mirror of
https://github.com/NixOS/nix
synced 2024-09-20 23:28:26 -04:00
91dc023665
Whenever Nix attempts to realise a derivation for which a closure is already known, but this closure cannot be realised, fall back on normalising the derivation. The most common scenario in which this is useful is when we have registered substitutes in order to perform binary distribution from, say, a network repository. If the repository is down, the realisation of the derivation will fail. When this option is specified, Nix will build the derivation instead. Thus, binary installation falls back on a source installation. This option is not the default since it is generally not desirable for a transient failure in obtaining the substitutes to lead to a full build from source (with the related consumption of resources).
572 lines
15 KiB
C++
572 lines
15 KiB
C++
#include <iostream>
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#include <algorithm>
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#include <sys/wait.h>
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#include <unistd.h>
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#include "store.hh"
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#include "globals.hh"
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#include "db.hh"
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#include "archive.hh"
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#include "pathlocks.hh"
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/* Nix database. */
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static Database nixDB;
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/* Database tables. */
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/* dbValidPaths :: Path -> ()
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The existence of a key $p$ indicates that path $p$ is valid (that
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is, produced by a succesful build). */
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static TableId dbValidPaths;
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/* dbSuccessors :: Path -> Path
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Each pair $(p_1, p_2)$ in this mapping records the fact that the
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Nix expression stored at path $p_1$ has a successor expression
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stored at path $p_2$.
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Note that a term $y$ is a successor of $x$ iff there exists a
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sequence of rewrite steps that rewrites $x$ into $y$.
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*/
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static TableId dbSuccessors;
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/* dbSuccessorsRev :: Path -> [Path]
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The reverse mapping of dbSuccessors (i.e., it stores the
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predecessors of a Nix expression).
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*/
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static TableId dbSuccessorsRev;
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/* dbSubstitutes :: Path -> [(Path, Path, [string])]
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Each pair $(p, subs)$ tells Nix that it can use any of the
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substitutes in $subs$ to build path $p$. Each substitute is a
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tuple $(storeExpr, program, args)$ (see the type `Substitute' in
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`store.hh').
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The main purpose of this is for distributed caching of derivates.
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One system can compute a derivate and put it on a website (as a Nix
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archive), for instance, and then another system can register a
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substitute for that derivate. The substitute in this case might be
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a Nix expression that fetches the Nix archive.
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*/
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static TableId dbSubstitutes;
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/* dbSubstitutesRev :: Path -> [Path]
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The reverse mapping of dbSubstitutes; it maps store expressions
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back to the paths for which they are substitutes.
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*/
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static TableId dbSubstitutesRev;
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bool Substitute::operator == (const Substitute & sub)
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{
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return storeExpr == sub.storeExpr
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&& program == sub.program
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&& args == sub.args;
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}
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void openDB()
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{
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nixDB.open(nixDBPath);
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dbValidPaths = nixDB.openTable("validpaths");
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dbSuccessors = nixDB.openTable("successors");
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dbSuccessorsRev = nixDB.openTable("successors-rev");
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dbSubstitutes = nixDB.openTable("substitutes");
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dbSubstitutesRev = nixDB.openTable("substitutes-rev");
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}
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void initDB()
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{
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}
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void createStoreTransaction(Transaction & txn)
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{
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Transaction txn2(nixDB);
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txn2.moveTo(txn);
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}
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/* Path copying. */
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struct CopySink : DumpSink
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{
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int fd;
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virtual void operator () (const unsigned char * data, unsigned int len)
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{
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writeFull(fd, data, len);
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}
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};
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struct CopySource : RestoreSource
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{
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int fd;
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virtual void operator () (unsigned char * data, unsigned int len)
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{
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readFull(fd, data, len);
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}
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};
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void copyPath(const Path & src, const Path & dst)
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{
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debug(format("copying `%1%' to `%2%'") % src % dst);
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/* Unfortunately C++ doesn't support coprocedures, so we have no
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nice way to chain CopySink and CopySource together. Instead we
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fork off a child to run the sink. (Fork-less platforms should
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use a thread). */
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/* Create a pipe. */
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Pipe pipe;
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pipe.create();
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/* Fork. */
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Pid pid;
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pid = fork();
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switch (pid) {
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case -1:
