Snap是一個在Ubuntu系統上一個新的技術．如果大家對這個技術還不是很理解的話，可以參閱文章＂安裝snap應用到Ubuntu 16.4桌面系統＂．我們知道MySQL及Tomcat是在Java服務器端常用的技術．那麼我們怎麼來把它打包到我們的snap應用中去呢？很多人可能以為這個很簡單．我們可以直接在snapcraft.yaml中使用stage-package來安裝現有的debian包，不就可以了嗎？其實，由於在snap系統的安全性限制，在一個snap應用被成功安裝後，它自己所在的目錄是只讀的，不可以寫入任何的數據．我們只有規定的部分目錄才是可以寫入的．我們以hello例程為例，我們有如下的目錄可以使用：
在上面，有兩個最重要的目錄：
name: tomcat-webapp-demo
version: 1.0
architectures:
- amd64
summary: Demo of Tomcat-hosted Webapp
description: This is a demo snap of a Tomcat-hosted webapp produced by snapcraft with maven.
confinement: strict
apps:
tomcat:
command: bin/wrapper
daemon: simple
plugs: [network-bind]
parts:
webapp:
plugin: maven
source: https://github.com/lool/snappy-mvn-demo.git
source-type: git
tomcat:
plugin: dump
source: https://archive.apache.org/dist/tomcat/tomcat-8/v8.0.29/bin/apache-tomcat-8.0.29.tar.gz
local-files:
plugin: make
source: .
從上面我們可以看出來，它使用了dump plugin．這個plugin只有在snapcraft 2.14中才開始適使用，並最終代替copy plugin. 對於以前的版本我們可以使用tar-content來代替dump．從上面的代碼中可以看出來，它知己從官網上下載所需要的版本，並做一個安裝．在啟動的時候，它使用bin/wrapper來啟動．wrapper的內容如下：
#!/bin/sh
set -e
set -x
# installation pathes are based of CATALINA_HOME
export CATALINA_HOME="$SNAP"
# writable pathes are based of CATALINA_BASE
export CATALINA_BASE="$SNAP_DATA"
# create runtime data
mkdir -p "$CATALINA_BASE/logs"
mkdir -p "$CATALINA_BASE/temp"
if ! [ -d $CATALINA_BASE/conf ]; then
echo "conf directory does not exist"
cp -rd $CATALINA_HOME/tomcat-conf $CATALINA_BASE/conf
fi
if ! [ -d $CATALINA_BASE/webapps ]; then
echo "webapps directory does not exist"
cp -rd $CATALINA_HOME/webapps $CATALINA_BASE/
cp $CATALINA_HOME/war/*.war $CATALINA_BASE/webapps/
fi
$CATALINA_HOME/bin/catalina.sh run
# Download the boost headers for MySQL. Note that the version used may need to
# be updated if the version of MySQL changes.
boost:
plugin: copy
source: http://sourceforge.net/projects/boost/files/boost/1.59.0/boost_1_59_0.tar.gz
files:
'*': boost/
snap:
- -*
mysql:
plugin: cmake
source: https://github.com/kyrofa/mysql-server.git
source-type: git
source-branch: feature/support_no_setpriority
after: [boost]
configflags:
- -DWITH_BOOST=$SNAPCRAFT_STAGE/boost
- -DWITH_INNODB_PAGE_CLEANER_PRIORITY=OFF
- -DCMAKE_INSTALL_PREFIX=/
- -DBUILD_CONFIG=mysql_release
- -DWITH_UNIT_TESTS=OFF
- -DWITH_EMBEDDED_SERVER=OFF
- -DWITH_EMBEDDED_SHARED_LIBRARY=OFF
- -DWITH_ARCHIVE_STORAGE_ENGINE=OFF
- -DWITH_BLACKHOLE_STORAGE_ENGINE=OFF
- -DWITH_FEDERATED_STORAGE_ENGINE=OFF
- -DWITH_PARTITION_STORAGE_ENGINE=OFF
- -DINSTALL_MYSQLTESTDIR=
build-packages:
- wget
- g++
- cmake
- bison
- libncurses5-dev
- libaio-dev
stage:
# Remove scripts that we'll be replacing with our own
- -support-files/mysql.server
snap:
# Remove scripts that we'll be replacing with our own
- -support-files/mysql.server
# Remove unused binaries that waste space
- -bin/innochecksum
- -bin/lz4_decompress
- -bin/myisam*
- -bin/mysqladmin
- -bin/mysqlbinlog
- -bin/mysql_client_test
- -bin/mysql_config*
- -bin/mysqld_multi
- -bin/mysqldump*
- -bin/mysqlimport
- -bin/mysql_install_db
- -bin/mysql_plugin
- -bin/mysqlpump
- -bin/mysql_secure_installation
- -bin/mysqlshow
- -bin/mysqlslap
- -bin/mysql_ssl_rsa_setup
- -bin/mysqltest
- -bin/mysql_tzinfo_to_sql
- -bin/perror
- -bin/replace
- -bin/resolveip
- -bin/resolve_stack_dump
- -bin/zlib_decompress
# Copy over our MySQL scripts
mysql-customizations:
plugin: copy
files:
