rpc/lib/client: add jitter for exponential backoff of WSClient by odeke-em · Pull Request #775 · tendermint/tendermint

odeke-em · 2017-10-24T09:05:43Z

Fixes #751.

Adds jitter to our exponential backoff to mitigate a self DDOS
vector. The jitter is a randomly picked percentage of a second
whose purpose is to ensure that each exponential backoff retry
occurs within (1<<attempts) == 2**attempts, but with the delay
each client will have a random buffer time before it tries to
reconnect instead of all at once reconnections that might even
bring back the previous conditions that might have caused the
dial to the WSServer to have failed e.g

Network outage
File descriptor exhaustion
False positives from firewalls
etc

Fixes #751. Adds jitter to our exponential backoff to mitigate a self DDOS vector. The jitter is a randomly picked percentage of a second whose purpose is to ensure that each exponential backoff retry occurs within (1<<attempts) == 2**attempts, but with the delay each client will have a random buffer time before it tries to reconnect instead of all at once reconnections that might even bring back the previous conditions that might have caused the dial to the WSServer to have failed e.g * Network outage * File descriptor exhaustion * False positives from firewalls etc

melekes · 2017-10-24T09:38:39Z

rpc/lib/client/ws_client.go

+	_1sAsNs := float64(time.Second.Nanoseconds())
 	for {
-		c.Logger.Info("reconnecting", "attempt", attempt+1)
+		jitter := time.Duration(rand.Float64() * _1sAsNs)


how big can jitter be? 1sAsNs is 1000000000, right? so given rand.Float() returned 1.0, max jitter is 1000000000 seconds?

maybe oneSecondAsNanoseconds... :0?

yeah, don't like the name too

billionNS ?

how big can jitter be? 1sAsNs is 1000000000, right? so given rand.Float() returned 1.0, max jitter is 1000000000 seconds?
So time.Durations units are in ns NOT seconds https://golang.org/pkg/time/#Duration, therefore the max value of rand.Float() * 1sAsNs is 1e9ns * 1.0 --> 1s

Ahaha we've bikeshed on the name. @silasdavis that seems too verbose to me :), I can try to fly with @ebuchman's but I believe I was trying to convey the number of nano seconds within a second without having to whip out a calculator to convert between seconds and nanoseconds.

melekes · 2017-10-24T09:39:31Z

rpc/lib/client/ws_client_test.go

 	}
 }
+
+func TestWSClientReconnectWithJitter(t *testing.T) {


good that you wrote a test, but don't think we needed to test that specifically

Agree that this might not be the most useful test, especially given how much code it is. We'd also have to start using -skip, and let's not.

That said, I like the idea of adding more advanced tests like this, but let's keep them separate from the unit testing. Perhaps we can come up with a good schema for starting to add all these longer-running, more nuanced tests, including the fuzzer stuff. We can run those tests on release, but they don't need to run every time with the unit tests.

You can use a build tag like 'integration' (e.g. https://github.com/hyperledger/burrow/blob/master/rpc/tendermint/test/rpc_client_test.go#L1-L2 - note you need the blank line after - run as https://github.com/hyperledger/burrow/blob/master/Makefile#L129). This will skip entire packages marked as integration - and they probably should be separate packages - unless test is run with the tag explicitly.

good that you wrote a test, but don't think we needed to test that specifically
Agree that this might not be the most useful test, especially given how much code it is. We'd also have to start using -skip, and let's not.
See the problem here is that that code can be changed at anytime and without a comprehensive test, we'd never know what changed at all. Perhaps we need some middle ground, like @ebuchman mentioned, perhaps as a release test.

Great suggestion @silasdavis, thank you.

ebuchman

Let's merge the jitter, and either deactivate the test or save it for another time.

ebuchman · 2017-10-24T21:20:10Z

rpc/lib/client/ws_client.go

+	_1sAsNs := float64(time.Second.Nanoseconds())
 	for {
-		c.Logger.Info("reconnecting", "attempt", attempt+1)
+		jitter := time.Duration(rand.Float64() * _1sAsNs)


billionNS ?

ebuchman · 2017-10-24T21:25:44Z

rpc/lib/client/ws_client_test.go

 	}
 }
+
+func TestWSClientReconnectWithJitter(t *testing.T) {


Agree that this might not be the most useful test, especially given how much code it is. We'd also have to start using -skip, and let's not.

