A fix and a test case for gh-125: fiber cancel by numeric id.

Update the user guide.

doc/user/stored-procedures.xml

@@ -2623,6 +2623,26 @@ procedures.
         </listitem>
     </varlistentry>
 
+    <varlistentry>
+        <term>
+            <emphasis role="lua" xml:id="box.fiber.kill">box.fiber.kill(<replaceable>id</replaceable>) </emphasis>
+        </term>
+        <listitem>
+            <para>
+              Locate a fiber by its numeric id and cancel it. In
+              other words, combines <emphasis
+              role="lua">box.fiber.find()</emphasis> and <emphasis
+              role="lua">box.fiber.cancel()</emphasis> into one
+            </para>
+            <para>
+              Parameters: <code>id</code> = the id of the fiber to be cancelled.
+            </para>
+            <para>
+              Possible errors: the specified fiber does not exist or does not permit cancel.
+            </para>
+        </listitem>
+    </varlistentry>
+
     <varlistentry>
         <term>
             <emphasis role="lua" xml:id="box.fiber.testcancel">box.fiber.testcancel()</emphasis>

src/lua/init.cc

@@ -917,6 +917,26 @@ lbox_fiber_cancel(struct lua_State *L)
 	return 0;
 }
 
+/**
+ * Running and suspended fibers can be cancelled.
+ * Zombie fibers can't.
+ */
+static int
+lbox_fiber_kill(struct lua_State *L)
+{
+	if (lua_gettop(L) != 1)
+		luaL_error(L, "fiber.kill(): bad arguments");
+	int fid = lua_tointeger(L, -1);
+	struct fiber *f = fiber_find(fid);
+	if (f == NULL)
+		luaL_error(L, "fiber.kill(): fiber not found");
+	if (! (f->flags & FIBER_USER_MODE))
+		luaL_error(L, "fiber.kill(): subject fiber does "
+			   "not permit cancel");
+	fiber_cancel(f);
+	return 0;
+}
+
 /**
  * Check if this current fiber has been cancelled and
  * throw an exception if this is the case.
@@ -947,6 +967,7 @@ static const struct luaL_reg fiberlib[] = {
 	{"id", lbox_fiber_id},
 	{"find", lbox_fiber_find},
 	{"cancel", lbox_fiber_cancel},
+	{"kill", lbox_fiber_kill},
 	{"testcancel", lbox_fiber_testcancel},
 	{"create", lbox_fiber_create},
 	{"resume", lbox_fiber_resume},

test/box/fiber.test

@@ -107,3 +107,9 @@ exec admin "lua f:resume()"
 exec admin "lua fib_id = box.fiber.wrap(testfun):id()"
 exec admin "lua box.fiber.find(fib_id):cancel()"
 exec admin "lua box.fiber.find(fib_id)"
+# gh-125 box.fiber.cancel() by numeric id
+exec admin "lua function y() print('started') while true do box.replace(0, 'test', os.time()) box.fiber.sleep(0.001) end end"
+exec admin "lua f = box.fiber.wrap(y)"
+exec admin "lua box.fiber.kill(f:id())"
+exec admin "lua while box.fiber.status(f) ~= 'dead' do box.fiber.sleep(0.01) end"
+exec admin "lua box.space[0]:truncate()"