From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5933DC47094 for ; Thu, 10 Jun 2021 07:21:21 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D002761359 for ; Thu, 10 Jun 2021 07:21:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D002761359 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:43816 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lrF0B-0004dB-LG for qemu-devel@archiver.kernel.org; Thu, 10 Jun 2021 03:21:19 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34380) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lrEyT-00032i-TK for qemu-devel@nongnu.org; Thu, 10 Jun 2021 03:19:34 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:42600) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lrEyQ-00058B-K3 for qemu-devel@nongnu.org; Thu, 10 Jun 2021 03:19:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623309568; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=AxnuI3e8822lKBzWzvjfQyTAqR+LBsvjcNBHuYtGlIo=; b=bDwHVFMm8SUXhK+48Bi72RDyj7pSsSlpoJTUbipngcywIDGu2NJ+tqFLTr+l0Q8q2gfFwn sOL3NOaskw/cgAWVAlru+hjb5ybmvGhuF7ko/gpzq8sEENOgbtk6Ez9Dud8Khg7Z6T1R4J +V3R92bqsVAdyf86R/LK3ajNleyIBxs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-448-2Ja8NMrMNhK2N-PC1VM91A-1; Thu, 10 Jun 2021 03:19:24 -0400 X-MC-Unique: 2Ja8NMrMNhK2N-PC1VM91A-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 60A6710C1ADC; Thu, 10 Jun 2021 07:19:23 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-112-222.ams2.redhat.com [10.36.112.222]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 81F08105C877; Thu, 10 Jun 2021 07:19:16 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 1D232113865F; Thu, 10 Jun 2021 09:19:15 +0200 (CEST) From: Markus Armbruster To: John Snow Subject: Re: GSoC Intro - TUI interface for QMP References: <87czswxuwn.fsf@dusky.pond.sub.org> <1577ce78-bf98-3f3d-7594-2b91d84967ec@redhat.com> <87sg1rp7yg.fsf@dusky.pond.sub.org> <879a774d-4aa2-9333-b413-bb59ef035525@redhat.com> Date: Thu, 10 Jun 2021 09:19:15 +0200 In-Reply-To: <879a774d-4aa2-9333-b413-bb59ef035525@redhat.com> (John Snow's message of "Wed, 9 Jun 2021 13:06:15 -0400") Message-ID: <874ke6gpak.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.199, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, ehabkost@redhat.com, qemu-devel@nongnu.org, wainersm@redhat.com, "Niteesh G. S." , Stefan Hajnoczi Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" John Snow writes: > On 6/9/21 7:56 AM, Markus Armbruster wrote: >>> The client could cache the information. (Against what kind of an >>> identifier? Can QEMU report some kind of token that uniquely >>> identifies its binary or uniquely identifies the set of QAPI commands >>> it supports?) > >> I proposed something like it to permit QMP clients cache >> query-qmp-schema output. Libvirt didn't want it, so it never got beyond >> the idea stage. >> > > What ideas did you have for a cache key? We don't need to uniquely > identify every instance or even every binary. > > I suppose we could use an md5/sha1 checksum of the QMP introspection output? commit 39a181581650f4d50f4445bc6276d9716cece050 Author: Markus Armbruster Date: Wed Sep 16 13:06:28 2015 +0200 qapi: New QMP command query-qmp-schema for QMP introspection [...] New QMP command query-qmp-schema takes its return value from that variable. Its reply is some 85KiBytes for me right now. Has since grown to ~160KiB. If this turns out to be too much, we have a couple of options: * We can use shorter names in the JSON. Not the QMP style. * Optionally return the sub-schema for commands and events given as arguments. Right now qmp_query_schema() sends the string literal computed by qmp-introspect.py. To compute sub-schema at run time, we'd have to duplicate parts of qapi-introspect.py in C. Unattractive. * Let clients cache the output of query-qmp-schema. It changes only on QEMU upgrades, i.e. rarely. Provide a command query-qmp-schema-hash. Clients can have a cache indexed by hash, and re-query the schema only when they don't have it cached. Even simpler: put the hash in the QMP greeting. Signed-off-by: Markus Armbruster Reviewed-by: Eric Blake Note this glosses over what exactly is hashed. Back then, we generated query-qmp-schema's output as a string, so we would have hashed that. Today, we generate a QLitObject. Less trivial to hash. Quite feasible all the same. NB: Commit messages are love letters to your future self :) [...]