Bitten Build Output Processing
An important characteristic of any continuous integration system is how it processes the output of a build. Output can be provided as text messages written to the console by the build tool and the commands it executes, but also as files created by the build process. This page discusses the former.
Examples of Build Output
The format of textual messages is specific to the build tool in use. Following are a couple of examples of output by build tools such as Make and Ant.
Make
For example, the output of a Make-driven build of a C project (in this case, vim) might look like this:
make[1]: Entering directory `/var/tmp/portage/vim-6.3.075/work/vim63/src'
gcc -c -I. -Iproto -DHAVE_CONFIG_H -O2 -mcpu=i686 -fomit-frame-pointer -pipe -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm -I/usr/lib/perl5/5.8.6/i686-linux/CORE -I/usr/include/python2.3 -pthread -I/usr/lib/ruby/1.8/i686-linux -o objects/buffer.o buffer.c
gcc -c -I. -Iproto -DHAVE_CONFIG_H -O2 -mcpu=i686 -fomit-frame-pointer -pipe -D_LARGEFILE_SOURCE -
...
gcc -c -I. -Iproto -DHAVE_CONFIG_H -O2 -mcpu=i686 -fomit-frame-pointer -pipe -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm -I/usr/lib/perl5/5.8.6/i686-linux/CORE -I/usr/include/python2.3 -pthread -I/usr/lib/ruby/1.8/i686-linux -o objects/if_python.o if_python.c
In file included from /usr/include/python2.3/Python.h:8,
from if_python.c:43:
/usr/include/python2.3/pyconfig.h:856:1: warning: "_POSIX_C_SOURCE" redefined
In file included from /usr/include/stdio.h:28,
from os_unix.h:21,
from vim.h:195,
from if_python.c:20:
/usr/include/features.h:190:1: warning: this is the location of the previous definition
...
gcc -rdynamic -Wl,-export-dynamic -rdynamic -L/usr/local/lib -o vim objects/buffer.o objects/charset.o objects/diff.o objects/digraph.o objects/edit.o objects/eval.o objects/ex_cmds.o objects/ex_cmds2.o objects/ex_docmd.o objects/ex_eval.o objects/ex_getln.o objects/fileio.o objects/fold.o objects/getchar.o objects/if_cscope.o objects/if_xcmdsrv.o objects/main.o objects/mark.o objects/memfile.o objects/memline.o objects/menu.o objects/message.o objects/misc1.o objects/misc2.o objects/move.o objects/mbyte.o objects/normal.o objects/ops.o objects/option.o objects/os_unix.o objects/pathdef.o objects/quickfix.o objects/regexp.o objects/screen.o objects/search.o objects/syntax.o objects/tag.o objects/term.o objects/ui.o objects/undo.o objects/window.o objects/if_perl.o objects/if_perlsfio.o objects/if_python.o objects/py_config.o objects/if_ruby.o objects/netbeans.o objects/version.o -lnsl -lncurses -lgpm -ldl -rdynamic -L/usr/local/lib /usr/lib/perl5/5.8.6/i686-linux/auto/DynaLoader/DynaLoader.a -L/usr/lib/perl5/5.8.6/i686-linux/CORE -lperl -lpthread -lnsl -ldl -lm -lcrypt -lutil -lc -L/usr/lib/python2.3/config -lpython2.3 -lpthread -ldl -lutil -lm -Xlinker -export-dynamic -Wl,-R -Wl,/usr/lib -L/usr/lib -L/usr/lib -lruby18 -lpthread -ldl -lcrypt -lm
/usr/lib/python2.3/config/libpython2.3.a(posixmodule.o)(.text+0x4259): In function `posix_tempnam':
: warning: the use of `tempnam' is dangerous, better use `mkstemp'
/usr/lib/python2.3/config/libpython2.3.a(posixmodule.o)(.text+0x432e): In function `posix_tmpnam':
: warning: the use of `tmpnam_r' is dangerous, better use `mkstemp'
This text is the output from make, the compiler and the linker. Most of the output shows what the build is currently doing, but some of the messages are warnings (commonly written to the standard error stream). Not shown here are errors that completely terminate the build.
