Example of ghc-mod's auto command being slow

README.md

stack exec ghc-mod -- auto app/Main.hs 24 12 starts consuming gigs of memory and seems to hang.

Main.hs

{-# LANGUAGE OverloadedStrings #-}

module AFoo where

import qualified Database.Bloodhound as B
import Network.HTTP.Client (defaultManagerSettings)
import Control.Monad
import Control.Lens ((^.), (^?), (^..))
import Data.Aeson
import Data.Aeson.Lens
import Network.Wreq
import Data.Aeson.Encode.Pretty
import qualified Data.ByteString.Lazy.Char8 as BSLC
import qualified Data.Text as T
import qualified Data.Vector as V

server = B.Server "http://localhost:9200"
index = B.IndexName "test"
mapping = B.MappingName "test"
indexSettings = B.IndexSettings (B.ShardCount 100) (B.ReplicaCount 0)

es = es' True
es' verbose action = do
  reply <- _ defaultManagerSettings server action
  when (verbose && not (B.isSuccess reply)) $ case decode (reply ^. responseBody) :: Maybe Value of
    Nothing -> print $ reply ^. responseBody
    Just v -> BSLC.putStrLn . encodePretty $ v
  return reply

mkBulk docId = B.BulkCreate index mapping (B.DocId docId) (object [("hi", "there")])

main = do
  es' False $ B.deleteIndex index
  es $ B.createIndex indexSettings index
  reply <- es $ B.bulk (V.fromList $ map (mkBulk . T.pack . show) [1 .. 130])
  mapM_ print $ filter (/= 201) $ reply ^.. responseBody . key "items" . values . key "create" . key "status" . _Number
  es $ B.refreshIndex index
  searchReply <- es $ B.searchByIndex index (B.mkSearch (Just $ B.MatchAllQuery Nothing) Nothing)
  print (searchReply ^? responseBody . key "hits" . key "total")

slow-ghc-mod-auto.cabal

name:                slow-ghc-mod-auto
version:             0.1.0.0
synopsis:            Initial project template from stack
description:         Please see README.md
homepage:            https://github.com/githubuser/slow-ghc-mod-auto#readme
license:             BSD3
license-file:        LICENSE
author:              Author name here
maintainer:          [email protected]
copyright:           2016 Author name here
category:            Web
build-type:          Simple
-- extra-source-files:
cabal-version:       >=1.10

library
  hs-source-dirs:      src
  exposed-modules:     Lib
  build-depends:       base >= 4.7 && < 5
  default-language:    Haskell2010

executable slow-ghc-mod-auto-exe
  hs-source-dirs:      app
  main-is:             Main.hs
  ghc-options:         -threaded -rtsopts -with-rtsopts=-N
  build-depends:       base
                     , slow-ghc-mod-auto
                     , bytestring
                     , lens-aeson
                     , bloodhound
                     , vector
                     , wreq
                     , lens
                     , aeson
                     , text
                     , http-client
                     , aeson-pretty
  default-language:    Haskell2010

test-suite slow-ghc-mod-auto-test
  type:                exitcode-stdio-1.0
  hs-source-dirs:      test
  main-is:             Spec.hs
  build-depends:       base
                     , slow-ghc-mod-auto
  ghc-options:         -threaded -rtsopts -with-rtsopts=-N
  default-language:    Haskell2010

source-repository head
  type:     git
  location: https://github.com/githubuser/slow-ghc-mod-auto

stack.yaml

# This file was automatically generated by 'stack init'
#
# Some commonly used options have been documented as comments in this file.
# For advanced use and comprehensive documentation of the format, please see:
# http://docs.haskellstack.org/en/stable/yaml_configuration/

# Resolver to choose a 'specific' stackage snapshot or a compiler version.
# A snapshot resolver dictates the compiler version and the set of packages
# to be used for project dependencies. For example:
#
# resolver: lts-3.5
# resolver: nightly-2015-09-21
# resolver: ghc-7.10.2
# resolver: ghcjs-0.1.0_ghc-7.10.2
# resolver:
#  name: custom-snapshot
#  location: "./custom-snapshot.yaml"
resolver: lts-6.16

# User packages to be built.
# Various formats can be used as shown in the example below.
#
# packages:
# - some-directory
# - https://example.com/foo/bar/baz-0.0.2.tar.gz
# - location:
#    git: https://github.com/commercialhaskell/stack.git
#    commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
# - location: https://github.com/commercialhaskell/stack/commit/e7b331f14bcffb8367cd58fbfc8b40ec7642100a
#   extra-dep: true
#  subdirs:
#  - auto-update
#  - wai
#
# A package marked 'extra-dep: true' will only be built if demanded by a
# non-dependency (i.e. a user package), and its test suites and benchmarks
# will not be run. This is useful for tweaking upstream packages.
packages:
- '.'
# Dependency packages to be pulled from upstream that are not in the resolver
# (e.g., acme-missiles-0.3)
extra-deps: []

# Override default flag values for local packages and extra-deps
flags: {}

# Extra package databases containing global packages
extra-package-dbs: []

# Control whether we use the GHC we find on the path
# system-ghc: true
#
# Require a specific version of stack, using version ranges
# require-stack-version: -any # Default
# require-stack-version: ">=1.2"
#
# Override the architecture used by stack, especially useful on Windows
# arch: i386
# arch: x86_64
#
# Extra directories used by stack for building
# extra-include-dirs: [/path/to/dir]
# extra-lib-dirs: [/path/to/dir]
#
# Allow a newer minor version of GHC than the snapshot specifies
# compiler-check: newer-minor

Check out the memory usage: