fix(bigquery): retry on tcp timeout errors

[MartinSahlen]

Description

The cloud.google.com/go/bigquery client does not automatically retry API calls that fail with a dial tcp: i/o timeout error. This type of error is a common transient network failure, especially in distributed cloud environments, and often occurs when initiating a connection.

The underlying Go error wrapper correctly identifies this as a retryable error (as seen by retryable: true in the error message), but the BigQuery client's internal retry predicate fails to catch it, immediately propagating the error to the user. This forces developers to build their own complex retry wrappers around the client, which should ideally be handled by the library's built-in resilience mechanisms.

Expected Behavior

When an API call (such as jobs.insert or jobs.query) fails with a dial tcp: i/o timeout, the client library should recognize this as a transient, retryable error and automatically retry the operation using its built-in exponential backoff strategy.

Actual Behavior

The API call fails immediately and returns the i/o timeout error directly to the caller. No retry is attempted by the library.
The full error message is similar to the following:

update table from struct: Post \"https://.../bigquery/v2/projects/.../jobs?alt=json&prettyPrint=false&uploadType=multipart\": dial tcp 34.50.146.6:443: i/o timeout (type: wrapError, retryable: true): Post \"https://.../bigquery/v2/projects/.../jobs?alt=json&prettyPrint=false&uploadType=multipart\": dial tcp 34.50.146.6:443: i/o timeout

Code Snippet

The issue can be observed with any standard API call that initiates a network request. For example, when using a Loader to start a job:

package main

import (
	"context"
	"log"

	"cloud.google.com/go/bigquery"
)

func main() {
	ctx := context.Background()
	projectID := "your-project-id"

	client, err := bigquery.NewClient(ctx, projectID)
	if err!= nil {
		log.Fatalf("bigquery.NewClient: %v", err)
	}
	defer client.Close()

	// Assume 'gcsRef' is a *bigquery.GCSReference pointing to a file.
	// This call to Run() initiates a jobs.insert API call.
	loader := client.Dataset("my_dataset").Table("my_table").LoaderFrom(gcsRef)
	
	job, err := loader.Run(ctx)
	if err!= nil {
		// When a "dial tcp: i/o timeout" occurs, the error is returned here
		// immediately without any retry attempts from the library.
		log.Fatalf("Failed to start load job: %v", err)
	}

	//... wait for job completion
}

Additional Context & Analysis

The root cause appears to be in the library's internal retryableError predicate. This function does not check for errors that satisfy the net.Error Timeout() method.
The current implementation checks for interface{ Temporary() bool }:

//...
	case interface{ Temporary() bool }:
		if e.Temporary() {
			return true
		}
//...

However, a dial tcp: i/o timeout is a net.Error where Timeout() returns true, but Temporary() may not. The Temporary() method was deprecated in Go 1.18 because its definition was ambiguous and ill-defined. Most errors that were once "temporary" are now more accurately classified as timeouts.

Because the library's predicate relies on this deprecated method and omits a check for the Timeout() method, it fails to identify one of the most common types of transient network errors.

The proposed fix in this PR is to update the retryableError predicate to also include a check for timeout errors, for example:

//...
	case interface{ Timeout() bool }:
		if e.Timeout() {
			return true
		}
	case interface{ Temporary() bool }:
//...

Adding this case will improve the client's resilience and align its behavior with the expectation that transient network timeouts are handled automatically.

Hoping for positive feedback on this one and that we can get it merged quickly. Cheers!

[google-cla]

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[gemini-code-assist]

Summary of Changes

Hello @MartinSahlen, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the resilience of the cloud.google.com/go/bigquery client by modifying its error retry mechanism. It addresses a critical gap where dial tcp: i/o timeout errors, common in distributed cloud environments, were not being automatically retried. By incorporating a check for Timeout() errors, the client will now transparently handle these transient network issues with its built-in exponential backoff strategy, improving application stability and reducing the need for manual retry implementations.

Highlights

• BigQuery Client Retry Logic: The BigQuery client's internal retryableError predicate has been updated to correctly identify dial tcp: i/o timeout errors as retryable. Previously, these transient network failures were not retried automatically, forcing users to implement custom retry logic.

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[gemini-code-assist]

Code Review

This pull request provides a valuable fix for an important resilience issue in the BigQuery client. The detailed description accurately identifies that dial tcp: i/o timeout errors were not being automatically retried. The implemented change, which adds a check for timeout errors using the Timeout() method in the retryableError function, is the correct and modern approach in Go for handling such transient network issues. This small and targeted modification will significantly improve the client's robustness and user experience by handling common network timeouts automatically. The change is well-implemented and I have no further suggestions. It is ready for merging.

[alvarowolfx]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

@MartinSahlen can you sign the CLA ?

[MartinSahlen]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

@MartinSahlen can you sign the CLA ?

Yes I did shortly after submitting the PR and also retriggered the test which passed already.

[shollyman]

Thanks for the PR and the detailed writeup!

One minor request: Could you add a testcase for this to TestRetryableErrors in bigquery_test.go? It looks like https://pkg.go.dev/net#DNSError gives us an easy to use example error for this case.

[MartinSahlen]

Thanks for the PR and the detailed writeup!

One minor request: Could you add a testcase for this to TestRetryableErrors in bigquery_test.go? It looks like https://pkg.go.dev/net#DNSError gives us an easy to use example error for this case.

Thanks! I can give it a go. Firstly I need to understand the test structure and how to set up some mock errors/responses, will give a shout if I get stuck.