Ant
For a Java project built with Ant, the output is quite different. First, the output from each target is clearly separated from the previous target. Also, the output of every task is prefixed with the task name in square brackets.
prepare:
[mkdir] Created dir: /usr/local/src/commons-collections-3.1/build
compile:
[mkdir] Created dir: /usr/local/src/commons-collections-3.1/build/classes
[javac] Compiling 267 source files to /usr/local/src/commons-collections-3.1/build/classes
[javac] /usr/local/src/commons-collections-3.1/src/java/org/apache/commons/collections/CursorableLinkedList.java:1197: warning: org.apache.commons.collections.CursorableLinkedList in org.apache.commons.collections has been deprecated
[javac] class CursorableSubList extends CursorableLinkedList implements List {
[javac] ^
[javac] /usr/local/src/commons-collections-3.1/src/java/org/apache/commons/collections/CursorableLinkedList.java:1201: warning: org.apache.commons.collections.CursorableLinkedList in org.apache.commons.collections has been deprecated
[javac] CursorableSubList(CursorableLinkedList list, int from, int to) {
[javac] ^
...
[javac] 9 warnings
jar:
[mkdir] Created dir: /usr/local/src/commons-collections-3.1/build/classes/META-INF
[copy] Copying 1 file to /usr/local/src/commons-collections-3.1/build/classes/META-INF
[copy] Copying 1 file to /usr/local/src/commons-collections-3.1/build/classes/META-INF
[mkdir] Created dir: /usr/local/src/commons-collections-3.1/build/conf
[copy] Copying 1 file to /usr/local/src/commons-collections-3.1/build/conf
[jar] Building jar: /usr/local/src/commons-collections-3.1/build/commons-collections-3.1.jar
BUILD SUCCESSFUL
Total time: 9 seconds
(this is from the build of Apache Commons Collections)
The output here also includes informational as well as status messages. Error messages are written to the standard error stream, but warnings go to standard output. The output from Ant can also be modified in a couple of ways: for example, there's an -emacs option for generating the output in a less verbose format that is better handled by Emacs. Also, a custom logger can be specified using the -logger option, which can be used to output messages in a completely different format. For exampe, Ant includes an XmlLogger class that logs the output in XML:
<?xml version="1.0" encoding="UTF-8"?> <?xml-stylesheet type="text/xsl" href="log.xsl"?> <build time="1 second"> ... <task location="/usr/local/src/commons-collections-3.1/build.xml:394: " name="patternset" time="0 seconds"></task> <target name="clean" time="0 seconds"> <task location="/usr/local/src/commons-collections-3.1/build.xml:95: " name="delete" time="0 seconds"> <message priority="info"><![CDATA[Deleting directory /usr/local/src/commons-collections-3.1/build]]></message> </task> </target> </build>
Separating Output and Error Streams
Without further knowledge about the build tool in use, the only option is to treat the output as a generic list of lines that go either to the standard output or the standard error stream. Messages on the error stream can be highlighted when presented, under the assumption that they represent warnings or errors.
Parsing the Output
Richer handling of output can be provided if the output of the tool is known and consistent. This applies for example to Ant output in XML format. Based on an XML-formatted build log, Bitten could break up the output into targets, tasks and messages. Messages are always qualified with a “priority” in the XML log, which is one of “debug”, “verbose”, “info”, “warning” or “error”. This allows more fine grained handling of build messages than just differentiating between messages written to the output or error streams.
Note: The XmlLogger option is employed by the CI system CruiseControl to get the build output in a way that can later be transformed into a human-readable HTML rendering using XSLT.
But parsing the messages themselves can also be helpful, even for builds with output not structured as XML. Many tools use formatting conventions such as prepending messages with labels such as warning:, which can be used adjust the level/priority of the message. Also, many messages related to problems in files are formatted in a consistent way, commonly known to be compatible with Emacs and other tools, for example:
filename:line:column severity: message
Microsoft tools and some others use a different format, but many can be supported using regular expression matching against the log message.
The filename and line number information extracted this way can be used to link directly from the build log to the corresponding part of the file in the Trac repository browser.
