Await availability of resources.
This can be useful in the context of Docker Compose where a service needs to wait for other dependent services.
Optionally a timeout can be provided to specify how long to wait for all
dependent resources to become available. On success the command returns code
0
, on failure it returns code 1
.
Additionally a command can be specified which gets executed after all dependent resources became available.
This repository is a fork of Betalo's await
.
Since the company decided to no longer support it,
I forked it and started adding features myself.
This repository will only contain versions 1.2 and above due to that.
go get -u github.com/fcristovao/await
or
curl -s -f -L -o await https://github.com/fcristovao/await/releases/download/v1.2.1/await-linux-amd64
chmod +x await
$ await -h
Usage: await [options...] <res>... [ -- <cmd>]
Await availability of resources.
-V Show version
-f Force running the command even after giving up
-i string
Read resources from file, '-' to read from stdin
-q Set quiet mode
-t duration
Set timeout duration before giving up (default 1m0s)
-v Set verbose output mode
-vv
Set more verbose output mode
All dependent resources must be specified as URLs or escaped command.
Some resources provided additional functionally encoded as fragment
(#<fragment>
). The syntax follows the URL query syntax:
k1|k1=|k1=v1,v2,v3...[&k2=v1&...]
.
E.g.: http://example.com/#ssl&foo=bar,baz&i=j
Valid resources are: HTTP, Websocket, TCP, File, PostgreSQL, MySQL, Kafka and Command.
Availability: Available when a connection to a given server is established and an empty request returns the response status code is 2xx. Unavailable otherwise.
URL syntax: http[s]://[<user>[:<pass>]@]<host>[:<port>][<path>][?<query>][#<fragment>]
Fragment:
tls=skip-verify
: When used, it skips TLS check forhttps
resources.
Availability: Available when a connection to a given server is established. Unavailable otherwise.
URL syntax: ws[s]://[<user>[:<pass>]@]<host>[:<port>][<path>][?<query>]
Availability: Available when a connection to a given server is established. Unavailable otherwise.
URL syntax: tcp[4|6]://<host>:<port>
Availability: Available when given path is a file and the file exists or, if declared absent, the file does not exist. Unavailable otherwise.
URL syntax: file://<path>[#<fragment>]
absent
key: If present, the resource is defined as available, when the specific file is absent, rather than existing.
Availability: Available when a connection to a given PostgreSQL database server is established and optional a given database could be found and optional any tables or a set of tables could be found. Unavailable otherwise.
URL syntax: postgres://[<user>[:<pass>]@]<host>[:<port>][/<dbname>][?<dbparams>][#<fragment>]
The URL defines a DSN.
The database name <dbname>
is optional. If provided, the resource is
classified as available as soon as the database was found.
DB Parameters:
sslmode=[verify-ca|require]
:sslmode=verify-ca
enables TLS/SSL encrypted connection to the server. Usesslmode=require
if you want to use a self-signed or invalid certificate (server side). See lib/pq for more details.
Fragment:
tables[=t1,t2,...]
key-value: If key present and value absent, the resource's database scheme must at least contain one table. If key present and value present, the resource's database scheme must at least contain the specified tables. Using this key requires to provide a database name.
Availability: Available when a connection to a given MySQL database server is established and optional a given database could be found and optional any tables or a set of tables could be found. Unavailable otherwise.
URL syntax: mysql://[<user>[:<pass>]@]<host>[:<port>][/<dbname>][?<dbparams>][#<fragment>]
The URL defines a DSN.
The database name <dbname>
is optional. If provided, the resource is
classified as available as soon as the database was found.
DB Parameters:
tls=[true|skip-verify]
:tls=true
enables TLS/SSL encrypted connection to the server. Usetls=skip-verify
if you want to use a self-signed or invalid certificate (server side). See go-sql-driver/mysql for more details.
Fragment:
tables[=t1,t2,...]
key-value: If key present and value absent, the resource's database scheme must at least contain one table. If key present and value present, the resource's database scheme must at least contain the specified tables. Using this key requires to provide a database name.
Availability: Available when a connection to a given Kafka broker is established and, optionally, a set of topics could be found. Unavailable otherwise.
URL syntax: kafka[s]://[<user>[:<pass>]@]<host>[:<port>][#<fragment>]
Using kafkas
scheme enables TLS/SSL encrypted connection to the server.
If no port
is set, 9092
will be used as default for kafka
scheme, or
9093
for kafkas
scheme.
Fragment:
-
topics[=t1,t2,...]
: Iftopics
present but with no values, the resource's broker must at least contain one topic. Iftopics
present with values set, the resource's broker must at least contain the specified topics (comma-separated names). -
tls=skip-verify
: When used, it skips TLS check forkafkas
resources. -
sasl=[plain|scram-sha-256|scram-sha-512]
: Only relevant when setting username and password. Default isplain
. See Kafka's SASL configuration and Kafka's SASL SCRAM configuration for more details.
Does not follow the URL syntax and is used as generic fallback for invalid URLs (i.e. schema is absent).
Availability: Available when command return status code 0
. Unavailable
otherwise.
URL syntax: <path> [<arg>...]
Once Docker-Compose support the Docker HEALTHCHECK
directive for awaiting
services being up, this tool could become deprecated.
Many alternative solutions exist, most of them avoiding to interpret the resource type, leaving only options like tcp and http, or having a specific focus on Docker Compose. A few of them listed below:
- ContainerPilot
- controlled-compose
- crane
- docker-wait
- dockerize
- wait-for-it
- wait_for_db
- wait_to_start.sh
- waitforservices
MIT License. See LICENSE.