chainreg: use getnetworkinfo to count outbound peers (bitcoind backend)

[starius]

Change Description

Use getnetworkinfo.connections_out for bitcoind outbound peer checks instead of getpeerinfo. This keeps the isolation-safety signal while avoiding heavier per-peer work. This helper is bitcoind-specific, btcd does not currently implement it.

Also made two unrelated cleanups to use structured rpcclient methods instead of RawRequest in the same file.

See #10641 This should partially address it, switching to lighter calls for health-checks. CC @jogc

Fixes #10568

Steps to Test

Verification done in signet:

1. lncli getinfo works and shows correct block_height.
2. grep -nE "Health check: chain backend failed after|SRVR: Health check|timed out after" ~/.lnd/logs/bitcoin/signet/lnd.log returns nothing
3. grep -nE "insufficient number of connected outbound peers|Skipping chain backend peer check" ~/.lnd/logs/bitcoin/signet/lnd.log returns nothing

Also tested loop out and loop in on that node.

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[gemini-code-assist]

Summary of Changes

Hello, 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 improves the efficiency of chain backend health checks when using bitcoind by utilizing a lighter RPC call for monitoring outbound peer connections. Additionally, it refactors existing code to leverage structured RPC methods, reducing reliance on raw JSON parsing.

Highlights

• Optimized Peer Health Checks: Switched from using 'getpeerinfo' to 'getnetworkinfo.connections_out' for bitcoind outbound peer checks to reduce resource usage.
• Code Cleanup: Replaced several instances of 'RawRequest' with structured rpcclient methods for improved type safety and maintainability.

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[gemini-code-assist]

Code Review

This pull request refactors the retrieval of bitcoind network information and ZMQ notifications by replacing raw RPC requests and manual JSON unmarshaling with typed methods from the rpcclient. It also introduces a bitcoind-specific outbound peer check and extracts the peer count warning logic into a shared helper function. I have no feedback to provide.

[jogc]

I don't really know anything about the behavior of getnetworkinfo so I can't say.

Here is the latency data I do have if it's of any use (frequency + seconds):

getnetworkinfo

    3         0.00056 -    0.00065
    5         0.00065 -    0.00074
    0         0.00074 -    0.00083
    0         0.00083 -    0.00092
    0         0.00092 -    0.00101
    1         0.00101 -     0.0011
    1          0.0011 -    0.00119
    0         0.00119 -    0.00128
    3         0.00128 -    0.00137
    0         0.00137 -    0.00146
    1         0.00146 -    0.00154
    0         0.00154 -    0.00163
    1         0.00163 -    0.00172
    0         0.00172 -    0.00181
    0         0.00181 -     0.0019
    0          0.0019 -    0.00199
    0         0.00199 -    0.00208
    0         0.00208 -    0.00217
    0         0.00217 -    0.00226
    1         0.00226 -    0.00235

getpeerinfo

19251         0.00088 -   20.21323
   68        20.21323 -   40.42558
   30        40.42558 -   60.63793
   15        60.63793 -   80.85027
   13        80.85027 -  101.06262
   11       101.06262 -  121.27497
    5       121.27497 -  141.48732
    3       141.48732 -  161.69967
    2       161.69967 -  181.91202
    2       181.91202 -  202.12436
    2       202.12436 -  222.33671
    2       222.33671 -  242.54906
    1       242.54906 -  262.76141
    2       262.76141 -  282.97376
    2       282.97376 -   303.1861
    0        303.1861 -  323.39845
    0       323.39845 -   343.6108
    3        343.6108 -  363.82315
    0       363.82315 -   384.0355
    1        384.0355 -  404.24784

uptime

16109         0.00056 -    0.00984
   12         0.00984 -    0.01912
    4         0.01912 -     0.0284
    0          0.0284 -    0.03768
    0         0.03768 -    0.04696
    0         0.04696 -    0.05624
    0         0.05624 -    0.06552
    0         0.06552 -     0.0748
    0          0.0748 -    0.08408
    0         0.08408 -    0.09336
    0         0.09336 -    0.10264
    0         0.10264 -    0.11192
    0         0.11192 -     0.1212
    0          0.1212 -    0.13048
    0         0.13048 -    0.13976
    0         0.13976 -    0.14904
    0         0.14904 -    0.15832
    0         0.15832 -     0.1676
    0          0.1676 -    0.17688
    1         0.17688 -    0.18616

[jogc]

By the way since you are looking at chainreg/chainregistry.go you might want to check out #6483 as well

[starius]

@jogc Thanks for sharing the latency data! If I read it correctly, getnetworkinfo is much faster than getpeerinfo, especially in its tail. So the transition makes sense.

By the way since you are looking at chainreg/chainregistry.go you might want to check out #6483 as well

Can you elaborate on that, please? That PR replaced an error with a warning. I just refactored the checking code there, to use a higher level method of rpcclient instead of RawRequest. Do you think that code can be further improved?

[jogc]

@jogc Thanks for sharing the latency data! If I read it correctly, getnetworkinfo is much faster than getpeerinfo, especially in its tail. So the transition makes sense.

No. There are not enough requests recorded to say anything regarding getnetworkinfo. I assume you have some other reason to believe getnetworkinfo is faster than getpeerinfo.

By the way since you are looking at chainreg/chainregistry.go you might want to check out #6483 as well

Can you elaborate on that, please? That PR replaced an error with a warning. I just refactored the checking code there, to use a higher level method of rpcclient instead of RawRequest. Do you think that code can be further improved?

Sorry I meant #10568

[starius]

@jogc Thanks for sharing the latency data! If I read it correctly, getnetworkinfo is much faster than getpeerinfo, especially in its tail. So the transition makes sense.

No. There are not enough requests recorded to say anything regarding getnetworkinfo. I assume you have some other reason to believe getnetworkinfo is faster than getpeerinfo.

I'm judging from Bitcoin Core code. Latency of getpeerinfo is O(number of peers), while getnetworkinfo is constant. getnetworkinfo is significantly faster under high load.

Here is AI provided table comparing latencies of these two calls based on recent bitcoin core version (0831173c0171de33f95b96324db4041c4799b163).

Aspect	getnetworkinfo	getpeerinfo
Complexity	O(1)	O(N) where N = peers
cs_main hold	1×, brief work inside	N× acquisitions (once per peer)
m_nodes_mutex	3× for counting only	1× held for full iteration + per-node locks
Per-peer locks	None	~9 locks × N peers
Data volume	~20 scalar fields	~40 fields × N peers
Worst-case under contention	Waits once for cs_main	Waits N times for cs_main + blocks connection mgmt via m_nodes_mutex
Typical latency	Sub-millisecond	Scales linearly with peer count; seconds under contention

Sorry I meant #10568

I fixed the issue with warnings' texts in another commit.