"PhabricatorApplicationTransactionCommentView->setDraft()" has exactly two callers: one in Slowvote...

Resolved by D21824.

Thank you!

In T13588#256950, @cspeckmim wrote:

A user just ran into this exception with Arcanist...

A user just ran into this exception with Arcanist (current master changeset) while running arc diff (using Mercurial) with PHP 8.1. I haven't looked too in depth but it seems similar to other PHP 8.1 issues.

[2022-05-17 20:49:47] EXCEPTION: (RuntimeException) substr(): Passing null to parameter #1 ($string) of type string is deprecated at [<arcanist>/src/error/PhutilErrorHandler.php:261]
arcanist(head=master, ref.master=3cc486d5c156)
  #0 PhutilErrorHandler::handleError(integer, string, string, integer)
  #1 substr(NULL, integer, integer) called at [<arcanist>/src/repository/api/ArcanistRepositoryAPI.php:807]
  #2 ArcanistRepositoryAPI::getDisplayHash(NULL) called at [<arcanist>/src/repository/marker/ArcanistRepositoryMarkerQuery.php:67]
  #3 ArcanistRepositoryMarkerQuery::execute() called at [<arcanist>/src/repository/query/ArcanistRepositoryQuery.php:20]
  #4 ArcanistRepositoryQuery::executeOne() called at [<arcanist>/src/repository/api/ArcanistMercurialAPI.php:988]
  #5 ArcanistMercurialAPI::getActiveBookmark() called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:2253]
  #6 ArcanistDiffWorkflow::buildDiffSpecification() called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:380]
  #7 ArcanistDiffWorkflow::run() called at [<arcanist>/scripts/arcanist.php:427]
<<< [1] (+8,567) <exec> 8,567,426 us

I am pretty sure that this error message does not exist prior to PHP 8.1, and PHP 7.4 can not possibly emit it. See here for some evidence that this is true -- note that the error message is not present in the script output until PHP 8.1:

Trying to fresh install using PHP 7.4 or PHP 8.1, have the same result when executing:

• ./bin/config set phd.user root

[2022-05-10 02:01:12] EXCEPTION: (RuntimeException) strlen(): Passing null to parameter #1 ($string) of type string is deprecated at [<arcanist>/src/error/PhutilErrorHandler.php:261]
arcanist(head=master, ref.master=fc5b228db537), phabricator(head=master, ref.master=698ada2470b1)
  #0 PhutilErrorHandler::handleError(integer, string, string, integer) called at [<phabricator>/src/infrastructure/env/PhabricatorEnv.php:128]
  #1 PhabricatorEnv::initializeCommonEnvironment(boolean) called at [<phabricator>/src/infrastructure/env/PhabricatorEnv.php:75]
  #2 PhabricatorEnv::initializeScriptEnvironment(boolean) called at [<phabricator>/scripts/init/lib.php:26]
  #3 init_phabricator_script(array) called at [<phabricator>/scripts/init/init-setup.php:11]
  #4 require_once(string) called at [<phabricator>/scripts/setup/manage_config.php:5]

There may be additional work here, but presuming this is more or less resolved until evidence to the contrary arises.

I believe D21811 covers this completely.

When this mechanism is removed (by commenting out the logic that cares about the 25% limit), we'd expect Drydock to build 8 resources at a time (limited by number of taskmasters). It actually builds ~1-4...

We may fopen() an additional stdout and/or stderr handle, but do not fclose() it?

I am suspicious that D21794 may have broken something subtle with unix magic, since I'm seeing some hangs out of deployment scripts wrapping daemon management scripts. I think the issue is probably one of:

The outline above isn't quite sufficient because when the active resource list is nonempty, we don't actually reach the "new allocation" logic. Broadly, executeAllocator() is kind of wonky and needs some additional restructuring to cover both the D19762 case ("allocate up to the resource limit before reusing resources") and the normal set of cases. The proper logic is something like:

This issue partially reproduces (consistent with the original report, not immediately consistent with my theorizing about a root cause in PHI2177 -- actually, looks like both parts are right, see below): Drydock builds ~1 working copy per minute serially until it reaches a pool size of 5 resources. Then, it begins allocating 2 simultaneous resources.

