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copied!<p>This is a great question! Here's a first cut.</p> <blockquote> <p>Be able to log at multiple levels (ex: debug, warning, etc.).</p> </blockquote> <p><a href="http://hackage.haskell.org/package/hslogger" rel="noreferrer">hslogger</a> is easily the most popular logging framework. </p> <blockquote> <p>Be able to collect and share metrics/statistics about the types of work the program is doing and how long that work is taking. Ideally, the collected metrics are available in a format that's compatible with commonly-used monitoring tools like Ganglia, or can be so munged.</p> </blockquote> <p>I'm not aware of any standardized reporting tools, however, extracting reports from <code>+RTS -s</code> streams (or via profiling output flags) has been something I've done in the past. </p> <pre><code>$ ./A +RTS -s 64,952 bytes allocated in the heap 1 MB total memory in use %GC time 0.0% (6.1% elapsed) Productivity 100.0% of total user, 0.0% of total elapsed </code></pre> <p>You can get this in machine-readable format too:</p> <pre><code>$ ./A +RTS -t --machine-readable [("bytes allocated", "64952") ,("num_GCs", "1") ,("average_bytes_used", "43784") ,("max_bytes_used", "43784") ,("num_byte_usage_samples", "1") ,("peak_megabytes_allocated", "1") ,("init_cpu_seconds", "0.00") ,("init_wall_seconds", "0.00") ,("mutator_cpu_seconds", "0.00") ,("mutator_wall_seconds", "0.00") ,("GC_cpu_seconds", "0.00") ,("GC_wall_seconds", "0.00") ] </code></pre> <p>Ideally you could attach to a running GHC runtime over a socket and look at these GC stats interactively, but currently that's not super easy (needs an FFI bindings to the "rts/Stats.h" interface). You can attach to a process using <a href="http://research.microsoft.com/en-us/projects/threadscope/" rel="noreferrer"><code>ThreadScope</code></a> and monitor GC and threading behavior.</p> <p>Similar flags are available for incremental, logged <a href="http://book.realworldhaskell.org/read/profiling-and-optimization.html#id677833" rel="noreferrer">time</a> and <a href="http://book.realworldhaskell.org/read/profiling-and-optimization.html#id678078" rel="noreferrer">space</a> profiling, which can be used for monitoring (e.g. these <a href="https://i.stack.imgur.com/Hryc5.png" rel="noreferrer">graphs</a> can be built incrementally).</p> <p><a href="http://hackage.haskell.org/package/hpc" rel="noreferrer"><code>hpc</code></a> collects a lot of statistics about program execution, via its <code>Tix</code> type, and people have <a href="http://hackage.haskell.org/package/hpc-strobe" rel="noreferrer">written tools</a> to log by time-slice what code is executing.</p> <blockquote> <p>Be configurable, ideally via a system that allows configured properties in running programs to be updated without restarting said programs.</p> </blockquote> <p>Several tools are available for this, you can do xmonad-style state reloading; or move up to code hotswapping via <a href="http://hackage.haskell.org/package/direct-plugins" rel="noreferrer"><code>plugins</code></a>* packages or <a href="http://hackage.haskell.org/package/hint" rel="noreferrer"><code>hint</code></a>. Some of these are more experimental than others.</p> <blockquote> <p>Reproducible deployments</p> </blockquote> <p>Galois recently released <a href="http://hackage.haskell.org/package/cabal-dev" rel="noreferrer"><code>cabal-dev</code></a>, which is a tool for doing reproducible builds (i.e. dependencies are scoped and controlled).</p>

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