Kristen Kozak created LOG4J2-2449:
-------------------------------------
Summary: ClassCastException with ContextDataInjector override,
SortedArrayStringMap, and Context Map Lookup
Key: LOG4J2-2449
URL: https://issues.apache.org/jira/browse/LOG4J2-2449
Project: Log4j 2
Issue Type: Bug
Components: Lookups, Plugins
Affects Versions: 2.11.1
Environment: Linux, Java 8
Reporter: Kristen Kozak
I am working on a library for inserting opencensus-java distributed tracing
data into Log4j LogEvents. I used a custom ContextDataInjector that reads the
current tracing data and inserts it into the context data. The context data
must be returned as a StringMap
([https://logging.apache.org/log4j/2.0/log4j-api/apidocs/org/apache/logging/log4j/util/SortedArrayStringMap.html#putValue(java.lang.String,%20java.lang.Object)|https://logging.apache.org/log4j/2.0/log4j-api/apidocs/org/apache/logging/log4j/util/SortedArrayStringMap.html#putValue(java.lang.String,%20java.lang.Object)]).]
), so I used a SortedArrayStringMap. I used
SortedArrayStringMap.putValue(String, Object) to insert objects for lazily
formatting tracing data, for example, an object with a toString() method that
formats a trace ID as lowercase base 16
([https://github.com/census-instrumentation/opencensus-java/blob/eabbc41366340e2833295894bc0f4d5dcddba1dd/contrib/log_correlation/log4j2/src/main/java/io/opencensus/contrib/logcorrelation/log4j2/ContextDataUtils.java#L151-L162]
). I noticed that multiple Log4j code paths call toString() on the values
when the String is finally needed. However, when I tried using a JsonLayout
and Context Map Lookup to put tracing data into a JSON structure, I got a
ClassCastException, because the values were only cast to Strings.
The original issue for the ClassCastException in opencensus-java is
[https://github.com/census-instrumentation/opencensus-java/issues/1436|https://github.com/census-instrumentation/opencensus-java/issues/1436.]
. The error is:
{{2018-09-14 20:59:52,690 main ERROR An exception occurred processing Appender
File java.lang.ClassCastException:
io.opencensus.contrib.logcorrelation.log4j2.ContextDataUtils$TraceIdToLowerBase16Formatter
cannot be cast to java.lang.String}}
{{ at
org.apache.logging.log4j.core.lookup.ContextMapLookup.lookup(ContextMapLookup.java:58)}}
{{ at
org.apache.logging.log4j.core.lookup.Interpolator.lookup(Interpolator.java:188)}}
{{ at
org.apache.logging.log4j.core.lookup.StrSubstitutor.resolveVariable(StrSubstitutor.java:1060)}}
{{ at
org.apache.logging.log4j.core.lookup.StrSubstitutor.substitute(StrSubstitutor.java:982)}}
{{ at
org.apache.logging.log4j.core.lookup.StrSubstitutor.substitute(StrSubstitutor.java:878)}}
{{ at
org.apache.logging.log4j.core.lookup.StrSubstitutor.replace(StrSubstitutor.java:433)}}
{{ at
org.apache.logging.log4j.core.layout.AbstractJacksonLayout.resolveAdditionalFields(AbstractJacksonLayout.java:292)}}
{{ at
org.apache.logging.log4j.core.layout.AbstractJacksonLayout.wrapLogEvent(AbstractJacksonLayout.java:274)}}
{{ at
org.apache.logging.log4j.core.layout.AbstractJacksonLayout.toSerializable(AbstractJacksonLayout.java:304)}}
{{ at
org.apache.logging.log4j.core.layout.JsonLayout.toSerializable(JsonLayout.java:291)}}
{{ at
org.apache.logging.log4j.core.layout.AbstractJacksonLayout.toSerializable(AbstractJacksonLayout.java:255)}}
{{ at
org.apache.logging.log4j.core.layout.JsonLayout.toSerializable(JsonLayout.java:68)}}
{{ at
org.apache.logging.log4j.core.layout.AbstractJacksonLayout.toSerializable(AbstractJacksonLayout.java:44)}}
{{ at
org.apache.logging.log4j.core.layout.AbstractStringLayout.toByteArray(AbstractStringLayout.java:304)}}
{{ at
org.apache.logging.log4j.core.layout.AbstractLayout.encode(AbstractLayout.java:210)}}
{{ at
org.apache.logging.log4j.core.layout.AbstractLayout.encode(AbstractLayout.java:37)}}
{{ at
org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.directEncodeEvent(AbstractOutputStreamAppender.java:177)}}
{{ at
org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.tryAppend(AbstractOutputStreamAppender.java:170)}}
{{ at
org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(AbstractOutputStreamAppender.java:161)}}
{{ at
org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:156)}}
{{ at
org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:129)}}
{{ at
org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:120)}}
{{ at
org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84)}}
{{ at
org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:464)}}
{{ at
org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:448)}}
{{ at
org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:431)}}
{{ at
org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:406)}}
{{ at
org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:63)}}
{{ at org.apache.logging.log4j.core.Logger.logMessage(Logger.java:146)}}
{{ at
org.apache.logging.log4j.spi.AbstractLogger.tryLogMessage(AbstractLogger.java:2170)}}
{{ at
org.apache.logging.log4j.spi.AbstractLogger.logMessageTrackRecursion(AbstractLogger.java:2125)}}
{{ at
org.apache.logging.log4j.spi.AbstractLogger.logMessageSafely(AbstractLogger.java:2108)}}
{{ at
org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:2002)}}
{{ at
org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1974)}}
{{ at
org.apache.logging.log4j.spi.AbstractLogger.warn(AbstractLogger.java:2624)}}
{{ at
io.opencensus.contrib.logcorrelation.log4j.demo.OpenCensusLog4jLogCorrelationDemo.doWork(OpenCensusLog4jLogCorrelationDemo.java:60)}}
{{ at
io.opencensus.contrib.logcorrelation.log4j.demo.OpenCensusLog4jLogCorrelationDemo.createSampledTrace(OpenCensusLog4jLogCorrelationDemo.java:50)}}
{{ at
io.opencensus.contrib.logcorrelation.log4j.demo.OpenCensusLog4jLogCorrelationDemo.main(OpenCensusLog4jLogCorrelationDemo.java:44)}}
I'm not sure whether this is a bug or StringMap is not meant to hold lazy
formatting objects.
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