What options exist for inter-process communication?

Here's how I'm thinking about overengineering this:

This was resolved as part of T13630. I didn't actually put it in the UI anywhere, but all requests will now originate from 13.56.71.101, and this isn't likely to change given the wind-down of Phacility hosting.

D21801, motivated by T13676, made this more practical.

This is somewhat resolved and neither next steps or motivation are clear any longer, so I'm going to call it done until evidence to the contrary arises.

Perhaps a philosophical question here is: do we care about which repositories are checked out in a working copy resource?

Before, instant reclaim after lease destruction:

To create resource pressure, I'm now going to try this -- I guess I don't really need the --count flag, but it does make the terminal juggling slightly easier:

The blueprint thing was on the way toward creating allocation pressure, so D21802 allows you to select a blueprint (or a set of possible blueprints) with --blueprint. You can specify an ID or PHID:

That patch is reasonable, and shouldn't break anything as long as the list you provide is a subset of the possible list.

fill in the details a bit.

After D21796:

(one orthogonal bug I found is that bin/drydock lease discards any blueprints provided in an attributes JSON)

(one orthogonal bug I found is that bin/drydock lease discards any blueprints provided in an attributes JSON)

Grab a test lease on the host with:

Harbormaster needs a "Working Copy" blueprint, not just a "Host" blueprint.

Here's a fairly simple way to reproduce this:

How do modern servers written in C/C++ handle parallelizing requests?

Just for my own notes:

FWIW I've found by far the easiest way to work with microcontrollers is using micropython / circuitpython on any of these chips: ESP32, ATSAMD21/ATSAMD51 and RP2040. The esp32 is in many ways the easiest and most practical because it's extremely cheap and includes a wifi radio.

What are the practical limits of multi-system or multi-architecture binaries?

Just for visibility, this is I believe the change that broke Diffusion (which was fixed in rP52df4ff515b7), where the error message is something like

I generated D21794 with a native binary that has no dependency on system PHP (but does depend on system cURL).

Another open question is: before we call posix_isatty(STDOUT), how do we test whether STDOUT is a valid handle?

1. PHP doesn't link cURL statically and doesn't appear (?) to provide any easy way to link it statically.
   1. • Possible solution: build static cURL.
      • Possible solution: link cURL dynamically.
      • Possible solution: replace cURL with mbedTLS + a first-party HTTP client, since we don't care about 99% of what cURL does. Or implement first-party TLS hahaha except I'm half-serious? If HTTP/HTTPS is going to happen from an embedded context on my coffee maker I need a healthy embeddable TLS + HTTP stack anyway.
   2. The STDERR and STDOUT constants are defined by the CLI SAPI, and not present in the embed SAPI.
      • Possible solution: define them in the C wrapper.
      • Possible solution: polyfill them at startup in PHP (I'm not entirely sure this is possible).
      • Possible solution: abstract around them and use php://stderr and php://stdout instead. See also T13556. This is likely desirable anyway.
   3. When arc tries to load PHP code, it needs to read data out of the executable binary in some set of conditions (e.g., "if we miss on disk").
      • Possible solution: hook zend_compile_file(), which seems to be the expected way to approach this. The flow in phar_compile_file() seems similar.
   4. To run unit tests, arc depends on the presence of a php binary on the system.
      • Possible solution: accept that you must also have PHP to run arc's tests (and that system PHP may differ from arc php).
      • Possible solution: also include the PHP CLI wrapper and invoke it when arc is executed as php, providing what is essentially a fallback toolset.
      • Possible solution: provide a "unit test helper" fallback toolset.
      • Possible solution: rewrite the 5 trivial cases where we need this (support/unit/*) in shell script (but: the reason to do these in PHP in the first place was so that they're portable to Windows).

Can we build a single binary with a bunch of data in it (e.g., a picture of a cat) without breaking anything?