MCP UI doesn't work because of StackOverflowError exception

[cylinder-y]

Required Information

• AEM Version, including Service Packs, Cumulative Fix Packs, etc: 6.4.2
• ACS AEM Commons Version: 3.19.1
• Reproducible on Latest? yes

Manage Controlled Process window doesn't work, we can't run Asset Url Ingestor and Asset Ingestor.

Steps to reproduce:

1. Open /etc/acs-commons/manage-controlled-processes.html 
2. Configure and run any process

Actual result:

1. We can't see archived processes
2. Triggered process doesn't displayed

Acceptance criteria:

1. We could see archived processes
2. We could see processes that are in progress

Something breaks it between the following commits : 875ce4e and a5d148d

Message from logs:

16.01.2019 16:20:44.372 ERROR [0:0:0:0:0:0:0:1 [1547644844116] GET /etc/acs-commons/manage-controlled-processes/jcr:content.list.json HTTP/1.1] com.day.cq.wcm.core.impl.WCMDebugFilter Error during include of SlingRequestPathInfo: path='/etc/acs-commons/manage-controlled-processes/jcr:content', selectorString='list', extension='json', suffix='null'
java.lang.StackOverflowError: null
at org.eclipse.jetty.util.BufferUtil.fill(BufferUtil.java:449) [org.apache.felix.http.jetty:4.0.2]
at org.eclipse.jetty.server.HttpOutput.write(HttpOutput.java:501) [org.apache.felix.http.jetty:4.0.2]
at java.io.ByteArrayOutputStream.writeTo(Unknown Source)
at org.eclipse.jetty.server.Iso88591HttpWriter.write(Iso88591HttpWriter.java:70) [org.apache.felix.http.jetty:4.0.2]
at org.eclipse.jetty.server.ResponseWriter.write(ResponseWriter.java:203) [org.apache.felix.http.jetty:4.0.2]
at java.io.PrintWriter.write(Unknown Source)
at org.apache.sling.engine.impl.log.RequestLoggerResponse$LoggerResponseWriter.write(RequestLoggerResponse.java:457) [org.apache.sling.engine:2.6.12]
at org.apache.sling.engine.impl.SlingHttpServletResponseImpl$1.write(SlingHttpServletResponseImpl.java:321) [org.apache.sling.engine:2.6.12]
at com.day.cq.rewriter.htmlparser.SAXWriter.characters(SAXWriter.java:186) [com.day.cq.cq-rewriter:5.11.24]
at com.day.cq.rewriter.processor.impl.SAXWriterFactory$1.characters(SAXWriterFactory.java:76) [com.day.cq.cq-rewriter:5.11.24]
at com.adobe.acs.commons.rewriter.AbstractTransformer.characters(AbstractTransformer.java:48) [com.adobe.acs.acs-aem-commons-bundle:3.19.1.SNAPSHOT]
at org.apache.cocoon.xml.sax.AbstractSAXPipe.characters(AbstractSAXPipe.java:126) [org.apache.cocoon.cocoon-xml:2.0.2]
at com.day.cq.wcm.contentsync.impl.rewriter.PathRewriterTransformer.characters(PathRewriterTransformer.java:154) [com.day.cq.wcm.cq-wcm-content-sync:5.11.2]
at org.apache.cocoon.xml.sax.AbstractSAXPipe.characters(AbstractSAXPipe.java:126) [org.apache.cocoon.cocoon-xml:2.0.2]
at org.apache.cocoon.xml.sax.AbstractSAXPipe.characters(AbstractSAXPipe.java:126) [org.apache.cocoon.cocoon-xml:2.0.2]
at org.apache.cocoon.xml.sax.AbstractSAXPipe.characters(AbstractSAXPipe.java:126) [org.apache.cocoon.cocoon-xml:2.0.2]
at org.apache.cocoon.xml.sax.AbstractSAXPipe.characters(AbstractSAXPipe.java:126) [org.apache.cocoon.cocoon-xml:2.0.2]
at com.day.cq.rewriter.htmlparser.DocumentHandlerToSAXAdapter.characters(DocumentHandlerToSAXAdapter.java:59) [com.day.cq.cq-rewriter:5.11.24]
at com.day.cq.rewriter.htmlparser.HtmlParser.update(HtmlParser.java:542) [com.day.cq.cq-rewriter:5.11.24]
at com.day.cq.rewriter.htmlparser.HtmlParser.write(HtmlParser.java:199) [com.day.cq.cq-rewriter:5.11.24]
at java.io.Writer.write(Unknown Source)
at java.io.PrintWriter.write(Unknown Source)
at com.google.gson.stream.JsonWriter.string(JsonWriter.java:591) [com.adobe.cq.gson:2.8.2]
at com.google.gson.stream.JsonWriter.writeDeferredName(JsonWriter.java:402) [com.adobe.cq.gson:2.8.2]
at com.google.gson.stream.JsonWriter.value(JsonWriter.java:480) [com.adobe.cq.gson:2.8.2]
at com.google.gson.internal.bind.TypeAdapters$3.write(TypeAdapters.java:147) [com.adobe.cq.gson:2.8.2]
at com.google.gson.internal.bind.TypeAdapters$3.write(TypeAdapters.java:133) [com.adobe.cq.gson:2.8.2]
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69) [com.adobe.cq.gson:2.8.2]
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:125) [com.adobe.cq.gson:2.8.2]

[badvision]

I wonder what it was doing? It seems it was serializing content to JSON but hit an unfortunate snag and the buffer overflowed. Does this happen on one machine specifically or any?

[badvision]

Also if you added any variables to any process classes (or subclasses) make sure you have declared them as transient, ESPECIALLY things like loggers.

[cylinder-y]

Hi @badvision,

I have debugged code, and I see that ControlledProcessManagerServlet fails when it serializing List of ProcessInstance's

Issue is reproducible on several machines.
We didn't add any code between the following commits : 875ce4e and a5d148d.
I was able to view list of archived and active items when I have uploaded 875ce4e changes to AEM.
But when I have uploaded a5d148d commit, MCP UI wasn't work

--Yaraslau

[cylinder-y]

Well there was non transient injected resource, see #1701

[badvision]

I'll also update the mcp servlet to not serialize resources as this could reoccur in the future.