I have two tasks in task group
1) a db task to bring up a db and
2) the app that needs the db to be up.
Both start in parallel and the db tasks takes a lil bit time but by then the app recognizes that db is not up and kills the db task. Any solutions? Please advise.
It's somewhat common to have an entrypoint script that checks if the db is healthy. Here's a script i've used before:
#!/bin/sh
set -e
cmd="$*"
postgres_ready() {
if test -z "${NO_DB}"
then
PGPASSWORD="${RDS_PASSWORD}" psql -h "${RDS_HOSTNAME}" -U "${RDS_USERNAME}" -d "${RDS_DB_NAME}" -c '\l'
return $?
else
echo "NO_DB Postgres will pretend to be up"
return 0
fi
}
until postgres_ready
do
>&2 echo "Postgres is unavailable - sleeping"
sleep 1
done
>&2 echo "Postgres is up - continuing..."
exec "${cmd}"
You could save it as entrypoint.sh and run it with your application start script as the argument. eg: entrypoint.sh python main.py
Related
I'm writing a unix script to check for database connectivity in a server. When my database connection gets errored out or when there is delay observed in connecting to the database, I want the output as "Not connected". In case it gets connected, my output should be "Connected". It is a Oracle databse.
When there is delay in database connectivity, my code is not working and my script gets hung. What changes should I make in my code so that it is able to handle both the conditions(when I get an error connecting to the database and when there is delay observed in connecting to the database)??
if sqlplus $DB_USER/$DB_PASS#$DB_INSTANCE< /dev/null | grep 'Connected to'; then
echo "Connectivity is OK"
else
echo "No Connectivity"
fi
The first thing to add to your code is a timeout. Checking database connectivity is not easy and there can be all kinds of problems in the various layers that your connection passes. A timeout gives you the option to break out of a hanging session and continue the task with reporting that the connection failed.
googleFu gave me a few nice examples:
Timeout a command in bash without unnecessary delay
If you are using Linux, you can use the timeout command to do what you want. So the following will have three outcomes, setting the variable RC as follows:
"Connected to" successful: RC set to 0
"Connected to" not found: RC set to 1
sqlplus command timed out after 5 minutes: RC set to 124
WAIT_MINUTES=5
SP_OUTPUT=$(timeout ${WAIT_MINUTES}m sqlplus $DB_USER/$DB_PASS#$DB_INSTANCE < /dev/null )
CMD_RC=$?
if [ $CMD_RC -eq 124 ]
then
ERR_MSG="Connection attempt timed out after $WAIT_MINUES minutes"
RC=$CMD_RC
else
echo $SP_OUTPUT | grep -q 'Connected to'
GREP_RC=$?
if [ $GREP_RC -eq 0 ]
then
echo "Connectivity is OK"
RC=0
else
ERR_MSG="Connectivity or user information is bad"
RC=1
fi
fi
if [ $RC -gt 0 ]
then
# Add code to send email with subject of $ERR_MSG and body of $SP_OUTPUT
echo Need to email someone about $ERR_MSG
fi
exit $RC
I'm sure there are several improvements to this, but this will get you started.
Briefly, we use the timeout command to wait the specified time for the sqlplus command to run. I separated out the grep as a separate command to allow the use of timeout and to allow more flexibility in checking additional text messages.
There are several examples on StackOverflow on sending email from a Linux script.
I have a database for my app and I want to create it in run time docker
I have a file CreateDB.sh and it creates all the tables and stored procedure that I want.
I tried this :
FROM mcr.microsoft.com/mssql/server
ENV ACCEPT_EULA=Y \
SA_PASSWORD=qwe123QWE
USER root
RUN mkdir /home/db
COPY ./db /home/db
RUN chmod +x /home/db/DbScriptLinux.sh
WORKDIR /home/db/
CMD ["/bin/bash", "/home/db/DbScriptLinux.sh"]
but it returns an error :
LoginTimeout
is there any way to run my script after all services (sql-server) start?
You can use an if statement, for example, RUN if [[ -z "$arg" ]] ; then echo Argument not provided ; else echo Argument is $arg ; fi
Another way would be to use command1 && command2 so if the command 1 is successfull, then command 2 would run afterwards.
Your last line CMD ["/bin/bash", "/home/db/DbScriptLinux.sh"] if this is to start the database every time you start the container, as your default command to run, then should be alright, otherwise it would be better to use the RUN command.
i am on creating a deb package for ubuntu
in my postinst script i use
# Configure database
dbc_mysql_createdb_encoding="UTF8"
if ! dbc_go portal3 $# ; then
echo 'Automatic configuration using dbconfig-db_version 2.0common failed!'
fi
to create the database what works fine.
In the postrm file i have:
echo "Remove database"
if [ -f /usr/share/debconf/confmodule ]; then
. /usr/share/debconf/confmodule
fi
if [ -f /usr/share/dbconfig-common/dpkg/postrm ]; then
. /usr/share/dbconfig-common/dpkg/postrm
if ! dbc_go portal3 $# ; then
echo 'Automatic configuration using dbconfig-common failed!'
fi
fi
but this don’t drop the created user or database.
There is no response on console or anything else that helps me to debug the issue.
Has anyone an idea how to drop database and user created while installation?
It also requires an prerm script like
#!/bin/sh
set -e
. /usr/share/debconf/confmodule
. /usr/share/dbconfig-common/dpkg/prerm.mysql
if ! dbc_go portal3 $# ; then
echo 'Automatic configuration using dbconfig-common failed!'
fi
# dh_installdeb will replace this with shell code automatically
# generated by other debhelper scripts.
exit 0
Otherwise dbconfig-commond dont know what database needs to be dropt.
