Cancel c-ares queries after a timeout to avoid getting stuck by apolcyn · Pull Request #17354 · grpc/grpc

apolcyn · 2018-11-30T10:22:11Z

The background for this is there is a multi-channel benchmark involving a large number of channels that connect to a grpclb-in-DNS based benchmark service. Frequently, this benchmark actually fails to run because one or more client channels fails to connect (reach "channel connectivtity state == ready") to the benchmark backend within a 3-and-half minute timeout. I found that when this happens, there is at least one c-ares fd notify on read without a matching on_readable; at least one DNS query gets stuck. Currently, this makes a channel effectively stuck for the rest of its lifetime because there aren't any effective deadline for UDP queries made by c-ares. But I think this is just an inherent problem with UDP/DNS queries that they risk being dropped. By cancelling queries after a reasonable timeout, channels can retry them and become unstuck.

This PR is a draft (I'm not sure if the 10 second timeout is best), but I've verified that this change fixes the problem in the benchmark.

grpc-testing · 2018-11-30T10:27:54Z

****************************************************************

libgrpc.so

     VM SIZE                                                                                      FILE SIZE
 ++++++++++++++ GROWING                                                                        ++++++++++++++
  +0.0%     +66 [None]                                                                         +1.28Ki  +0.0%
  +6.4%    +166 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.cc    +166  +6.4%
      +280%     +70 grpc_ares_ev_driver_start_locked                                                   +70  +280%
      [NEW]     +38 on_timeout_locked                                                                  +38  [NEW]
      +5.5%     +31 grpc_ares_ev_driver_create_locked                                                  +31  +5.5%
      +189%     +17 grpc_ares_ev_driver_on_queries_complete_locked                                     +17  +189%
       +12%     +10 [Unmapped]                                                                         +10   +12%

  +0.0%    +232 TOTAL                                                                          +1.45Ki  +0.0%


****************************************************************

libgrpc++.so

     VM SIZE        FILE SIZE
 ++++++++++++++  ++++++++++++++

  [ = ]       0        0  [ = ]

grpc-testing · 2018-11-30T10:35:54Z

[trickle] No significant performance differences

grpc-testing · 2018-11-30T11:11:47Z

Objective-C binary sizes
*****************STATIC******************
  New size                      Old size
 2,020,410      Total (=)      2,020,410

 No significant differences in binary sizes

***************FRAMEWORKS****************
  New size                      Old size
11,174,082      Total (>)     11,174,078

 No significant differences in binary sizes

grpc-testing · 2018-11-30T11:20:12Z

Corrupt JSON data (indicates timeout or crash): 
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.new: 10
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.old: 10


[microbenchmarks] No significant performance differences

markdroth

Having a timeout here seems like a good idea. Just a couple of comments about the implementation.

src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.cc

grpc-testing · 2018-11-30T20:19:31Z

****************************************************************

libgrpc.so

     VM SIZE                                                                                            FILE SIZE
 ++++++++++++++ GROWING                                                                              ++++++++++++++
  +0.0%    +333 [None]                                                                               +1.75Ki  +0.0%
   +13%    +331 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.cc          +331   +13%
      [NEW]    +611 grpc_ares_ev_driver_create_locked                                                       +611  [NEW]
      [NEW]    +134 on_timeout_locked                                                                       +134  [NEW]
      +492%    +123 grpc_ares_ev_driver_start_locked                                                        +123  +492%
      +189%     +17 grpc_ares_ev_driver_on_queries_complete_locked                                           +17  +189%
      +9.9%      +8 [Unmapped]                                                                                +8  +9.9%
  +1.5%     +64 src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc             +64  +1.5%
       +11%     +64 grpc_core::(anonymous namespace)::AresDnsResolverFactory::CreateResolver(grpc_core::     +64   +11%
      +3.3%      +8 grpc_core::(anonymous namespace)::AresDnsResolver::StartResolvingLocked                   +8  +3.3%
  +0.3%     +16 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.cc             +16  +0.3%
      [NEW] +1.33Ki grpc_dns_lookup_ares_continue_after_check_localhost_and_ip_literals_locked           +1.33Ki  [NEW]
      [NEW]    +808 grpc_dns_lookup_ares_locked_impl                                                        +808  [NEW]
       +10%      +7 [Unmapped]                                                                                +7   +10%
      +1.8%      +1 grpc_resolve_address_invoke_dns_lookup_ares_locked                                        +1  +1.8%

