Add daemon.sh.

lib/bash/daemon.sh

@@ -0,0 +1,75 @@
+# This program is copyright 2011 Percona Inc.
+# Feedback and improvements are welcome.
+#
+# THIS PROGRAM IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
+# WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+# MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation, version 2; OR the Perl Artistic License.  On UNIX and similar
+# systems, you can issue `man perlgpl' or `man perlartistic' to read these
+# licenses.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+# Place, Suite 330, Boston, MA  02111-1307  USA.
+# ###########################################################################
+# daemon package
+# ###########################################################################
+
+# Package: daemon
+# daemon handles daemon related tasks like checking a PID file.
+
+set -u
+
+# Sub: make_pid_file
+#   Check and make a PID file.
+#
+# Arguments:
+#   file - File to write PID to.
+#   pid  - PID to write into file.
+#
+# Required Global Variables:
+#   ON_EXIT - String to append "remove_pid_file file".
+make_pid_file() {
+   local file=$1
+   local pid=$2
+
+   # Yes there's a race condition here, between checking if the file exists
+   # and creating it, but it's not important enough to handle.
+
+   if [ -f "$file" ]; then
+      # PID file already exists.  See if the pid it contains is still running.
+      # If yes, then die.  Else, the pid file is stale and we can reclaim it.
+      local old_pid=$(cat $file)
+      if [ -z "$old_pid" ]; then
+         # PID file is empty, so be safe and die since we can't check a
+         # non-existent pid.
+         die "PID file $file already exists but it is empty"
+      else
+         kill -0 $old_pid 2>/dev/null
+         if [ $? -eq 0 ]; then
+            die "PID file $file already exists and its PID ($old_pid) is running"
+         else
+            echo "Overwriting PID file $file because its PID ($old_pid)" \
+                 "is not running"
+         fi
+      fi
+   fi
+
+   # PID file doesn't exist, or it does but its pid is stale.
+   echo "$pid" > $file
+   ON_EXIT="$ON_EXIT; remove_pid_file $file"
+}
+
+remove_pid_file() {
+   local file=$1
+   if [ -f "$file" ]; then
+      rm $file
+   fi
+}
+
+# ###########################################################################
+# End daemon package
+# ###########################################################################

t/lib/bash/daemon.sh

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+#!/usr/bin/env bash
+
+TESTS=8
+
+TMPDIR="$TEST_TMPDIR"
+ON_EXIT=":"
+local file="$TMPDIR/pid-file"
+
+source "$LIB_DIR/log_warn_die.sh"
+source "$LIB_DIR/daemon.sh"
+
+cmd_ok \
+   "test ! -f $file" \
+   "PID file doesn't exist"
+
+make_pid_file $file $$
+
+cmd_ok \
+   "test -f $file" \
+   "PID file created"
+
+local pid=`cat $file`
+is \
+   "$pid" \
+   "$$" \
+   "Correct PID"
+
+remove_pid_file $file
+
+cmd_ok \
+   "test ! -f $file" \
+   "PID file removed"
+
+is \
+   "$ON_EXIT" \
+   ":; remove_pid_file $file" \
+   "Sets ON_EXIT to remove PID file"
+
+# ###########################################################################
+# PID file already exists and proc is running.
+# ###########################################################################
+ON_EXIT=""
+echo $$ > $file
+
+(
+   make_pid_file $file $$ >$TMPDIR/output 2>&1
+)
+
+cmd_ok \
+   "grep -q \"PID file /tmp/percona-toolkit.test/pid-file already exists and its PID ($$) is running\" $TMPDIR/output" \
+   "Does not overwrite PID file is PID is running"
+
+echo 999999 > $file
+
+make_pid_file $file $$ >$TMPDIR/output 2>&1
+
+cmd_ok \
+   "grep -q 'Overwriting PID file /tmp/percona-toolkit.test/pid-file because its PID (999999) is not running' $TMPDIR/output" \
+   "Overwrites PID file if PID is not running"
+
+pid=`cat $file`
+is \
+   "$pid" \
+   "$$" \
+   "Correct PID"
+
+rm $file
+rm $TMPDIR/output
+
+# ###########################################################################
+# Done.
+# ###########################################################################