The First Draft: Building a Load Test Utility for S3

In the middle of an intensive coding session to build a horizontally scalable S3-compatible storage system, a single message captures the moment when a developer transitions from exploration to creation. Message 930 in this conversation is the first attempt at writing a comprehensive load testing utility for the S3 frontend proxy. It is a message that reveals as much through its errors as through its intentions—a snapshot of a developer working at the boundary between understanding an existing codebase and extending it with new functionality.

The Message

The assistant writes:

Now I understand the structure. Let me create a comprehensive loadtest utility. I'll create a new file loadtest.go:

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[write] /home/theuser/gw/integrations/ritool/loadtest.go Wrote file successfully.

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LSP errors detected in this file, please fix:

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ERROR [8:2] "encoding/hex" imported and not used ERROR [18:2] could not import github.com/cheggaaa/pb/v3 (no required module provides package "github.com/cheggaaa/pb/v3") ERROR [343:56] not enough arguments in call to http.NewRequestWithContext have (context.Context, string, string) want (context.Context, string, string, io.Reader) ERROR [365:59] not eno...

On its surface, this is a simple status update: the assistant has written a file, and the language server has found errors. But beneath that surface lies a rich story about how software gets built in practice—the iterative cycle of writing, checking, and fixing that characterizes real development work.

Context and Motivation: Why This Message Was Written

To understand why this message exists, we need to trace backward through the conversation. The user's request in message 925 was explicit and ambitious:

Write a loadtest utility in ritool, util that writes objects, incl multiparts, into the endpoints, X to Y kb/mb per object, some read/write ratio. The tool should test throughput and correctness of read-after-write guarantee.

This is a natural next step after the team had spent significant effort building and debugging a three-layer S3 architecture: stateless frontend proxies routing requests to Kuri storage nodes backed by YugabyteDB. The architecture was working—the cluster monitoring dashboard showed live metrics, round-robin distribution was verified, and the test cluster was operational. But how do you know it works well? How do you know it can handle real traffic patterns? How do you verify that objects written can be read back correctly under load?

The loadtest utility was the answer to all of these questions. It would simulate realistic traffic patterns with configurable object sizes, read/write ratios, and concurrency levels. It would verify read-after-write correctness using checksums. It would report throughput and latency percentiles. In short, it would transform the test cluster from a demonstration of functionality into a platform for performance validation.

The assistant's first step was to understand the existing codebase. Messages 926 through 929 show a systematic exploration of the ritool directory structure, reading the main entry point (main.go), studying existing command implementations (like carlog.go), and understanding the patterns used for CLI command registration with the urfave/cli/v2 library. This exploration phase was essential—the assistant needed to know how commands were registered, how flags were defined, and what libraries were already available before writing new code.

The Assumptions Embedded in the First Draft

The LSP errors in message 930 reveal several assumptions the assistant made—some reasonable, some less so.

Assumption 1: The pb progress bar library uses the v3 API. The error could not import github.com/cheggaaa/pb/v3 indicates the assistant imported the v3 path of the progress bar library. However, examining the existing carlog.go file (which the assistant had read in message 927) would have shown that the project uses the older github.com/cheggaaa/pb package, not the v3 sub-path. The older API uses pb.New64() and pb.Start() rather than the pb/v3 options-based API. This is a subtle but important mismatch—using the wrong import path means the code won't compile at all, and even if it did, the API would be completely different.

Assumption 2: http.NewRequestWithContext can be called without a body parameter. The error at line 343 shows the assistant called http.NewRequestWithContext(ctx, "PUT", url) with only three arguments, but the function signature requires four: (ctx, method, url, body io.Reader). For requests without a body (like GET requests), the correct approach is to pass nil or http.NoBody. This is a common Go API gotcha—the function signature changed between Go versions, and the body parameter is required even when empty.

Assumption 3: The encoding/hex import would be needed. The unused import at line 8 suggests the assistant anticipated needing hex encoding (likely for MD5 checksum formatting) but either didn't use it yet or used a different approach. This is a minor issue but indicates the code was written in a single pass rather than incrementally.

These assumptions aren't failures—they're the natural result of writing code without the ability to compile-check it. The assistant was working from memory and pattern-matching, not from a live compilation environment. The LSP diagnostics provided the immediate feedback needed to correct these issues.

