processes to keep started in advance and waiting for new clients." type="uint" default="1">1</num_prespawn_children>
     <per_document desc="Document-specific settings, including LO Core settings.">
         <max_concurrency desc="The maximum number of threads to use while processing a document." type="uint" default="4">4</max_concurrency>
+        <idle_timeout_secs desc="The maximum number of seconds before unloading an idle document. Defaults to 1 hour." type="uint" default="3600">3600</idle_timeout_secs>
     </per_document>
 
     <loleaflet_html desc="Allows UI customization by replacing the single endpoint of loleaflet.html" type="string" default="loleaflet.html">loleaflet.html</loleaflet_html>
@@ -51,13 +52,13 @@
         <cert_file_path desc="Path to the cert file" relative="false">/etc/loolwsd/cert.pem</cert_file_path>
         <key_file_path desc="Path to the key file" relative="false">/etc/loolwsd/key.pem</key_file_path>
         <ca_file_path desc="Path to the ca file" relative="false">/etc/loolwsd/ca-chain.cert.pem</ca_file_path>
-	<hpkp desc="Enable HTTP Public key pinning" enable="false" report_only="false">
-	    <max_age desc="HPKP's max-age directive - time in seconds browser should remember the pins" enable="true">1000</max_age>
-	    <report_uri desc="HPKP's report-uri directive - pin validation failure are reported at this URL" enable="false"></report_uri>
-	    <pins desc="Base64 encoded SPKI fingerprints of keys to be pinned">
-	      <pin></pin>
-	    </pins>
-	</hpkp>
+        <hpkp desc="Enable HTTP Public key pinning" enable="false" report_only="false">
+            <max_age desc="HPKP's max-age directive - time in seconds browser should remember the pins" enable="true">1000</max_age>
+            <report_uri desc="HPKP's report-uri directive - pin validation failure are reported at this URL" enable="false"></report_uri>
+            <pins desc="Base64 encoded SPKI fingerprints of keys to be pinned">
+            <pin></pin>
+            </pins>
+        </hpkp>
     </ssl>
 
     <storage desc="Backend storage">

wsd/DocumentBroker.cpp

@@ -222,6 +222,8 @@ void DocumentBroker::pollThread()
     auto last30SecCheckTime = std::chrono::steady_clock::now();
 
     static const bool AutoSaveEnabled = !std::getenv("LOOL_NO_AUTOSAVE");
+    static const size_t IdleDocTimeoutSecs = LOOLWSD::getConfigValue<int>(
+                                                      "per_document.idle_timeout_secs", 3600);
 
     // Main polling loop goodness.
     while (!_stop && _poll->continuePolling() && !TerminationFlag)
@@ -273,7 +275,7 @@ void DocumentBroker::pollThread()
         }
 
         // Remove idle documents after 1 hour.
-        const bool idle = (getIdleTimeSecs() >= 3600);
+        const bool idle = (getIdleTimeSecs() >= IdleDocTimeoutSecs);
 
         // If all sessions have been removed, no reason to linger.
         if ((isLoaded() || _markToDestroy) && (_sessions.empty() || idle))

wsd/LOOLWSD.cpp

@@ -622,6 +622,7 @@ void LOOLWSD::initialize(Application& self)
             { "file_server_root_path", "loleaflet/.." },
             { "num_prespawn_children", "1" },
             { "per_document.max_concurrency", "4" },
+            { "per_document.idle_timeout_secs", "3600" },
             { "loleaflet_html", "loleaflet.html" },
             { "logging.color", "true" },
             { "logging.level", "trace" },

wsd/LOOLWSD.hpp

@@ -81,6 +81,15 @@ public:
         return LOOLWSD::SSLTermination.get();
     }
 
+    /// Returns the value of the specified application configuration,
+    /// of the default, if one doesn't exist.
+    template<typename T>
+    static
+    T getConfigValue(const std::string& name, const T def)
+    {
+        return getConfigValue(Application::instance().config(), name, def);
+    }
+
     /// Trace a new session and take a snapshot of the file.
     static void dumpNewSessionTrace(const std::string& id, const std::string& sessionId, const std::string& uri, const std::string& path);