[FEATURE] Support for Failure Sink in Elasticsearch.Serilog.Sink

[learnevolve]

Hi Team,

In the earlier Serilog.Sinks.Elasticsearch package, there was support for a failure sink mechanism. This was extremely useful — when there were issues pushing logs to Elasticsearch (e.g., network failures, serialization issues), the failure sink or failure callback would be triggered, allowing us to route the failed logs to alternative destinations (e.g., a file sink or another fallback system).

However, in the newer Elasticsearch.Serilog.Sink package, it seems this feature is missing or not clearly documented.

Request:
Could you please confirm whether there is an equivalent option in the new package for handling failed log events (such as a failure sink or a failure callback)? If not, would it be possible to consider adding this feature? It is critical for production environments where log loss is unacceptable, and having a fallback mechanism is essential for observability and troubleshooting.

Thanks for the great work on the package!

[learnevolve]

@Mpdreamz

Could you please assist with this? We are planning to incorporate it for production support and are checking if there is a way to capture the Failures.

[Mpdreamz]

This is now a builtin feature in serilog!

https://nblumhardt.com/2024/10/fallback-logging/

I just opened #502 for us to bump our serilog lowest dependency to one that supports fallback logging and updates our sink implementations to explicitly emit dropped items to it.

[Mpdreamz]

#502 is now released as part of https://www.nuget.org/packages/Elastic.CommonSchema/8.18.0

[learnevolve]

@Mpdreamz, Thank you for quickly implementing the feature upon request.

If possible, could you please provide an example demonstrating the use of a fallback sink for the event viewer or file sink?

Updating the documentation with this example would be very helpful.