# This one is what creates the initial database and account for ownCloud.
src/mysql/start_mysql: bin/
src/mysql/my.cnf: my.cnf
src/mysql/mysql.server: support-files/
sample.war: war/sample.war
mysql-connector-java-6.0.3.jar: lib/mysql-connector-java-6.0.3.jar
snap:
- -*
就想我們之前snap我們的tomcat時一樣，我們需要對MySQL的配置進行改變才可以：
[mysqld] user=root max_allowed_packet=100M secure-file-priv=NULL port=3306 bind-address=0.0.0.0 [client] protocol=tcp在這裡，我們配置了所需要的port號碼及使用的協議TCP．這樣我們的數據庫可以位於任何一個單獨的服務器中（我們可以修改這裡的bind-address）．在我們的設計中，MySQL的數據庫位於本機．這樣當我們的MySQL服務器運行時，可以看到：
liuxg@liuxg:~$ netstat -lnp46 | grep -w 3306 (Not all processes could be identified, non-owned process info will not be shown, you would have to be root to see it all.) tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN -
$SNAP/support-files/mysql.server start
#!/bin/sh
# Copyright Abandoned 1996 TCX DataKonsult AB & Monty Program KB & Detron HB
# This file is public domain and comes with NO WARRANTY of any kind
# MySQL daemon start/stop script.
# Usually this is put in /etc/init.d (at least on machines SYSV R4 based
# systems) and linked to /etc/rc3.d/S99mysql and /etc/rc0.d/K01mysql.
# When this is done the mysql server will be started when the machine is
# started and shut down when the systems goes down.
# Comments to support chkconfig on RedHat Linux
# chkconfig: 2345 64 36
# description: A very fast and reliable SQL database engine.
# Comments to support LSB init script conventions
### BEGIN INIT INFO
# Provides: mysql
# Required-Start: $local_fs $network $remote_fs
# Should-Start: ypbind nscd ldap ntpd xntpd
# Required-Stop: $local_fs $network $remote_fs
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: start and stop MySQL
# Description: MySQL is a very fast and reliable SQL database engine.
### END INIT INFO
# If you install MySQL on some other places than /, then you
# have to do one of the following things for this script to work:
#
# - Run this script from within the MySQL installation directory
# - Create a /etc/my.cnf file with the following information:
# [mysqld]
# basedir=<path-to-mysql-installation-directory>
# - Add the above to any other configuration file (for example ~/.my.ini)
# and copy my_print_defaults to /usr/bin
# - Add the path to the mysql-installation-directory to the basedir variable
# below.
#
# If you want to affect other MySQL variables, you should make your changes
# in the /etc/my.cnf, ~/.my.cnf or other MySQL configuration files.
# If you change base dir, you must also change datadir. These may get
# overwritten by settings in the MySQL configuration files.
basedir=$SNAP
datadir=$SNAP_DATA/mysql
# Default value, in seconds, afterwhich the script should timeout waiting
# for server start.
# Value here is overriden by value in my.cnf.
# 0 means don't wait at all
# Negative numbers mean to wait indefinitely
service_startup_timeout=900
# Lock directory for RedHat / SUSE.
lockdir="$SNAP_DATA/mysql/lock"
lock_file_path="$lockdir/mysql"
