dsmiley commented on code in PR #3997: URL: https://github.com/apache/solr/pull/3997#discussion_r2659275927
########## solr/core/src/java/org/apache/solr/servlet/EssentialSolrRequestFilter.java: ########## @@ -0,0 +1,97 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.solr.servlet; + +import jakarta.servlet.FilterChain; +import jakarta.servlet.ServletException; +import jakarta.servlet.http.HttpServletRequest; +import jakarta.servlet.http.HttpServletResponse; +import java.io.IOException; +import java.lang.invoke.MethodHandles; +import org.apache.solr.common.util.SuppressForbidden; +import org.apache.solr.logging.MDCLoggingContext; +import org.apache.solr.logging.MDCSnapshot; +import org.apache.solr.request.SolrRequestInfo; +import org.apache.solr.util.RTimerTree; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * Servlet Filter to set up and tear down a various things that downstream code in solr relies on. + * It is expected that solr will fail to function as intended without the conditions initialized in + * this filter. Before adding anything to this filter ask yourself if a user could run without the + * feature you are adding (either with an alternative implementation or without it at all to reduce + * cpu/memory/dependencies). If it is not essential, it should have its own separate filter. Also, + * please include a comment indicating why the thing added is essential. + */ +public class EssentialSolrRequestFilter extends CoreContainerAwareHttpFilter { + + // Best to put constant here because solr is not supposed to be functional (or compile) + // without this filter. + public static final String CORE_CONTAINER_REQUEST_ATTRIBUTE = "org.apache.solr.CoreContainer"; + private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass()); + + @Override + @SuppressForbidden( + reason = + "Set the thread contextClassLoader for all 3rd party dependencies that we cannot control") + protected void doFilter(HttpServletRequest req, HttpServletResponse res, FilterChain chain) + throws IOException, ServletException { + ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader(); + // this autocloseable is here to invoke MDCSnapshot.close() which restores captured state + try (var mdcSnapshot = MDCSnapshot.create()) { + + // MDC logging *shouldn't* be essential but currently is, see SOLR-18050. + // Our use of SLF4J indicates that we intend logging to be pluggable, and + // some implementations won't have an MDC, so having it as essential limits + // logging implementations. Review Comment: Thanks for filing SOLR-18050. It would be nice to get that fixed sometime. But why do you reference that here? Even JUL, which doesn't have MDC, nonetheless effectively does via SLF4J [as seen here](https://github.com/qos-ch/slf4j/blob/master/slf4j-jdk14/src/main/java/org/slf4j/jul/JULServiceProvider.java). Even if it didn't, I'd expect no-op behavior. Thus, we need the code you are lamenting is in this filter. ########## solr/core/src/java/org/apache/solr/servlet/EssentialSolrRequestFilter.java: ########## @@ -0,0 +1,97 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.solr.servlet; + +import jakarta.servlet.FilterChain; +import jakarta.servlet.ServletException; +import jakarta.servlet.http.HttpServletRequest; +import jakarta.servlet.http.HttpServletResponse; +import java.io.IOException; +import java.lang.invoke.MethodHandles; +import org.apache.solr.common.util.SuppressForbidden; +import org.apache.solr.logging.MDCLoggingContext; +import org.apache.solr.logging.MDCSnapshot; +import org.apache.solr.request.SolrRequestInfo; +import org.apache.solr.util.RTimerTree; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * Servlet Filter to set up and tear down a various things that downstream code in solr relies on. + * It is expected that solr will fail to function as intended without the conditions initialized in + * this filter. Before adding anything to this filter ask yourself if a user could run without the + * feature you are adding (either with an alternative implementation or without it at all to reduce + * cpu/memory/dependencies). If it is not essential, it should have its own separate filter. Also, + * please include a comment indicating why the thing added is essential. + */ +public class EssentialSolrRequestFilter extends CoreContainerAwareHttpFilter { Review Comment: I really dislike the name "Essential". Maybe swap in "Primary". IMO it's essentialness isn't very relevant. ########## solr/core/src/java/org/apache/solr/servlet/EssentialSolrRequestFilter.java: ########## @@ -0,0 +1,97 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.solr.servlet; + +import jakarta.servlet.FilterChain; +import jakarta.servlet.ServletException; +import jakarta.servlet.http.HttpServletRequest; +import jakarta.servlet.http.HttpServletResponse; +import java.io.IOException; +import java.lang.invoke.MethodHandles; +import org.apache.solr.common.util.SuppressForbidden; +import org.apache.solr.logging.MDCLoggingContext; +import org.apache.solr.logging.MDCSnapshot; +import org.apache.solr.request.SolrRequestInfo; +import org.apache.solr.util.RTimerTree; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * Servlet Filter to set up and tear down a various things that downstream code in solr relies on. + * It is expected that solr will fail to function as intended without the conditions initialized in + * this filter. Before adding anything to this filter ask yourself if a user could run without the + * feature you are adding (either with an alternative implementation or without it at all to reduce + * cpu/memory/dependencies). If it is not essential, it should have its own separate filter. Also, + * please include a comment indicating why the thing added is essential. + */ +public class EssentialSolrRequestFilter extends CoreContainerAwareHttpFilter { + + // Best to put constant here because solr is not supposed to be functional (or compile) + // without this filter. + public static final String CORE_CONTAINER_REQUEST_ATTRIBUTE = "org.apache.solr.CoreContainer"; Review Comment: minor: just do `CoreContainer.class.getName()` and inline it (no constant) -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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