Race condition writing same file dest on client #1581
Description
Problem
When two outputs: files structs have the same dest path there is a race condition and/or partial file truncation issue that means the plan is not idempotent. Repeatedly calling dagger --europa up followed by cat ./test in the example below will give different outputs. The order of the contents strings as well as --no-cache options seem to possibly affect the outputs as well. The export order of the files (test -> test2 versus test2 -> test below) seems to be consistent across the outputs.
package main
import "dagger.io/dagger"
dagger.#Plan & {
outputs: {
files: {
test: {
dest: "./test"
contents: "kale\n"
}
test2: {
dest: "./test"
contents: "carrots\n"
}
}
}
}
Test script:
#!/bin/bash
while true
do
dagger --europa up
#dagger --europa --no-cache up
cat ./test
sleep 1;
done
Output:
[✔] outputs.files.test 0.0s
[✔] outputs.files.test2 0.0s
carrots
[✔] outputs.files.test2 0.0s
[✔] outputs.files.test 0.0s
kale
ts
[✔] outputs.files.test2 0.0s
[✔] outputs.files.test 0.0s
kale
[✔] outputs.files.test 0.0s
[✔] outputs.files.test2 0.0s
carrots
[✔] outputs.files.test2 0.0s
[✔] outputs.files.test 0.0s
kale
ts
[✔] outputs.files.test 0.0s
[✔] outputs.files.test2 0.0s
carrots
Solution
Depends on desired behavior, but I would have expected that two output file structs with the same dest and different contents would not be allowed and would throw an error.