sadpandajoe commented on code in PR #42811:
URL: https://github.com/apache/superset/pull/42811#discussion_r3740981445
##########
superset-frontend/webpack.proxy-config.js:
##########
@@ -133,23 +133,30 @@ function processHTML(proxyResponse, response) {
} else if (responseEncoding === 'zstd') {
uncompress = ZSTDDecompress();
}
- if (uncompress) {
- originalResponse.pipe(uncompress);
- originalResponse = uncompress;
- }
- originalResponse
- .on('data', data => {
- body = Buffer.concat([body, data]);
- })
- .on('error', error => {
- // eslint-disable-next-line no-console
- console.error(error);
- response.end(`Error fetching proxied request: ${error.message}`);
- })
- .on('end', () => {
- response.end(toDevHTML(body.toString()));
- });
+ const chunks = [];
+ const collector = new Writable({
+ write(chunk, encoding, callback) {
+ chunks.push(chunk);
+ callback();
+ },
+ });
+
+ // `pipeline` (unlike `.pipe()`) destroys every stream in the chain -- and
+ // rejects -- as soon as any one of them errors or closes prematurely. A
+ // proxied backend connection dying mid-response (e.g. the Flask dev
+ // server's reloader restarting on a file save) is exactly that case:
+ // plain `.pipe()` never forwards the upstream error/close to `uncompress`,
+ // so `uncompress` (and, for `zstd`, the child process backing it) sits
+ // waiting for input that will never arrive, `end`/`error` never fire, and
+ // the client-facing response hangs forever instead of failing fast.
+ await pipeline(
+ ...(uncompress
+ ? [proxyResponse, uncompress, collector]
Review Comment:
On an interrupted zstd response, `pipeline` rejects and destroys this outer
duplex, but `[email protected]` does not forward that destruction to its
`/usr/bin/zstd -d` child; the child remains alive with stdin open. Repeated
interrupted reloads therefore leak a process, and the focused Jest run does not
exit after its assertions pass. Could we explicitly terminate that child
(including the race before `started` fires) or use a decoder whose lifecycle is
owned by the pipeline?
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