Summary:
see D1618704 and D1604575
Really need to make a decision about making a push for EventBaseManager everywhere. Getting/setting EBs when there's only ever one seems so silly, but in (e.g.) tests where one-off EBs are used without using the EBM, stuff like this will break.

Test Plan: definitely compiles and sorta works, will write unit tests if the dust settles

Reviewed By: davejwatson@fb.com

Subscribers: folly-diffs@, trunkagent, fugalh, njormrod

FB internal diff: D1618727

Summary:
* Unroll readVarint() - no loops in the fast path
* Split Cursor::skip() into fast and slow paths

Test Plan:
```
------ old ------   ------ new ------
Benchmark                               time/iter  iters/s  time/iter  iters/s        win
=========================================================================================
CompactProtocol_read_Empty                13.21ns   75.69M    13.21ns   75.71M      0.03%
CompactProtocol_read_SmallInt             29.95ns   33.39M    28.96ns   34.53M      3.41%
CompactProtocol_read_BigInt               67.83ns   14.74M    36.77ns   27.19M     84.46%
CompactProtocol_read_SmallString          55.72ns   17.95M    54.04ns   18.50M      3.06%
CompactProtocol_read_BigString           342.93ns    2.92M   332.18ns    3.01M      3.08%
CompactProtocol_read_BigBinary           186.18ns    5.37M   181.45ns    5.51M      2.61%
CompactProtocol_read_LargeBinary         190.65ns    5.25M   184.85ns    5.41M      3.05%
CompactProtocol_read_Mixed               101.97ns    9.81M    97.06ns   10.30M      4.99%
CompactProtocol_read_SmallListInt        148.09ns    6.75M   139.52ns    7.17M      6.22%
CompactProtocol_read_BigListInt           71.69us   13.95K    63.34us   15.79K     13.19%
CompactProtocol_read_BigListMixed          1.26ms   790.67     1.18ms   845.66      6.95%
CompactProtocol_read_LargeListMixed      139.80ms     7.15   134.68ms     7.42      3.78%
```

Reviewed By: davejwatson@fb.com

Subscribers: trunkagent, alandau, bmatheny, njormrod, mshneer, folly-diffs@

FB internal diff: D1681244

Signature: t1:1681244:1416265579:f630c53f9c31788f847d0af72198bbd9e5ea43f1

Summary: this should address some of the wordiness issues with exception_wrapper, i.e. always having to use make_exception_wrapper

Test Plan: wrote a little test to make sure everything compiles (or doesn't) as expected, not worth committing

Reviewed By: davejwatson@fb.com

Subscribers: njormrod, folly-diffs@

FB internal diff: D1679460

Signature: t1:1679460:1416265170:5cd72d95dd855cd4e594dbbc49d0c53d012fbc99

Summary:
In unusual but possible circumstances, the EventBase and thus pending tasks will outlive the pool, so we shouldn't keep references of any kind to the pool in the task.
The only reference we were keeping was used to access the task stats rx subject. Store the subject as a shared ptr and give a copy of the ptr to the Thread object, which is itself
owned by a shared ptr and captured by every task. I thought this had to do with the thread local leak in mentioned in the test plan of D1682860 but this patch doesn't actually fix that :(
Thankfully, while task surfing I saw @phillip's awesome D1682698. Patching that in fixes the leak! Woo. Either way, this is more correct.

Test Plan: unit under clang/asan

Reviewed By: davejwatson@fb.com

Subscribers: trunkagent, fugalh, njormrod, folly-diffs@, philipp

FB internal diff: D1683221

Tasks: 5336655

Signature: t1:1683221:1416264933:946d29b5a3eb22ed08812f2adefb7284b1899e4e

Summary:
just extend CPUThreadPoolExecutor to use a queue that is itself composed of N mpmc queues, one per priority

the verbosity is starting to kill me, i had thought before of truncating Executor of all these pool types and now I'm definitely going to do that unless someone fights me.

