[LOGBACK-540] Filtering out selected stack trace frames

[nurkiewicz]

This PR adds capability of filtering selected stack frames if it's decided that they are irrelevant. You can use it by defining patterns that, if are contained within stack line, suppress displaying it:

<property name="ignored" value="
  AbstractPlainSocketImpl,
  sun.net.www.http.HttpClient,
  sun.net.www.protocol.http.HttpURLConnection.connect
"/>

<!-- and later: -->
<pattern>%d{HH:mm:ss.SSS} | %m%n%rEx{full,${ignored}}</pattern>

<!-- or directly: -->
<pattern>%d{HH:mm:ss.SSS} | %m%n%rEx{full,AbstractPlainSocketImpl,
  sun.net.www.http.HttpClient,
  sun.net.www.protocol.http.HttpURLConnection.connect}</pattern>

If some stack lines were ignored while showing stack trace, small indicator tells how many lines were skipped:

java.net.UnknownHostException: sopsdsfjdskjfskjfdskj.com
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_31] [1 skipped]
    at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_31]
    at java.net.Socket.connect(Socket.java:538) ~[na:1.8.0_31]
    at sun.net.NetworkClient.doConnect(NetworkClient.java:180) ~[na:1.8.0_31]
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1168) ~[na:1.8.0_31] [5 skipped]
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1104) ~[na:1.8.0_31]
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:998) ~[na:1.8.0_31]
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1512) ~[na:1.8.0_31] [1 skipped]
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1440) ~[na:1.8.0_31]
    at Foo.main(Foo.java:12) ~[test-classes/:na]

Issues is discussed in [LOGBACK-540] and further discussed here: Filtering irrelevant stack trace lines in logs

[tony19]

Thanks for the contribution, @nurkiewicz. Please add a comment here with release notes (see rule P7 of CONTRIBUTING.md).

[nurkiewicz]

Thanks @tony19 for review, fixed. Release notes comment:

<p>Irrelevant or internal stack trace lines can now be omitted. Pull request provided by
    Tomasz Nurkiewicz (<a href="http://jira.qos.ch/browse/LOGBACK-540">LOGBACK-540</a>).
</p>

[tony19]

@nurkiewicz, please also update the docs to indicate this new feature. Thanks

[nurkiewicz]

Thanks, I'm about to leave for vacation for two weeks, will do a separate PR with documentation changes after that.

[DanielJonesEB]

@nurkiewicz Did you get a chance to raise the documentation PR? I had a quick look for it, but couldn't find it. I'm having difficulty getting the cool new functionality to work.

[nurkiewicz]

No, sorry. I will document this feature within next few days. In the meantime feel free to reach me directly, I'll try to help.

[DanielJonesEB]

@nurkiewicz Ah, turns out it was a PEBKAC issue! All working splendidly now. Thanks very much, this feature is helping me mitigate a production log velocity issue.

[redron]

Hi,
I am trying to combine this feature with replace statement:
%replace(%ex{full, org.springframework}){'\n', '|||'}%nopex
and it seems that there is no support of such an expressions yet. I wasn't able to find any workarounds so far.
Can you please advice on it?
Thanks.

[ndjensen]

Is this going to be documented in the layouts page of the guide?

Also it doesn't seem to work well when using logback's colors for patterns.