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SOLR-18537: Proxy requests to a node via X-Solr-targetNode - #5112

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dsmiley wants to merge 11 commits into
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dsmiley:SOLR-18537-proxyRequestsByHeader
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SOLR-18537: Proxy requests to a node via X-Solr-targetNode#5112
dsmiley wants to merge 11 commits into
apache:mainfrom
dsmiley:SOLR-18537-proxyRequestsByHeader

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@dsmiley

@dsmiley dsmiley commented Oct 12, 2026

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https://issues.apache.org/jira/browse/SOLR-18537

It can be very useful for Solr to proxy requests to another node, specified in a header or param. The intended scenario is when there's an HTTP proxy in front of Solr, and the backing Solr nodes aren't directly reachable. Solr is doing that now for a few admin endpoints that have already been coded for it, using GenericV1RequestProxy internally (e.g. for logging, info, ...). The issue here instead proposes a generic mechanism that doesn't require Solr handlers to be coded any differently.

@dsmiley @claude
SOLR-18537: Proxy requests to a node via X-Solr-targetNode
ab0ebb8 
Header or param.
Useful to reach a specific node.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
@dsmiley
dsmiley requested review from gerlowskija and janhoy October 12, 2026 23:12
@dsmiley

dsmiley commented Oct 12, 2026

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FYI I've been using this for awhile at work.
Marking as Draft because needs a test and documentation.

Are there security concerns here? I don't think so. This is live-nodes only.

@janhoy janhoy mentioned this pull request Oct 20, 2026
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@dsmiley
test + ref guide.
4616e92 
code: use Solr's URL param parsing
@github-actions github-actions Bot added documentation Improvements or additions to documentation test-framework tests labels Oct 20, 2026
@dsmiley
dsmiley marked this pull request as ready for review October 20, 2026 20:42
@janhoy
janhoy requested a balanced review from Copilot October 21, 2026 08:49
Copilot AI reviewed Oct 21, 2026

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Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

janhoy
janhoy reviewed Oct 21, 2026
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I delegate review to Copilot who is probably better at servlet spec than me. I do like the general solution and I believe the security aspect is handled so so far a LGTM from me from 10.000 ft

janhoy
janhoy reviewed Oct 21, 2026
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Some manual review comments as I'm out of copilot credit...

Comment thread solr/core/src/java/org/apache/solr/servlet/NodeTargetProxyFilter.java Outdated
Comment thread solr/core/src/java/org/apache/solr/servlet/NodeTargetProxyFilter.java Outdated
Comment thread solr/core/src/java/org/apache/solr/servlet/NodeTargetProxyFilter.java Outdated
zkStateReader.getBaseUrlForNodeName(resolvedNode) + ServletUtils.getPathAfterContext(req);
String queryString = req.getQueryString();
if (queryString != null) {
url = url + "?" + queryString;

@janhoy janhoy Oct 21, 2026

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Should we use the URL class for url manipulation instead of String?

@dsmiley dsmiley Oct 22, 2026

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I'm rather sympathetic. We have an addiction to untyped Strings, and it'd behove us to adopt URI as Jetty has done. I'll push an improvement.

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janhoy requested a balanced review from Copilot October 21, 2026 09:07
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🟡 Changes recommended

Caller identity preservation and request-routing correctness need correction before approval.

5 open issues

Review effort: Balanced

Comment thread solr/core/src/java/org/apache/solr/servlet/NodeTargetProxyFilter.java Outdated
Comment on lines +99 to +101
HttpClient httpClient =
((HttpJettySolrClient) cores.getDefaultHttpSolrClient()).getHttpClient();
HttpSolrProxy.doHttpProxy(httpClient, req, resp, url);

@dsmiley dsmiley Oct 22, 2026

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I'm investigating this separately.

Comment thread solr/core/src/java/org/apache/solr/servlet/NodeTargetProxyFilter.java Outdated
Comment thread solr/core/src/java/org/apache/solr/servlet/NodeTargetProxyFilter.java
Comment thread solr/core/src/java/org/apache/solr/servlet/NodeTargetProxyFilter.java Outdated
Comment thread solr/core/src/java/org/apache/solr/servlet/NodeTargetProxyFilter.java Outdated
dsmiley and others added 9 commits October 21, 2026 19:43
@dsmiley @claude
NodeTargetProxyFilter: review tweaks
d1882d9 
Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
@dsmiley @claude
NodeTargetProxyFilter: preserve full node names with dotless hosts
176ffcb 
Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
@dsmiley
rename var to match super
7c66491
@dsmiley @claude
NodeTargetProxyFilter: consume the targeting header/param to avoid ro…
1d7fc1a 
…uting loops

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
@dsmiley @claude
NodeTargetProxyFilter: proxy using the still-encoded request path
b5cb63b 
Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
@dsmiley @claude
NodeTargetProxyFilterTest: use SolrJ so it works with SSL
b4dba65 
Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
@dsmiley @claude
NodeTargetProxyFilter: report errors directly so they survive Authent…
de525ca 
…icationFilter

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
@dsmiley @claude
NodeTargetProxyFilterAuthTest: proxied requests are authorized as the…
d033e8b 
… caller

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
@dsmiley @claude
HttpSolrProxy: take a URI; build it with an encoded path and query
b4fa46f 
Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
@dsmiley

dsmiley commented Oct 22, 2026

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It's really remarkable how much this PR has improved/evolved as a result of such peer-review/scrutiny.

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