Add Reverse Diagnostics Server #33307

josalem · 2020-03-06T22:28:05Z

This PR adds the ability for the runtime to connect to a pre-existing IPC Transport for the Diagnostics Server. This enables several interesting scenarios, including:

Many apps connecting to a single diagnostics agent
tracing via IPC at startup (imagine doing dotnet trace run <executable> ...)
A busybox-esque agent being configurable in a side-car container
A host-based agent running and tracing an application in a container

This is achieved, by adding the non-blocking Accept (think listen on Linux), Connect, and Poll APIs to the diagnostics PAL. Using these, the runtime is able to listen on the original IPC Transport it creates ($TMPDIR/dotnet-diagnostics-<pid>) and this reversed connection if configured.

This reversed connection is opt-in and only activates when a path is specified in the DOTNET_DiagnosticsMonitorAddress environment variable.

The following logic is almost entirely inside DiagnosticsIpcFactory::GetNExtAvailableStream(...)

If a user configures this mechanism, the runtime will infinitely attempt to connect the specified transport and is resilient to that transport closing and reopening. The retry logic is as follows:

Reverse connection is not configured => infinitely block on server connection
Reverse connection is configured
- Reverse connection is successful => cache connection, set timeout to max (30s)
- Reverse connection is unsuccessful or closed => set timeout to minimum (250ms) and poll on other connections, multiply by falloff factor (2) for each attempt until max (30s)

The runtime caches reverse connections so that it is not constantly attaching to the reverse transport every time poll times out or the server connection is used. These cache entries get cleared when a connection is used or the connection is hung up.

~~This PR is currently missing~~ The following will be a separate PR:

Semantics for blocking startup of the runtime
- To enable collecting startup events, we would add a configurable blocking timeout to runtime startup
- an environment variable will take a value of -1 (infinite), or 0 to n milliseconds
- this value will be used to determine how long to block eemain before an EventPipe session is started.
- the default will be 0 (no block)

CC - @tommcdon @shirhatti @noahfalk @sywhang

Dotnet-GitSync-Bot · 2020-03-06T22:28:09Z

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noahfalk

Added a few comments and questions. Holding off on a more detailed review in expectation that things are still changing : )

src/coreclr/src/vm/diagnosticserver.cpp

src/coreclr/src/inc/clrconfigvalues.h

src/coreclr/src/debug/debug-pal/win/diagnosticsipc.cpp

src/coreclr/src/vm/diagnosticsserverprotocolhelper.h

noahfalk

Its shaping up but will still need some more work to be robust. Happy to chat if you've got questions about anything.

src/coreclr/src/vm/diagnosticserver.cpp

src/coreclr/src/vm/diagnosticsipcfactory.cpp

src/coreclr/src/vm/diagnosticsprotocol.h

src/coreclr/src/vm/diagnosticsipcfactory.cpp

src/coreclr/src/debug/inc/diagnosticsipc.h

src/coreclr/src/debug/debug-pal/win/diagnosticsipc.cpp

noahfalk · 2020-03-22T12:13:21Z

src/coreclr/src/debug/debug-pal/win/diagnosticsipc.cpp


        const BOOL fSuccessCloseHandle = ::CloseHandle(_hPipe);
-        assert(fSuccessCloseHandle != 0);
+        _ASSERTE(fSuccessCloseHandle != 0);


I would add an assert that that OVERLAPPED operation is complete. I would also test to confirm that DisconnectNamedPipe() finishes a ConnectNamedPipe operation when it is still pending. Destroying an OVERLAPPED struct before the operation ends usually causes painful to debug memory corruption issues.

src/coreclr/src/vm/diagnosticsipcfactory.cpp

* no select on unix * untested on unix

* Change DOTNET_DiagnosticsServerAddress to DOTNET_DiagnosticsClientModeAddress * works for original connection mode * untested for client mode

* fix array alloc * properly cast array size

* Adds ConnectionState class for hiding server/client diff * simplifies code for easier reading

* test was creating a pipe with a 0 buffer * runtime needs to handle a 0 buffer namedpipe

* makes advertisement not block for more than 100 ms * TODO: implement on non-windows

josalem · 2020-04-17T17:18:30Z

/azp run runtime

azure-pipelines · 2020-04-17T17:18:55Z

Azure Pipelines successfully started running 1 pipeline(s).

noahfalk

Alright, things are starting to look ship shape 👍 I did find a few more minor potential issues, comments inline.

src/coreclr/src/debug/debug-pal/win/diagnosticsipc.cpp

src/coreclr/src/debug/inc/diagnosticsipc.h

src/coreclr/src/vm/diagnosticsprotocol.h

src/coreclr/src/vm/ipcstreamfactory.cpp

noahfalk · 2020-04-18T01:34:46Z

src/coreclr/src/vm/ipcstreamfactory.h

+                _pIpc->Close(callback);
+            if (_pStream != nullptr)
+                _pStream->Close(callback);
+        }


_pIpc and _pStream need to be deleted (not that a leak on shutdown would really matter, but may as well clean up properly)

I specifically leaked these since the PAL is unaware of shutdown paths and has access to these pointers. This method is specifically called from a different thread than the server thread. If we delete them in this code path it can lead to AVs on the server thread in the PAL (inside IpcStream::DiagnosticsIpc::Poll specifically). Rather than introduce some form of knowledge of runtime state to the PAL or potentially adding locks protecting access I opted to just leak the memory on shutdown, since that is the only place this method is called. I should add a comment that calls out this assumption, though.

src/coreclr/tests/src/tracing/eventpipe/reverse/reverse.cs

josalem · 2020-04-20T06:32:39Z

Remaining failure appears to be an AzDO Package Feed or NuGet manifest error. All test runs passed.

