Jack created LOGBACK-1287:
-----------------------------
Summary: Breaking change? Custom appender can not be assigned to
OutputStreamAppender
Key: LOGBACK-1287
URL: https://jira.qos.ch/browse/LOGBACK-1287
Project: logback
Issue Type: Bug
Components: logback-core
Affects Versions: 1.2.2, 1.2.1
Reporter: Jack
Assignee: Logback dev list
Priority: Blocker
With the release of logback 1.2.1 our custom appender does not work anymore and
Joran fails with the error below:
{noformat}
INFO in ch.qos.logback.core.joran.action.NestedComplexPropertyIA - Assuming
default type [ch.qos.logback.classic.encoder.PatternLayoutEncoder] for
[encoder] property
ERROR in ch.qos.logback.core.joran.util.PropertySetter@434f3900 - A
"com.example.logging.logback.extensions.DebugFileDumper" object is not
assignable to a "ch.qos.logback.core.OutputStreamAppender" variable. The class
"ch.qos.logback.core.OutputStreamAppender" was loaded by
[startJarLoader@2d95ebec] whereas object of type
"com.example.logging.logback.extensions.DebugFileDumper" was loaded by
[startJarLoader@2d95ebec].
{noformat}
I think the issue has been introduced by commit:
[https://github.com/qos-ch/logback/commit/d3d704c12e7b8e6503187744ac2200c244088c63]
which makes {{LayoutWrappingEncoder}} assume that it is always owned by an
OutputstreamAppender:
[https://github.com/qos-ch/logback/commit/d3d704c12e7b8e6503187744ac2200c244088c63#diff-3b83fcf26e3af7434aec2f08b2461be6R35])
However our custom Appender extends AppenderBase and uses composition to use
two FileAppenders internally. The encoder of one of those FileAppenders can be
configured in logback.xml while the other has a fixed encoding. Basically the
Java code delegates setEncoder() to a FileAppender. Code roughly looks like:
{code:java}
public class DebugFileDumper extends AppenderBase<ILoggingEvent> {
// writes a debug-timestamp.log from a cyclic buffer
private FileAppender<ILoggingEvent> debugBufferFileDumper;
// writes a debug-timestamp.meta containing corresponding meta infos stored
in MDC in an easy to parse key=value format for further processing by external
tools.
private FileAppender<ILoggingEvent> mdcFileDumper;
// ... additional properties
public DebugFileDumper() {
mdcFileDumper.setEncoder(new MdcOnlyEncoder());
}
public void setEncoder(Encoder<ILoggingEvent> encoder) {
debugBufferFileDumper.setEncoder(encoder);
}
public Encoder<ILoggingEvent> getEncoder() {
return debugBufferFileDumper.getEncoder();
}
// .. additional methods
}
{code}
With configuration like:
{code:xml}
<appender name="debugDumper"
class="com.example.logging.logback.extensions.DebugFileDumper">
<discriminator class="ch.qos.logback.classic.sift.MDCBasedDiscriminator">
<key>SESSION_ID</key>
<defaultValue>server</defaultValue>
</discriminator>
<evaluator class="ch.qos.logback.classic.boolex.OnErrorEvaluator" />
<cyclicBufferTracker class="ch.qos.logback.core.spi.CyclicBufferTracker">
<bufferSize>128</bufferSize>
<maxComponents>128</maxComponents>
<timeout>1800000</timeout>
</cyclicBufferTracker>
<folder>${logback.logs}/dumps</folder>
<encoder>
<pattern>[SOME PATTERN FOR DEBUG LOG FILE]</pattern>
</encoder>
</appender>
{code}
I think our implementation strategy is valid and the assumption made in the
mentioned commit, that an encoder configuration block always belongs to an
OutputStreamAppender, is a bit too strict. Basically composition/delegation
pattern hasn't been taken into account.
Currently we would need to rewrite our appender in order to make it work with
Logback 1.2.1+, so I thought I should let you know about that implicit breaking
change. Maybe it was not intended on your side and you can relax the assumption
to fix our issue.
--
This message was sent by Atlassian JIRA
(v7.3.1#73012)
_______________________________________________
logback-dev mailing list
logback-dev@qos.ch
http://mailman.qos.ch/mailman/listinfo/logback-dev
