waitfor

waitfor (or wfor) waits until some condition is fulfilled and then either execs a specified binary or exits with returncode 0. Currently the following things can be waited for:

• -path PATH: Wait until PATH can be sucessfully stat-ed
• -http SPEC: Wait until a response according to SPEC is received. SPEC has the following format URL|AcceptedHTTPCodes|Regex, where URL is the URL that the request will be sent to. AcceptedHTTPCodes is a list / range of HTTP Status codes that are considered OK by the check. If ommitted any HTTP status will be accepted. Regex is a regular expression that will be matched against the response body. If ommitted the response content will not be looked at to determine success. Look at Examples for further details.
• -tcp HOSTPORT: Wait until a connection to HOSTPORT can be established. The connection timeout is currently hard-coded to 500ms
• -udp HOSTPORT: Wait until at least one byte could be read from HOSTPORT. The read timeout is currently hard-coded to 500ms

Any number of these conditions can be specified. Use the -and / -or flags to control how they will be evaluated. -and / -or affect all conditions, so you can either wait until all conditions or any one of them are fulfilled. By default conditions are and-ed.

Anything after -- on the commandline is interpreted as a binary (including parameters) that will be executed (as in using the exec syscall) after waiting finishes successfully.

-interval controls how often the conditions are checked, default is 10s, minimum is 1s. -timeout controls the amount of time after which wfor will stop checking, default is 5m. Both parameters use the golang time.ParseDuration syntax.

The -debug parameter enables verbose logging.

Examples

# Start nginx after the database is up (path exists AND port is open)
wfor -path /tmp/db.dat -tcp localhost:3306 -- nginx -g 'daemon off;'

# or alternatively if run in a shell
wfor -path /tmp/db.dat -tcp localhost:3306 && nginx -g 'daemon off;'

# Check URL, accept status 200-208 and 226, require "Authenticated as .*" in the response body
wfor -http "http://some-service.acme.org:8080/secret|200-208,226|Authenticated as .*" && echo "User is authenticated"

# Check URL, accept any status, require "Hello" in response body
wfor -http "http://some-service.acme.org:8080/secret||Hello" && echo "Greeting received"

# Check URL, accept any status, any content
wfor -http "http://some-service.acme.org:8080/" && echo "Seems up"