Question

Django app/postgres don't respond after running Snapshot!?

Posted October 8, 2014 4.5k views

I made a Snapshot yesterday of a Django app running on a development server. I made sure to run sudo poweroff before the Power Cycle.

After the App restarted, I couldn’t access the domain in my browser. I then try to dump my database, but I get the following error:

pg_dump: [archiver (db)] connection to database "db" failed: could not connect to server: Connection refused
    Is the server running on host "####" and accepting
    TCP/IP connections on port ###?

It actually seems like I can’t get any response from the DB or the app.

Response from nmap ip##
Host is up (0.00012s latency).
PORT STATE SERVICE
80/tcp closed http

But the logs from the Django app tell me that it should be running.
How do I retrieve the data from my database and get the app running again?

Thank you!

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simonbillinge
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simonbillinge
6 comments
  • ryanpq October 8, 2014
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    Have you attempted to restart your postgres after you encountered this issue? These messages would appear to indicate that the database is not currently running

    sudo service postgresql restart
  • simonbillinge October 8, 2014
    Reply Report

    I get the same error after restarting postgresql

  • kamaln7 October 8, 2014
    Reply Report

    Is Postgres running? What’s the output of 

    sudo ps wwaux | grep postgres
  • simonbillinge October 8, 2014
    Reply Report

    Yes it seems to be running. I get the following output.

    root       588  0.0  0.2  46628  1392 ?        S    12:38   0:00 su postgres sh -c /usr/lib/postgresql/9.3/bin/postgres           -D  /var/lib/postgresql/9.3/main  -c config_file=/etc/postgresql/9.3/main/postgresql.conf  -c listen_addresses=*
message+   589  0.0  3.1 244852 16036 ?        Ss   12:38   0:00 /usr/lib/postgresql/9.3/bin/postgres -D /var/lib/postgresql/9.3/main -c config_file=/etc/postgresql/9.3/main/postgresql.conf -c listen_addresses=*
message+   591  0.0  0.3 244852  1860 ?        Ss   12:38   0:00 postgres: checkpointer process                                                                                                                    
message+   592  0.0  0.5 244852  2660 ?        Ss   12:38   0:00 postgres: writer process                                                                                                                          
message+   593  0.0  0.3 244852  1648 ?        Ss   12:38   0:00 postgres: wal writer process                                                                                                                      
message+   594  0.0  0.5 245704  2976 ?        Ss   12:38   0:00 postgres: autovacuum launcher process                                                                                                             
message+   595  0.0  0.3 100672  1760 ?        Ss   12:38   0:00 postgres: stats collector process                                                                                                                 
root      2251  0.0  0.1  11748   900 pts/0    S+   13:35   0:00 grep --color=auto postgres
postgres 32480  0.0  3.0 247716 15504 ?        S    12:18   0:00 /usr/lib/postgresql/9.3/bin/postgres -D /var/lib/postgresql/9.3/main -c config_file=/etc/postgresql/9.3/main/postgresql.conf
postgres 32482  0.0  0.3 247716  1872 ?        Ss   12:18   0:00 postgres: checkpointer process                                                                                              
postgres 32483  0.0  0.5 247716  2676 ?        Ss   12:18   0:00 postgres: writer process                                                                                                    
postgres 32484  0.0  0.3 247716  1660 ?        Ss   12:18   0:00 postgres: wal writer process                                                                                                
postgres 32485  0.0  0.5 248576  2972 ?        Ss   12:18   0:00 postgres: autovacuum launcher process                                                                                       
postgres 32486  0.0  0.3 103524  1788 ?        Ss   12:18   0:00 postgres: stats collector process
  • simonbillinge October 8, 2014
    Reply Report

    I tried running the script from this forum: https://coderwall.com/p/wtqlca

    Which restarted my app properly. However, my database name is different from the app name I’m using, so a new database container was created, which is obviously empty.

    I’m not sure if dokku postgresql:create original_db_name is going to erase my original database, or just restart the container.

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1 answer
asb October 8, 2014

Hi!

So it sounds like you are using the Dokku postgres plugin. If that’s the case, then to dump a database, you’ll need to do it with Dokku as it is running inside a container.

dokku postgresql:dump dbname > foo.sql

and to restore one:

dokku postgresql:restore dbname < foo.sql

As to the question of will dokku postgresql:create original_db_name will destroy the old one, looking at the code:

    if [[ -f "$DOKKU_ROOT/.postgresql/volume_$APP" ]]; then
        VOLUME="`cat $DOKKU_ROOT/.postgresql/volume_$APP`:/opt/postgresql"
        echo
        echo "-----> Reusing postgresql/$APP database"
    else
        VOLUME="/opt/postgresql"
        # Generate a random password for DB user
        DB_PASSWORD=$(< /dev/urandom tr -dc A-Za-z0-9 | head -c 16)
        echo $DB_PASSWORD > "$DOKKU_ROOT/.postgresql/pwd_$APP"
        chown dokku: "$DOKKU_ROOT/.postgresql/pwd_$APP"
        chmod 700 "$DOKKU_ROOT/.postgresql/pwd_$APP"
    fi

it looks like it will attempt to reuse the persistent volume.

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