Reid Draper reiddraper

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I am reiddraper on github.
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Debugging Erlang Applications In Real Time

Reid Draper @reiddraper

We'll be using a tool called redbug, which is an abstraction and safety layer of Erlang's built-in dbg tracing facilities. You can follow along at home:

	<html>
	<head>
	<title>This is the title</title>
	</head>
	</html>

	terraform plan -var-file terraform.tfvars -out terraform.tfplan
	Refreshing Terraform state in-memory prior to plan...
	The refreshed state will be used to calculate this plan, but
	will not be persisted to local or remote state storage.

	[0m[1maws_ebs_volume.build-freebsd-01_sdf: Refreshing state... (ID: vol-1291439a)[0m
	[0m[1maws_ebs_volume.pg6_sdh: Refreshing state... (ID: vol-33cb1587)[0m
	[0m[1maws_ebs_volume.pg7_sdf: Refreshing state... (ID: vol-3b9f4db3)[0m
	[0m[1maws_eip.nat-2a: Refreshing state... (ID: eipalloc-cb74a9ac)[0m
	[0m[1maws_ebs_volume.build-debian-01_sdf: Refreshing state... (ID: vol-65a266e6)[0m

	Here's an explanation from 30k ft. of the generator namespace. There are three monads
	involved, one of which simply contains the other two (but is not a monad transformer). They're
	not named explicitly like this in the module, but let's call them: RoseTree, Generator and Gen.
	Gen is the monad that is a wrapper around Gen (RoseTree a), to use Haskell types. A RoseTree
	is simply an n-ary. In Haskell, it'd be defined like:

	data RoseTree a = RoseTree a [RoseTree a]

	In Clojure I represent it as a two-element vector, the first element being the node's value,
	and the second being a lazy-sequence of the children. Since we use a lazy-seq, we can

	make[1]: *** [libraries/Cabal/Cabal/dist-boot/package-data.mk] Segmentation fault (core dumped)
	make[1]: *** Waiting for unfinished jobs....
	make[1]: *** [utils/hsc2hs/dist/package-data.mk] Segmentation fault (core dumped)
	make: *** [all] Error 2
	make -j8 131.49s user 2.92s system 99% cpu 2:15.43 total

	select(2, [0 1], NULL, NULL, {900, 0}) = 1 (in [0], left {899, 949910})
	wait4(1401, 0x7fffe90edd0c, WNOHANG, NULL) = 0
	read(0, "10:53:10.322 [error] Supervisor "..., 8192) = 438
	lseek(2, 0, SEEK_END) = 90736
	write(2, "10:53:10.322 [error] Supervisor "..., 438) = 438
	select(2, [0 1], NULL, NULL, {900, 0}) = 1 (in [0], left {899, 958221})
	wait4(1401, 0x7fffe90edd0c, WNOHANG, NULL) = 0
	read(0, "10:53:14.135 [error] Supervisor "..., 8192) = 461
	lseek(2, 0, SEEK_END)

	dd if=/dev/zero of=/tmp/output bs=25k count=1k
	for i in {1..10}; do time curl -X PUT localhost:8098/riak/foo/a --data-binary @/tmp/output > foo; done

	12:50:24 <{mochiweb_acceptor,init,3}> {riak_client,new,2}

	12:50:24 <{mochiweb_acceptor,init,3}> {riak_client,instance,2}

	12:50:24 <{mochiweb_acceptor,init,3}> {riak_client,get,4}

	12:50:24 <{mochiweb_acceptor,init,3}> {riak_client,mk_reqid,1}

	12:50:24 <{mochiweb_acceptor,init,3}> {riak_client,recv_timeout,2}

	(require '[simple-check.core :as sc])
	(require '[simple-check.generators :as gen])
	(require '[simple-check.properties :as prop])

	(def sort-idempotent-prop
	(prop/for-all [v (gen/vector gen/int)]
	(= (sort v) (sort (sort v)))))

	(sc/quick-check 100 sort-idempotent-prop)
	;; => {:result true, :num-tests 100, :seed 1382488326530}