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throw SysError("unable to fork");
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case 0: /* child */
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try {
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pipe.writeSide.close();
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CopySource source;
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source.fd = pipe.readSide;
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restorePath(dst, source);
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_exit(0);
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} catch (exception & e) {
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cerr << "error: " << e.what() << endl;
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}
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_exit(1);
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}
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/* Parent. */
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pipe.readSide.close();
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CopySink sink;
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sink.fd = pipe.writeSide;
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dumpPath(src, sink);
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/* Wait for the child to finish. */
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int status = pid.wait(true);
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if (!statusOk(status))
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throw Error(format("cannot copy `%1% to `%2%': child %3%")
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% src % dst % statusToString(status));
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}
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static bool isInStore(const Path & path)
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{
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return path[0] == '/'
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&& path.compare(0, nixStore.size(), nixStore) == 0
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&& path.size() >= nixStore.size() + 2
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&& path[nixStore.size()] == '/'
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&& path.find('/', nixStore.size() + 1) == Path::npos;
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}
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void assertStorePath(const Path & path)
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{
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if (!isInStore(path))
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throw Error(format("path `%1%' is not in the Nix store") % path);
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}
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static bool isValidPathTxn(const Path & path, const Transaction & txn)
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{
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string s;
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return nixDB.queryString(txn, dbValidPaths, path, s);
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}
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bool isValidPath(const Path & path)
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{
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return isValidPathTxn(path, noTxn);
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}
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static bool isUsablePathTxn(const Path & path, const Transaction & txn)
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{
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if (isValidPathTxn(path, txn)) return true;
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Paths subs;
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nixDB.queryStrings(txn, dbSubstitutes, path, subs);
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return subs.size() > 0;
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}
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void registerSuccessor(const Transaction & txn,
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const Path & srcPath, const Path & sucPath)
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{
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assertStorePath(srcPath);
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assertStorePath(sucPath);
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if (!isUsablePathTxn(sucPath, txn)) throw Error(
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format("path `%1%' cannot be a successor, since it is not usable")
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% sucPath);
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Path known;
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if (nixDB.queryString(txn, dbSuccessors, srcPath, known) &&
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known != sucPath)
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{
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throw Error(format(
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"the `impossible' happened: expression in path "
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"`%1%' appears to have multiple successors "
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"(known `%2%', new `%3%'")
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% srcPath % known % sucPath);
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}
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Paths revs;
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nixDB.queryStrings(txn, dbSuccessorsRev, sucPath, revs);
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if (find(revs.begin(), revs.end(), srcPath) == revs.end())
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revs.push_back(srcPath);
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nixDB.setString(txn, dbSuccessors, srcPath, sucPath);
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nixDB.setStrings(txn, dbSuccessorsRev, sucPath, revs);
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}
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void unregisterSuccessor(const Path & srcPath)
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{
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assertStorePath(srcPath);
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Transaction txn(nixDB);
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Path sucPath;
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if (!nixDB.queryString(txn, dbSuccessors, srcPath, sucPath)) {
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txn.abort();
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return;
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}
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nixDB.delPair(txn, dbSuccessors, srcPath);
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Paths revs;
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nixDB.queryStrings(txn, dbSuccessorsRev, sucPath, revs);
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Paths::iterator i = find(revs.begin(), revs.end(), srcPath);
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assert(i != revs.end());
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revs.erase(i);
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nixDB.setStrings(txn, dbSuccessorsRev, sucPath, revs);
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txn.commit();
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}
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bool querySuccessor(const Path & srcPath, Path & sucPath)
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{
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return nixDB.queryString(noTxn, dbSuccessors, srcPath, sucPath);
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}
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Paths queryPredecessors(const Path & sucPath)
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{
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Paths revs;
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nixDB.queryStrings(noTxn, dbSuccessorsRev, sucPath, revs);
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return revs;
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}
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static Substitutes readSubstitutes(const Transaction & txn,
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const Path & srcPath)
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{
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Strings ss;
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nixDB.queryStrings(txn, dbSubstitutes, srcPath, ss);
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Substitutes subs;
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for (Strings::iterator i = ss.begin(); i != ss.end(); ++i) {
