Sometimes we need to have the application configured differently, for instance between different environments. Args and profiles are 2 Acorn concepts which are often used together to provide a dynamic configuration to an application so it can defined a different set of default for each environment.
- args defines arguments that can be modified at build or runtime by the user
- profiles specify default arguments for different contexts
Let's see this in action on the VotingApp.
First, change the Acornfile adding this section at the very beginning:
args: {
replicas: 3
}
profiles: {
dev: {
replicas: 1
}
test: {
replicas: 2
}
}
The change above defines a default value for the replicas value. It also ensures this default value is modified if the app is ran using a specific profile (*dev or test in this example).
Next modify the definition of the voteui container adding the scale property so it looks as follows, the number of voteui containers now depends on the value of the replicas arguments:
voteui: {
if args.dev {
dirs: {
"/usr/share/nginx/html": "./vote-ui"
}
}
build: {
context: "./vote-ui"
}
ports: publish : "80/http"
scale: args.replicas
memory: 128Mi
}
You can now test the following actions:
- run the app without args nor profile information
make sure the following command uses the default value of the replicas args, it should create 3 voteui containers:
acorn run -n vote --update .
Note: you can verify the running containers with acorn all (which lists all the Acorn resources) or with acorn containers (which only lists containers)
$ acorn containers
NAME APP IMAGE STATE RESTARTCOUNT CREATED MESSAGE
vote.db-54b8487bc5-jsvq7 vote postgres:15.0-alpine3.16 running 0 30s ago
vote.result-6f6dff8dd8-7gzkn vote sha256:805ece5530411a09e8e97e59eb9477355ef260c9d9a4204667ce2a364cddcc53 running 0 30s ago
vote.worker-57bcd65d56-ml9cl vote sha256:f97cb92018967769330da09bba644da395c176f549e1d11bf48da3a8927cb62e running 0 30s ago
vote.redis-86c6745f86-hs667 vote redis:7.0.5-alpine3.16 running 0 31s ago
vote.resultui-64f48dd775-dm9ht vote sha256:a6f9230076947f698858df6793097f6b239f3eef108297e4e4d62e9b6f258d9a running 0 31s ago
vote.vote-6f448d9c4b-45lsw vote sha256:73836e77179e1eb068d4aa54d58350c0bc2ebf32b45aab80997273278fbd2373 running 0 31s ago
vote.voteui-86bb4b699f-bw4z4 vote sha256:069dcc1ab8846d2eb6e8b57d39a29f07607a477f74ecde66d0ef0e02289300d6 running 0 31s ago
vote.voteui-86bb4b699f-nm2n9 vote sha256:069dcc1ab8846d2eb6e8b57d39a29f07607a477f74ecde66d0ef0e02289300d6 running 0 31s ago
vote.voteui-86bb4b699f-zshbf vote sha256:069dcc1ab8846d2eb6e8b57d39a29f07607a477f74ecde66d0ef0e02289300d6 running 0 31s ago
- running the app overwriting the default args
The following command will not use the default value of the replicas args but it will use the user supplied value instead. Make sure it creates 5 voteui containers:
acorn run -n vote --update . --replicas=5
- running the app specifying a profile
The following command will not use the default value of the replicas args but it will use the value defined in the test profile instead. Make sure it creates 2 containers for the voteui microservice:
acorn run -n vote --update --profile test .
We only used the voteui container to illustrate the usage of args / profile but we could have used other stateless containers in the same way. Also, we only specified a simple args (a string) but more complex structure could be used as well.
Acornfile you should have at the end of this step...
args: {
replicas: 3
}
profiles: {
dev: {
replicas: 1
}
test: {
replicas: 2
}
}
containers: {
voteui: {
if args.dev {
dirs: {
"/usr/share/nginx/html": "./vote-ui"
}
}
build: {
context: "./vote-ui"
}
ports: publish : "80/http"
scale: args.replicas
memory: 128Mi
}
vote: {
build: {
target: std.ifelse(args.dev, "dev", "production")
context: "./vote"
}
if args.dev {
dirs: {
"/app": "./vote"
}
}
ports: "5000/http"
memory: 128Mi
}
redis: {
image: "redis:7.0.5-alpine3.16"
ports: "6379/tcp"
dirs: {
if !args.dev {
"/data": "volume://redis"
}
}
memory: 128Mi
}
worker: {
build: "./worker/go"
env: {
"POSTGRES_USER": "secret://db-creds/username"
"POSTGRES_PASSWORD": "secret://db-creds/password"
}
memory: 128Mi
}
db: {
image: "postgres:15.0-alpine3.16"
ports: "5432/tcp"
env: {
"POSTGRES_USER": "secret://db-creds/username"
"POSTGRES_PASSWORD": "secret://db-creds/password"
"PGDATA": "/var/lib/postgresql/data/db"
}
dirs: {
if !args.dev {
"/var/lib/postgresql/data": "volume://db"
}
}
memory: 128Mi
}
result: {
build: {
target: std.ifelse(args.dev, "dev", "production")
context: "./result"
}
if args.dev {
dirs: {
"/app": "./result"
}
}
ports: "5000/http"
env: {
"POSTGRES_USER": "secret://db-creds/username"
"POSTGRES_PASSWORD": "secret://db-creds/password"
}
memory: 128Mi
}
resultui: {
build: {
target: std.ifelse(args.dev, "dev", "production")
context: "./result-ui"
}
if args.dev {
dirs: {
"/app": "./result-ui"
}
}
ports: publish : "80/http"
memory: std.ifelse(args.dev, 1Gi, 128Mi)
}
}
secrets: {
"db-creds": {
type: "basic"
params: {
usernameLength: 7
usernameCharacters: "a-z"
passwordLength: 10
passwordCharacters: "A-Za-z0-9"
}
data: {
username: ""
password: ""
}
}
}
volumes: {
if !args.dev {
"db": {
size: "100M"
}
"redis": {
size: "100M"
}
}
}
Note: you can find more information about Arguments and Profiles in the Acorn documentation