Klibs: syslog improvements #1674
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francescolavra
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This can be used by Nanos to identify the image where it is running (see e.g. nanovms/nanos#1674).
This was referenced Feb 2, 2022
In case of failure to resolve the syslog server name, using a pure exponential backoff delay for retrying DNS resolution can cause logs to be shipped long after a previousy unresolvable server became resolvable. This commit puts a 1-minute limit to the backoff delay. The current code stops resolving the syslog server name after a successful resolution, and this can cause issues if the server IP address changes. To solve this problem, the dns_gethostbyname() function is now called even after the server name has been successfully resolved, so that when the cached DNS entry expires a new DNS request will be sent.
With this change, if the IMAGE_NAME environment variable is present it is used to populate the APP_NAME field in syslog messages, while the program name is used as a fallback.
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This PR contains miscellaneous improvements to the syslog klib:
successfully resolved, so that when the cached DNS entry expires a new DNS request will be sent and any changes to the server IP address will be observed
the program name is used as a fallback