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Remove $NIX_BUILD_HOOK and $NIX_CURRENT_LOAD
This is to simplify remote build configuration. These environment variables predate nix.conf. The build hook now has a sensible default (namely build-remote). The current load is kept in the Nix state directory now.
This commit is contained in:
Eelco Dolstra
parent
ca9f589a93
commit
d7653dfc6d
6 changed files with 12 additions and 156 deletions
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@ -148,139 +148,6 @@ $ mount -o bind /mnt/otherdisk/nix /nix</screen>
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</varlistentry>
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<varlistentry xml:id="envar-build-hook"><term><envar>NIX_BUILD_HOOK</envar></term>
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<listitem>
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<para>Specifies the location of the <emphasis>build hook</emphasis>,
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which is a program (typically some script) that Nix will call
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whenever it wants to build a derivation. This is used to implement
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distributed builds<phrase condition="manual"> (see <xref
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linkend="chap-distributed-builds" />)</phrase>.</para>
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<!--
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The protocol by
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which the calling Nix process and the build hook communicate is as
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follows.
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<para>The build hook is called with the following command-line
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arguments:
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<orderedlist>
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<listitem><para>A boolean value <literal>0</literal> or
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<literal>1</literal> specifying whether Nix can locally execute
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more builds, as per the <link
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linkend="opt-max-jobs"><option>- -max-jobs</option> option</link>.
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The purpose of this argument is to allow the hook to not have to
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maintain bookkeeping for the local machine.</para></listitem>
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<listitem><para>The Nix platform identifier for the local machine
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(e.g., <literal>i686-linux</literal>).</para></listitem>
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<listitem><para>The Nix platform identifier for the derivation,
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i.e., its <link linkend="attr-system"><varname>system</varname>
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attribute</link>.</para></listitem>
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<listitem><para>The store path of the derivation.</para></listitem>
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</orderedlist>
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</para>
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<para>On the basis of this information, and whatever persistent
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state the build hook keeps about other machines and their current
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load, it has to decide what to do with the build. It should print
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out on standard error one of the following responses (terminated by
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a newline, <literal>"\n"</literal>):
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<variablelist>
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<varlistentry><term><literal># decline</literal></term>
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<listitem><para>The build hook is not willing or able to perform
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the build; the calling Nix process should do the build itself,
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if possible.</para></listitem>
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</varlistentry>
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<varlistentry><term><literal># postpone</literal></term>
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<listitem><para>The build hook cannot perform the build now, but
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can do so in the future (e.g., because all available build slots
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on remote machines are in use). The calling Nix process should
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postpone this build until at least one currently running build
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has terminated.</para></listitem>
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</varlistentry>
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<varlistentry><term><literal># accept</literal></term>
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<listitem><para>The build hook has accepted the
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build.</para></listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>After sending <literal># accept</literal>, the hook should
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read one line from standard input, which will be the string
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<literal>okay</literal>. It can then proceed with the build.
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Before sending <literal>okay</literal>, Nix will store in the hook’s
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current directory a number of text files that contain information
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about the derivation:
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<variablelist>
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<varlistentry><term><filename>inputs</filename></term>
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<listitem><para>The set of store paths that are inputs to the
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build process (one per line). These have to be copied
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<emphasis>to</emphasis> the remote machine (in addition to the
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store derivation itself).</para></listitem>
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</varlistentry>
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<varlistentry><term><filename>outputs</filename></term>
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<listitem><para>The set of store paths that are outputs of the
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derivation (one per line). These have to be copied
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<emphasis>from</emphasis> the remote machine if the build
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succeeds.</para></listitem>
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</varlistentry>
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<varlistentry><term><filename>references</filename></term>
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<listitem><para>The reference graph of the inputs, in the format
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accepted by the command <command>nix-store
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- -register-validity</command>. It is necessary to run this
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command on the remote machine after copying the inputs to inform
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Nix on the remote machine that the inputs are valid
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paths.</para></listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>The hook should copy the inputs to the remote machine,
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register the validity of the inputs, perform the remote build, and
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copy the outputs back to the local machine. An exit code other than
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<literal>0</literal> indicates that the hook has failed. An exit
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code equal to 100 means that the remote build failed (as opposed to,
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e.g., a network error).</para>
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-->
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</listitem>
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</varlistentry>
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<varlistentry xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
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<listitem><para>This variable should be set to
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