# The following variables are only set for letting mysql.server find things.
# Set some defaults
mysqld_pid_file_path=
if test -z "$basedir"
then
basedir=/
bindir=//bin
if test -z "$datadir"
then
datadir=//data
fi
sbindir=//bin
libexecdir=//bin
else
bindir="$basedir/bin"
if test -z "$datadir"
then
datadir="$basedir/data"
fi
sbindir="$basedir/sbin"
libexecdir="$basedir/libexec"
fi
# datadir_set is used to determine if datadir was set (and so should be
# *not* set inside of the --basedir= handler.)
datadir_set=
#
# Use LSB init script functions for printing messages, if possible
#
lsb_functions="/lib/lsb/init-functions"
if test -f $lsb_functions ; then
. $lsb_functions
else
log_success_msg()
{
echo " SUCCESS! $@"
}
log_failure_msg()
{
echo " ERROR! $@"
}
fi
PATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin"
export PATH
mode=$1 # start or stop
[ $# -ge 1 ] && shift
other_args="$*" # uncommon, but needed when called from an RPM upgrade action
# Expected: "--skip-networking --skip-grant-tables"
# They are not checked here, intentionally, as it is the resposibility
# of the "spec" file author to give correct arguments only.
case `echo "testing\c"`,`echo -n testing` in
*c*,-n*) echo_n= echo_c= ;;
*c*,*) echo_n=-n echo_c= ;;
*) echo_n= echo_c='\c' ;;
esac
parse_server_arguments() {
for arg do
case "$arg" in
--basedir=*) basedir=`echo "$arg" | sed -e 's/^[^=]*=//'`
bindir="$basedir/bin"
if test -z "$datadir_set"; then
datadir="$basedir/data"
fi
sbindir="$basedir/sbin"
libexecdir="$basedir/libexec"
;;
--datadir=*) datadir=`echo "$arg" | sed -e 's/^[^=]*=//'`
datadir_set=1
;;
--pid-file=*) mysqld_pid_file_path=`echo "$arg" | sed -e 's/^[^=]*=//'` ;;
--service-startup-timeout=*) service_startup_timeout=`echo "$arg" | sed -e 's/^[^=]*=//'` ;;
esac
done
}
wait_for_pid () {
verb="$1" # created | removed
pid="$2" # process ID of the program operating on the pid-file
pid_file_path="$3" # path to the PID file.
i=0
avoid_race_condition="by checking again"
while test $i -ne $service_startup_timeout ; do
case "$verb" in
'created')
# wait for a PID-file to pop into existence.
test -s "$pid_file_path" && i='' && break
;;
'removed')
# wait for this PID-file to disappear
test ! -s "$pid_file_path" && i='' && break
;;
*)
echo "wait_for_pid () usage: wait_for_pid created|removed pid pid_file_path"
exit 1
;;
esac
# if server isn't running, then pid-file will never be updated
if test -n "$pid"; then
if kill -0 "$pid" 2>/dev/null; then
: # the server still runs
else
# The server may have exited between the last pid-file check and now.
if test -n "$avoid_race_condition"; then
avoid_race_condition=""
continue # Check again.
fi
# there's nothing that will affect the file.
log_failure_msg "The server quit without updating PID file ($pid_file_path)."
return 1 # not waiting any more.