That said, I like the idea of adding more advanced tests like this, but let's keep them separate from the unit testing. Perhaps we can come up with a good schema for starting to add all these longer-running, more nuanced tests, including the fuzzer stuff. We can run those tests on release, but they don't need to run every time with the unit tests.

ebuchman · 2017-10-24T21:29:05Z

Test failed, not sure if its related to this change or not, but looks like a port is trying to be reused:

I[10-24|09:15:08.558] Added new address                            address=127.0.0.1:41288 total=1^M                                                      
--- FAIL: TestPEXReactorRunning (4.02s)^M                                                                                                                 
panic: Panicked on a Crisis: listen tcp 127.0.0.1:41288: bind: address already in use [recovered]^M                                                       
    panic: Panicked on a Crisis: listen tcp 127.0.0.1:41288: bind: address already in use^M                                                               
^M                                                                                                                                                        
goroutine 88 [running]:^M                                                                                                                                 
testing.tRunner.func1(0xc4201ba870)^M                                                                                                                     
    /usr/local/go/src/testing/testing.go:711 +0x5d9^M                                                                                                     
panic(0x8f48e0, 0xc42003d480)^M                                                                                                                           
    /usr/local/go/src/runtime/panic.go:491 +0x2a2^M                                                                                                       
github.com/tendermint/tendermint/vendor/github.com/tendermint/tmlibs/common.PanicCrisis(0x91b2e0, 0xc42006a910)^M                                         
    /go/src/github.com/tendermint/tendermint/vendor/github.com/tendermint/tmlibs/common/errors.go:33 +0x120^M                                             
github.com/tendermint/tendermint/p2p.NewDefaultListener(0x97c276, 0x3, 0xc4200173d0, 0xf, 0x1, 0xcc8020, 0xc4201945d0, 0xc42018e400, 0xc420121768)^M      
    github.com/tendermint/tendermint/p2p/_test/_obj_test/listener.go:80 +0xc61^M                                                                          github.com/tendermint/tendermint/p2p.TestPEXReactorRunning(0xc4201ba870)^M                                                                                    /go/src/github.com/tendermint/tendermint/p2p/pex_reactor_test.go:92 +0x4f1^M                                                                          testing.tRunner(0xc4201ba870, 0xab73f8)^M                                                                                                                     /usr/local/go/src/testing/testing.go:746 +0x16d^M

odeke-em · 2017-10-26T01:40:57Z

@ebuchman this test doesn't bind to any port at all, it just triggers the reconnect routine and since the network is never setup the tests are bound to run until we exceed max attempts. I think that's an unrelated test flake.

@melekes

* Updated code with feedback from @melekes, @ebuchman and @silasdavis. * Added Makefile clause `release` to only run the test on seeing tag `release` during releases i.e ```shell make release ``` which will run the comprehensive and long integration-ish tests.

odeke-em · 2017-10-26T02:23:39Z

Thank you @melekes @ebuchman and @silasdavis for the first round of review. PTAL, I've updated the code to address your suggestions.

codecov-io · 2017-10-26T02:43:58Z

Codecov Report

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The diff coverage is 100%.

@@            Coverage Diff             @@
##             develop     #775   +/-   ##
==========================================
  Coverage           ?   57.47%           
==========================================
  Files              ?       82           
  Lines              ?     8439           
  Branches           ?        0           
==========================================
  Hits               ?     4850           
  Misses             ?     3169           
  Partials           ?      420

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odeke-em requested a review from ebuchman as a code owner October 24, 2017 09:05

odeke-em requested a review from melekes October 24, 2017 09:05

melekes reviewed Oct 24, 2017

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ebuchman approved these changes Oct 24, 2017

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ebuchman merged commit 376f47e into develop Oct 26, 2017

ebuchman deleted the rpc-client-jitter branch October 26, 2017 02:53

odeke-em mentioned this pull request Oct 26, 2017

rpc/lib/client: introduce jitter for ExponentialBackoff to avoid potential self DDOS vector #751

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