Fixes blank lines & buffer lag, add alternative formatting options

README.md

@@ -4,28 +4,96 @@ A simple [supervisord](http://supervisord.org/) event listener to relay
 process output to supervisor's stdout.
 
 This is useful in situations where the output will be collected and set to
-external logging framework, such as Heroku.
+external logging framework, such as Heroku, Docker, Kubernetes, or AWS ECS/Fargate.
 
 ## Installation
 
 Just install via pip or add to your requirements.txt:
 
     pip install supervisor-stdout
 
+## Installation for Docker
+
+If you're building a Docker container and you find Linux distro has outdated `supervisor` packages,
+that the pip `supervisor-stdout` package is very outdated, that `venv` makes `pip` use difficult,
+and that `pipx install` doesn't work because `supervisord` can't resolve the handler name,
+then you might like to forceably install the latest version from github as follows.
+
+```
+RUN pip install git+https://github.com/Supervisor/supervisor.git --break-system-packages && \
+    pip install git+https://github.com/coderanger/supervisor-stdout.git --break-system-packages
+```
+
+If you find that the 'coderanger/supervisor-stdout' repo hasn't merged this pull request,
+then can use this person's fork as follows.
+
+```
+RUN pip install git+https://github.com/Supervisor/supervisor.git --break-system-packages && \
+    pip install git+git+https://github.com/whereisaaron/supervisor-stdout.git --break-system-packages
+```
+
 ## Usage
 
-An example supervisord.conf:
+An example `supervisord.conf`:
 
     [supervisord]
     nodaemon = true
+    logfile=/dev/null
+    logfile_maxbytes=0
 
     [program:web]
     command = ...
     stdout_events_enabled = true
     stderr_events_enabled = true
+    stdout_logfile = NONE
+    stderr_logfile = NONE
 
     [eventlistener:stdout]
     command = supervisor_stdout
     buffer_size = 100
     events = PROCESS_LOG
     result_handler = supervisor_stdout:event_handler
+    stdout_logfile = NONE
+    stderr_logfile = NONE
+
+## Advanced Usage
+
+The default `event_handler` prefixes log lines with the process name and channel,
+e.g. `apache stderr | <your log line here>`
+
+If you would prefer simpler prefix, or no prefix at all, you can use the alternative
+hander names `process_event_handler` and `plain_event_handler`.
+
+`process_event_handler` prefixes logs line with just the process name, e.g. `apache | <your log line here>`.
+
+    [eventlistener:stdout]
+    command = supervisor_stdout
+    buffer_size = 100
+    events = PROCESS_LOG
+    result_handler = supervisor_stdout:process_event_handler
+    stdout_logfile = NONE
+    stderr_logfile = NONE
+
+`plain_event_handler` passed the log line unaltered, without any prefix, e.g. `<your log line here>`.
+
+    [eventlistener:stdout]
+    command = supervisor_stdout
+    buffer_size = 100
+    events = PROCESS_LOG
+    result_handler = supervisor_stdout:plain_event_handler
+    stdout_logfile = NONE
+    stderr_logfile = NONE
+
+## Change Log
+
+Forked from @coderanger's excellent [`supervisor-stdout`](https://github.com/coderanger/supervisor-stdout/) plug-in at the following commit.
+
+https://github.com/coderanger/supervisor-stdout/commit/973ba19967cdaf46d9c1634d1675fc65b9574f6e
+
+Changes:
+- Eliminated the blank line emitted after every log line
+- Eliminated the block buffering lag that delayed log lines being relayed to supervisor's stdout
+- Added alternative handler names that enable relaying log lines unaltered, or with only the process name.
+
+Breaking Changes:
+- None, remain compatible with original forked version

supervisor_stdout.py

@@ -18,12 +18,21 @@ def main():
         write_stdout('RESULT %s\n%s'%(len(data.encode("utf-8")), data)) # transition from READY to ACKNOWLEDGED
 
 def event_handler(event, response):
+    formatted_event_handler(event, response, '{0} {1} | ')
+
+def process_event_handler(event, response):
+    formatted_event_handler(event, response, '{0} | ')
+
+def plain_event_handler(event, response):
+    formatted_event_handler(event, response, '')
+
+def formatted_event_handler(event, response, format):
     response = response.decode()
     line, data = response.split('\n', 1)
     headers = dict([ x.split(':') for x in line.split() ])
-    lines = data.split('\n')
-    prefix = '%s %s | '%(headers['processname'], headers['channel'])
-    print('\n'.join([ prefix + l for l in lines ]))
+    lines = data.splitlines()
+    prefix = format.format(headers['processname'], headers['channel'])
+    print('\n'.join([ prefix + l for l in lines ]), flush=True)
 
 if __name__ == '__main__':
     main()