Test Plan: added unit; maybe i'm not being clever enough as i couldn't think of many ways to test this reliably so there's just a basic preemption test

Reviewed By: davejwatson@fb.com

Subscribers: trunkagent, fugalh, njormrod, folly-diffs@, bmatheny

FB internal diff: D1676452

Tasks: 5002392

Signature: t1:1676452:1416263990:cdf5d44e4a50a6180ba547a3ed4c0c24d4ffdd8f

Summary: Fix addition bug instead of string concat

Test Plan: ?? It compiles?  The only call paths are when syscalls fail, it would be a lot of work to stub them out

Reviewed By: mshneer@fb.com

Subscribers: trunkagent, doug, njormrod, folly-diffs@

FB internal diff: D1679713

Tasks: 5604354

Signature: t1:1679713:1415925209:ed05d3d1ce3e7e8db32c4afc86c5f24748d9c65b

Summary:
Initial pass at moving acceptor to wangle.  Involves moving most of the config stuff from proxygen/lib/services, and *all* of the ssl stuff from proxygen/lib/ssl.

Only minor changes:
* Acceptor can be overriden to use thrift socket types, so I don't have to change TTransportException everywhere just yet
* proxygen::Exception to std::runtime_exception in a few spots - looks like it is entirely bad config exceptions, so it should be okay
* Just used std::chrono directly instead of stuff in Time.h (which is just typedefs and simple helpers)

Test Plan:
used in D1539327

fbconfig -r proxygen/httpserver; fbmake runtests

Probably other projects are broken, will iterate to fix

None of the failling tests look related

Reviewed By: dcsommer@fb.com

Subscribers: oleksandr, netego-diffs@, hphp-diffs@, ps, trunkagent, doug, fugalh, alandau, bmatheny, njormrod, mshneer, folly-diffs@

FB internal diff: D1638358

Tasks: 5002353

Signature: t1:1638358:1414526683:87a405e3c24711078707c00b62a50b0e960bf126

Summary:
See this LSan abort: https://phabricator.fb.com/P17233565.

Destructor of the object stored in `folly::ThreadLocal` itself may be using
`folly::ThreadLocal` with the same tag, with the current implementation these
objects may escape cleanup happening on thread exit.

Test Plan:
_build/opt/folly/test/thread_local_test --gtest_filter=ThreadLocalPtr.CreateOnThreadExit

Reviewed By: lucian@fb.com

Subscribers: njormrod, folly-diffs@

FB internal diff: D1682698

Tasks: 5596043

Signature: t1:1682698:1416006810:100aaa5c17cecceeea568165d552d9d7907f38d0

Summary:
Add a specialized Cursor method that reads exactly 1 byte, in
addition to the existing one that reads into a buffer. Use it when
reading varints and standalone bytes in a CompactProtocol struct.

Test Plan:
```
------ old ------   ------ new ------
Benchmark                               time/iter  iters/s  time/iter  iters/s        win
=========================================================================================
CompactProtocol_read_Empty                18.68ns   53.54M    13.21ns   75.69M     41.37%
CompactProtocol_read_SmallInt             42.60ns   23.47M    29.95ns   33.39M     42.27%
CompactProtocol_read_BigInt               83.62ns   11.96M    68.40ns   14.62M     22.24%
CompactProtocol_read_SmallString          67.33ns   14.85M    55.62ns   17.98M     21.08%
CompactProtocol_read_BigString           353.83ns    2.83M   330.19ns    3.03M      7.07%
CompactProtocol_read_BigBinary           190.82ns    5.24M   182.90ns    5.47M      4.39%
CompactProtocol_read_LargeBinary         200.95ns    4.98M   187.00ns    5.35M      7.43%
CompactProtocol_read_Mixed               137.42ns    7.28M   102.98ns    9.71M     33.38%
CompactProtocol_read_SmallListInt        203.98ns    4.90M   146.68ns    6.82M     39.18%
CompactProtocol_read_BigListInt          120.50us    8.30K    71.56us   13.97K     68.31%
CompactProtocol_read_BigListMixed          1.62ms   617.07     1.26ms   795.60     28.93%
CompactProtocol_read_LargeListMixed      177.50ms     5.63   140.73ms     7.11     26.29%
```

Reviewed By: haijunz@fb.com

Subscribers: trunkagent, alandau, bmatheny, njormrod, mshneer, folly-diffs@

FB internal diff: D1678077

Signature: t1:1678077:1415923409:22accee6b62b6e2bf471f3758a290f71978a8c4e

Summary: Introduces a Singleton which keeps a map persistence_id => mcrouter_t*. Makes mcrouter instance not know if it's managed by McrouterManager.

