Add restart functionality

ChangeLog

@@ -1,5 +1,15 @@
+2018-01-05  Richard Frith-Macdonald <rfm@gnu.org>
+
+	EcProcess.h:
+	EcProcess.m: New -ecRestart: method called when we pass the maximum
+	memory usage limit or when a restart command is issued.  The default
+	implementation calls the -ecQuitFor:status: method using a status of
+	minus one so that the Command server will restart the program after
+	it shuts down.
+
 2018-01-04  Richard Frith-Macdonald <rfm@gnu.org>
 
+	EcProcess.h: Improve comments.
 	EcProcess.m: Avoid warning about unknown connection on shutdown.
 	Rewrite config update code to catch exceptions, ensure that methods
 	are called in the correct order so that -cmdUpdated is always last,

EcProcess.h

@@ -540,6 +540,17 @@ extern NSString*	cmdVersion(NSString *ver);
  */
 - (oneway void) ecQuitFor: (NSString*)reason with: (NSInteger)status; 
 
+/** This method is designed for handling an orderly restart.<br />
+ * The default implementation calls -ecQuitFor:status: with minus one as
+ * the status code so that the Command server will start the process
+ * again.<br />
+ * The method is called automatically when the MemoryMaximum limit is
+ * exceeded (to gracefully handle memory leaks by restarting).<br />
+ * Subclasses may override this method to allow the shutdown process to be
+ * handled differently.
+ */
+- (oneway void) ecRestart: (NSString*)reason;
+
 /** Return the timestamp at which this process started up (when the
  * receiver was initialised).
  */

EcProcess.m

@@ -1104,6 +1104,7 @@ findMode(NSDictionary* d, NSString* s)
 
 @interface	EcProcess (Private)
 - (void) cmdMesgrelease: (NSArray*)msg;
+- (void) cmdMesgrestart: (NSArray*)msg;
 - (void) cmdMesgtesting: (NSArray*)msg;
 - (void) _memCheck;
 - (NSString*) _moveLog: (NSString*)name to: (NSDate*)when;
@@ -1916,7 +1917,7 @@ static BOOL     ecDidAwaken = NO;
   return ecIsQuitting();
 }
 
-- (oneway void) ecQuitFor: (NSString*) reason with: (NSInteger)status
+- (oneway void) ecQuitFor: (NSString*)reason with: (NSInteger)status
 {
   [self ecWillQuit: reason];
   if (class_getMethodImplementation([EcProcess class], @selector(cmdQuit:))
@@ -1936,6 +1937,18 @@ static BOOL     ecDidAwaken = NO;
     }
 }
 
+- (oneway void) ecRestart: (NSString*)reason
+{
+  if (NO == [NSThread isMainThread])
+    {
+      [self performSelectorOnMainThread: _cmd
+                             withObject: reason
+                          waitUntilDone: NO];
+      return;
+    }
+  [self ecQuitFor: reason with: -1];
+}
+
 - (void) ecLoggersChanged: (NSNotification*)n
 {
   DESTROY(alertLogger);
@@ -4789,6 +4802,34 @@ With two parameters ('maximum' and a number),\n\
     }
 }
 
+- (void) cmdMesgrestart: (NSArray*)msg
+{
+  if ([msg count] == 0)
+    {
+      [self cmdPrintf: @"requests a restart"];
+    }
+  else
+    {
+      if ([[msg objectAtIndex: 0] caseInsensitiveCompare: @"help"]
+        == NSOrderedSame)
+	{
+	  [self cmdPrintf: @"\nThe restart command is used to request a"];
+	  [self cmdPrintf: @" restart of the process.\n"];
+	  [self cmdPrintf: @"This is like quitting the process but with"];
+	  [self cmdPrintf: @" a new process started by the Command\n"];
+	  [self cmdPrintf: @" server and potentially different shutdown"];
+	  [self cmdPrintf: @" behavior.\n"];
+	}
+      else
+	{
+          [self performSelectorOnMainThread: @selector(ecRestart:)
+                                 withObject: @"Console restart command"
+                              waitUntilDone: NO];
+	  [self cmdPrintf: @"A restart is being requested.\n"];
+	}
+    }
+}
+
 - (void) cmdMesgtesting: (NSArray*)msg
 {
   if ([msg count] == 0)
@@ -4968,13 +5009,16 @@ With two parameters ('maximum' and a number),\n\
     }
 
   /* If we have a defined maximum memory usage for the process,
-   * we should shut down with a non-zero status to get a restart.
+   * we should perform a restart once that limit is passed.
    */
   if (memMaximum > 0 && memPeak > (memMaximum * 1024 * 1024))
     {
-      if (NO == ecIsQuitting())
+      static BOOL       memRestart = NO;
+
+      if (NO == memRestart)
         {
-          [self ecQuitFor: @"memory usage limit reached" with: -1];
+          memRestart = YES;
+          [self ecRestart: @"memory usage limit reached"];
         }
       return;
     }