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if (i->size() < 4 || (*i)[3] != 0) {
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/* Old-style substitute. !!! remove this code
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eventually? */
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break;
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}
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Strings ss2 = unpackStrings(*i);
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if (ss2.size() != 3) throw Error("malformed substitute");
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Strings::iterator j = ss2.begin();
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Substitute sub;
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sub.storeExpr = *j++;
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sub.program = *j++;
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sub.args = unpackStrings(*j++);
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subs.push_back(sub);
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}
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return subs;
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}
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static void writeSubstitutes(const Transaction & txn,
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const Path & srcPath, const Substitutes & subs)
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{
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Strings ss;
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for (Substitutes::const_iterator i = subs.begin();
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i != subs.end(); ++i)
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{
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Strings ss2;
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ss2.push_back(i->storeExpr);
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ss2.push_back(i->program);
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ss2.push_back(packStrings(i->args));
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ss.push_back(packStrings(ss2));
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}
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nixDB.setStrings(txn, dbSubstitutes, srcPath, ss);
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}
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void registerSubstitute(const Transaction & txn,
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const Path & srcPath, const Substitute & sub)
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{
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assertStorePath(srcPath);
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assertStorePath(sub.storeExpr);
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Substitutes subs = readSubstitutes(txn, srcPath);
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if (find(subs.begin(), subs.end(), sub) != subs.end()) {
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/* Nothing to do if the substitute is already known. */
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return;
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}
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subs.push_front(sub); /* new substitutes take precedence */
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writeSubstitutes(txn, srcPath, subs);
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Paths revs;
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nixDB.queryStrings(txn, dbSubstitutesRev, sub.storeExpr, revs);
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if (find(revs.begin(), revs.end(), srcPath) == revs.end())
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revs.push_back(srcPath);
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// !!! O(n^2) complexity in building this
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// nixDB.setStrings(txn, dbSubstitutesRev, sub.storeExpr, revs);
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}
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Substitutes querySubstitutes(const Path & srcPath)
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{
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return readSubstitutes(noTxn, srcPath);
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}
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void registerValidPath(const Transaction & txn, const Path & _path)
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{
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Path path(canonPath(_path));
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assertStorePath(path);
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debug(format("registering path `%1%'") % path);
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nixDB.setString(txn, dbValidPaths, path, "");
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}
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static void invalidatePath(const Path & path, Transaction & txn)
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{
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debug(format("unregistering path `%1%'") % path);
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nixDB.delPair(txn, dbValidPaths, path);
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/* Remove any successor mappings to this path (but not *from*
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it). */
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Paths revs;
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nixDB.queryStrings(txn, dbSuccessorsRev, path, revs);
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for (Paths::iterator i = revs.begin(); i != revs.end(); ++i)
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nixDB.delPair(txn, dbSuccessors, *i);
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nixDB.delPair(txn, dbSuccessorsRev, path);
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/* Remove any substitute mappings to this path. */
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revs.clear();
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nixDB.queryStrings(txn, dbSubstitutesRev, path, revs);
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for (Paths::iterator i = revs.begin(); i != revs.end(); ++i) {
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Substitutes subs = readSubstitutes(txn, *i), subs2;
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bool found = false;
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for (Substitutes::iterator j = subs.begin(); j != subs.end(); ++j)
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if (j->storeExpr != path)
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subs2.push_back(*j);
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else
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found = true;
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if (!found) throw Error("integrity error in substitutes mapping");
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writeSubstitutes(txn, *i, subs);
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/* If path *i now has no substitutes left, and is not valid,
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then it too should be invalidated. This is because it may
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be a substitute or successor. */
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if (subs.size() == 0 && !isValidPathTxn(*i, txn))
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invalidatePath(*i, txn);
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}
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nixDB.delPair(txn, dbSubstitutesRev, path);
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}
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Path addToStore(const Path & _srcPath)
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{
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Path srcPath(absPath(_srcPath));
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debug(format("adding `%1%' to the store") % srcPath);
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Hash h = hashPath(srcPath);
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string baseName = baseNameOf(srcPath);
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Path dstPath = canonPath(nixStore + "/" + (string) h + "-" + baseName);
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if (!isValidPath(dstPath)) {
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/* The first check above is an optimisation to prevent
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unnecessary lock acquisition. */
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PathSet lockPaths;
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lockPaths.insert(dstPath);
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PathLocks outputLock(lockPaths);