Test Plan: unit tests

Reviewed By: pavlo@fb.com

Subscribers: trunkagent, alikhtarov, njormrod, folly-diffs@

FB internal diff: D1673274

Signature: t1:1673274:1415735863:c990a6a526f9525c68cc23892d690a9b3cb94ace

Summary:
It already does the work (`runInEventBaseThread`) but it will now be convenient to pass an `EventBase` where wangle wants an `Executor`.

Had to rip off the `boost::noncopyable` from `wangle::Executor` which is an interface and does not require non-copyability so that didn't really belong there in the first place I think. (Without this change, you get an obscure compiler error because of the double-inheritance from `boost::noncopyable`).

Test Plan: Things build, tests pass

Reviewed By: davejwatson@fb.com

Subscribers: jsedgwick, trunkagent, fugalh, exa, njormrod, folly-diffs@, andrii

FB internal diff: D1671500

Signature: t1:1671500:1415727572:a7dba33c669ca122aecaee3c700f9e53e54838d1

Summary:
Patch D1585087 exposes two flaws in EventBase().  It introduces IO
worker threads to the ThriftServer which are constructed/destructed in
parallel.

Within the construction phase, a new EventBase() is instantiated for
each thread and unwound in destruction.

When using the BaseControllerTask (in Python), the following sequence
is observed:

a = event_init() [ThriftServer]
b = event_init() [IO worker 1]
c = event_init() [IO worker 2]
...
event_base_free(c)
event_base_free(b)
event_base_free(a)  -> segfault

1. event_init() should only ever be called once.  It internally
modifies a global variable in libevent, current_base to match the
return value.  event_base_free() will set current_base back to NULL if
the passed in arg matches current_base.   Therefore subsequent calls
must use event_base_new().

2. Since current_base is a global and EventBase() is called by multiple
threads, it is important to guard with a mutex.  The guard itself also
exposed the bug because:

a = event_init()  [current_base = a]
b = event_init()  [current_base = b]
...
event_base_free(b) [b == current_base -> current_base = NULL]

So current_base ends up prematurely set to NULL.

Test Plan:
Run dba/core/daemons/dbstatus/dbstatus_tests.lpar, which no longer
segfaults

Reviewed By: jsedgwick@fb.com, davejwatson@fb.com

Subscribers: dihde, evanelias, trunkagent, njormrod, ncoffield, lachlan, folly-diffs@

FB internal diff: D1663654

Tasks: 5545819

Signature: t1:1663654:1415732265:d51c4c4cae99c1ac371460bf18d26d4f917a3c52

Blame Revision: D1585087

Summary: find a non-loopback ipv4 or ipv6 address and feed it to folly::IPAddress::hash

Test Plan:
1)
fbconfig -r mcrouter
fbmake runtests

2)
compare hostids on different hosts

Reviewed By: pavlo@fb.com

Subscribers: njormrod, folly-diffs@, trunkagent, ps, bmatheny, alikhtarov

FB internal diff: D1668944

Tasks: 5557721

Signature: t1:1668944:1415736928:fb4b042a575c0b00f52780f3abf54bf7630b3a97

Summary: Using a ThreadLocal cleans up the code quite a bit.  Also reuse the shared_ptr in create instead of creating a new one saves an allocation

Test Plan:
fbconfig thrift/lib/cpp/test:RequestContextTest; fbmake runtests

fbconfig common/services/cpp/test:trace_test; fbmake runtests

Reviewed By: hans@fb.com

Subscribers: trunkagent, doug, alandau, bmatheny, njormrod, mshneer, folly-diffs@, vloh

FB internal diff: D1663960

Signature: t1:1663960:1415390250:36d9b772016d2a12d804e98edbc1725af882e507

Summary:
All pretty trivial:

https://github.com/facebook/folly/issues/99
https://github.com/facebook/folly/issues/98
https://github.com/facebook/folly/issues/45

Test Plan: Will watch jenkins fbthrift build

Reviewed By: dcsommer@fb.com

Subscribers: doug, njormrod, folly-diffs@

FB internal diff: D1669952

Signature: t1:1669952:1415643677:906234f0a89f38645b0072d3c88762d8fa2729dc

Summary:
Inside `set()` we can do pruning, but it will happen
with default pruneHook.
Adding it as an optional param makes API more convenient.
(Instead, the users of API could just call `setPruneHook(pruneHook)` before `set`,
and then `setPruneHook(nullptr)` afterwards -- but it looks too ugly)

