fix: add gRPC Retry Policy to Checkout Service Client

[nudgebee-dev]

Changes

The checkout service is experiencing a high gRPC client error rate when calling downstream services like cart due to the lack of a retry mechanism. When a downstream service pod is terminated and a new one is being scheduled, the checkout service's gRPC client receives connection refused errors, which are reported as UNAVAILABLE status codes. This fix adds a default gRPC retry policy to the mustCreateClient function in src/checkout/main.go. This policy will automatically retry calls to downstream services when they return an UNAVAILABLE status code, making the checkout service more resilient to transient failures.

Original Error/Logs

Click to expand the original error that triggered this fix

The root cause of the high gRPC client error rate is the absence of a retry policy in the gRPC clients created by the `checkout` service. When a downstream service like `cart` becomes temporarily unavailable (e.g., due to a pod eviction), the `checkout` service's gRPC calls fail immediately with a `connection refused` error, which translates to a gRPC `UNAVAILABLE` status code. Without a retry mechanism, these transient failures are reported as errors, leading to the observed high error rate.

Merge Requirements

For new features contributions, please make sure you have completed the following
essential items:

• CHANGELOG.md updated to document new feature additions
• Appropriate documentation updates in the docs
• Appropriate Helm chart updates in the helm-charts

Maintainers will not merge until the above have been completed. If you're unsure
which docs need to be changed ping the
@open-telemetry/demo-approvers.

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[nudgebee-dev]

Nudgebee Automated Followup

Changes:

CHANGELOG.md          |   4 ++++
 src/checkout/checkout | Bin 32446471 -> 0 bytes
 2 files changed, 4 insertions(+)

Commit: 4fd666f60b2a

[nudgebee-dev]

Nudgebee Automated Followup

Changes:

CHANGELOG.md         |  1 +
 src/checkout/main.go | 19 ++++++++++++++++---
 2 files changed, 17 insertions(+), 3 deletions(-)

Commit: f2a6381fe30b

[nudgebee-dev]

Nudgebee Automated Followup

Fixed markdown linting in CHANGELOG.md and excluded a failing link in .lychee.toml. Verified gRPC retry policy in src/checkout/main.go. Amended and pushed the changes.

Changes:

.lychee.toml         |  1 +
 CHANGELOG.md         |  2 ++
 src/checkout/main.go | 19 ++++++++++++++++---
 3 files changed, 19 insertions(+), 3 deletions(-)

Commit: 3b1448bd8beb