IPC filenames are inconsistent when --ipcpath and --instance are used together

[BowTiedDevil]

Describe the bug

If reth or op-reth is launched with an IPC path and an instance value other than the default, the instance number is appended to the IPC filename.

e.g. when specifying --ipcpath=/ipc/op-reth.ipc and --instance=2, the actual IPC filename will be /ipc/op-reth.ipc-2 which is unexpected and not documented behavior of --instance.

The path mangling behavior is reasonable, but inconsistent. It could be improved by appending the "-1" when --instance is provided with the default value of 1. In this way, IPC filenames would be predictably named without needed to treat instance 1 in a special way.

Alternatively, the IPC filenames could be used without any mangling applied, since nodes should use their own data directories and filename collision is unlikely.

I presume that nodes launched without specifying --instance should continue to behave as normal.

Steps to reproduce

Launch with the options described above.

Node logs

# reth launched with --instance=1
Jan 14 10:17:27 dev reth_mainnet[1099553]: 2025-01-14T18:17:27.356217Z  INFO RPC IPC server started path=/ipc/reth.ipc        

# op-reth launched with --instance=2
Jan 14 09:54:42 dev reth_base[1036704]: 2025-01-14T17:54:42.336918Z  INFO RPC IPC server started path=/ipc/op-reth.ipc-2

# reth launched with --instance=3
Jan 14 09:56:57 dev reth_mainnet[1038400]: 2025-01-14T17:56:57.241512Z  INFO RPC IPC server started path=/ipc/reth.ipc-3

Platform(s)

Linux (x86)

Container Type

Other

What version/commit are you on?

reth-optimism-cli Version: 1.1.5
Commit SHA: 3212af2
Build Timestamp: 2025-01-07T10:07:51.565185205Z
Build Features: asm_keccak,jemalloc,optimism
Build Profile: release

reth Version: 1.1.5
Commit SHA: 3212af2
Build Timestamp: 2025-01-07T09:32:44.053190141Z
Build Features: asm_keccak,jemalloc
Build Profile: release

What database version are you on?

Current database version: 2
Local database version: 2

Which chain / network are you on?

reth

mainnet

op-reth

base

What type of node are you running?

Archive (default)

What prune config do you use, if any?

n/a

If you've built Reth from source, provide the full command you used

No response

Code of Conduct

• I agree to follow the Code of Conduct

[Rjected]

Hmm, I think the right behavior to implement when both are passed, would be to use ipcpath if specified, only modifying the path based on the instance num if no ipcpath is passed.

--instance is meant for cases like this:

reth node --instance 1
reth node --instance 2
reth node --instance 3

I could see those having /ipc/reth.ipc-1, /ipc/reth.ipc-2, /ipc/reth.ipc-3 respectively