Test Plan:
```
fbconfig -r folly/ && fbmake runtests
```
passes:
```
Summary (total time 60.11s):
PASS: 1758
FAIL: 0
SKIP: 0
FATAL: 0
TIMEOUT: 0
```

Reviewed By: njormrod@fb.com

Subscribers: trunkagent, agartrell, njormrod, folly-diffs@

FB internal diff: D1665690

Tasks: 5551091

Signature: t1:1665690:1415391406:e4d2a956f9212aed70ab518159dbb19553764ce4

Summary:
Fix EOF whitespace
for file in `find folly -type f` ; do if [ -z "`tail -n1 $file`" ] ; then sed -i '$d' $file ; fi ; done

Test Plan: unit tests

Reviewed By: robbert@fb.com

Subscribers: trunkagent, sdwilsh, njormrod, folly-diffs@

FB internal diff: D1644130

Tasks: 5486739

Signature: t1:1644130:1414715392:b6c783851aa030ad1148f84a98139a5dca207da0

Summary: title

Test Plan: unit tests

Reviewed By: andrei.bajenov@fb.com

Subscribers: trunkagent, mcduff, hitesh, alandau, bmatheny, njormrod, mshneer, folly-diffs@, andreib, davejwatson

FB internal diff: D1666499

Tasks: 5563183

Signature: t1:1666499:1415347256:d58c8bbe952385c1c96f7f8cc6ae7f02216c56bb

Summary: One of the last thrift -> folly moves.  The only change was the exception types - there are small wrapper classes in thrift/lib/cpp/async left to convert from AsyncSocketException to TTransportException.

Test Plan: run unit tests

Reviewed By: dcsommer@fb.com

Subscribers: jdperlow, trunkagent, doug, bmatheny, ssl-diffs@, njormrod, mshneer, folly-diffs@, fugalh, jsedgwick, andrewcox, alandau

FB internal diff: D1632425

Signature: t1:1632425:1414526483:339ae107bacb073bdd8cf0942fd0f6b70990feb4

Summary: Not needed, I don't know why I put them there before.

Test Plan: Run the unit test

Reviewed By: njormrod@fb.com

Subscribers: njormrod, folly-diffs@

FB internal diff: D1665689

Tasks: 5487902

Signature: t1:1665689:1415323144:0998e7f700a3b40652615a36c3b9c9f661fbdadf

Summary: There was a bit of gap in test coverage for bracketed ipv6

Test Plan: unit tests

Reviewed By: viswanath@fb.com

Subscribers: doug, ps, bmatheny, njormrod, folly-diffs@

FB internal diff: D1664783

Signature: t1:1664783:1415316694:b17e0dc1fcfece06c6e04e5f65e2095c66d28cc4

Summary:
`bm_max_secs` has type int32
So when this value is more than 2, expression
```
FLAGS_bm_max_secs * 1000000000;
```
overflows

Test Plan:
I did put a
```
LOG(INFO) << timeBudgetInNs;
```
and observed correct values (before fix they were overflowed)

Reviewed By: antonl@fb.com

Subscribers: njormrod, folly-diffs@

FB internal diff: D1663247

Signature: t1:1663247:1415261814:c9154ffde183b2a4f5403e534e47e52e8276c61b

Summary:
This diff updates `folly::CpuId` with support of extended features (EAX =
7, ECX = 0) to provide detection logic for BMI1 introduced in Haswell, and
provides support for `BLSR` instruction in `EliasFanoReader`.

Test Plan:
I used clang to compile the logic and run unittests

Reviewed By: lucian@fb.com

Subscribers: fbcode-common-diffs@, trunkagent, chaoyc, search-fbcode-diffs@, unicorn-diffs@, njormrod, folly-diffs@

FB internal diff: D1658100

Signature: t1:1658100:1415126635:d1820b8eb41c9e9786b5c8062b801cf1e2049a97

Summary:
`calledBack_` could be seen as true by both threads in this conditional. Classic rookie mistake. :-/

Test Plan: run unit tests

Reviewed By: darshan@fb.com

Subscribers: trunkagent, hannesr, net-systems@, fugalh, exa, njormrod, folly-diffs@