Here's my full bash script:
#!/bin/bash
logs="$HOME/sitedb_backups/log"
mysql_user="user"
mysql_password="pass"
mysql=/usr/bin/mysql
mysqldump=/usr/bin/mysqldump
tbackups="$HOME/sitedb_backups/today"
ybackups="$HOME/sitedb_backups/yesterday"
echo "`date`" > $logs/backups.log
rm $ybackups/* >> $logs/backups.log
mv $tbackups/* $ybackups/ >> $logs/backups.log
databases=`$mysql --user=$mysql_user -p$mysql_password -e "SHOW DATABASES;" | grep -Ev "(Database|information_schema)"`
for db in $databases ; do
$mysqldump --force --opt --user=$mysql_user -p$mysql_password --databases $db | gzip > "$tbackups/$db.gz"
echo -e "\r\nBackup of $db successfull" >> $logs/backups.log
done
mail -s "Your DB backups is ready!" yourmail#gmail.com <<< "Today: "`date`"
DB backups of every site is ready."
exit 0
Problem is when i try to import it with mysql i am gettint error 1044 error connecting to oldname_db. When i opened sql file i have noticed on the first line CREATE command so it tries to create that database with the old name. How can i solve that problem?
SOLVED.
Using --databases parameter in my case is not necessary and because of --databases it was generating CREATE and USE action in the beginning of the sql file, hope it helps somebody else.
Use the --no-create-db option of mysqldump.
From man mysqldump:
--no-create-db, -n
This option suppresses the CREATE DATABASE statements that are
otherwise included in the output if the --databases or --all-databases
option is given.
I am trying to write a shell script to check database connectivity. Within my script I am using the command
sqlplus uid/pwd#database-schemaname
to connect to my Oracle database.
Now I want to save the output generated by this command (before it drops to SQL prompt) in a temp file and then grep / find the string "Connected to" from that file to see if the connectivity is fine or not.
Can anyone please help me to catch the output and get out of that prompt and test whether connectivity is fine?
Use a script like this:
#!/bin/sh
echo "exit" | sqlplus -L uid/pwd#dbname | grep Connected > /dev/null
if [ $? -eq 0 ]
then
echo "OK"
else
echo "NOT OK"
fi
echo "exit" assures that your program exits immediately (this gets piped to sqlplus).
-L assures that sqlplus won't ask for password if credentials are not ok (which would make it get stuck as well).
(> /dev/null just hides output from grep, which we don't need because the results are accessed via $? in this case)
You can avoid the SQL prompt by doing:
sqlplus uid/pwd#database-schemaname < /dev/null
SqlPlus exits immediately.
Now just grep the output of the above as:
if sqlplus uid/pwd#database-schemaname < /dev/null | grep 'Connected to'; then
# have connectivity to Oracle
else
# No connectivity
fi
#! /bin/sh
if echo "exit;" | sqlplus UID/PWD#database-schemaname 2>&1 | grep -q "Connected to"
then echo connected OK
else echo connection FAIL
fi
Not knowing whether the "Connected to" message is put to standard output or standard error, this checks both. "qrep -q" instead of "grep... >/dev/null" assumes Linux.
#!/bin/bash
output=`sqlplus -s "user/pass#POLIGON.TEST " <<EOF
set heading off feedback off verify off
select distinct machine from v\\$session;
exit
EOF
`
echo $output
if [[ $output =~ ERROR ]]; then
echo "ERROR"
else
echo "OK"
fi
Here's a good option which does not expose the password on the command line
#!/bin/bash
CONNECT_STRING=<USERNAME>/<PASS>#<SID>
sqlplus -s -L /NOLOG <<EOF
whenever sqlerror exit 1
whenever oserror exit 1
CONNECT $CONNECT_STRING
exit
EOF
SQLPLUS_RC=$?
echo "RC=$SQLPLUS_RC"
[ $SQLPLUS_RC -eq 0 ] && echo "Connected successfully"
[ $SQLPLUS_RC -ne 0 ] && echo "Failed to connect"
exit SQLPLUS_RC
none of the proposed solutions works for me, as my script is executed in machines running several countries, with different locales, I can't simply check for one String simply because this string in the other machine is translated to a different language. As a solution I'm using SQLcl
https://www.oracle.com/database/technologies/appdev/sqlcl.html
which is compatible with all sql*plus scripts and allow you to test the database connectivity like this:
echo "disconnect" | sql -L $DB_CONNECTION_STRING > /dev/null || fail "cannot check connectivity with the database, check your settings"
#!/bin/sh
echo "exit" | sqlplus -S -L uid/pwd#dbname
if [ $? -eq 0 ]
then
echo "OK"
else
echo "NOT OK"
fi
For connection validation -S would be sufficient.
The "silent" mode doesn't prevent terminal output. All it does is:
-S Sets silent mode which suppresses the display of
the SQL*Plus banner, prompts, and echoing of
commands.
If you want to suppress all terminal output, then you'll need to do something like:
sqlplus ... > /dev/null 2>&1
This was my one-liner for docker container to wait until DB is ready:
until sqlplus -s sys/Oracle18#oracledbxe/XE as sysdba <<< "SELECT 13376411 FROM DUAL; exit;" | grep "13376411"; do echo "Could not connect to oracle... sleep for a while"; sleep 3; done
And the same in multiple lines:
until sqlplus -s sys/Oracle18#oracledbxe/XE as sysdba <<< "SELECT 13376411 FROM DUAL; exit;" | grep "13376411";
do
echo "Could not connect to oracle... sleep for a while";
sleep 3;
done
So it basically does select with magic number and checks that correct number was actually returned.