Hello, Guix In developing a test suite for the internals of 'guix deploy', the virtual machine I spun up spat out an OpenSSH error that I've never encountered before.
Jun 24 16:59:26 localhost sshd[235]: error: no more sessions This is, initially, quite curious. Creating the SSH session with #:log-verbosity set to 'protocol gives some insight. ;;; [2019/06/24 13:08:36.711847, 2] channel_open: Creating a channel 43 with 64000 window and 32768 max packet ;;; [2019/06/24 13:08:36.711959, 2] ssh_packet_global_request: Received SSH_MSG_GLOBAL_REQUEST packet ;;; [2019/06/24 13:08:36.711987, 2] ssh_packet_global_request: UNKNOWN SSH_MSG_GLOBAL_REQUEST hostkeys...@openssh.com 0 ;;; [2019/06/24 13:08:36.712010, 1] ssh_packet_process: Couldn't do anything with packet type 80 ;;; [2019/06/24 13:08:36.712197, 2] ssh_packet_channel_open_conf: Received a CHANNEL_OPEN_CONFIRMATION for channel 43:0 ;;; [2019/06/24 13:08:36.712219, 2] ssh_packet_channel_open_conf: Remote window : 0, maxpacket : 32768 ;;; [2019/06/24 13:08:36.712618, 2] channel_rcv_change_window: Adding 2097152 bytes to channel (43:0) (from 0 bytes) ;;; [2019/06/24 13:08:36.712651, 2] channel_request: Channel request exec success ... ;;; [2019/06/24 12:59:26.296022, 2] channel_open: Creating a channel 74 with 64000 window and 32768 max packet ;;; [2019/06/24 12:59:26.296262, 2] ssh_packet_channel_open_conf: Received a CHANNEL_OPEN_CONFIRMATION for channel 74:8 ;;; [2019/06/24 12:59:26.296308, 2] ssh_packet_channel_open_conf: Remote window : 0, maxpacket : 32768 ;;; [2019/06/24 12:59:26.296667, 2] channel_rcv_change_window: Adding 2097152 bytes to channel (74:8) (from 0 bytes) ;;; [2019/06/24 12:59:26.296721, 2] channel_request: Channel request exec success ;;; [2019/06/24 12:59:26.487339, 2] grow_window: growing window (channel 74:8) to 1280000 bytes ;;; [2019/06/24 12:59:26.489031, 2] channel_open: Creating a channel 75 with 64000 window and 32768 max packet ;;; [2019/06/24 12:59:26.489376, 2] ssh_packet_channel_open_conf: Received a CHANNEL_OPEN_CONFIRMATION for channel 75:8 ;;; [2019/06/24 12:59:26.489402, 2] ssh_packet_channel_open_conf: Remote window : 0, maxpacket : 32768 ;;; [2019/06/24 12:59:26.489858, 2] channel_rcv_change_window: Adding 2097152 bytes to channel (75:8) (from 0 bytes) ;;; [2019/06/24 12:59:26.489906, 2] channel_request: Channel request exec success ;;; [2019/06/24 12:59:26.542586, 2] grow_window: growing window (channel 75:8) to 1280000 bytes ;;; [2019/06/24 12:59:26.546104, 2] channel_open: Creating a channel 76 with 64000 window and 32768 max packet ;;; [2019/06/24 12:59:26.546407, 2] ssh_packet_channel_open_conf: Received a CHANNEL_OPEN_CONFIRMATION for channel 76:9 ;;; [2019/06/24 12:59:26.546438, 2] ssh_packet_channel_open_conf: Remote window : 0, maxpacket : 32768 ;;; [2019/06/24 12:59:26.546839, 2] channel_rcv_change_window: Adding 2097152 bytes to channel (76:9) (from 0 bytes) ;;; [2019/06/24 12:59:26.546865, 2] channel_request: Channel request exec success ;;; [2019/06/24 12:59:26.630055, 2] grow_window: growing window (channel 76:9) to 1280000 bytes ;;; [2019/06/24 12:59:27.272139, 2] channel_open: Creating a channel 77 with 64000 window and 32768 max packet ;;; [2019/06/24 12:59:27.272846, 1] ssh_packet_channel_open_fail: Channel opening failure: channel 77 error (2) open failed I will admit that my knowledge of the SSH protocol is limited, but the rising channel number gives me the impression that channels are going out of scope and aren't being cleaned up. For reference, this occurs when 'remote-eval' is invoked multiple times -- which, in turn, invokes 'send-files'. building path(s) `/gnu/store/3rfkwdbayg7m3wdrydmcljnfqhvrady5-remote-exp.scm' sending 1 store item (0 MiB) to 'localhost'... exporting path `/gnu/store/3rfkwdbayg7m3wdrydmcljnfqhvrady5-remote-exp.scm' building path(s) `/gnu/store/ib59b0pnypsw4vf59f2gwpwhn343xnzb-remote-exp.scm' sending 1 store item (0 MiB) to 'localhost'... exporting path `/gnu/store/ib59b0pnypsw4vf59f2gwpwhn343xnzb-remote-exp.scm' [this is where the "no more sessions" error occurs] Currently, my code performs all of these 'remote-eval' calls with the same session. I suppose it would be possible to create a new session for each call, but I feel I should raise this as it may cause issues down the line: do we need to do something about cleaning up SSH channels? If a reproducible example is necessary, you can look to the temporary 'tests/machine.scm' in 64ffe453b0c71f417927737fa808dffe858359cd on my personal branch.[1] Regards, Jakob [1]: https://git.sr.ht/~jakob/guix/
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