fi
fi
echo $echo_n ".$echo_c"
i=`expr $i + 1`
sleep 1
done
if test -z "$i" ; then
log_success_msg
return 0
else
log_failure_msg
return 1
fi
}
# Get arguments from the my.cnf file,
# the only group, which is read from now on is [mysqld]
if test -x ./bin/my_print_defaults
then
print_defaults="./bin/my_print_defaults"
elif test -x $bindir/my_print_defaults
then
print_defaults="$bindir/my_print_defaults"
elif test -x $bindir/mysql_print_defaults
then
print_defaults="$bindir/mysql_print_defaults"
else
# Try to find basedir in /etc/my.cnf
conf=/etc/my.cnf
print_defaults=
if test -r $conf
then
subpat='^[^=]*basedir[^=]*=\(.*\)$'
dirs=`sed -e "/$subpat/!d" -e 's//\1/' $conf`
for d in $dirs
do
d=`echo $d | sed -e 's/[ ]//g'`
if test -x "$d/bin/my_print_defaults"
then
print_defaults="$d/bin/my_print_defaults"
break
fi
if test -x "$d/bin/mysql_print_defaults"
then
print_defaults="$d/bin/mysql_print_defaults"
break
fi
done
fi
# Hope it's in the PATH ... but I doubt it
test -z "$print_defaults" && print_defaults="my_print_defaults"
fi
#
# Read defaults file from 'basedir'. If there is no defaults file there
# check if it's in the old (depricated) place (datadir) and read it from there
#
extra_args=""
if test -r "$basedir/my.cnf"
then
extra_args="-e $basedir/my.cnf"
else
if test -r "$datadir/my.cnf"
then
extra_args="-e $datadir/my.cnf"
fi
fi
parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`
#
# Set pid file if not given
#
if test -z "$mysqld_pid_file_path"
then
mysqld_pid_file_path=$datadir/`hostname`.pid
else
case "$mysqld_pid_file_path" in
/* ) ;;
* ) mysqld_pid_file_path="$datadir/$mysqld_pid_file_path" ;;
esac
fi
case "$mode" in
'start')
# Start daemon
# Safeguard (relative paths, core dumps..)
cd $basedir
echo $echo_n "Starting MySQL"
if test -x $bindir/mysqld_safe
then
# Give extra arguments to mysqld with the my.cnf file. This script
# may be overwritten at next upgrade.
$bindir/mysqld_safe --datadir="$datadir" --pid-file="$mysqld_pid_file_path" --lc-messages-dir="$SNAP/share" $other_args >/dev/null 2>&1 &
wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$?
# Make lock for RedHat / SuSE
if test -w "$lockdir"
then
touch "$lock_file_path"
fi
exit $return_value
else
log_failure_msg "Couldn't find MySQL server ($bindir/mysqld_safe)"
fi
;;
'stop')
# Stop daemon. We use a signal here to avoid having to know the
# root password.
if test -s "$mysqld_pid_file_path"
then
# signal mysqld_safe that it needs to stop
touch "$mysqld_pid_file_path.shutdown"
mysqld_pid=`cat "$mysqld_pid_file_path"`
if (kill -0 $mysqld_pid 2>/dev/null)
then
echo $echo_n "Shutting down MySQL"
kill $mysqld_pid
# mysqld should remove the pid file when it exits, so wait for it.
wait_for_pid removed "$mysqld_pid" "$mysqld_pid_file_path"; return_value=$?
else
log_failure_msg "MySQL server process #$mysqld_pid is not running!"
rm "$mysqld_pid_file_path"
fi
# Delete lock for RedHat / SuSE
if test -f "$lock_file_path"
then
rm -f "$lock_file_path"
fi
exit $return_value
else
log_failure_msg "MySQL server PID file could not be found!"
fi
;;
'restart')
# Stop the service and regardless of whether it was
# running or not, start it again.
if $0 stop $other_args; then
$0 start $other_args
else
log_failure_msg "Failed to stop running server, so refusing to try to start."
exit 1
fi
;;
'reload'|'force-reload')
if test -s "$mysqld_pid_file_path" ; then
read mysqld_pid < "$mysqld_pid_file_path"
kill -HUP $mysqld_pid && log_success_msg "Reloading service MySQL"
touch "$mysqld_pid_file_path"
else
log_failure_msg "MySQL PID file could not be found!"
