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Merged
DaveCTurner merged 4 commits into from
Nov 24, 2025
+76 −29
Merged

Return ETag from S3 fixture GetObject API #138514

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1309313
Return `ETag` header from S3 fixture
DaveCTurner Nov 24, 2025
20bcdbb
Merge branch 'main' into 2025/11/24/s3-fixture-etag
DaveCTurner Nov 24, 2025
6e98292
Reinstate canned-value hash tests
DaveCTurner Nov 24, 2025
da4e70e
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DaveCTurner Nov 24, 2025
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20 changes: 2 additions & 18 deletions ...itory-s3/src/test/java/org/elasticsearch/repositories/s3/S3BlobContainerRetriesTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,6 @@
import org.elasticsearch.common.blobstore.OptionalBytesReference;
import org.elasticsearch.common.bytes.BytesArray;
import org.elasticsearch.common.bytes.BytesReference;
import org.elasticsearch.common.hash.MessageDigests;
import org.elasticsearch.common.io.Streams;
import org.elasticsearch.common.lucene.store.ByteArrayIndexInput;
import org.elasticsearch.common.lucene.store.InputStreamIndexInput;
Expand Down Expand Up @@ -430,7 +429,7 @@ public void testWriteLargeBlob() throws Exception {
assertThat(contentLength, anyOf(equalTo(lastPartSize), equalTo(bufferSize.getBytes())));

if (countDownUploads.decrementAndGet() % 2 == 0) {
exchange.getResponseHeaders().add("ETag", getBase16MD5Digest(bytes));
exchange.getResponseHeaders().add("ETag", S3HttpHandler.getEtagFromContents(bytes));
exchange.sendResponseHeaders(HttpStatus.SC_OK, -1);
exchange.close();
return;
Expand Down Expand Up @@ -529,7 +528,7 @@ public void testWriteLargeBlobStreaming() throws Exception {

if (counterUploads.incrementAndGet() % 2 == 0) {
bytesReceived.addAndGet(bytes.length());
exchange.getResponseHeaders().add("ETag", getBase16MD5Digest(bytes));
exchange.getResponseHeaders().add("ETag", S3HttpHandler.getEtagFromContents(bytes));
exchange.sendResponseHeaders(HttpStatus.SC_OK, -1);
exchange.close();
return;
Expand Down Expand Up @@ -1382,21 +1381,6 @@ public void handle(HttpExchange exchange) throws IOException {
);
}

private static String getBase16MD5Digest(BytesReference bytesReference) {
return MessageDigests.toHexString(MessageDigests.digest(bytesReference, MessageDigests.md5()));
}

public void testGetBase16MD5Digest() {
// from Wikipedia, see also org.elasticsearch.common.hash.MessageDigestsTests.testMd5
assertBase16MD5Digest("", "d41d8cd98f00b204e9800998ecf8427e");
assertBase16MD5Digest("The quick brown fox jumps over the lazy dog", "9e107d9d372bb6826bd81d3542a419d6");
assertBase16MD5Digest("The quick brown fox jumps over the lazy dog.", "e4d909c290d0fb1ca068ffaddf22cbd0");
}

private static void assertBase16MD5Digest(String input, String expectedDigestString) {
assertEquals(expectedDigestString, getBase16MD5Digest(new BytesArray(input)));
}

@Override
protected Matcher<Integer> getMaxRetriesMatcher(int maxRetries) {
// some attempts make meaningful progress and do not count towards the max retry limit
Expand Down
16 changes: 15 additions & 1 deletion test/fixtures/s3-fixture/src/main/java/fixture/s3/S3HttpHandler.java
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Expand Up @@ -84,6 +84,8 @@ public S3HttpHandler(final String bucket, @Nullable final String basePath) {
*/
private static final Set<String> METHODS_HAVING_NO_REQUEST_BODY = Set.of("GET", "HEAD", "DELETE");

private static final String SHA_256_ETAG_PREFIX = "es-test-sha-256-";
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@joshua-adams-1 joshua-adams-1 Nov 24, 2025

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Is this string going to be visible?

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@DaveCTurner DaveCTurner Nov 24, 2025

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No, this is only in the test fixture, I'm using something descriptive here just to aid future troubleshooting. It's treated as an opaque string everywhere else.


@Override
public void handle(final HttpExchange exchange) throws IOException {
// Remove custom query parameters before processing the request. This simulates how S3 ignores them.
Expand Down Expand Up @@ -322,6 +324,9 @@ public void handle(final HttpExchange exchange) throws IOException {
exchange.sendResponseHeaders(RestStatus.NOT_FOUND.getStatus(), -1);
return;
}

exchange.getResponseHeaders().add("ETag", getEtagFromContents(blob));
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@joshua-adams-1 joshua-adams-1 Nov 24, 2025

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Could we have a brief comment here explaining what an ETag is?

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@DaveCTurner DaveCTurner Nov 24, 2025

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I added a comment in da4e70e. Not sure where to put it really, ETag is a pretty standard piece of HTTP.

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@mhl-b mhl-b Nov 24, 2025

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AFAIK S3 returns ETag on creation(PutObject, MPU) too, but our fixture does not return ETag unless there is precondition failure. Should we add ETag to all operations that suppose to have one?

