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Merge pull request #2995 from tweag/post-build-hook

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Add a post build hook
This commit is contained in:
Eelco Dolstra 2019-08-07 15:02:29 +02:00 committed by GitHub
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13 changed files with 337 additions and 4 deletions
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1
doc/manual/advanced-topics/advanced-topics.xml
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@ -9,5 +9,6 @@
<xi:include href="distributed-builds.xml" />
<xi:include href="cores-vs-jobs.xml" />
<xi:include href="diff-hook.xml" />
<xi:include href="post-build-hook.xml" />
</part>

160
doc/manual/advanced-topics/post-build-hook.xml Normal file
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@ -0,0 +1,160 @@
<chapter xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="chap-post-build-hook"
version="5.0"
>
<title>Using the <xref linkend="conf-post-build-hook" /></title>
<subtitle>Uploading to an S3-compatible binary cache after each build</subtitle>
<section xml:id="chap-post-build-hook-caveats">
<title>Implementation Caveats</title>
<para>Here we use the post-build hook to upload to a binary cache.
This is a simple and working example, but it is not suitable for all
use cases.</para>
<para>The post build hook program runs after each executed build,
and blocks the build loop. The build loop exits if the hook program
fails.</para>
<para>Concretely, this implementation will make Nix slow or unusable
when the internet is slow or unreliable.</para>
<para>A more advanced implementation might pass the store paths to a
user-supplied daemon or queue for processing the store paths outside
of the build loop.</para>
</section>
<section>
<title>Prerequisites</title>
<para>
This tutorial assumes you have configured an S3-compatible binary cache
according to the instructions at
<xref linkend="ssec-s3-substituter-authenticated-writes" />, and
that the <literal>root</literal> user's default AWS profile can
upload to the bucket.
</para>
</section>
<section>
<title>Set up a Signing Key</title>
<para>Use <command>nix-store --generate-binary-cache-key</command> to
create our public and private signing keys. We will sign paths
with the private key, and distribute the public key for verifying
the authenticity of the paths.</para>
<screen>
# nix-store --generate-binary-cache-key example-nix-cache-1 /etc/nix/key.private /etc/nix/key.public
# cat /etc/nix/key.public
example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
</screen>
<para>Then, add the public key and the cache URL to your
<filename>nix.conf</filename>'s <xref linkend="conf-trusted-public-keys" />
and <xref linkend="conf-substituters" /> like:</para>
<programlisting>
substituters = https://cache.nixos.org/ s3://example-nix-cache
trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
</programlisting>
<para>we will restart the Nix daemon a later step.</para>
</section>
<section>
<title>Implementing the build hook</title>
<para>Write the following script to
<filename>/etc/nix/upload-to-cache.sh</filename>:
</para>
<programlisting>
#!/bin/sh
set -eu
set -f # disable globbing
export IFS=' '
echo "Signing paths" $OUT_PATHS
nix sign-paths --key-file /etc/nix/key.private $OUT_PATHS
echo "Uploading paths" $OUT_PATHS
exec nix copy --to 's3://example-nix-cache' $OUT_PATHS
</programlisting>
<note>
<title>Should <literal>$OUT_PATHS</literal> be quoted?</title>
<para>
The <literal>$OUT_PATHS</literal> variable is a space-separated
list of Nix store paths. In this case, we expect and want the
shell to perform word splitting to make each output path its
own argument to <command>nix sign-paths</command>. Nix guarantees
the paths will not contain any spaces, however a store path
might contain glob characters. The <command>set -f</command>
disables globbing in the shell.
</para>
</note>
<para>
Then make sure the hook program is executable by the <literal>root</literal> user:
<screen>
# chmod +x /etc/nix/upload-to-cache.sh
</screen></para>
</section>
<section>
<title>Updating Nix Configuration</title>
<para>Edit <filename>/etc/nix/nix.conf</filename> to run our hook,
by adding the following configuration snippet at the end:</para>
<programlisting>
post-build-hook = /etc/nix/upload-to-cache.sh
</programlisting>
<para>Then, restart the <command>nix-daemon</command>.</para>
</section>
<section>
<title>Testing</title>
<para>Build any derivation, for example:</para>
<screen>
$ nix-build -E '(import &lt;nixpkgs&gt; {}).writeText "example" (builtins.toString builtins.currentTime)'
these derivations will be built:
/nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv
building '/nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv'...
running post-build-hook '/home/grahamc/projects/github.com/NixOS/nix/post-hook.sh'...
post-build-hook: Signing paths /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
post-build-hook: Uploading paths /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
/nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
</screen>
<para>Then delete the path from the store, and try substituting it from the binary cache:</para>
<screen>
$ rm ./result
$ nix-store --delete /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
</screen>
<para>Now, copy the path back from the cache:</para>
<screen>
$ nix store --realize /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
copying path '/nix/store/m8bmqwrch6l3h8s0k3d673xpmipcdpsa-example from 's3://example-nix-cache'...
warning: you did not specify '--add-root'; the result might be removed by the garbage collector
/nix/store/m8bmqwrch6l3h8s0k3d673xpmipcdpsa-example
</screen>
</section>
<section>
<title>Conclusion</title>
<para>
We now have a Nix installation configured to automatically sign and
upload every local build to a remote binary cache.
</para>
<para>
Before deploying this to production, be sure to consider the
implementation caveats in <xref linkend="chap-post-build-hook-caveats" />.
</para>
</section>
</chapter>