exit 1
fi
;;
'status')
# First, check to see if pid file exists
if test -s "$mysqld_pid_file_path" ; then
read mysqld_pid < "$mysqld_pid_file_path"
if kill -0 $mysqld_pid 2>/dev/null ; then
log_success_msg "MySQL running ($mysqld_pid)"
exit 0
else
log_failure_msg "MySQL is not running, but PID file exists"
exit 1
fi
else
# Try to find appropriate mysqld process
mysqld_pid=`pidof $libexecdir/mysqld`
# test if multiple pids exist
pid_count=`echo $mysqld_pid | wc -w`
if test $pid_count -gt 1 ; then
log_failure_msg "Multiple MySQL running but PID file could not be found ($mysqld_pid)"
exit 5
elif test -z $mysqld_pid ; then
if test -f "$lock_file_path" ; then
log_failure_msg "MySQL is not running, but lock file ($lock_file_path) exists"
exit 2
fi
log_failure_msg "MySQL is not running"
exit 3
else
log_failure_msg "MySQL is running but PID file could not be found"
exit 4
fi
fi
;;
*)
# usage
basename=`basename "$0"`
echo "Usage: $basename {start|stop|restart|reload|force-reload|status} [ MySQL server options ]"
exit 1
;;
esac
exit 0
basedir=$SNAP datadir=$SNAP_DATA/mysql這個地方的改變是為了提供我們運行文件的參考目錄位置及數據庫的文件位置．
mysql: command: start_mysql stop-command: support-files/mysql.server stop daemon: simple plugs: [network, network-bind]顯然這是一個daemon應用．它的內容如下：
#!/bin/sh
root_option_file="$SNAP_DATA/mysql/root.ini"
demouser_password_file="$SNAP_DATA/mysql/demouser_password"
mysqld_pid_file_path=$SNAP_DATA/mysql/`hostname`.pid
#mysql_socket_file_path=$SNAP_DATA/mysql/mysql.sock
new_install=false
# Make sure the database is initialized (this is safe to run if already
# initialized)
mysqld --initialize-insecure --basedir="$SNAP" --datadir="$SNAP_DATA/mysql" --lc-messages-dir="$SNAP/share"
# If the above command succeeded, it means this is a new installation.
if [ $? -eq 0 ]; then
echo "it is new install"
new_install=true
fi
# Start mysql
$SNAP/support-files/mysql.server start
# Initialize new installation if necessary.
if [ $new_install = true ]; then
# Generate a password for the root mysql user.
echo -n "Generating root mysql password... "
root_password="123"
echo "done."
# Generate a password for the owncloud mysql user.
echo -n "Generating owncloud mysql password... "
demouser_password="123"
echo "done."
# Save root user information
echo "writing client"
echo "[client]" >> $root_option_file
echo "writing user=root"
echo "user=root" >> $root_option_file
chmod 600 $root_option_file
echo "dump the root option file"
cat $root_option_file
# Now set everything up in one step:
# 1) Set the root user's password
# 2) Create the 'demouser' user
# 3) Create the 'demodb' database
# 4) Grant the 'demodb' user privileges on the 'demodb' database
echo -n "Setting up users and owncloud database... "
mysql --defaults-file=$root_option_file <<SQL
ALTER USER 'root'@'localhost' IDENTIFIED BY '$root_password';
CREATE USER 'demouser'@'localhost' IDENTIFIED BY '$demouser_password';
CREATE DATABASE demodb;
GRANT ALL PRIVILEGES ON demodb.* TO 'demouser'@'localhost' IDENTIFIED BY '$demouser_password';
USE demodb;
create table Employees
(
id int not null,
age int not null,
first varchar (255),
last varchar (255)
);
INSERT INTO Employees VALUES (100, 18, 'Zara', 'Ali');
INSERT INTO Employees VALUES (101, 25, 'Mahnaz', 'Fatma');
INSERT INTO Employees VALUES (102, 30, 'Zaid', 'Khan');
INSERT INTO Employees VALUES (103, 28, 'Sumit', 'Mittal');
SQL
if [ $? -eq 0 ]; then
echo "done."
else
echo "Failed to initialize-- reverting..."
$SNAP/support-files/mysql.server stop
rm -rf $SNAP_DATA/mysql/*
fi
# Now the root mysql user has a password. Save that as well.
echo "writing root password"
echo "password=$root_password" >> $root_option_file
fi
# Wait here until mysql is running
echo "Waiting for server..."
#while [ ! -f "$mysqld_pid_file_path" -o ! -S "$mysql_socket_file_path" ]; do
while [ ! -f "$mysqld_pid_file_path" -o ]; do
sleep 1
done
# Check and upgrade mysql tables if necessary. This will return 0 if the upgrade
# succeeded, in which case we need to restart mysql.
echo "Checking/upgrading mysql tables if necessary..."
mysql_upgrade --defaults-file=$root_option_file
if [ $? -eq 0 ]; then
echo "Restarting mysql server after upgrade..."