Also can compute ETag once on creation and store together with blob

record Blob (BytesReference bytes, String etag) {}
private final ConcurrentMap<String, Blob> blobs = new ConcurrentHashMap<>();

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@DaveCTurner DaveCTurner Nov 24, 2025

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We have no plans to use the ETag returned by the PutObject and CompleteMultipartUpload APIs so I'm hesitant to add them now. It'd be easy enough to add later if needed.

I did consider tracking etags alongside the object contents but it's a bigger change and not really necessary. This is purely test fixture code, and indeed a bit of latency here and there is helpful for test coverage.


final String rangeHeader = exchange.getRequestHeaders().getFirst("Range");
if (rangeHeader == null) {
exchange.getResponseHeaders().add("Content-Type", "application/octet-stream");
Expand Down Expand Up @@ -413,6 +418,15 @@ private boolean updateBlobContents(HttpExchange exchange, String path, BytesRefe
}
}

/**
* Etags are opaque identifiers for the contents of an object.
*
* @see <a href="https://en.wikipedia.org/wiki/HTTP_ETag">HTTP ETag on Wikipedia</a>.
*/
public static String getEtagFromContents(BytesReference blobContents) {
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@joshua-adams-1 joshua-adams-1 Nov 24, 2025

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Is there any value adding a specific unit test for this method?

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@DaveCTurner DaveCTurner Nov 24, 2025

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Eh possibly, I meant to at least. Added in 6e98292.

return '"' + SHA_256_ETAG_PREFIX + MessageDigests.toHexString(MessageDigests.digest(blobContents, MessageDigests.sha256())) + '"';
}

public Map<String, BytesReference> blobs() {
return blobs;
}
Expand Down Expand Up @@ -490,7 +504,7 @@ private static Tuple<String, BytesReference> parseRequestBody(final HttpExchange
);
}
}
return Tuple.tuple(MessageDigests.toHexString(MessageDigests.digest(bytesReference, MessageDigests.md5())), bytesReference);
return Tuple.tuple(getEtagFromContents(bytesReference), bytesReference);
} catch (Exception e) {
logger.error("exception in parseRequestBody", e);
exchange.sendResponseHeaders(500, 0);
Expand Down
69 changes: 59 additions & 10 deletions test/fixtures/s3-fixture/src/test/java/fixture/s3/S3HttpHandlerTests.java
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Expand Up @@ -83,9 +83,12 @@ public void testSimpleObjectOperations() {
<?xml version="1.0" encoding="UTF-8"?><ListBucketResult><Prefix></Prefix><IsTruncated>false</IsTruncated>\
</ListBucketResult>""");

final var body = randomAlphaOfLength(50);
final var body = new BytesArray(randomAlphaOfLength(50).getBytes(StandardCharsets.UTF_8));
assertEquals(RestStatus.OK, handleRequest(handler, "PUT", "/bucket/path/blob", body).status());
assertEquals(new TestHttpResponse(RestStatus.OK, body), handleRequest(handler, "GET", "/bucket/path/blob"));
assertEquals(
new TestHttpResponse(RestStatus.OK, body, addETag(S3HttpHandler.getEtagFromContents(body), TestHttpExchange.EMPTY_HEADERS)),
handleRequest(handler, "GET", "/bucket/path/blob")
);

assertListObjectsResponse(handler, "", null, """
<?xml version="1.0" encoding="UTF-8"?><ListBucketResult><Prefix></Prefix><IsTruncated>false</IsTruncated>\
Expand Down Expand Up @@ -135,39 +138,53 @@ public void testGetWithBytesRange() {
final var blobBytes = randomBytesReference(256);
assertEquals(RestStatus.OK, handleRequest(handler, "PUT", blobPath, blobBytes).status());

final var expectedEtag = S3HttpHandler.getEtagFromContents(blobBytes);

assertEquals(
"No Range",
new TestHttpResponse(RestStatus.OK, blobBytes, TestHttpExchange.EMPTY_HEADERS),
new TestHttpResponse(RestStatus.OK, blobBytes, addETag(expectedEtag, TestHttpExchange.EMPTY_HEADERS)),
handleRequest(handler, "GET", blobPath)
);

var end = blobBytes.length() - 1;
assertEquals(
"Exact Range: bytes=0-" + end,
new TestHttpResponse(RestStatus.PARTIAL_CONTENT, blobBytes, contentRangeHeader(0, end, blobBytes.length())),
new TestHttpResponse(
RestStatus.PARTIAL_CONTENT,
blobBytes,
addETag(expectedEtag, contentRangeHeader(0, end, blobBytes.length()))
),
handleRequest(handler, "GET", blobPath, BytesArray.EMPTY, bytesRangeHeader(0, end))
);

