PHP runtime: Support for Cloud Logging daemon

[sonnysasaka]

In the Cloud Logging documentation, it's mentioned that app engine flex environment supports the enable_stackdriver_integration: true option that enables PHP apps to not be blocked by network due to sending batch logs to Cloud Logging, but instead sends the batch logs locally to another running daemon. However, testing reveals that this is not supported in the flex runtime ever since using this buildpacks (I can only find evidence that this is supported in the previous docker-based runtime https://github.com/GoogleCloudPlatform/php-docker).

Some questions, requests, and recommendations:

1. If this is true, please update the documentation to reflect the case that this is not supported in the buildpacks-based flex environment. Otherwise customers may be disappointed by misleading information.
2. Supporting this flag out of the box may be difficult and cannot be delivered soon, but I think there is a quick workaround that can unblock customers to use this feature very quickly:

• Document how to customize the runtime, e.g. supervisord config to run the background logger, something like:

  [program:stackdriver-batch-daemon]
  command=php vendor/bin/google-cloud-batch daemon
  autostart=true
  ...
  

  And set the environment variable IS_BATCH_DAEMON_RUNNING=1.
  I got this from hacking the https://github.com/GoogleCloudPlatform/php-docker and tested that this works. If this is the right way, Google could document this to be a "supported" customization to enable this feature.
• In order for that configuration to work, the missing thing from the PHP runtime is enabling the extensions sysvmsg, sysvsem, and sysvshm (https://github.com/googleapis/google-cloud-php-core/blob/686ffd0bb1328cd2ee963c4444e2ab4b111ba3ba/src/SysvTrait.php#L59). I tested from php -i that the current runtime only supports sysvshm.

As a customer needing this feature, I can just handle the supervisord config manually for now, but I need support to enable the sysv* extensions from Google, as this can only be delivered via the downloadable runtime at https://dl.google.com/runtimes/*/php/* (

buildpacks/pkg/runtime/install.go

Line 201 in e4b3705

if err := fetch.Tarball(runtimeURL, layer.Path, stripComponents); err != nil {

).

TL;DR: Would Google be able to satisfy the small request to build PHP with --enable-sysv*? If this PHP runtime is also open source, please let me know if I can help contribute to it. (cc: @jama22 @kennethye1)