Format multi-line log entries

When tracebacks are sent to a log file or stderr using the default
configurations, it can be difficult to work with those logs.  Using
"grep" to search for messages or time periods will typically only
produce a single line of the error.

Further, on a busy system the error may be interleaved with other
log lines making extraction even harder.

To address both of these issues, add a formatter which formats every
line of a multi-line log message using the same format specifier.
This is quite readable when streaming or viewing a standard log file,
and it should cause all log lines to automatically appear in
ELK/splunk setups since they will all have the same message format.
(Though, those setups are probably better served with a native
logging configuration that sends the entire record together.)

It may be somewhat difficult if a multi-line log entry is recorded
on a busy system with multiple threads.  However, some judicious
grepping should help with that since all related lineswill have the
exact same timestamp (including microseconds).  Advanced users/devs
could specify a logging format with the thread id if necessary, though
I don't think we should do that by default.

Since this is implemented as a standard logging formatter, it can
be opted-out via logging config files.  This enables it by default,
which I think is reasonable for new users, but if we decide that we
would prefer opt-in, that is a simple change.

Sample output (from Zuul):

2021-01-29 10:59:02,004 DEBUG zuul.Scheduler: Run handler awake
2021-01-29 10:59:02,004 ERROR zuul.Scheduler: Exception in run handler:
2021-01-29 10:59:02,004 ERROR zuul.Scheduler:   Traceback (most recent call last):
2021-01-29 10:59:02,004 ERROR zuul.Scheduler:     File "/home/corvus/git/zuul/zuul/zuul/scheduler.py", line 1254, in run
2021-01-29 10:59:02,004 ERROR zuul.Scheduler:       raise Exception("Test")
2021-01-29 10:59:02,004 ERROR zuul.Scheduler:   Exception: Test
2021-01-29 10:59:02,005 DEBUG zuul.Scheduler: Run handler sleeping

Change-Id: I6d7e7e7a9e19d46a744f9ffac8d532fc6b4bba01
changes/40/773540/5
James E. Blair 2 years ago
parent 12d128c170
commit 6fc61ab201

@ -25,6 +25,7 @@ _DEFAULT_SERVER_LOGGING_CONFIG = {
'version': 1,
'formatters': {
'simple': {
'class': 'nodepool.logconfig.MultiLineFormatter',
'format': '%(asctime)s %(levelname)s %(name)s: %(message)s'
},
},
@ -89,6 +90,24 @@ def load_config(filename: str):
return FileLoggingConfig(filename)
class MultiLineFormatter(logging.Formatter):
def format(self, record):
rec = super().format(record)
ret = []
# Save the existing message and re-use this record object to
# format each line.
saved_msg = record.message
for i, line in enumerate(rec.split('\n')):
if i:
record.message = ' ' + line
ret.append(self.formatMessage(record))
else:
ret.append(line)
# Restore the message
record.message = saved_msg
return '\n'.join(ret)
class LoggingConfig(object, metaclass=abc.ABCMeta):
@abc.abstractmethod

@ -0,0 +1,5 @@
---
features:
- |
Multi-line log messages (such as tracebacks from image builds) are now
prefixed in the same manner as single-line messages.
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