  +0.0%    +744 TOTAL                                                                                +2.15Ki  +0.0%


****************************************************************

libgrpc++.so

     VM SIZE        FILE SIZE
 ++++++++++++++  ++++++++++++++

  [ = ]       0        0  [ = ]

grpc-testing · 2018-11-30T20:24:00Z

****************************************************************

libgrpc.so

     VM SIZE                                                                                            FILE SIZE
 ++++++++++++++ GROWING                                                                              ++++++++++++++
  +0.0%    +333 [None]                                                                               +1.75Ki  +0.0%
   +13%    +331 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.cc          +331   +13%
      [NEW]    +611 grpc_ares_ev_driver_create_locked                                                       +611  [NEW]
      [NEW]    +134 on_timeout_locked                                                                       +134  [NEW]
      +492%    +123 grpc_ares_ev_driver_start_locked                                                        +123  +492%
      +189%     +17 grpc_ares_ev_driver_on_queries_complete_locked                                           +17  +189%
      +9.9%      +8 [Unmapped]                                                                                +8  +9.9%
  +1.5%     +64 src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc             +64  +1.5%
       +11%     +64 grpc_core::(anonymous namespace)::AresDnsResolverFactory::CreateResolver(grpc_core::     +64   +11%
      +3.3%      +8 grpc_core::(anonymous namespace)::AresDnsResolver::StartResolvingLocked                   +8  +3.3%
  +0.3%     +16 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.cc             +16  +0.3%
      [NEW] +1.33Ki grpc_dns_lookup_ares_continue_after_check_localhost_and_ip_literals_locked           +1.33Ki  [NEW]
      [NEW]    +808 grpc_dns_lookup_ares_locked_impl                                                        +808  [NEW]
       +10%      +7 [Unmapped]                                                                                +7   +10%
      +1.8%      +1 grpc_resolve_address_invoke_dns_lookup_ares_locked                                        +1  +1.8%

  +0.0%    +744 TOTAL                                                                                +2.15Ki  +0.0%


****************************************************************

libgrpc++.so

     VM SIZE        FILE SIZE
 ++++++++++++++  ++++++++++++++

  [ = ]       0        0  [ = ]

grpc-testing · 2018-11-30T20:26:40Z

[trickle] No significant performance differences

markdroth

Looks good, just a few minor comments.

include/grpc/impl/codegen/grpc_types.h

src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.cc

src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.cc

grpc-testing · 2018-11-30T20:37:27Z

[trickle] No significant performance differences

grpc-testing · 2018-11-30T21:01:28Z

Objective-C binary sizes
*****************STATIC******************
  New size                      Old size
 2,020,410      Total (=)      2,020,410

 No significant differences in binary sizes

***************FRAMEWORKS****************
  New size                      Old size
11,174,079      Total (>)     11,174,077

 No significant differences in binary sizes

grpc-testing · 2018-11-30T21:05:43Z

Objective-C binary sizes
*****************STATIC******************
  New size                      Old size
 2,020,410      Total (=)      2,020,410

 No significant differences in binary sizes

***************FRAMEWORKS****************
  New size                      Old size
11,174,078      Total (<)     11,174,083

 No significant differences in binary sizes

grpc-testing · 2018-11-30T21:11:42Z

Corrupt JSON data (indicates timeout or crash): 
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.new: 10
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.old: 10


[microbenchmarks] No significant performance differences

grpc-testing · 2018-11-30T21:16:33Z

Corrupt JSON data (indicates timeout or crash): 
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.new: 10
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.old: 10


