The Stuck Deal Check Loop: Debugging a Production Deadlock in a Distributed Storage System

Introduction

In the trenches of production debugging, few moments are as telling as the one captured in message 2269 of this coding session. The assistant, deep in the process of diagnosing a stalled Filecoin Gateway (FGW) cluster, finds themselves staring at a perplexing contradiction: a CIDgravity API call that should have timed out in 30 seconds has been running for over two minutes with no resolution. The message is a snapshot of real-time investigative work—a developer running terminal commands against a live production system, trying to understand why a critical background process has frozen. This article examines that single message in detail, unpacking the reasoning, assumptions, technical context, and thinking process that it reveals.

The Message

The assistant writes:

The deal check started at 10:33:42 and hasn't finished yet after 2+ minutes. The 30s timeout should have triggered. Let me check if it's still running or if there's an issue:

>

``bash # Check if deal tracker is stuck ssh 10.1.232.83 "sudo journalctl -u kuri -f --no-pager" & JPID=$! sleep 15 kill $JPID 2>/dev/null || true ``

>

`` Feb 04 10:35:55 fgw-ribs1 kuri[29838]: 2026-02-04T10:35:55.747Z WARN rpc go-jsonrpc@v0.8.0/handler.go:425 error in RPC call to 'RIBS.BalanceManagerInfo': get wallet balance: Feb 04 10:35:55 fgw-ribs1 kuri[29838]: github.com/CIDgravity/filecoin-gateway/rbdeal.(*ribs).BalanceManagerInfo Feb 04 10:35:55 fgw-ribs1 kuri[29838]: /home/theuser/gw/rbdeal/wallet.go:117 Feb 04 10:35:55 fgw-ribs1 kuri[29838]: - RPC client error: sendRequest failed: request failed, ... ``

This brief exchange—a shell command, a 15-second wait, and a stack trace—encapsulates an entire debugging session's tension. The assistant is trying to determine whether the deal check loop is genuinely stuck or merely slow, and the output reveals a different problem entirely: an RPC call to BalanceManagerInfo is failing, which may be the root cause of the stall.

The Broader Context: Why This Message Was Written

To understand why this message exists, one must understand the production environment it inhabits. The FGW system is a horizontally scalable S3-compatible storage architecture built on the Filecoin network. It uses "Kuri" storage nodes that manage data groups, track deals with Filecoin storage providers, and maintain a distributed database via YugabyteDB. A critical component is the "deal tracker"—a background loop that periodically checks the state of on-chain deals through the CIDgravity API, identifies groups ready for new deals, and initiates storage proposals.

Earlier in the session, the assistant had been wrestling with two production issues simultaneously. First, the Lotus API endpoint (api.chain.love) was returning HTTP 429 rate-limiting errors, requiring a migration to pac-l-gw.devtty.eu. Second, the repair worker's staging directory was configured to /data/repair-staging, which sat on a read-only partition instead of the writable /data/fgw/ mount. The assistant had fixed both issues, rebuilt the binary, redeployed to both Kuri nodes, and restarted the services.

But the redeployment revealed a new problem: the CIDgravity deal check loop—the very mechanism that drives the system's core function of making Filecoin deals—was not completing. The assistant had confirmed earlier that the CIDgravity API itself was responsive (returning 5.3MB of data in 2.6 seconds when called directly via curl with the correct X-API-KEY header). Yet the Go HTTP client inside the Kuri process was apparently timing out after 30 seconds, according to the code's configuration. The logs showed the deal check starting at 10:33:42, but by 10:35:55—over two minutes later—there was still no "deal check loop finished" message.

This is the precise moment message 2269 was written. The assistant is confronting an anomaly: a timeout that should have fired but didn't, or a process that is stuck in a way that bypasses the normal timeout mechanism. The message is a diagnostic probe, designed to determine the state of the running process.## The Reasoning and Motivation Behind the Diagnostic

The assistant's decision to run journalctl -f (follow mode) and capture 15 seconds of live logs is a deliberate investigative technique. The goal is not merely to confirm that the process is running, but to observe its real-time behavior. A static log query would show past events; a follow command shows what the process is doing right now. By backgrounding the journalctl process, sleeping for 15 seconds, and then killing it, the assistant captures a window of live activity without leaving an interactive session hanging.

The motivation is clear: the assistant needs to distinguish between two possible failure modes. The first possibility is that the HTTP client is genuinely waiting for a response that never arrives, and the 30-second timeout is not being enforced due to a bug or configuration issue. The second possibility is that the deal check loop completed the CIDgravity call but then got stuck elsewhere—perhaps in the subsequent runSPDealCheckLoop or in some other synchronous operation. The live log capture is designed to reveal which case is occurring.

What the Log Output Reveals

The captured output is revealing, but not in the way the assistant might have expected. Instead of seeing the CIDgravity call complete or time out, the logs show a WARN message from the RPC handler: an error in an RPC call to RIBS.BalanceManagerInfo. The stack trace points to rbdeal/wallet.go:117, indicating that the wallet balance manager is failing. The error message is truncated in the output, but the visible portion—"RPC client error: sendRequest failed: request failed"—suggests a network-level failure within the YugabyteDB-backed RPC layer.

