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Write job artifact files atomically #2419

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Write job artifact files atomically #2419

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27 changes: 26 additions & 1 deletion inc/Core/JobArtifacts.php
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Original file line number Diff line number Diff line change
Expand Up @@ -511,7 +511,7 @@ private function write_artifact_file( int $job_id, string $artifact_key, array $
}

$json .= "\n";
if ( false === file_put_contents( $file_path, $json ) ) { // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_file_put_contents
if ( ! $this->write_atomic_file( $file_path, $json ) ) {
return array(
'success' => false,
'error' => sprintf( 'Failed to write %s artifact for job %d.', $artifact_key, $job_id ),
Expand All @@ -537,6 +537,31 @@ private function write_artifact_file( int $job_id, string $artifact_key, array $
);
}

private function write_atomic_file( string $file_path, string $contents ): bool {
$directory = dirname( $file_path );
if ( ! is_dir( $directory ) || ! is_writable( $directory ) ) {
return false;
}

$temp_path = tempnam( $directory, '.tmp-artifact-' ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_tempnam
if ( false === $temp_path ) {
return false;
}

$written = file_put_contents( $temp_path, $contents, LOCK_EX ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_file_put_contents
if ( strlen( $contents ) !== $written ) {
@unlink( $temp_path ); // phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink
return false;
}

if ( ! @rename( $temp_path, $file_path ) ) { // phpcs:ignore WordPress.WP.AlternativeFunctions.rename_rename
@unlink( $temp_path ); // phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink
return false;
}

return true;
}

/** @return array<string,mixed> */
private function with_payload_hash( array $payload ): array {
$payload['sha256'] = $this->hash_payload( $payload );
Expand Down
17 changes: 17 additions & 0 deletions tests/job-artifact-hashable-smoke.php
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Original file line number Diff line number Diff line change
Expand Up @@ -237,12 +237,29 @@ function wp_strip_all_tags( $value ): string {
$assert_true( $tool_trace_artifact['sha256'] === $refs['tool_trace']['sha256'], 'artifact refs expose tool trace hash' );
$assert_true( $tool_trace_artifact['artifact_ref'] === $refs['tool_trace']['artifact_ref'], 'artifact refs expose stable tool trace ref' );

$upload_dir = wp_upload_dir();
$artifact_job_dir = trailingslashit( $upload_dir['basedir'] ) . 'datamachine-artifacts/jobs/123';
$tool_trace_path = trailingslashit( $artifact_job_dir ) . 'tool-trace.json';
$leftover_temp_glob = trailingslashit( $artifact_job_dir ) . '.tmp-artifact-*';
wp_mkdir_p( $artifact_job_dir );
foreach ( glob( $leftover_temp_glob ) ?: array() as $leftover_temp_path ) {
@unlink( $leftover_temp_path );
}
file_put_contents( $tool_trace_path, "stale\n" );

$file_result = $invoke( $artifacts, 'write_artifact_file', array( 123, 'tool_trace', $tool_trace_artifact ) );
$assert_true( true === ( $file_result['success'] ?? false ), 'tool trace artifact file write succeeds' );
$assert_true( is_file( $file_result['file']['path'] ?? '' ), 'tool trace artifact file exists on disk' );
$assert_true( 'datamachine-artifacts/jobs/123/tool-trace.json' === ( $file_result['file']['relative_path'] ?? '' ), 'artifact file has stable relative path' );
$assert_true( $tool_trace_artifact['sha256'] === ( $file_result['file']['payload_sha256'] ?? '' ), 'artifact file references payload hash' );
$assert_true( hash_file( 'sha256', $file_result['file']['path'] ) === ( $file_result['file']['sha256'] ?? '' ), 'artifact file hash matches written bytes' );
$assert_true( "stale\n" !== file_get_contents( $tool_trace_path ), 'artifact file atomically replaces stale final contents' );

$second_file_result = $invoke( $artifacts, 'write_artifact_file', array( 123, 'tool_trace', $tool_trace_artifact ) );
$assert_true( true === ( $second_file_result['success'] ?? false ), 'repeat tool trace artifact write succeeds' );
$assert_true( $file_result['file']['path'] === ( $second_file_result['file']['path'] ?? '' ), 'repeat artifact write targets same stable path' );
$assert_true( $file_result['file']['sha256'] === ( $second_file_result['file']['sha256'] ?? '' ), 'repeat artifact write is byte-idempotent' );
$assert_true( array() === ( glob( $leftover_temp_glob ) ?: array() ), 'atomic artifact write leaves no temp files behind' );

$transcript_file_result = $invoke( $artifacts, 'write_artifact_file', array( 123, 'transcript', $transcript_artifact ) );
$assert_true( true === ( $transcript_file_result['success'] ?? false ), 'transcript artifact file write succeeds' );
Expand Down
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