[microbenchmarks] No significant performance differences

grpc-testing · 2018-11-30T21:58:56Z

****************************************************************

libgrpc.so

     VM SIZE                                                                                            FILE SIZE
 ++++++++++++++ GROWING                                                                              ++++++++++++++
  +0.0%    +338 [None]                                                                               +1.74Ki  +0.0%
   +14%    +358 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.cc          +358   +14%
      [NEW]    +611 grpc_ares_ev_driver_create_locked                                                       +611  [NEW]
      +600%    +150 grpc_ares_ev_driver_start_locked                                                        +150  +600%
      [NEW]    +134 on_timeout_locked                                                                       +134  [NEW]
      +189%     +17 grpc_ares_ev_driver_on_queries_complete_locked                                           +17  +189%
      +9.9%      +8 [Unmapped]                                                                                +8  +9.9%
  +1.5%     +64 src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc             +64  +1.5%
       +11%     +64 grpc_core::(anonymous namespace)::AresDnsResolverFactory::CreateResolver(grpc_core::     +64   +11%
      +3.3%      +8 grpc_core::(anonymous namespace)::AresDnsResolver::StartResolvingLocked                   +8  +3.3%
  +0.3%     +16 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.cc             +16  +0.3%
      [NEW] +1.33Ki grpc_dns_lookup_ares_continue_after_check_localhost_and_ip_literals_locked           +1.33Ki  [NEW]
      [NEW]    +808 grpc_dns_lookup_ares_locked_impl                                                        +808  [NEW]
       +10%      +7 [Unmapped]                                                                                +7   +10%
      +1.8%      +1 grpc_resolve_address_invoke_dns_lookup_ares_locked                                        +1  +1.8%

  +0.0%    +776 TOTAL                                                                                +2.17Ki  +0.0%


****************************************************************

libgrpc++.so

     VM SIZE        FILE SIZE
 ++++++++++++++  ++++++++++++++

  [ = ]       0        0  [ = ]

test/cpp/naming/cancel_ares_query_test.cc

grpc-testing · 2018-11-30T22:05:58Z

[trickle] No significant performance differences

markdroth

Thanks for doing this!

grpc-testing · 2018-11-30T22:19:22Z

****************************************************************

libgrpc.so

     VM SIZE                                                                                            FILE SIZE
 ++++++++++++++ GROWING                                                                              ++++++++++++++
  +0.0%    +338 [None]                                                                               +1.74Ki  +0.0%
   +14%    +358 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.cc          +358   +14%
      [NEW]    +611 grpc_ares_ev_driver_create_locked                                                       +611  [NEW]
      +600%    +150 grpc_ares_ev_driver_start_locked                                                        +150  +600%
      [NEW]    +134 on_timeout_locked                                                                       +134  [NEW]
      +189%     +17 grpc_ares_ev_driver_on_queries_complete_locked                                           +17  +189%
      +9.9%      +8 [Unmapped]                                                                                +8  +9.9%
  +1.5%     +64 src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc             +64  +1.5%
       +11%     +64 grpc_core::(anonymous namespace)::AresDnsResolverFactory::CreateResolver(grpc_core::     +64   +11%
      +3.3%      +8 grpc_core::(anonymous namespace)::AresDnsResolver::StartResolvingLocked                   +8  +3.3%
  +0.3%     +16 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.cc             +16  +0.3%
      [NEW] +1.33Ki grpc_dns_lookup_ares_continue_after_check_localhost_and_ip_literals_locked           +1.33Ki  [NEW]
      [NEW]    +808 grpc_dns_lookup_ares_locked_impl                                                        +808  [NEW]
       +10%      +7 [Unmapped]                                                                                +7   +10%
      +1.8%      +1 grpc_resolve_address_invoke_dns_lookup_ares_locked                                        +1  +1.8%

  +0.0%    +776 TOTAL                                                                                +2.17Ki  +0.0%


****************************************************************

libgrpc++.so

     VM SIZE        FILE SIZE
 ++++++++++++++  ++++++++++++++

  [ = ]       0        0  [ = ]

grpc-testing · 2018-11-30T22:27:25Z

[trickle] No significant performance differences

apolcyn · 2018-11-30T22:27:45Z

thanks for the review!

