From 544807ba79f7e0c27f665761a3962c113601ec19 Mon Sep 17 00:00:00 2001
From: Danielle Lancashire <dani@hashicorp.com>
Date: Mon, 16 Dec 2019 10:56:32 +0100
Subject: [PATCH] env_aws: Disable Retries and set Session cfg
Previously, Nomad used hand rolled HTTP requests to interact with the
EC2 metadata API. Recently however, we switched to using the AWS SDK for
this fingerprinting.
The default behaviour of the AWS SDK is to perform retries with
exponential backoff when a request fails. This is problematic for Nomad,
because interacting with the EC2 API is in our client start path.
Here we revert to our pre-existing behaviour of not performing retries
in the fast path, as if the metadata service is unavailable, it's likely
that nomad is not running in AWS.
---
client/fingerprint/env_aws.go | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/client/fingerprint/env_aws.go b/client/fingerprint/env_aws.go
index f468af39b3..55163ff03c 100644
--- a/client/fingerprint/env_aws.go
+++ b/client/fingerprint/env_aws.go
@@ -75,7 +75,10 @@ func (f *EnvAWSFingerprint) Fingerprint(request *FingerprintRequest, response *F
timeout = 1 * time.Millisecond
}
- ec2meta := ec2MetaClient(f.endpoint, timeout)
+ ec2meta, err := ec2MetaClient(f.endpoint, timeout)
+ if err != nil {
+ return fmt.Errorf("failed to setup ec2 client: %v", err)
+ }
if !ec2meta.Available() {
return nil
@@ -191,15 +194,20 @@ func (f *EnvAWSFingerprint) linkSpeed(ec2meta *ec2metadata.EC2Metadata) int {
return netSpeed
}
-func ec2MetaClient(endpoint string, timeout time.Duration) *ec2metadata.EC2Metadata {
+func ec2MetaClient(endpoint string, timeout time.Duration) (*ec2metadata.EC2Metadata, error) {
client := &http.Client{
Timeout: timeout,
Transport: cleanhttp.DefaultTransport(),
}
- c := aws.NewConfig().WithHTTPClient(client)
+ c := aws.NewConfig().WithHTTPClient(client).WithMaxRetries(0)
if endpoint != "" {
c = c.WithEndpoint(endpoint)
}
- return ec2metadata.New(session.New(), c)
+
+ session, err := session.NewSession(c)
+ if err != nil {
+ return nil, err
+ }
+ return ec2metadata.New(session, c), nil
}
--
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