end = randomIntBetween(blobBytes.length() - 1, Integer.MAX_VALUE);
assertEquals(
"Larger Range: bytes=0-" + end,
new TestHttpResponse(RestStatus.PARTIAL_CONTENT, blobBytes, contentRangeHeader(0, blobBytes.length() - 1, blobBytes.length())),
new TestHttpResponse(
RestStatus.PARTIAL_CONTENT,
blobBytes,
addETag(expectedEtag, contentRangeHeader(0, blobBytes.length() - 1, blobBytes.length()))
),
handleRequest(handler, "GET", blobPath, BytesArray.EMPTY, bytesRangeHeader(0, end))
);

var start = randomIntBetween(blobBytes.length(), Integer.MAX_VALUE - 1);
end = randomIntBetween(start, Integer.MAX_VALUE);
assertEquals(
"Invalid Range: bytes=" + start + '-' + end,
new TestHttpResponse(RestStatus.REQUESTED_RANGE_NOT_SATISFIED, BytesArray.EMPTY, TestHttpExchange.EMPTY_HEADERS),
new TestHttpResponse(
RestStatus.REQUESTED_RANGE_NOT_SATISFIED,
BytesArray.EMPTY,
addETag(expectedEtag, TestHttpExchange.EMPTY_HEADERS)
),
handleRequest(handler, "GET", blobPath, BytesArray.EMPTY, bytesRangeHeader(start, end))
);

start = randomIntBetween(2, Integer.MAX_VALUE - 1);
end = randomIntBetween(0, start - 1);
assertEquals(
"Weird Valid Range: bytes=" + start + '-' + end,
new TestHttpResponse(RestStatus.OK, blobBytes, TestHttpExchange.EMPTY_HEADERS),
new TestHttpResponse(RestStatus.OK, blobBytes, addETag(expectedEtag, TestHttpExchange.EMPTY_HEADERS)),
handleRequest(handler, "GET", blobPath, BytesArray.EMPTY, bytesRangeHeader(start, end))
);

Expand All @@ -179,7 +196,7 @@ public void testGetWithBytesRange() {
new TestHttpResponse(
RestStatus.PARTIAL_CONTENT,
blobBytes.slice(start, length),
contentRangeHeader(start, end, blobBytes.length())
addETag(expectedEtag, contentRangeHeader(start, end, blobBytes.length()))
),
handleRequest(handler, "GET", blobPath, BytesArray.EMPTY, bytesRangeHeader(start, end))
);
Expand Down Expand Up @@ -245,7 +262,15 @@ public void testSingleMultipartUpload() {
<Contents><Key>path/blob</Key><Size>100</Size></Contents>\
</ListBucketResult>""");

assertEquals(new TestHttpResponse(RestStatus.OK, part1 + part2), handleRequest(handler, "GET", "/bucket/path/blob"));
final var expectedContents = new BytesArray((part1 + part2).getBytes(StandardCharsets.UTF_8));
assertEquals(
new TestHttpResponse(
RestStatus.OK,
expectedContents,
addETag(S3HttpHandler.getEtagFromContents(expectedContents), TestHttpExchange.EMPTY_HEADERS)
),
handleRequest(handler, "GET", "/bucket/path/blob")
);

assertEquals(new TestHttpResponse(RestStatus.OK, """
<?xml version='1.0' encoding='UTF-8'?>\
Expand Down Expand Up @@ -416,7 +441,11 @@ public void testPreventObjectOverwrite() throws InterruptedException {
});

assertEquals(
new TestHttpResponse(RestStatus.OK, successfulTasks.getFirst().body, TestHttpExchange.EMPTY_HEADERS),
new TestHttpResponse(
RestStatus.OK,
successfulTasks.getFirst().body,
addETag(S3HttpHandler.getEtagFromContents(successfulTasks.getFirst().body), TestHttpExchange.EMPTY_HEADERS)
),
handleRequest(handler, "GET", "/bucket/path/blob")
);
}
Expand Down Expand Up @@ -459,6 +488,20 @@ private static TestWriteTask createMultipartUploadTask(S3HttpHandler handler) {
return multipartUploadTask;
}

public void testGetETagFromContents() {
// empty-string value from Wikipedia, see also org.elasticsearch.common.hash.MessageDigestsTests.testSha256
assertETag("", "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855");
assertETag("The quick brown fox jumps over the lazy dog", "d7a8fbb307d7809469ca9abcb0082e4f8d5651e46d3cdb762d02d0bf37c9e592");
assertETag("The quick brown fox jumps over the lazy cog", "e4c4d8f3bf76b692de791a173e05321150f7a345b46484fe427f6acc7ecc81be");
}

private static void assertETag(String input, String expectedHash) {
assertEquals(
"\"es-test-sha-256-" + expectedHash + '"',
S3HttpHandler.getEtagFromContents(new BytesArray(input.getBytes(StandardCharsets.UTF_8)))
);
}

private static class TestWriteTask {
final BytesReference body;
final Runnable consumer;
Expand Down Expand Up @@ -562,6 +605,12 @@ private static Headers ifNoneMatchHeader() {
return headers;
}

private static Headers addETag(String eTag, Headers headers) {
final var newHeaders = new Headers(headers);
newHeaders.add("ETag", eTag);
return newHeaders;
}

private static class TestHttpExchange extends HttpExchange {

private static final Headers EMPTY_HEADERS = new Headers();
Expand Down