grpc-testing · 2018-11-30T22:33:27Z

****************************************************************

libgrpc.so

     VM SIZE                                                                                            FILE SIZE
 ++++++++++++++ GROWING                                                                              ++++++++++++++
  +0.0%    +338 [None]                                                                               +1.74Ki  +0.0%
   +14%    +358 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.cc          +358   +14%
      [NEW]    +611 grpc_ares_ev_driver_create_locked                                                       +611  [NEW]
      +600%    +150 grpc_ares_ev_driver_start_locked                                                        +150  +600%
      [NEW]    +134 on_timeout_locked                                                                       +134  [NEW]
      +189%     +17 grpc_ares_ev_driver_on_queries_complete_locked                                           +17  +189%
      +9.9%      +8 [Unmapped]                                                                                +8  +9.9%
  +1.5%     +64 src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc             +64  +1.5%
       +11%     +64 grpc_core::(anonymous namespace)::AresDnsResolverFactory::CreateResolver(grpc_core::     +64   +11%
      +3.3%      +8 grpc_core::(anonymous namespace)::AresDnsResolver::StartResolvingLocked                   +8  +3.3%
  +0.3%     +16 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.cc             +16  +0.3%
      [NEW] +1.33Ki grpc_dns_lookup_ares_continue_after_check_localhost_and_ip_literals_locked           +1.33Ki  [NEW]
      [NEW]    +808 grpc_dns_lookup_ares_locked_impl                                                        +808  [NEW]
       +10%      +7 [Unmapped]                                                                                +7   +10%
      +1.8%      +1 grpc_resolve_address_invoke_dns_lookup_ares_locked                                        +1  +1.8%

  +0.0%    +776 TOTAL                                                                                +2.17Ki  +0.0%


****************************************************************

libgrpc++.so

     VM SIZE        FILE SIZE
 ++++++++++++++  ++++++++++++++

  [ = ]       0        0  [ = ]

grpc-testing · 2018-11-30T22:39:45Z

[trickle] No significant performance differences

grpc-testing · 2018-11-30T22:40:20Z

Objective-C binary sizes
*****************STATIC******************
  New size                      Old size
 2,020,410      Total (=)      2,020,410

 No significant differences in binary sizes

***************FRAMEWORKS****************
  New size                      Old size
11,174,076      Total (<)     11,174,078

 No significant differences in binary sizes

grpc-testing · 2018-11-30T22:50:43Z

Corrupt JSON data (indicates timeout or crash): 
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.new: 10
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.old: 10


[microbenchmarks] No significant performance differences

grpc-testing · 2018-11-30T23:01:17Z

Objective-C binary sizes
*****************STATIC******************
  New size                      Old size
 2,020,410      Total (=)      2,020,410

 No significant differences in binary sizes

***************FRAMEWORKS****************
  New size                      Old size
11,174,082      Total (>)     11,174,075

 No significant differences in binary sizes

…f deadlock

grpc-testing · 2018-11-30T23:12:12Z

Corrupt JSON data (indicates timeout or crash): 
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.new: 10
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.old: 10


[microbenchmarks] No significant performance differences

grpc-testing · 2018-11-30T23:12:44Z

Objective-C binary sizes
*****************STATIC******************
  New size                      Old size
 2,020,410      Total (=)      2,020,410

 No significant differences in binary sizes

***************FRAMEWORKS****************
  New size                      Old size
11,174,078      Total (>)     11,174,075

