FrankChen021 commented on code in PR #20151:
URL: https://github.com/apache/druid/pull/20151#discussion_r3968993729
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server/src/main/java/org/apache/druid/client/DirectDruidClient.java:
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@@ -238,11 +249,139 @@ private InputStream dequeue() throws InterruptedException
return holder.getStream();
}
+ /**
+ * Scans past leading whitespace in {@code buffer} looking for the
first content byte, without consuming
+ * (advancing the reader index of) the buffer, and returns it. Once a
non-whitespace byte is found, the prefix
+ * is considered resolved (see {@link #bodyPrefixResolved}) and later
calls return null. If {@code buffer} is
+ * empty or entirely whitespace, the prefix remains unresolved (and
null is returned) so a later call, from a
+ * subsequent chunk, can retry the check; this matters for chunked
responses, where the initial
+ * {@link HttpResponse} can carry an empty body and the real content,
HTML or otherwise, only arrives via
+ * {@link #handleChunk}.
+ */
+ @Nullable
+ private Byte bodyPrefixByte(ChannelBuffer buffer)
+ {
+ if (bodyPrefixResolved.get()) {
+ return null;
+ }
+ final int readerIndex = buffer.readerIndex();
+ final int readable = buffer.readableBytes();
+ for (int i = 0; i < readable; i++) {
+ byte b = buffer.getByte(readerIndex + i);
+ if (b == ' ' || b == '\n' || b == '\r' || b == '\t') {
+ continue;
+ }
+ bodyPrefixResolved.set(true);
+ return b;
+ }
+ return null;
+ }
+
+ /**
+ * Classifies the body prefix in {@code buffer} (see {@link
#bodyPrefixByte}) and fails the query if it is not
+ * JSON. HTML always fails; any other non-JSON body fails only when
the status is 429/503, since Druid itself
+ * never sends a non-JSON body with those statuses but proxies
routinely do (an HTML error page from nginx or
+ * a load balancer, a plain-text "upstream connect error" from Envoy).
A JSON body, whatever the status, is
+ * left alone so that the normal parse path can surface the server's
own structured error.
+ *
+ * @param contentType Content-Type header of the initial response,
possibly null; a text/html value fails the
+ * query regardless of the body prefix
+ * @param chunkNum 0 for the initial response body, else the chunk
number
+ */
+ private void failIfNonJsonBody(String contentType, ChannelBuffer
buffer, long chunkNum)
+ {
+ final boolean isHtmlContentType =
+ contentType != null &&
StringUtils.toLowerCase(contentType).contains("text/html");
+ final Byte prefix = bodyPrefixByte(buffer);
+ final boolean isHtml = isHtmlContentType || (prefix != null &&
prefix == '<');
+ final boolean isNonJson = prefix != null && prefix != '{' && prefix
!= '[';
+ final int statusCode = responseStatusCode;
+ if (isHtml || (isNonJson && (statusCode == 429 || statusCode ==
503))) {
+ throwForNonJsonBody(statusCode, contentType, buffer, chunkNum,
isHtml);
+ }
+ }
+
+ /**
+ * Returns up to 256 characters of {@code buffer} (read from at most
its first 512 bytes) for inclusion in an
+ * error message, without consuming the buffer.
+ */
+ private String bodyPreview(ChannelBuffer buffer)
+ {
+ final int len = Math.min(buffer.readableBytes(), 512);
+ if (len == 0) {
+ return "";
+ }
+ final byte[] previewBytes = new byte[len];
+ buffer.getBytes(buffer.readerIndex(), previewBytes);
+ final String preview = StringUtils.fromUtf8(previewBytes);
+ return preview.substring(0, Math.min(preview.length(), 256));
+ }
+
+ /**
+ * Fails the query because the response body is not JSON, typically an
error page produced by a load balancer
+ * or reverse proxy sitting in front of the data server. A 429/503
status is reported as
+ * {@link QueryCapacityExceededException} since that is what such
intermediaries return when the server is
+ * over capacity; any other status is reported as a {@link
QueryInterruptedException}. Either way, the caller
+ * gets a message that says what actually came back instead of a
{@code JsonParseException} on {@code '<'}.
+ *
+ * @param statusCode HTTP status of the initial response
+ * @param contentType Content-Type header of the initial response,
possibly null
+ * @param buffer the buffer in which the non-JSON body was
detected (the initial response body or a chunk)
+ * @param chunkNum 0 if detected in the initial response body, else
the chunk number
+ * @param isHtml whether the body was identified as HTML
specifically (vs. some other non-JSON content)
+ */
+ private void throwForNonJsonBody(
+ int statusCode,
+ String contentType,
+ ChannelBuffer buffer,
+ long chunkNum,
+ boolean isHtml
+ )
+ {
+ final String preview = bodyPreview(buffer);
Review Comment:
I think the finding above from the AI may be overstated
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