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content/Docker/Wait for mysql.md

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+[wait-for-it.sh](https://github.com/vishnubob/wait-for-it) doing a great job of waiting for different services to become alive, but on #MacOs #docker is binding port on container start, seconds before #mysql is ready to accept connections
+
+This script waits for first successful query from database or exits with non-zero status after timeout.
+
+Don't forget to change `$query` for the actually working one.
+
+```shell
+# Waits for mysql to become actually available
+wait_for_mysql() {
+  query="SELECT count(*) FROM users"
+  
+  timeout=180 # 3 minutes limit
+  i=0
+  
+  while ! docker exec -it "$1" mysql --user="$2" --password="$3" -e "$query" $4 >/dev/null 2>&1; do
+    sleep 1;
+
+    i=$(($i+1))
+    if [[ ${i} -ge ${timeout} ]]; then
+      echo "[Error] can't properly query MySQL after ${i} secs"
+      exit 1;
+    fi
+  done
+}
+
+# usage: wait_for_mysql miin-mysql-dev root password database
+```
+
+[Wait for redis](Wait%20for%20redis.md)