56
doc/manual/command-ref/conf-file.xml
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@ -664,6 +664,62 @@ password <replaceable>my-password</replaceable>
</varlistentry>
<varlistentry xml:id="conf-post-build-hook">
<term><literal>post-build-hook</literal></term>
<listitem>
<para>Optional. The path to a program to execute after each build.</para>
<para>This option is only settable in the global
<filename>nix.conf</filename>, or on the command line by trusted
users.</para>
<para>When using the nix-daemon, the daemon executes the hook as
<literal>root</literal>. If the nix-daemon is not involved, the
hook runs as the user executing the nix-build.</para>
<itemizedlist>
<listitem><para>The hook executes after an evaluation-time build.</para></listitem>
<listitem><para>The hook does not execute on substituted paths.</para></listitem>
<listitem><para>The hook's output always goes to the user's terminal.</para></listitem>
<listitem><para>If the hook fails, the build succeeds but no further builds execute.</para></listitem>
<listitem><para>The hook executes synchronously, and blocks other builds from progressing while it runs.</para>
</itemizedlist>
<para>The program executes with no arguments. The program's environment
contains the following environment variables:</para>
<variablelist>
<varlistentry>
<term><envar>DRV_PATH</envar></term>
<listitem>
<para>The derivation for the built paths.</para>
<para>Example:
<literal>/nix/store/5nihn1a7pa8b25l9zafqaqibznlvvp3f-bash-4.4-p23.drv</literal>
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><envar>OUT_PATHS</envar></term>
<listitem>
<para>Output paths of the built derivation, separated by a space character.</para>
<para>Example:
<literal>/nix/store/zf5lbh336mnzf1nlswdn11g4n2m8zh3g-bash-4.4-p23-dev
/nix/store/rjxwxwv1fpn9wa2x5ssk5phzwlcv4mna-bash-4.4-p23-doc
/nix/store/6bqvbzjkcp9695dq0dpl5y43nvy37pq1-bash-4.4-p23-info
/nix/store/r7fng3kk3vlpdlh2idnrbn37vh4imlj2-bash-4.4-p23-man
/nix/store/xfghy8ixrhz3kyy6p724iv3cxji088dx-bash-4.4-p23</literal>.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>See <xref linkend="chap-post-build-hook" /> for an example
implementation.</para>
</listitem>
</varlistentry>
<varlistentry xml:id="conf-repeat"><term><literal>repeat</literal></term>
<listitem><para>How many times to repeat builds to check whether