Input Knowledge Required to Understand This Message

A reader needs substantial context to understand what's happening in message 930. First, they need to know that ritool is a CLI tool within the project that provides various repository manipulation commands—it's the command-line interface for interacting with the storage system. The existing commands include head, carlog, idxLevel, ldbcid, group, and claimsExtend, each in its own .go file.

Second, the reader needs to understand the project's architecture: a horizontally scalable S3-compatible storage system with stateless frontend proxies routing to Kuri storage nodes. The loadtest utility targets the S3 frontend proxy at port 8078, which is the entry point for all S3 API operations.

Third, the reader needs familiarity with Go's CLI patterns using urfave/cli/v2, the pb progress bar library, and the standard net/http package. The LSP errors reference specific Go API details that would be opaque to someone without Go experience.

Output Knowledge Created by This Message

Message 930 created the initial version of loadtest.go—an 800+ line file that would become the foundation for the load testing infrastructure. While the message itself only shows the LSP errors, the subsequent messages in the conversation reveal the full scope of what was written:

• A CLI command structure with flags for endpoint URL, bucket name, concurrency, duration, min/max object sizes, multipart threshold, read ratio, verification, and cleanup
• A worker pool that generates random objects, writes them via PUT requests, reads them back via GET requests, and verifies MD5 checksums
• Support for multipart uploads using the S3 API's CreateMultipartUpload, UploadPart, and CompleteMultipartUpload sequence
• Progress bars for visual feedback during long-running tests
• Statistical reporting including throughput, latency percentiles, and error rates The message also created a debugging task: the LSP errors needed to be fixed before the code would compile. This led to a series of follow-up messages (931 through 937) where the assistant iteratively fixed each error, adapting to the older pb API, correcting the HTTP request signatures, and removing unused imports.

The Thinking Process Visible in the Message

The most telling phrase in message 930 is the opening: "Now I understand the structure." This reveals the assistant's cognitive process—it had spent several messages exploring and analyzing the codebase, and had reached a threshold of understanding sufficient to begin writing. The exploration phase (messages 926-929) involved:

1. Reading the main entry point to understand command registration
2. Reading an existing command (carlog.go) to understand the pattern
3. Checking for utility directories or shared code
4. Listing the directory contents to see all existing files The decision to create a single file (loadtest.go) rather than multiple files or a subdirectory follows the existing pattern—each command in ritool is a single file. The decision to use the pb progress bar library follows the precedent set by carlog.go. The decision to use http.NewRequestWithContext follows modern Go best practices for HTTP clients with timeout support. What's notable is what the message doesn't show: the actual content of the file. The LSP errors are the only visible output, serving as a proxy for the code that was written. This is a common pattern in AI-assisted coding—the tool writes a file, the language server validates it, and errors are surfaced for correction. The message is simultaneously a success (the file was written) and a failure (it has errors), reflecting the iterative nature of software development.

Mistakes and Their Significance

The most significant mistake in message 930 is the incorrect pb import path. This error cascaded through multiple subsequent edits (messages 931-937) as the assistant tried to adapt the progress bar code to match the older API. Each edit fixed one set of errors but revealed new ones—a classic debugging chain where fixing the import revealed API mismatches, which revealed method name differences, and so on.

The http.NewRequestWithContext error is more straightforward but equally important. It reveals that the assistant was writing HTTP client code without the body parameter, which would have caused compilation failures for PUT and POST requests. This is the kind of error that a compiler catches immediately but that's easy to miss when writing code in a text editor without live compilation.

The unused encoding/hex import is minor but suggests the assistant may have been writing code faster than it could track dependencies. It's a reminder that even with AI assistance, code review and cleanup are essential steps.

Conclusion

Message 930 is a microcosm of real-world software development: the moment of creation, the inevitable errors, and the beginning of the fix cycle. It's not the most polished message in the conversation—it's full of mistakes and incomplete information. But it's the most honest representation of how code actually gets written: not in a single perfect draft, but in a series of approximations, each one closer to the goal than the last.

The loadtest utility that emerged from this process (committed in message 947 as 2d748bd) would go on to be further optimized in subsequent segments, with pre-allocated buffers and shard-based data generation to eliminate bottlenecks. But it all started here, with a single message that said "Now I understand the structure" and a file full of errors waiting to be fixed.