fix(kafka): use sentinel file to eliminate starter-script race condition (#11682) - #11957
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klouds27 wants to merge 1 commit into
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fix(kafka): use sentinel file to eliminate starter-script race condition (#11682)#11957klouds27 wants to merge 1 commit into
klouds27 wants to merge 1 commit into
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…ion (testcontainers#11682) copyFileToContainer writes the startup script into the container over a Docker API call. On busy hosts the wait loop can detect the file the moment its inode is created, before the write completes, and attempt to execute an incomplete file. This produces ETXTBSY and exit code 126. The fix adds a sentinel file (STARTER_SCRIPT + ".ready") that is touched via execInContainer only after copyFileToContainer returns. The wait loop now checks for the sentinel instead of the script itself, so execution cannot begin until the script is fully written. Applied to KafkaHelper, org.testcontainers.kafka.KafkaContainer, org.testcontainers.kafka.ConfluentKafkaContainer, and the deprecated org.testcontainers.containers.KafkaContainer. Signed-off-by: klouds27 <adalwolf@gmail.com>
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Pull request overview
This PR fixes a Kafka container startup race where the entrypoint loop could execute /tmp/testcontainers_start.sh before it was fully written, intermittently causing Text file busy (exit code 126). It does this by introducing and waiting on a sentinel file that is only created after the startup script copy completes.
Changes:
- Add a sentinel file path (
/tmp/testcontainers_start.sh.ready) and update the shared Kafka startupCOMMANDto wait for the sentinel instead of the script. - After copying the startup script into the container, create the sentinel file so the entrypoint loop can safely proceed.
- Apply the same pattern to the deprecated
org.testcontainers.containers.KafkaContainerimplementation.
Reviewed changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.
| File | Description |
|---|---|
| modules/kafka/src/main/java/org/testcontainers/kafka/KafkaHelper.java | Introduces the sentinel constant and updates the shared startup command to wait on it. |
| modules/kafka/src/main/java/org/testcontainers/kafka/KafkaContainer.java | Touches the sentinel after copying the starter script to prevent early execution. |
| modules/kafka/src/main/java/org/testcontainers/kafka/ConfluentKafkaContainer.java | Touches the sentinel after copying the starter script to prevent early execution. |
| modules/kafka/src/main/java/org/testcontainers/containers/KafkaContainer.java | Adds sentinel + waits on it in the entry command, and touches it after script copy (deprecated container). |
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| try { | ||
| execInContainer("touch", KafkaHelper.STARTER_SCRIPT_SENTINEL); | ||
| } catch (IOException | InterruptedException e) { | ||
| throw new RuntimeException(e); | ||
| } |
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| try { | ||
| execInContainer("touch", KafkaHelper.STARTER_SCRIPT_SENTINEL); | ||
| } catch (IOException | InterruptedException e) { | ||
| throw new RuntimeException(e); | ||
| } |
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| try { | ||
| execInContainer("touch", STARTER_SCRIPT_SENTINEL); | ||
| } catch (IOException | InterruptedException e) { | ||
| throw new RuntimeException(e); | ||
| } |
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| static final String STARTER_SCRIPT_SENTINEL = STARTER_SCRIPT + ".ready"; | ||
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| static final String[] COMMAND = { | ||
| "sh", | ||
| "-c", | ||
| "while [ ! -f " + STARTER_SCRIPT + " ]; do sleep 0.1; done; " + STARTER_SCRIPT, | ||
| "while [ ! -f " + STARTER_SCRIPT_SENTINEL + " ]; do sleep 0.1; done; " + STARTER_SCRIPT, | ||
| }; |
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The Kafka containers start the broker by writing a startup script into the container via
copyFileToContainer, then executing it with a shell loop that polls for the file. Because the loop checks only for file existence, it can detect the script the instant its inode is created and attempt to execute it before the write completes. On busy hosts this producesText file busy(ETXTBSY) and a container exit code of 126.This was confirmed in #11682 by the reporter and a second commenter. The suggestion of checking file size with
[ -s file ]was also tested and failed for the same reason: size becomes non-zero before the write finishes.The fix introduces a sentinel file (
/tmp/testcontainers_start.sh.ready) that is created viaexecInContainer("touch", ...)only aftercopyFileToContainerreturns. The wait loop now polls for the sentinel instead of the script itself. BecausecopyFileToContainercompletes fully before the sentinel is touched, the loop cannot proceed until the script is both fully written and closed.The change is applied consistently to all affected containers:
org.testcontainers.kafka.KafkaHelper(shared COMMAND constant),org.testcontainers.kafka.KafkaContainer,org.testcontainers.kafka.ConfluentKafkaContainer, and the deprecatedorg.testcontainers.containers.KafkaContainer.Fixes #11682