├── Dockerfile
├── README.md
└── entrypoint.sh


/Dockerfile:
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1 | FROM alpine:3.6
2 | 
3 | ADD entrypoint.sh /usr/local/bin/entrypoint.sh
4 | 
5 | ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]
6 | 


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/README.md:
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 1 | ## Example usage:
 2 | 
 3 | Sample `docker-compose.yml`:
 4 | 
 5 | ```yaml
 6 | version: '2'
 7 | services:
 8 |   the_database:
 9 |     image: ubuntu:14.04
10 |     command: >
11 |       /bin/bash -c "
12 |         sleep 5;
13 |         nc -lk 0.0.0.0 5432;
14 |       "
15 |   another_service:
16 |     image: ubuntu:14.04
17 |     command: >
18 |       /bin/bash -c "
19 |         sleep 8;
20 |         nc -lk 0.0.0.0 5555;
21 |       "
22 | 
23 |   the_web_server:
24 |     image: ubuntu:14.04
25 |     depends_on:
26 |       - the_database
27 |       - another_service
28 |     command: >
29 |       /bin/bash -c "
30 |         nc -z the_database 5432 &&
31 |         echo Connected to DB and started!
32 |       "
33 | 
34 |   start_dependencies:
35 |     image: dadarek/wait-for-dependencies
36 |     depends_on:
37 |       - the_database
38 |       - another_service
39 |     command: the_database:5432 another_service:5555
40 | ```
41 | 
42 | Then, to guarantee that `the_database` and `another_service` are ready before running `the_web_server`:
43 | 
44 | ```bash
45 | $ docker-compose run --rm start_dependencies
46 | # Some output from docker compose
47 | $ docker-compose up the_web_server
48 | ```
49 | 
50 | By default, there will be a 2 second sleep time between each check. You can modify this by setting the `SLEEP_LENGTH` environment variable:
51 | 
52 | ```yaml
53 |   start_dependencies:
54 |     image: dadarek/wait-for-dependencies
55 |     environment:
56 |       - SLEEP_LENGTH: 0.5
57 | ```
58 | 
59 | By default, there will be a 300 seconds timeout before cancelling the wait_for. You can modify this by setting the `TIMEOUT_LENGTH` environment variable:
60 | 
61 | ```yaml
62 |   start_dependencies:
63 |     image: dadarek/wait-for-dependencies
64 |     environment:
65 |       - SLEEP_LENGTH: 1
66 |       - TIMEOUT_LENGTH: 60
67 | ```
68 | 


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/entrypoint.sh:
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 1 | #!/bin/sh
 2 | 
 3 | : ${SLEEP_LENGTH:=2}
 4 | : ${TIMEOUT_LENGTH:=300}
 5 | 
 6 | wait_for() {
 7 |   START=$(date +%s)
 8 |   echo "Waiting for $1 to listen on $2..."
 9 |   while ! nc -z $1 $2;
10 |     do
11 |     if [ $(($(date +%s) - $START)) -gt $TIMEOUT_LENGTH ]; then
12 |         echo "Service $1:$2 did not start within $TIMEOUT_LENGTH seconds. Aborting..."
13 |         exit 1
14 |     fi
15 |     echo "sleeping"
16 |     sleep $SLEEP_LENGTH
17 |   done
18 | }
19 | 
20 | for var in "$@"
21 | do
22 |   host=${var%:*}
23 |   port=${var#*:}
24 |   wait_for $host $port
25 | done
26 | 


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