From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <t.lamprecht@proxmox.com> Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id 1F89E71632 for <pbs-devel@lists.proxmox.com>; Thu, 12 May 2022 12:04:37 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id EF2982574B for <pbs-devel@lists.proxmox.com>; Thu, 12 May 2022 12:04:06 +0200 (CEST) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [94.136.29.106]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS id E04742573F for <pbs-devel@lists.proxmox.com>; Thu, 12 May 2022 12:04:05 +0200 (CEST) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id AC80143487 for <pbs-devel@lists.proxmox.com>; Thu, 12 May 2022 12:04:05 +0200 (CEST) Message-ID: <6a79b760-7f99-2dac-fbd6-365f4cc799c3@proxmox.com> Date: Thu, 12 May 2022 12:04:04 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:101.0) Gecko/20100101 Thunderbird/101.0 Content-Language: en-GB To: Proxmox Backup Server development discussion <pbs-devel@lists.proxmox.com>, Fabian Ebner <f.ebner@proxmox.com> References: <20220504113324.70300-1-f.ebner@proxmox.com> From: Thomas Lamprecht <t.lamprecht@proxmox.com> In-Reply-To: <20220504113324.70300-1-f.ebner@proxmox.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-SPAM-LEVEL: Spam detection results: 0 AWL 0.021 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record T_SCC_BODY_TEXT_LINE -0.01 - URIBL_BLOCKED 0.001 ADMINISTRATOR NOTICE: The query to URIBL was blocked. 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[proxmox-backup-api.rs, minimal-rest-server.rs, daemon.rs, proxmox-backup-proxy.rs] Subject: [pbs-devel] applied: [PATCH/RFC proxmox-backup] rest server: daemon: update PID file before sending MAINPID notification X-BeenThere: pbs-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Backup Server development discussion <pbs-devel.lists.proxmox.com> List-Unsubscribe: <https://lists.proxmox.com/cgi-bin/mailman/options/pbs-devel>, <mailto:pbs-devel-request@lists.proxmox.com?subject=unsubscribe> List-Archive: <http://lists.proxmox.com/pipermail/pbs-devel/> List-Post: <mailto:pbs-devel@lists.proxmox.com> List-Help: <mailto:pbs-devel-request@lists.proxmox.com?subject=help> List-Subscribe: <https://lists.proxmox.com/cgi-bin/mailman/listinfo/pbs-devel>, <mailto:pbs-devel-request@lists.proxmox.com?subject=subscribe> X-List-Received-Date: Thu, 12 May 2022 10:04:37 -0000 Am 5/4/22 um 13:33 schrieb Fabian Ebner: > There is a race upon reload, where it can happen that: > 1. systemd forks off /bin/kill -HUP $MAINPID > 2. Current instance forks off new one and notifies systemd with the > new MAINPID. > 3. systemd sets new MAINPID. > 4. systemd receives SIGCHLD for the kill process (which is the current > control process for the service) and reads the PID of the old > instance from the PID file, resetting MAINPID to the PID of the old > instance. > 5. Old instance exits. > 6. systemd receives SIGCHLD for the old instance, reads the PID of the > old instance from the PID file once more. systemd sees that the > MAINPID matches the child PID and considers the service exited. > 7. systemd receivese notification from the new PID and is confused. > The service won't get active, because the notification wasn't > handled. > > To fix it, update the PID file before sending the MAINPID > notification, similar to what a comment in systemd's > src/core/service.c suggests: >> /* Forking services may occasionally move to a new PID. >> * As long as they update the PID file before exiting the old >> * PID, they're fine. */ > but for our Type=notify "before sending the notification" rather than > "before exiting", because otherwise, the mix-up in 4. could still > happen (although it might not actually be problematic without the > mix-up in 6., it still seems better to avoid). > > Signed-off-by: Fabian Ebner <f.ebner@proxmox.com> > --- > > An alternative would be to not tell systemd about the PIDFile at all, > but there's two small downsides: > * The PID file isn't cleaned up automatically when the service exits. > * Having the PID file updated before sending the MAINPID notification > feels a bit cleaner (even if the PID file is not used by systemd). > > .../examples/minimal-rest-server.rs | 18 +++++++---- > proxmox-rest-server/src/daemon.rs | 16 ++++++++-- > src/bin/proxmox-backup-api.rs | 30 +++++++++-------- > src/bin/proxmox-backup-proxy.rs | 32 +++++++++++-------- > 4 files changed, 60 insertions(+), 36 deletions(-) > > applied, thanks!