This reverts commit 629dba5.

…t#35767)" This reverts commit 7a95cc8.

josalem added EventPipe area-Diagnostics-coreclr labels Mar 6, 2020

josalem added this to the 5.0 milestone Mar 6, 2020

josalem requested review from noahfalk and sywhang March 6, 2020 22:28

josalem self-assigned this Mar 6, 2020

noahfalk reviewed Mar 7, 2020

View reviewed changes

noahfalk mentioned this pull request Mar 12, 2020

[Feature request] dotnet-trace at startup dotnet/diagnostics#619

Closed

3 tasks

josalem marked this pull request as ready for review March 18, 2020 00:06

josalem requested a review from noahfalk March 18, 2020 00:06

josalem changed the title ~~[Draft] Add Reverse Diagnostics Server (client-mode)~~ Add Reverse Diagnostics Server (client-mode) Mar 18, 2020

This was referenced Mar 19, 2020

Allow tools to specify a specific OS transport dotnet/diagnostics#770

Closed

Add DiagnosticsAgent API dotnet/diagnostics#931

Closed

noahfalk requested changes Mar 22, 2020

View reviewed changes

josalem force-pushed the dev/josalem/diag-server-handshake branch from 9f108d8 to 20f3745 Compare April 1, 2020 22:41

John Salem added 11 commits April 2, 2020 14:59

Add Advertise IPC Command

bc21866

Add untested select connect and nonblocking accept

0255b37

Add select API on windows

7f8bb61

* no select on unix * untested on unix

Implement select for unix

4b97ca8

Update diagnostics server to use both modes

0cb1e88

* Change DOTNET_DiagnosticsServerAddress to DOTNET_DiagnosticsClientModeAddress * works for original connection mode * untested for client mode

Add DiagnosticsIpcFactory abstraction

dbc9624

Fix precondition

52cd9b0

* fix array alloc * properly cast array size

fix x86 build

3918060

Fixed errors

33da551

fix pipe connection on window

f7a28c4

fix gcc build

22e4476

John Salem added 7 commits April 13, 2020 16:33

Add ConnectionState abstraction

d93d846

* Adds ConnectionState class for hiding server/client diff * simplifies code for easier reading

Add test case

0fce7bc

Fix windows build

6e2f642

Fix test

18c9959

* test was creating a pipe with a 0 buffer * runtime needs to handle a 0 buffer namedpipe

Introduce a timeout to read/write

91d6d0e

* makes advertisement not block for more than 100 ms * TODO: implement on non-windows

Implement timeout read/write for unix

d4bf4c1

adjust poll timeout to be more aggressive

9311238

josalem requested a review from noahfalk April 17, 2020 22:18

noahfalk approved these changes Apr 18, 2020

View reviewed changes

John Salem added 6 commits April 19, 2020 18:41

Fix nits from review

b0e1218

simplify branching in GetIpcPollHandle

1cd8f29

Add 2 byte field to advertise

3530a25

Fix cast for advertize

67acd21

additional logging in tests

8c83f22

Loops unix send/recv to handle partial io

1cbb720

josalem changed the title ~~Add Reverse Diagnostics Server (client-mode)~~ Add Reverse Diagnostics Server Apr 20, 2020

josalem merged commit 629dba5 into dotnet:master Apr 20, 2020

jaredpar mentioned this pull request Apr 21, 2020

Builds legs getting abandoned due to agent notification issues #35223

Closed

jkotas mentioned this pull request Apr 30, 2020

Test hang in System.Diagnostics.Tracing.EventProvider.EventUnregister #35451

Closed

jkotas added a commit that referenced this pull request May 3, 2020

Revert "Add Reverse Diagnostics Server (#33307)"

7fd1313

This reverts commit 629dba5.

jkotas mentioned this pull request May 3, 2020

Revert "Add Reverse Diagnostics Server" #35767

Merged

jkotas added a commit that referenced this pull request May 3, 2020

Revert "Add Reverse Diagnostics Server (#33307)" (#35767)

7a95cc8

This reverts commit 629dba5.

josalem pushed a commit to josalem/runtime that referenced this pull request May 7, 2020

Revert "Revert "Add Reverse Diagnostics Server (dotnet#33307)" (dotne…

e623063

…t#35767)" This reverts commit 7a95cc8.

ghost locked as resolved and limited conversation to collaborators Dec 10, 2020

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Add Reverse Diagnostics Server #33307

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Add Reverse Diagnostics Server #33307

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