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xds: ignore keep_empty_value and discard header keys on empty mutations #12852

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xds: ignore keep_empty_value and discard header keys on empty mutations #12852

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36 changes: 27 additions & 9 deletions xds/src/main/java/io/grpc/xds/internal/headermutations/HeaderMutator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -67,24 +67,23 @@ private void applyHeaderUpdates(final Iterable<HeaderValueOption> headerOptions,
private void updateHeader(final HeaderValueOption option, Metadata mutableHeaders) {
HeaderValue header = option.header();
HeaderAppendAction action = option.appendAction();
boolean keepEmptyValue = option.keepEmptyValue();

@sauravzg sauravzg Jun 10, 2026

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We should probably delete the config field as well if unused.


if (header.key().endsWith(Metadata.BINARY_HEADER_SUFFIX)) {
if (header.rawValue().isPresent()) {
byte[] value = header.rawValue().get().toByteArray();
if (value.length > 0 || keepEmptyValue) {
updateHeader(action, Metadata.Key.of(header.key(), Metadata.BINARY_BYTE_MARSHALLER),
value, mutableHeaders);
Metadata.Key<byte[]> key = Metadata.Key.of(header.key(), Metadata.BINARY_BYTE_MARSHALLER);
updateHeader(action, key, header.rawValue().get().toByteArray(), mutableHeaders);
if (containsEmpty(key, mutableHeaders)) {
mutableHeaders.discardAll(key);
}
} else {
logger.fine("Missing binary rawValue for header: " + header.key());
}
} else {
if (header.value().isPresent()) {
String value = header.value().get();
if (!value.isEmpty() || keepEmptyValue) {
updateHeader(action, Metadata.Key.of(header.key(), Metadata.ASCII_STRING_MARSHALLER),
value, mutableHeaders);
Metadata.Key<String> key = Metadata.Key.of(header.key(), Metadata.ASCII_STRING_MARSHALLER);
updateHeader(action, key, header.value().get(), mutableHeaders);
if (containsEmpty(key, mutableHeaders)) {
mutableHeaders.discardAll(key);
}
} else {
logger.fine("Missing value for header: " + header.key());
Expand Down Expand Up @@ -119,5 +118,24 @@ private <T> void updateHeader(final HeaderAppendAction action, final Metadata.Ke
logger.fine("Unknown HeaderAppendAction: " + action);
}
}

private <T> boolean containsEmpty(Metadata.Key<T> key, Metadata headers) {
Iterable<T> values = headers.getAll(key);
if (values == null) {
return false;
}
for (T val : values) {
if (val instanceof String) {
if (((String) val).isEmpty()) {
return true;
}
} else if (val instanceof byte[]) {
if (((byte[]) val).length == 0) {
return true;
}
}
}
return false;
}
Comment on lines +122 to +139

@gemini-code-assist gemini-code-assist Bot Jun 10, 2026

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medium

Since empty mutations are now handled directly in updateHeader without needing to scan the metadata, the containsEmpty helper method is no longer needed and can be safely removed.

@sauravzg sauravzg Jun 10, 2026

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We might want to investigate the need for this function. I've added a comment here previously grpc/proposal#481 (comment)
about compliance with envoy behavior.

}

17 changes: 7 additions & 10 deletions xds/src/test/java/io/grpc/xds/internal/headermutations/HeaderMutatorTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -247,30 +247,27 @@ public void applyMutations_keepEmptyValue() {
headerMutator.applyMutations(mutations, headers);

assertThat(headers.containsKey(NEW_ADD_KEY)).isFalse();
assertThat(headers.getAll(APPEND_KEY)).containsExactly("existing-value");
assertThat(headers.get(OVERWRITE_KEY)).isEqualTo("existing-value");
assertThat(headers.containsKey(APPEND_KEY)).isFalse();
assertThat(headers.containsKey(OVERWRITE_KEY)).isFalse();
assertThat(headers.containsKey(ADD_KEY)).isFalse();
assertThat(headers.get(OVERWRITE_IF_EXISTS_KEY)).isEqualTo("existing-value");
assertThat(headers.containsKey(OVERWRITE_IF_EXISTS_KEY)).isFalse();

Metadata.Key<String> keepEmptyKey =
Metadata.Key.of("keep-empty-key", Metadata.ASCII_STRING_MARSHALLER);
Metadata.Key<String> keepEmptyOverwriteKey =
Metadata.Key.of("keep-empty-overwrite-key", Metadata.ASCII_STRING_MARSHALLER);

assertThat(headers.containsKey(keepEmptyKey)).isTrue();
assertThat(headers.get(keepEmptyKey)).isEqualTo("");
assertThat(headers.containsKey(keepEmptyOverwriteKey)).isTrue();
assertThat(headers.get(keepEmptyOverwriteKey)).isEqualTo("");
assertThat(headers.containsKey(keepEmptyKey)).isFalse();
assertThat(headers.containsKey(keepEmptyOverwriteKey)).isFalse();

Metadata.Key<byte[]> keepEmptyBinKey =
Metadata.Key.of("keep-empty-bin-key-bin", Metadata.BINARY_BYTE_MARSHALLER);
Metadata.Key<byte[]> ignoreEmptyBinKey =
Metadata.Key.of("ignore-empty-bin-key-bin", Metadata.BINARY_BYTE_MARSHALLER);

assertThat(headers.containsKey(keepEmptyBinKey)).isTrue();
assertThat(headers.get(keepEmptyBinKey)).isEqualTo(new byte[0]);
assertThat(headers.containsKey(keepEmptyBinKey)).isFalse();
assertThat(headers.containsKey(ignoreEmptyBinKey)).isFalse();
assertThat(headers.get(overwriteEmptyBinKey)).isEqualTo(originalBinValue);
assertThat(headers.containsKey(overwriteEmptyBinKey)).isFalse();
}

@Test
Expand Down
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