FB internal diff: D1661199

Tasks: 5542938, 5506504

Signature: t1:1661199:1415215840:fb69f56c8cf6f59beeca809724ce015b5260d9ad

Blame Revision: D1636487

Summary: Switch from dynamically allocating a File to using a raw fd for readRandomDevice. This prevents races at shutdown while also eliminating the memory leak

Test Plan: run unit tests

Reviewed By: meyering@fb.com

Subscribers: njormrod, folly-diffs@, tao-eng@

FB internal diff: D1662151

Signature: t1:1662151:1415229242:525b6294b27bb68b5dda70aadb8d3ba1cc61b815

Summary: The comment in readRandomDevice() lies - the PCHECK fails with "Bad file descriptor" in some tests. This is most likely due to a race where a background thread is calling readRandomDevice() while the main thread shuts down. Another possibility is bad destruction order, where rnadomDevice is destroyed before some other static object whose destructor calls readRandomDevice(). Either way, this fixes it without having to chace down every instance.

Test Plan: run unit tests

Reviewed By: meyering@fb.com

Subscribers: antonl, trunkagent, meyering, simpkins, njormrod, folly-diffs@, tao-eng@

FB internal diff: D1660903

Signature: t1:1660903:1415215895:7f1f96ab7416b45c4dc18e78173fb59eb27bd03b

Summary:
Race in `++ctx->count == ctx->total`. This ordering, while not very obvious or likely, is possible:

T1            T2
--            --
++ctx->count
++ctx->count
ctx->total
==
setValue
delete ctx
ctx->total
==
setValue
delete ctx

Test Plan:
That's the idea, anyway. I need some sleep, and it takes 20 minutes to build and test. I had a more convoluted fix (using `shared_ptr`) and it did seem to fix the error we were seeing, but I was seeing another error.

Reviewed By: darshan@fb.com

Subscribers: trunkagent, net-systems@, fugalh, exa, njormrod, folly-diffs@

FB internal diff: D1660663

Tasks: 5506504

Signature: t1:1660663:1415207632:49dc224363cec27736fc71fb211fa846be9e170f

Blame Revision: D1636487

folly: wangle: NamedThreadFactory: store of the thread prefix locally, don't assume they'll live forever

Summary: There's no real reason to store this as a StringPiece, is there?

Test Plan: n/a

Reviewed By: sdoroshenko@fb.com, robot9@fb.com

Subscribers: fugalh, njormrod, folly-diffs@

FB internal diff: D1659558

Tasks: 5538418

Signature: t1:1659558:1415147560:2c5b0c996893854c3ea9d0ad02b006bcc5960ffa

Summary:
There are two types of licenses used in folly, only one of
which is accepted by the linter.

This diff changes the license notices in pre-existing folly files!
Many folly/io/async/* files have the second type of license, but
without a Copyright notice. I have added copyright notices to these
files.

I have also added a compliant notice to
folly/test/function_benchmark/benchmark_impl.h, which was the sole file
in folly/test/function_benchmark/ that didn't have a standard license.

Test Plan:
The changes to folly are comment only.

Run all of folly against the linter, see no more license errors.

Reviewed By: davejwatson@fb.com

Subscribers: trunkagent, sdwilsh, njormrod, folly-diffs@, sjenkins

FB internal diff: D1648489

Tasks: 5486739

Signature: t1:1648489:1415035522:3d8bd9611eb7c7117b70d5e7f68de5768639a727

Summary:
Statics in headers are bad.

Test Plan: run unit tests

Reviewed By: robbert@fb.com

Subscribers: trunkagent, sdwilsh, njormrod, folly-diffs@

FB internal diff: D1646906

Tasks: 5486739

Signature: t1:1646906:1415042805:dc4d1cec54e9320f1e609808a73622c731a4cdc9

Summary:
Remove the protected inheritance from folly.

The code looks like the protected might be appropriate: there are some
derived classes which might want access to the AsyncTimeout.

