Triage Crawler Exceptions: DNS Failures when fetching

[brphelps]

exceptions | summarize DnsFailure = countif(outerMessage contains "getaddrinfo ENOTFOUND"),

[brphelps]

When triaging, make sure to identify whether this issue should or shouldn't be happening -- if it's not truly exceptional, try to convert to a less interesting tracing method (e.g. a warning trace).

[jeffmendoza]

Another case where the crawler is doing what it should, but finds invalid links. Should be a log and move on. Unfortunately this is also logged here:

https://github.com/clearlydefined/crawler/blob/master/ghcrawler/lib/crawler.js#L132

The stack trace doesn't point to the actual call