55
src/libstore/build.cc
View File

@ -1629,6 +1629,61 @@ void DerivationGoal::buildDone()
being valid. */
registerOutputs();
if (settings.postBuildHook != "") {
Activity act(*logger, lvlInfo, actPostBuildHook,
fmt("running post-build-hook '%s'", settings.postBuildHook),
Logger::Fields{drvPath});
PushActivity pact(act.id);
auto outputPaths = drv->outputPaths();
std::map<std::string, std::string> hookEnvironment = getEnv();
hookEnvironment.emplace("DRV_PATH", drvPath);
hookEnvironment.emplace("OUT_PATHS", chomp(concatStringsSep(" ", outputPaths)));
RunOptions opts(settings.postBuildHook, {});
opts.environment = hookEnvironment;
struct LogSink : Sink {
Activity & act;
std::string currentLine;
LogSink(Activity & act) : act(act) { }
void operator() (const unsigned char * data, size_t len) override {
for (size_t i = 0; i < len; i++) {
auto c = data[i];
if (c == '\n') {
flushLine();
} else {
currentLine += c;
}
}
}
void flushLine() {
if (settings.verboseBuild) {
printError("post-build-hook: " + currentLine);
} else {
act.result(resPostBuildLogLine, currentLine);
}
currentLine.clear();
}
~LogSink() {
if (currentLine != "") {
currentLine += '\n';
flushLine();
}
}
};
LogSink sink(act);
opts.standardOut = &sink;
opts.mergeStderrToStdout = true;
runProgram2(opts);
}
if (buildMode == bmCheck) {
done(BuildResult::Built);
return;

3
src/libstore/globals.hh
View File

@ -315,6 +315,9 @@ public:
"pre-build-hook",
"A program to run just before a build to set derivation-specific build settings."};
Setting<std::string> postBuildHook{this, "", "post-build-hook",
"A program to run just after each succesful build."};
Setting<std::string> netrcFile{this, fmt("%s/%s", nixConfDir, "netrc"), "netrc-file",
"Path to the netrc file used to obtain usernames/passwords for downloads."};

2
src/libutil/logging.hh
View File

@ -26,6 +26,7 @@ typedef enum {
actVerifyPaths = 107,
actSubstitute = 108,
actQueryPathInfo = 109,
actPostBuildHook = 110,
} ActivityType;
typedef enum {
@ -36,6 +37,7 @@ typedef enum {
resSetPhase = 104,
resProgress = 105,
resSetExpected = 106,
resPostBuildLogLine = 107,
} ResultType;
typedef uint64_t ActivityId;

23
src/libutil/util.cc
View File

@ -84,6 +84,15 @@ void clearEnv()
unsetenv(name.first.c_str());
}
void replaceEnv(std::map<std::string, std::string> newEnv)
{
clearEnv();
for (auto newEnvVar : newEnv)
{
setenv(newEnvVar.first.c_str(), newEnvVar.second.c_str(), 1);
}
}
Path absPath(Path path, Path dir)
{
@ -1019,10 +1028,22 @@ void runProgram2(const RunOptions & options)
if (options.standardOut) out.create();
if (source) in.create();
ProcessOptions processOptions;
// vfork implies that the environment of the main process and the fork will
// be shared (technically this is undefined, but in practice that's the
// case), so we can't use it if we alter the environment
if (options.environment)
processOptions.allowVfork = false;
/* Fork. */
Pid pid = startProcess([&]() {
if (options.environment)
replaceEnv(*options.environment);
if (options.standardOut && dup2(out.writeSide.get(), STDOUT_FILENO) == -1)
throw SysError("dupping stdout");
if (options.mergeStderrToStdout)
if (dup2(STDOUT_FILENO, STDERR_FILENO) == -1)
throw SysError("cannot dup stdout into stderr");
if (source && dup2(in.readSide.get(), STDIN_FILENO) == -1)
throw SysError("dupping stdin");
@ -1047,7 +1068,7 @@ void runProgram2(const RunOptions & options)
execv(options.program.c_str(), stringsToCharPtrs(args_).data());
throw SysError("executing '%1%'", options.program);
});
}, processOptions);
out.writeSide = -1;