 No significant differences in binary sizes

grpc-testing · 2018-11-30T23:16:05Z

****************************************************************

libgrpc.so

     VM SIZE                                                                                            FILE SIZE
 ++++++++++++++ GROWING                                                                              ++++++++++++++
  +0.0%    +338 [None]                                                                               +1.74Ki  +0.0%
   +14%    +358 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.cc          +358   +14%
      [NEW]    +611 grpc_ares_ev_driver_create_locked                                                       +611  [NEW]
      +600%    +150 grpc_ares_ev_driver_start_locked                                                        +150  +600%
      [NEW]    +134 on_timeout_locked                                                                       +134  [NEW]
      +189%     +17 grpc_ares_ev_driver_on_queries_complete_locked                                           +17  +189%
      +9.9%      +8 [Unmapped]                                                                                +8  +9.9%
  +1.5%     +64 src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc             +64  +1.5%
       +11%     +64 grpc_core::(anonymous namespace)::AresDnsResolverFactory::CreateResolver(grpc_core::     +64   +11%
      +3.3%      +8 grpc_core::(anonymous namespace)::AresDnsResolver::StartResolvingLocked                   +8  +3.3%
  +0.3%     +16 src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.cc             +16  +0.3%
      [NEW] +1.33Ki grpc_dns_lookup_ares_continue_after_check_localhost_and_ip_literals_locked           +1.33Ki  [NEW]
      [NEW]    +808 grpc_dns_lookup_ares_locked_impl                                                        +808  [NEW]
       +10%      +7 [Unmapped]                                                                                +7   +10%
      +1.8%      +1 grpc_resolve_address_invoke_dns_lookup_ares_locked                                        +1  +1.8%

  +0.0%    +776 TOTAL                                                                                +2.17Ki  +0.0%


****************************************************************

libgrpc++.so

     VM SIZE        FILE SIZE
 ++++++++++++++  ++++++++++++++

  [ = ]       0        0  [ = ]

grpc-testing · 2018-11-30T23:25:14Z

[trickle] No significant performance differences

grpc-testing · 2018-11-30T23:26:00Z

Corrupt JSON data (indicates timeout or crash): 
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.new: 10
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.old: 10


[microbenchmarks] No significant performance differences

grpc-testing · 2018-11-30T23:57:24Z

Objective-C binary sizes
*****************STATIC******************
  New size                      Old size
 2,020,410      Total (=)      2,020,410

 No significant differences in binary sizes

***************FRAMEWORKS****************
  New size                      Old size
11,174,077      Total (<)     11,174,083

 No significant differences in binary sizes

grpc-testing · 2018-12-01T00:10:57Z

Corrupt JSON data (indicates timeout or crash): 
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.new: 10
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.old: 10


[microbenchmarks] No significant performance differences

apolcyn added lang/core disposition/FOR DISCUSSION release notes: yes Indicates if PR needs to be in release notes labels Nov 30, 2018

apolcyn assigned markdroth Nov 30, 2018

apolcyn requested review from AspirinSJL and markdroth as code owners November 30, 2018 10:22

markdroth reviewed Nov 30, 2018

View reviewed changes

src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.cc Outdated Show resolved Hide resolved

src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.cc Outdated Show resolved Hide resolved

apolcyn changed the title ~~DRAFT: cancel c-ares queries after a timeout to avoid getting stuck~~ Cancel c-ares queries after a timeout to avoid getting stuck Nov 30, 2018

markdroth reviewed Nov 30, 2018

View reviewed changes

test/cpp/naming/cancel_ares_query_test.cc Outdated Show resolved Hide resolved

markdroth approved these changes Nov 30, 2018

View reviewed changes

Cancel still-active c-ares queries after 10 seconds to avoid chance o…

b203ed3

…f deadlock

apolcyn force-pushed the fix_ares_deadlocks branch from 667010b to b203ed3 Compare November 30, 2018 23:08

apolcyn merged commit 5fed8e5 into grpc:master Dec 1, 2018

muxi mentioned this pull request Dec 3, 2018

Better slice management for windows reads (for v1.17.x) #17378

Merged

apolcyn mentioned this pull request Dec 3, 2018

Cancel still-active c-ares queries after a timeout, for 1.17.x #17382

Merged

lock bot locked as resolved and limited conversation to collaborators Mar 1, 2019

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apolcyn commented Nov 30, 2018 •

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