$SNAP/support-files/mysql.server restart
echo "Waiting for server to come back after upgrade..."
# while [ ! -f "$mysqld_pid_file_path" -o ! -S "$mysql_socket_file_path" ]; do
while [ ! -f "$mysqld_pid_file_path" -o ]; do
sleep 1
done
fi
# If this was a new installation, wait until the server is all up and running
# before saving off the owncloud user's password. This way the presence of the
# file can be used as a signal that mysql is ready to be used.
if [ $new_install = true ]; then
echo "$demouser_password" > $demouser_password_file
fi
# Wait here until mysql exits (turn a forking service into simple). This is
# only needed for Ubuntu Core 15.04, as 16.04 supports forking services.
mysqld_pid=$(cat "$mysqld_pid_file_path")
while kill -0 $mysqld_pid 2>/dev/null; do
sleep 1
done
我們在table中也創建了幾個記錄．在這裡也請大家注意，我hard-code了數據庫的密碼＂123＂．這個密碼在我們以後的數據庫訪問中需要用到．注意我們在這裡已經創建了兩個用戶，一個叫做root，另外一個叫做demouser．
mysql --defaults-file=$root_option_file <<SQL
ALTER USER 'root'@'localhost' IDENTIFIED BY '$root_password';
CREATE USER 'demouser'@'localhost' IDENTIFIED BY '$demouser_password';
CREATE DATABASE demodb;
GRANT ALL PRIVILEGES ON demodb.* TO 'demouser'@'localhost' IDENTIFIED BY '$demouser_password';
USE demodb;
create table Employees
(
id int not null,
age int not null,
first varchar (255),
last varchar (255)
);
INSERT INTO Employees VALUES (100, 18, 'Zara', 'Ali');
INSERT INTO Employees VALUES (101, 25, 'Mahnaz', 'Fatma');
INSERT INTO Employees VALUES (102, 30, 'Zaid', 'Khan');
INSERT INTO Employees VALUES (103, 28, 'Sumit', 'Mittal');
SQL
mysql-client: command: mysql --defaults-file=$SNAP_DATA/mysql/root.ini --protocol=TCP plugs: [network, network-bind]由於在MySQL的命令行中需要訪問到數據庫，需要root權限．我們可以通過su命令進入到root用戶： 我們可以通過運行我們定義的命令來啟動MySQL客戶端．通過這個命令，我們可以創建我們的數據等操作．
<%@ page import="java.sql.*"%>
<html>
<head>
<title>JDBC Connection example</title>
</head>
<body>
<h1>JDBC Connection example</h1>
<%
String user = "demouser";
String password = "123";
try {
java.sql.Connection con;
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql://localhost:3306/demodb", user, password);
out.println (user + " account opens database successfully opened.");
String query="select * from Employees";
Statement stmt=con.createStatement();
ResultSet rs=stmt.executeQuery(query);
%>
<br />
<h3>The data read from database is:</h3>
<br />
<table border="2">
<tr>
<td>Id</td>
<td>Age</td>
<td>First</td>
<td>Last</td>
</tr>
<%
while(rs.next())
{
%>
<tr>
<td><%=rs.getInt("id")%></td>
<td><%=rs.getInt("age")%></td>
<td><%=rs.getString("first")%></td>
<td><%=rs.getString("last")%></td>
</tr>
<%
}
%>
</table>
<%
// close the connection
rs.close();
stmt.close();
con.close();
}
catch(SQLException e) {
out.println("SQLException caught: " +e.getMessage());
}
%>
</body>
</html>
最終打包我們的應用，並部署我們的應用．我們可以看到最終的結果為：
在實際的使用中，我們也可以把我們已經開發好的war包放入到我們的tomcat的目錄中：
mysql-customizations:
plugin: copy
files:
# This one is what creates the initial database and account for ownCloud.
src/mysql/start_mysql: bin/
src/mysql/my.cnf: my.cnf
src/mysql/mysql.server: support-files/
sample.war: war/sample.war
mysql-connector-java-6.0.3.jar: lib/mysql-connector-java-6.0.3.jar
比如上面的sample.war，我們可以通過如下的方式來運行該應用：