2
src/libutil/util.hh
View File

@ -270,12 +270,14 @@ struct RunOptions
std::optional<uid_t> uid;
std::optional<uid_t> gid;
std::optional<Path> chdir;
std::optional<std::map<std::string, std::string>> environment;
Path program;
bool searchPath = true;
Strings args;
std::optional<std::string> input;
Source * standardIn = nullptr;
Sink * standardOut = nullptr;
bool mergeStderrToStdout = false;
bool _killStderr = false;
RunOptions(const Path & program, const Strings & args)

16
src/nix/progress-bar.cc
View File

@ -170,6 +170,14 @@ public:
name, sub);
}
if (type == actPostBuildHook) {
auto name = storePathToName(getS(fields, 0));
if (hasSuffix(name, ".drv"))
name.resize(name.size() - 4);
i->s = fmt("post-build " ANSI_BOLD "%s" ANSI_NORMAL, name);
i->name = DrvName(name).name;
}
if (type == actQueryPathInfo) {
auto name = storePathToName(getS(fields, 0));
i->s = fmt("querying " ANSI_BOLD "%s" ANSI_NORMAL " on %s", name, getS(fields, 1));
@ -228,14 +236,18 @@ public:
update(*state);
}
else if (type == resBuildLogLine) {
else if (type == resBuildLogLine || type == resPostBuildLogLine) {
auto lastLine = trim(getS(fields, 0));
if (!lastLine.empty()) {
auto i = state->its.find(act);
assert(i != state->its.end());
ActInfo info = *i->second;
if (printBuildLogs) {
log(*state, lvlInfo, ANSI_FAINT + info.name.value_or("unnamed") + "> " + ANSI_NORMAL + lastLine);
auto suffix = "> ";
if (type == resPostBuildLogLine) {
suffix = " (post)> ";
}
log(*state, lvlInfo, ANSI_FAINT + info.name.value_or("unnamed") + suffix + ANSI_NORMAL + lastLine);
} else {
state->activities.erase(i->second);
info.lastLine = lastLine;

1
tests/dependencies.nix
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@ -17,6 +17,7 @@ let {
builder = ./dependencies.builder0.sh + "/FOOBAR/../.";
input1 = input1 + "/.";
input2 = "${input2}/.";
input1_drv = input1;
meta.description = "Random test package";
};

3
tests/local.mk
View File

@ -28,7 +28,8 @@ nix_tests = \
check.sh \
plugins.sh \
search.sh \
nix-copy-ssh.sh
nix-copy-ssh.sh \
post-hook.sh
# parallel.sh
install-tests += $(foreach x, $(nix_tests), tests/$(x))

15
tests/post-hook.sh Normal file
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@ -0,0 +1,15 @@
source common.sh
clearStore
export REMOTE_STORE=$TEST_ROOT/remote_store
# Build the dependencies and push them to the remote store
nix-build dependencies.nix --post-build-hook $PWD/push_to_store.sh
clearStore
# Ensure that we the remote store contains both the runtime and buildtime
# closure of what we've just built
nix copy --from "$REMOTE_STORE" --no-require-sigs -f dependencies.nix
nix copy --from "$REMOTE_STORE" --no-require-sigs -f dependencies.nix input1_drv

4
tests/push_to_store.sh Executable file
View File

@ -0,0 +1,4 @@
#!/bin/sh
echo Pushing "$@" to "$REMOTE_STORE"
echo -n "$OUT_PATHS" | xargs -d: nix copy --to "$REMOTE_STORE" --no-require-sigs