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if (!isValidPath(dstPath)) {
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if (pathExists(dstPath)) deletePath(dstPath);
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copyPath(srcPath, dstPath);
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Transaction txn(nixDB);
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registerValidPath(txn, dstPath);
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txn.commit();
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}
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outputLock.setDeletion(true);
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}
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return dstPath;
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}
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void addTextToStore(const Path & dstPath, const string & s)
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{
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assertStorePath(dstPath);
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if (!isValidPath(dstPath)) {
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PathSet lockPaths;
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lockPaths.insert(dstPath);
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PathLocks outputLock(lockPaths);
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if (!isValidPath(dstPath)) {
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if (pathExists(dstPath)) deletePath(dstPath);
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writeStringToFile(dstPath, s);
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Transaction txn(nixDB);
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registerValidPath(txn, dstPath);
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txn.commit();
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}
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outputLock.setDeletion(true);
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}
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}
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void deleteFromStore(const Path & _path)
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{
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Path path(canonPath(_path));
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assertStorePath(path);
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Transaction txn(nixDB);
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invalidatePath(path, txn);
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txn.commit();
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deletePath(path);
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}
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void verifyStore()
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{
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Transaction txn(nixDB);
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Paths paths;
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PathSet validPaths;
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nixDB.enumTable(txn, dbValidPaths, paths);
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for (Paths::iterator i = paths.begin(); i != paths.end(); ++i) {
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Path path = *i;
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if (!pathExists(path)) {
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printMsg(lvlError, format("path `%1%' disappeared") % path);
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invalidatePath(path, txn);
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} else if (!isInStore(path)) {
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printMsg(lvlError, format("path `%1%' is not in the Nix store") % path);
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invalidatePath(path, txn);
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} else
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validPaths.insert(path);
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}
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/* !!! the code below does not allow transitive substitutes.
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I.e., if B is a substitute of A, then B must be a valid path.
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B cannot itself be invalid but have a substitute. */
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/* "Usable" paths are those that are valid or have a substitute.
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These are the paths that are allowed to appear in the
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right-hand side of a sute mapping. */
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PathSet usablePaths(validPaths);
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/* Check that the values of the substitute mappings are valid
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paths. */
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Paths subKeys;
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nixDB.enumTable(txn, dbSubstitutes, subKeys);
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for (Paths::iterator i = subKeys.begin(); i != subKeys.end(); ++i) {
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Substitutes subs = readSubstitutes(txn, *i), subs2;
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for (Substitutes::iterator j = subs.begin(); j != subs.end(); ++j)
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if (validPaths.find(j->storeExpr) == validPaths.end())
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printMsg(lvlError,
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format("found substitute mapping to non-existent path `%1%'")
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% j->storeExpr);
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else
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subs2.push_back(*j);
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if (subs.size() != subs2.size())
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writeSubstitutes(txn, *i, subs2);
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if (subs2.size() > 0)
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usablePaths.insert(*i);
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}
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/* Check that the keys of the reverse substitute mappings are
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valid paths. */
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Paths rsubKeys;
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nixDB.enumTable(txn, dbSubstitutesRev, rsubKeys);
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for (Paths::iterator i = rsubKeys.begin(); i != rsubKeys.end(); ++i) {
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if (validPaths.find(*i) == validPaths.end()) {
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printMsg(lvlError,
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format("found reverse substitute mapping for non-existent path `%1%'") % *i);
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nixDB.delPair(txn, dbSubstitutesRev, *i);
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}
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}
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/* Check that the values of the successor mappings are usable
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paths. */
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Paths sucKeys;
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nixDB.enumTable(txn, dbSuccessors, sucKeys);
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for (Paths::iterator i = sucKeys.begin(); i != sucKeys.end(); ++i) {
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/* Note that *i itself does not have to be valid, just its
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successor. */
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Path sucPath;
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if (nixDB.queryString(txn, dbSuccessors, *i, sucPath) &&
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usablePaths.find(sucPath) == usablePaths.end())
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{
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printMsg(lvlError,
|
|
format("found successor mapping to non-existent path `%1%'") % sucPath);
|
|
nixDB.delPair(txn, dbSuccessors, *i);
|
|
}
|
|
}
|
|
|
|
/* Check that the keys of the reverse successor mappings are valid
|
|
paths. */
|
|
Paths rsucKeys;
|
|
nixDB.enumTable(txn, dbSuccessorsRev, rsucKeys);
|
|
for (Paths::iterator i = rsucKeys.begin(); i != rsucKeys.end(); ++i) {
|
|
if (usablePaths.find(*i) == usablePaths.end()) {
|
|
printMsg(lvlError,
|
|
format("found reverse successor mapping for non-existent path `%1%'") % *i);
|
|
nixDB.delPair(txn, dbSuccessorsRev, *i);
|
|
}
|
|
}
|
|
|
|
txn.commit();
|
|
}
|