Test Plan: run unit tests

Reviewed By: davejwatson@fb.com

Subscribers: trunkagent, sdwilsh, njormrod, folly-diffs@

FB internal diff: D1649686

Tasks: 5486739

Signature: t1:1649686:1415035288:18efd2cf9aae8caab66d8303c22cdc26c6b54ae5

Summary:
I wanted some foundational abstractions to start building out codecs on top of.
I also know that Blake gets very amused when I shamelessly copy Java/Netty abstractions, and I live to amuse Blake so I did it again.
So here's an implementation of something very similar to Netty's ChannelAdapters/ChannelPipelines
Only read() and write() for now, everything/anything else can easily be bolted on once the design is settled (if this is at all the direction we want to go)
I have a lot of thoughts about this design but I'm going to save my fingers and leave that to ad hoc discussions once folks take a look at this
A couple of things, though:
- It should be possible to dynamically add handlers to the chain. How I envision this working is that each original adapters keeps two lists of shared/unique ptrs to adapters of the correct type to sit next to them on either side, and dispatch to them appropriately when they're there.
- I was trying to do without separate ChannelHandlerContext objects altogether (keep the interface, but have ChannelPipeline act as the context itself) but ran into issues with virtual multiple inheritance. I might have another go at this.
- Only movable types are permitted. I hope this won't be too restrictive, because it would be a PITA to support both move-only and copy-only types.
- Why no Rx? Seems to me that any handlers that actually needs Rx (e.g. stats fanout or something) can deal with it themselves.
- If it turned out to be useful to nest these (for more flexible composition) that would also be doable. i.e. ChannelPipeline<ChannelPipeline<Handler1, Handler2>, ChannelPipeline<Handler3, Handler4>>

Test Plan: super basic test compiles and runs as expected

Reviewed By: davejwatson@fb.com

Subscribers: ajitb, folly-diffs@, ldbrandy, trunkagent, fugalh, njormrod

FB internal diff: D1604575

Tasks: 5002299

Signature: t1:1604575:1415034767:bc3b12fae726890aa6a55ed391286917ae23e56e

Summary: Folly should be able to compile with strict flags.

Test Plan: unit tests, review

Reviewed By: meyering@fb.com

Subscribers: meyering, trunkagent, doug, fugalh, njormrod, folly-diffs@

FB internal diff: D1627280

Signature: t1:1627280:1414792755:004f5a737ece1e93bcf4331718a98afc57e4f80c

Summary: it's useful to update the prefix after the construction.

Test Plan:
unit, that's it :/

Reviewed By: davejwatson@fb.com

Subscribers: mshneer, folly-diffs@, wch, atlas2-eng@, everstore-dev@, wormhole-diffs@, ads-dsp-eng@, bwester, trunkagent, fugalh, alandau, njormrod, bmatheny

FB internal diff: D1585087

Summary: Put back previous liger diffs

Test Plan: It builds

Reviewed By: seanc@fb.com

Subscribers: doug, ssl-diffs@, njormrod, folly-diffs@

FB internal diff: D1652754

Signature: t1:1652754:1414785984:df0fc7bf59dc2e89defd2c1a4ffe3b288238ba58

Summary:
Many lines that are too long contain URLs. This diff adds
url-like lines to the list of exceptions to 80-char limits. It also
fixed the locations in folly with line-too-long errors.

Test Plan: arc lint on folly, see no line-too-long errors.

Reviewed By: robbert@fb.com

Subscribers: sdwilsh, njormrod, folly-diffs@

FB internal diff: D1644151

Tasks: 5486739

Signature: t1:1644151:1414779408:76bcec1d14daaa8ed071c715bf26b108c8fe4b87

Summary:
Symbols which demangle to a string longer than 1024 bytes are
quite common in our code. This diff increases the size of the output
buffer to accommodate them.

Test Plan: run it

Reviewed By: lucian@fb.com

Subscribers: trunkagent, njormrod, folly-diffs@

FB internal diff: D1639801

Tasks: 5464222

Signature: t1:1639801:1414784601:2f59d5a58e434f4cf9df5b25b917c5094c8b133f

Summary: I had committed a change by mistake. Reverting it.

Test Plan: build it.

Reviewed By: lakshmiganesh@fb.com

Subscribers: njormrod, folly-diffs@

FB internal diff: D1652341

Signature: t1:1652341:1414779013:9f363acba95fbac1988200081659edf71ac63eec

Summary:
Some uses of volatile are legit. Add a hidden override.

Test Plan: run unit tests

Run flint against folly/Malloc.cpp, see no more volatile warning.

Reviewed By: andrei.alexandrescu@fb.com

Subscribers: sdwilsh, louisk, njormrod, folly-diffs@

FB internal diff: D1644493

Tasks: 5486739

Signature: t1:1644493:1414715317:491d0f631d8152a5b7ec66237e00c404530ab590