How to execute some task in background within a docker container

Question

I'm trying to perform some user operation(change admin-user), after Neo4j container boots up. But my background script doesn't wait for the neo4j to come up and dies before Neo4j comes online.

entrypoint.sh is something like

if [some condition]
    my_function &
fi

if [${cmd}" == "neo4j" ]; then
    exec neo4j console 
fi

helper_file.sh has my_function

function my_function {

    echo "Checking to see if Neo4j has started at http://${DB_HOST}:${DB_PORT}..."
    curl --retry-connrefused --retry 5 --retry-max-time 300  http://${DB_HOST}:${DB_PORT}
    if [ $? -ne 0 ]; then
       echo "Curl failed with error $?. Exiting.."
       return 1
    fi
    migrate_users <--- another function
}

the problem that I'm facing is Neo4j doesn't bootup till curl is doing the retries.

Tue Sep 20 12:46:35 UTC 2022 Checking to see if Neo4j has started at http://localhost:7474...
Tue Sep 20 12:46:35 UTC 2022   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
Tue Sep 20 12:46:35 UTC 2022                                  Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
Tue Sep 20 12:46:35 UTC 2022 curl: (7) Failed to connect to localhost port 7474: Connection refused
Tue Sep 20 12:46:35 UTC 2022 Curl failed with error 0. Exiting..
user: vmanage; command: neo4j
Directories in use:

How can I ensure that migrate_users function gets called after Neo4j has come up online completely?

Edit:

thank you for providing the suggestion.

If I go with the background process approach, I'm seeing that Neo4j doesn't boots up, till curl queries have finished

Tue Sep 20 18:57:34 UTC 2022 Checking to see if Neo4j has started 

at  http://localhost:7474...
Tue Sep 20 18:57:34 UTC 2022 Neo4j not ready
Tue Sep 20 18:57:34 UTC 2022 Connection refused
Tue Sep 20 18:57:34 UTC 2022 config-db is not up, try to setup password again

user: vmanage; command: neo4j
Directories in use:
home:         /var/lib/neo4j
config:       /var/lib/neo4j/conf
logs:         /log
plugins:      /var/lib/neo4j/plugins
import:       /var/lib/neo4j
data:         /data
certificates: /var/lib/neo4j/certificates
licenses:     /var/lib/neo4j/licenses
run:          /var/lib/neo4j/run
Starting Neo4j.

Going to try this : https://github.com/neo4j/docker-neo4j/issues/166#issuecomment-486890785

score 1 · Answer 1 · answered Sep 20 '22 at 20:48

1

You can add a loop inside your script to check the health of neo4j container. If the health check get pass only proceeed further in you script otherwise loop untill it pass.

answered Sep 20 '22 at 20:48

YJR

1,099
3
13

The thing that I didn't understand was CURL was supposed to retry for 5 times and wait time is also 300 sec. If you see the time in the logs.. it seems that curl just exited upon first try. – Amit G Sep 20 '22 at 21:03
May be it retry parellely. Not sure. if it is work that way 5 parellel requests take only 300s. – YJR Sep 20 '22 at 21:08

javierlga · Accepted Answer · 2022-09-21T03:33:24.430

1

Your function named my_function could use until to keep waiting for neo4j to start, for example:

function my_function {
    let RETRIES=0
    declare SUCCESS=0
    until [[ $SUCCESS -eq 1 ]] || [[ $RETRIES -eq 50 ]]; do
      echo "Checking to see if Neo4j has started at 
      http://${DB_HOST}:${DB_PORT}..."
      STATUS_CODE=$(curl -w %{http_code} -o /dev/null -s http://${DB_HOST}:${DB_PORT})
      if [[ $STATUS_CODE -eq 200 ]]; then
        echo "Neo4j is up and running" && SUCCESS=1 && exit 0
      else
        echo "Neo4j not ready" && let RETRIES+=1 && sleep 10
      fi
    done
    migrate_users
}

edited Sep 21 '22 at 03:33

answered Sep 20 '22 at 21:01

javierlga

1,409
9
14

thanks! I wanted to do this in the background while neo4j boots up. Looks like with this it will keep on executing curl without going to start the container. – Amit G Sep 20 '22 at 22:01

score 1 · Answer 3 · answered Sep 20 '22 at 21:16

You can use docker-compose with the depends_on + condition to do that. Even docker-compose documentation recommends to implement some kind of script to wait until the service is up. Take a look to the following links docker-compose and stackoverflow

But it could be something like:

version: "2"
services:
  neo4j-admin:
    build: .
    depends_on:
      - "neo4j"
    command: ["./wait-for-it.sh","--", "sh", "change_admin_passwd.sh"]
  neo4j:
    image: neo4j

How to execute some task in background within a docker container

3 Answers3