Reduce timeout for accessing EC2 instance metadata service #159
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Previously we were re-using our shared HTTP client, which has a rather high timeout (120 seconds) that causes the HTTP client to wait around for a long time. This is generally intentional (since it includes the time spent downloading a request body), but is a bad idea when running into EC2's IDMSv2 service that has a network-hop based limit. If that hop limit is exceeded, the requests just go to nowhere, causing the client to wait for a multiple of 120 seconds (~10 minutes were observed). This instead uses a special client for the EC2 instance metadata service that has a much lower timeout (1 second, like in the AWS SDK itself), to avoid the problem. See also aws/aws-sdk-go#2972
msakrejda
approved these changes
Mar 9, 2021
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Previously we were re-using our shared HTTP client, which has a rather
high timeout (120 seconds) that causes the HTTP client to wait around
for a long time. This is generally intentional (since it includes the
time spent downloading a request body), but is a bad idea when running
into EC2's IDMSv2 service that has a network-hop based limit. If that
hop limit is exceeded, the requests just go to nowhere, causing the
client to wait for a multiple of 120 seconds (~10 minutes were observed).
This instead uses a special client for the EC2 instance metadata service
that has a much lower timeout (1 second, like in the AWS SDK itself), to
avoid the problem.
See also aws/aws-sdk-go#2972