orchestrator: add inspect-nbd CLI tool and DevicePool.Status() - #3547
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orchestrator: add inspect-nbd CLI tool and DevicePool.Status()#3547AdaAibaby wants to merge 4 commits into
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Fixes e2b-dev#3546. The nbd kernel module is loaded with nbds_max=4096, pre-creating 4096 /dev/nbdX block devices on every sandbox node. `lsblk | grep nbd` produces 4096 lines of noise even when zero sandboxes are running, making it impossible to quickly identify which devices are actively connected. ConnectedDevices() in pool.go already scans /sys/block/nbdX/pid to find connected slots, but was not exposed via any operator-facing tool. Changes: - Add cmd/inspect-nbd: reads ConnectedDevices() and prints a table of active NBD slots with device path, size, and PID. Supports -json for machine-readable output. Linux-only (//go:build linux). - Add DevicePool.maxDevices field: stored at construction to avoid re-reading /sys/module/nbd/parameters/nbds_max on each call. - Add DevicePool.Status() -> PoolStatus: returns Max/Used/PreWarmed counts from the in-memory bitset without scanning sysfs — usable by future debug endpoints. Example output on a node with 4096 configured but only 1 connected: NBD devices: 1 connected / 4096 configured SLOT DEVICE SIZE (MB) PID 1 /dev/nbd1 22691 3321246
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jakubno
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August 7, 2026 07:34
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Fixes #3546.
Summary
cmd/inspect-nbd: new operator tool that shows only the NBD devices currently connected on the host, instead of all 4096 pre-allocated onesDevicePool.maxDevices: stored at construction to avoid re-reading/sys/module/nbd/parameters/nbds_maxon each callDevicePool.Status(): returnsPoolStatus{Max, Used, PreWarmed}from the in-memory bitset without scanning sysfs — for future debug endpointsMotivation
The
nbdmodule is loaded withnbds_max=4096(start-client.sh), pre-creating 4096/dev/nbdXblock devices.lsblk | grep nbdproduces 4096 lines of noise even with zero sandboxes running. When kernel errors likeblock nbd316: Receive control failedappear indmesg, there is no way to identify which sandbox is involved.ConnectedDevices()already had the right logic (scans/sys/block/nbdX/pid), but was only used internally for startup reclaim. This PR exposes it as a standalone tool.Usage
Verified on dev sandbox node (
192.168.162.80,nbds_max=4096, 1 sandbox running at test time).Not in scope
Slot → sandbox ID mapping (requires threading sandboxID through
GetDevicecall sites) — tracked in #3546 as follow-up.