vy commented on code in PR #3586:
URL: https://github.com/apache/logging-log4j2/pull/3586#discussion_r2046314420
##########
log4j-layout-template-json/src/main/resources/GcpLayout.json:
##########
@@ -49,25 +55,15 @@
"key": "span_id"
},
"logging.googleapis.com/trace_sampled": true,
- "_exception": {
- "class": {
- "$resolver": "exception",
- "field": "className"
- },
- "message": {
- "$resolver": "exception",
- "field": "message"
- },
- "stackTrace": {
- "$resolver": "pattern",
- "pattern": "%xEx"
- }
+ "exception": {
+ "$resolver": "pattern",
+ "pattern": "%xEx"
},
Review Comment:
I've figured what is going on. Guess what does `new
ActiveMQIllegalStateException().printStackTrace()` produce? `%xEx` output? Or
the JTL output? :wink: The JTL output. `Throwable::printStackTrace` (used by
both JTL and PL's `%ex`, but not `%xEx`) has the following logic:
```java
private void printStackTrace(PrintStreamOrWriter s) {
// ...
synchronized(s.lock()) {
s.println(this);
StackTraceElement[] trace = getOurStackTrace();
for (StackTraceElement traceElement : trace)
```
That is, first `ActiveMQIllegalStateException::toString` will be invoked
(due to `s.println(this)`) and then its stack trace will be dumped. But
`ActiveMQIllegalStateException` has a `toString()` override inherited from its
parent `ActiveMQException`:
```java
@Override
public String toString() {
return this.getClass().getSimpleName() + "[errorType=" + type + "
message=" + getMessage() + "]";
}
```
As a demonstration, consider the following Java program:
```java
ActiveMQIllegalStateException exception = new
ActiveMQIllegalStateException();
exception.printStackTrace();
System.out.println("---");
System.out.println(JsonTemplateLayout
.newBuilder()
.setConfiguration(new DefaultConfiguration())
.setEventTemplate(("{" +
"'jtl': {'$resolver': 'exception', 'field': 'stackTrace',
'stackTrace': {'stringified': true}}, " +
"'pl': {'$resolver': 'pattern', 'pattern': '%xEx'}" +
"}").replaceAll("'", "\""))
.build()
.toSerializable(Log4jLogEvent
.newBuilder()
.setMessage(new SimpleMessage("AMQ212028: error starting
server locator"))
.setThrown(exception)
.build()));
```
This produces the following output:
```
ActiveMQIllegalStateException[errorType=ILLEGAL_STATE message=]
at ci.yazi.volkan.Log4jPull3586Test.main(Log4jPull3586Test.java:11)
---
{"jtl":"ActiveMQIllegalStateException[errorType=ILLEGAL_STATE
message=]\n\tat
ci.yazi.volkan.Log4jPull3586Test.main(Log4jPull3586Test.java:11)\n","pl":"org.apache.activemq.artemis.api.core.ActiveMQIllegalStateException:
\n\tat ci.yazi.volkan.Log4jPull3586Test.main(Log4jPull3586Test.java:11)
[classes/:?]\n"}
```
In conclusion, JTL's `exception` resolver and PL's `%ex` delegates to
`Throwable::printStackTrace`, and, AFAICT, this is the correct behavior. OTOH,
PL's `%xEx` rolls out its own stack trace dumper, which _misses_ the
`s.println(this)` that `Throwable::printStackTrace` has (I'd qualify this as a
bug!), and hence, emits an output which directly starts with the stack trace
dump.
In the light of this, I'd prefer keeping JTL's exception resolver in
`GcpLayout.json` instead of relying on the (buggy?) behavior of PL's `%xEx`.
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