This is a critical finding. The BalanceManagerInfo RPC call is not part of the CIDgravity API; it's an internal RPC method exposed by the Kuri node itself. The fact that this call is failing means the node's internal RPC server is experiencing issues, potentially because the database connection is degraded or because some other resource is exhausted. The wallet balance manager is called by the deal tracker to check whether sufficient funds exist before proposing new deals. If the balance manager is failing, the deal check loop may be stuck waiting for a response that will never arrive.

Assumptions Made and Their Validity

The assistant makes several assumptions in this message, some explicit and some implicit. The most prominent assumption is that "the 30s timeout should have triggered." This is based on reading the code in get_deal_states.go, where the HTTP client is configured with a 30-second timeout. However, the assistant is implicitly assuming that this timeout applies to the entire request-response cycle, including DNS resolution, TLS handshake, and data transfer. In Go's net/http package, the Timeout field of http.Client covers the entire round-trip, so this assumption is technically correct.

But there is a subtler assumption at play: that the deal check loop is actually stuck on the CIDgravity HTTP call. The live log output suggests otherwise. The presence of a BalanceManagerInfo error indicates that the process is alive and processing RPC requests, but one of its internal components is failing. This could mean the deal check loop completed the CIDgravity call (or skipped it due to an error) and moved on to the internal deal-making logic, where it encountered the wallet balance failure.

Another implicit assumption is that the journalctl -f approach would capture the relevant log lines. The assistant only captures 15 seconds of output, which is a reasonable sample but may miss events that occur on a longer timescale. The deal check loop runs on a configurable interval; if the interval is longer than 15 seconds, the captured window might not show the loop's next iteration.

The Thinking Process Visible in the Message

The assistant's thinking process is visible in the structure of the diagnostic. The opening statement—"The deal check started at 10:33:42 and hasn't finished yet after 2+ minutes"—establishes the timeline and the anomaly. The phrase "The 30s timeout should have triggered" reveals the assistant's mental model of the system: the CIDgravity call has a known timeout, and exceeding that timeout by a factor of four indicates something is fundamentally wrong.

The decision to use journalctl -f with a background process and a sleep timer is a clever workaround. The assistant cannot keep an interactive SSH session open indefinitely while writing the next message, but they need to observe live behavior. By running the follow command in the background, capturing 15 seconds of output, and then cleaning up the background process, the assistant gets a snapshot of live activity without blocking their own workflow.

The final piece of thinking is visible in how the assistant interprets the output. The BalanceManagerInfo error is not dismissed as noise; it is recognized as potentially significant. The assistant does not immediately jump to conclusions about the CIDgravity timeout being the sole issue. Instead, the message ends with a stack trace that opens a new line of inquiry: perhaps the deal check loop is not stuck on the CIDgravity API at all, but on an internal RPC call that is failing silently.

Input Knowledge Required to Understand This Message

To fully grasp this message, a reader needs familiarity with several technical domains. First, an understanding of the FGW architecture: that Kuri nodes run a deal tracker loop that alternates between external API calls (CIDgravity) and internal logic (SP deal checking, balance management). Second, knowledge of Go's HTTP client behavior, particularly how timeouts work and how they interact with context deadlines. Third, familiarity with systemd's journalctl tool and its -f (follow) mode. Fourth, an understanding of RPC-based internal communication within a Go service—the stack trace shows a call through go-jsonrpc, indicating that the Kuri node exposes internal methods via JSON-RPC, and that the deal tracker calls these methods as part of its loop.

Without this context, the message reads as a simple "check if the process is stuck" command. With this context, it becomes a nuanced diagnostic probe targeting a specific failure mode in a complex distributed system.

Output Knowledge Created by This Message

The primary output of this message is new information: the deal check loop is not simply timing out on the CIDgravity API, but is instead experiencing internal RPC failures related to wallet balance management. This shifts the debugging focus from the external API (which was confirmed working earlier) to the internal database-backed RPC layer. The assistant now knows to investigate why BalanceManagerInfo is failing—perhaps the YugabyteDB connection is degraded, or the wallet state is corrupted, or the RPC handler has a bug that causes it to hang under certain conditions.

The message also creates a temporal anchor: the deal check started at 10:33:42 and the RPC error appeared at 10:35:55, establishing a 2-minute-and-13-second window in which the failure occurred. This timing information helps narrow down which code paths were executing during that window.

Mistakes and Incorrect Assumptions

The most notable potential mistake in this message is the assumption that the 30-second timeout is the relevant constraint. The assistant later discovers that the CIDgravity API call is using a context deadline rather than an HTTP client timeout, and that the context deadline may be set differently than expected. The code in get_deal_states.go uses context.WithTimeout with a 30-second deadline, but if the context is being cancelled or replaced elsewhere in the call chain, the timeout may not apply as expected.

Additionally, the assistant's diagnostic approach—capturing only 15 seconds of live logs—may miss the actual moment of failure. If the deal check loop's iteration takes longer than 15 seconds (which it clearly does, given the 2+ minute window), the captured snapshot may not include the critical log line that explains the stall. A longer observation period might have revealed the exact point of failure.

Conclusion

Message 2269 is a masterclass in production debugging under uncertainty. It captures the moment when a developer realizes that their mental model of a system's behavior does not match reality—the timeout that should have fired did not fire, and a different error has surfaced instead. The assistant's response is measured and methodical: observe, capture, analyze. The message is a bridge between two phases of debugging: the phase of confirming that the external API works, and the phase of discovering that the internal system is broken. It is a reminder that in complex distributed systems, the most elusive bugs are often not where you expect them to be.