A Layer 7 (Application) aware way to detect when services are fully initialized.
Reliable integration and service tests require accurately detecting when services are fully initialized before beginning test execution. While solutions like wait-for-it.sh can reliably detect when services are listening and able to receive connections many services require a deeper check. wait-for provides application specific detection for service initialization.
wait-for is useful in integration and service tests, where the test suite expects all services to be initialized before
execution. For many applications a TCP (level 4) initialization check isn't sufficient. Services begin listening
on sockets before they are fully initialized and able to begin performing work.
For example consider Hashicorp's Vault. Upon startup it quickly begins to listen so a wait-for-it.sh check would pass. But true application level initialization can lag behind seconds after it begins to listen, and necessitates an application level check:
EXPECTED="{\"initialized\":true,\"sealed\":false,\"standby\":false}"
VAULT_STATUS=$(curl -s http://127.0.0.1:8200/v1/sys/health | jq -r -j -S -c '{initialized, sealed, standby}')
until [ "$VAULT_STATUS" = "$EXPECTED" ]; do
VAULT_STATUS=$(curl -s http://127.0.0.1:8200/v1/sys/health | jq -r -j -S -c '{initialized, sealed, standby}')
echo "$SCRIPT polling vault status, expected: $EXPECTED received: $VAULT_STATUS"
sleep 1
done
wait-for contains logic necessary to perform these application level checks. Additionally, it offers the same
functionality as wait-for-it.sh by providing TCP/UDP based checks. wait-for also supports generic HTTP checks.
$ ./wait-for
NAME:
wait-for - wait for a service to become available
USAGE:
wait-for [global options] command [command options] [arguments...]
VERSION:
0.0.0
COMMANDS:
http
mysql
postgres
help, h Shows a list of commands or help for one command
GLOBAL OPTIONS:
--timeout value, -t value duration to wait until marking as failure and returning (default: 5m0s)
--poll-interval value, --pi value interval (default: 100ms)
--help, -h show help
--version, -v print the version
```
$ ./wait-for http --url=http://google.com/
{"level":"info","msg":"polling","time":"2018-08-26T00:50:39Z"}
{"level":"debug","module":"poller.HTTP","msg":"http_response","status_code":200,"time":"2018-08-26T00:50:40Z"}
$ echo $?
0
```
```
$ ./wait-for -t 500ms http --url=http://www.google.com/1/2
{"level":"info","msg":"polling","time":"2018-08-28T12:43:30Z"}
{"level":"debug","module":"poller.HTTP","msg":"http_response","status_code":404,"time":"2018-08-28T12:43:30Z"}
{"level":"info","msg":"polling","time":"2018-08-28T12:43:30Z"}
{"level":"debug","module":"poller.HTTP","msg":"http_response","status_code":404,"time":"2018-08-28T12:43:30Z"}
{"level":"info","msg":"polling","time":"2018-08-28T12:43:30Z"}
{"level":"debug","module":"poller.HTTP","msg":"http_response","status_code":404,"time":"2018-08-28T12:43:31Z"}
{"level":"info","msg":"polling","time":"2018-08-28T12:43:31Z"}
{"level":"debug","module":"poller.HTTP","msg":"http_response","status_code":404,"time":"2018-08-28T12:43:31Z"}
{"level":"info","msg":"polling","time":"2018-08-28T12:43:31Z"}
{"level":"debug","module":"poller.HTTP","msg":"http_response","status_code":404,"time":"2018-08-28T12:43:31Z"}
{"level":"info","msg":"polling","time":"2018-08-28T12:43:31Z"}
{"level":"debug","module":"poller.HTTP","msg":"http_response","status_code":404,"time":"2018-08-28T12:43:31Z"}
{"level":"info","msg":"timeout_reached","time":"2018-08-28T12:43:31Z"}
{"level":"fatal","msg":"timeout reached: 500ms","time":"2018-08-28T12:43:31Z"}
$ echo $?
1
```