NAME
    log-defer-viz - command-line utility for rendering log messages created
    by Log::Defer

DESCRIPTION
    Log::Defer is a module that creates structured logs. The Log::Defer
    documentation explains structured logging and its benefits over ad-hoc
    logging.

    This module installs a command-line script that parses structured logs
    created by Log::Defer and displays them in a readable manner.

INPUT METHODS
        $ cat file.log | log-defer-viz
        $ log-defer-viz < file.log
        $ log-defer-viz file.log
        $ log-defer-viz -f file.log # continuously tail file
        $ log-defer-viz file.log file2.log
        $ log-defer-viz archived.log.gz more_logs.bz2

INPUT FORMAT
        $ log-defer-viz --input-format=json  ## default is newline separated JSON
        $ log-defer-viz --input-format=sereal  ## Sereal::Decoder (not impl)
        $ log-defer-viz --input-format=messagepack  ## Data::MessagePack (not impl)
        $ log-defer-viz --input-format=storable  ## Storable (not impl)

    Note: The only input format currently implemented is newline-separated
    JSON.

LOG MESSAGES
        $ log-defer-viz  ## by default shows error, warn, and info logs
        $ log-defer-viz -v  ## verbose mode (adds debug logs and more)
        $ log-defer-viz --debug  ## show debug logs
        $ log-defer-viz --quiet  ## only errors and warnings
        $ log-defer-viz --verbosity 25  ## numeric verbosity threshold
        $ log-defer-viz --nowarn  ## muffle warn logs (so show error and info)
        $ log-defer-viz --nologs  ## don't show log section
        $ log-defer-viz --nocolour  ## turn off terminal colours
        $ log-defer-viz --preserve-newlines # dont indent log messages to align with log-defer-viz output

TIMERS
        $ log-defer-viz --timer-columns 80  ## width of timer chart
        $ log-defer-viz --since-now  ## show relative to now times
                                     ##   like "34 minutes ago"
        $ log-defer-viz --notimers  ## don't show timer chart
        $ log-defer-viz --tz UTC  ## show times in UTC, not local

DATA SECTION
    Applications can optionally log information in a "data" hash. This
    information is mostly designed to be extracted by programs so
    "log-defer-viz" doesn't display it by default. Use the "--data" option
    to display it anyway, and the "--data-format" option to choose the
    format to display it in. The available formats are "pretty-json",
    "json", "yaml", and "dumper".

        $ log-defer-viz --data  ## show data section. default is pretty-json
        $ log-defer-viz --data-format=json  ## compact, not pretty
        $ log-defer-viz --data-format=dumper  ## Data::Dumper
        $ log-defer-viz --data-only  ## only show data

COUNT
    The count parameter provides a method to count the number of times a
    specific key/value appears in the data section of the log file.

        $ log-defer-viz --data --count ip_address ## Display how many log lines for each ip address
        $ log-defer-viz --data --count ip_address --count user_id ## Display how many log lines for each ip address and each user_id

MISC
        $ log-defer-viz --help  ## the text you're reading now
        $ log-defer-viz --grep '$_->{data}'  ## grep for records that have a data section.
                                             ## $_ is the entire Log::Defer entry.
        $ log-defer-viz --map '$_->{data}->{username}'  ## Extract username from data

GREPING
    As shown above, there is a "--grep" command-line option. This lets you
    filter log messages using arbitrary perl code. If the expression returns
    true, the log message is processed and displayed as usual.

    Being able to do this easily is an important advantage of structured
    logs. With unstructured logs it is often difficult to extract all of the
    information related to a request and nothing else.

    For example, here is how to grep for all requests that took longer than
    500 milliseconds:

        $ log-defer-viz --grep '$_->{end} > .5' server.log

    Depending on your underlying storage format, it may be meaningful to
    grep before passing to "log-defer-viz". Currently the only supported
    storage format is newline-separated JSON which *is* designed to be
    pre-grepable. If your search string appears anywhere in the object, the
    entire log message will be displayed:

        $ grep 10.9.1.2 app.log | log-defer-viz

    The final and most error-prone way to grep Log::Defer logs is to grep
    the unstructured output of "log-defer-viz" (not recommended):

        $ log-defer-viz app.log | grep 10.9.1.2

MAPPING
    Similar to "--grep", there is also a "--map" command-line option. If
    this option is passed in, the only output is whatever your "--map"
    expression returns.

    For example, if you are putting the PID into the data section with
    "$log->data->{pid} = $$", then you can extract the PID like so:

        $ log-defer-viz --map '$_->{data}->{pid}' < app.log
        9765
        9768
        9771

    Join together fields with a pipe:

        $ log-defer-viz --map 'join "|", $_->{data}{pid}, $_->{start}' < app.log
        9765|1362166673.95104
        9768|1362168038.85611
        9771|1362169482.39561

    Make dates readable ("localtime" in scalar context makes a timestamp
    readable):

        $ log-defer-viz --map 'join "|", $_->{data}{pid}, "".localtime($_->{start})' < app.log
        9765|Fri Mar  1 14:37:53 2013
        9768|Fri Mar  1 15:00:38 2013
        9771|Fri Mar  1 15:24:42 2013

    As with "--grep", you have access to any perl functions you might need.
    Also, you can combine "--map" and "--grep". The grep filtering will be
    applied before the mapping.

    For example, here is how to do a "pass-through grep" where the output is
    another valid JSON-encoded Log::Defer file:

        $ export USER=jimmy
        $ log-defer-viz -g "_->{data}{username} eq '$USER'" \
                        -m "encode_json _"                  \
                        < requests.log                      \
                        > jimmys-requests.log

    Note that the above also demonstrates two shortcut features: First, the
    "-g" and "-m" switches are abbreviations for "--grep" and "--map"
    respectively. Second, in grep and map expressions the "_" function is an
    abbreviation for $_. Although this is one character shorter, the main
    reason this exists is so that you can use double-quoted strings without
    having to worry about escaping "$" characters from your shell.

SEE ALSO
    Log::Defer

    Log::Defer::Viz github repo <https://github.com/hoytech/Log-Defer-Viz>

    The "log-defer-viz" is also useful for visualising logs created by
    Michael Pucyk's LogDefer Python module
    <https://github.com/mikep/LogDefer> (since it outputs the same format)

AUTHOR
    Doug Hoyte, "<doug@hcsw.org>"

CONTRIBUTORS
    Matt Phillips, "<mattp@cpan.org>"

COPYRIGHT & LICENSE
    Copyright 2013-2014 Doug Hoyte and contributors.

    This module is licensed under the same terms as perl itself.

