* Put the garbage collector in nix-store: operation `--gc',

suboperations `--print-live', `--print-dead', and `--delete'.  The
  roots are not determined by nix-store; they are read from standard
  input.  This is to make it easy to customise what the roots are.

  The collector now no longer fails when store expressions are missing
  (which legally happens when using substitutes).  It never tries to
  fetch paths through substitutes.

  TODO: acquire a global lock on the store while garbage collecting.
  
* Removed `nix-store --delete'.
This commit is contained in:
Eelco Dolstra 2004-08-25 11:43:49 +00:00
parent 9994c1dd9f
commit 818047881e
6 changed files with 167 additions and 19 deletions

View file

@ -4,7 +4,8 @@ libstore_a_SOURCES = \
store.cc store.hh storeexpr.cc storeexpr.hh \
normalise.cc misc.cc normalise.hh \
globals.cc globals.hh db.cc db.hh \
references.cc references.hh pathlocks.cc pathlocks.hh
references.cc references.hh pathlocks.cc pathlocks.hh \
gc.cc gc.hh
AM_CXXFLAGS = -Wall \
-I.. ${bdb_include} ${aterm_include} -I../libutil

83
src/libstore/gc.cc Normal file
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@ -0,0 +1,83 @@
#include "normalise.hh"
#include "globals.hh"
void followLivePaths(Path nePath, PathSet & live)
{
/* Just to be sure, canonicalise the path. It is important to do
this here and in findDeadPath() to ensure that a live path is
not mistaken for a dead path due to some non-canonical
representation. */
nePath = canonPath(nePath);
if (live.find(nePath) != live.end()) return;
live.insert(nePath);
startNest(nest, lvlDebug, format("following `%1%'") % nePath);
assertStorePath(nePath);
if (isValidPath(nePath)) {
/* !!! should make sure that no substitutes are used */
StoreExpr ne = storeExprFromPath(nePath);
/* !!! painfully similar to requisitesWorker() */
if (ne.type == StoreExpr::neClosure)
for (ClosureElems::iterator i = ne.closure.elems.begin();
i != ne.closure.elems.end(); ++i)
{
Path p = canonPath(i->first);
if (live.find(p) == live.end()) {
debug(format("found live `%1%'") % p);
assertStorePath(p);
live.insert(p);
}
}
else if (ne.type == StoreExpr::neDerivation)
for (PathSet::iterator i = ne.derivation.inputs.begin();
i != ne.derivation.inputs.end(); ++i)
followLivePaths(*i, live);
else abort();
}
Path nfPath;
if (querySuccessor(nePath, nfPath))
followLivePaths(nfPath, live);
}
PathSet findLivePaths(const Paths & roots)
{
PathSet live;
startNest(nest, lvlDebug, "finding live paths");
for (Paths::const_iterator i = roots.begin(); i != roots.end(); ++i)
followLivePaths(*i, live);
return live;
}
PathSet findDeadPaths(const PathSet & live)
{
PathSet dead;
startNest(nest, lvlDebug, "finding dead paths");
Strings storeNames = readDirectory(nixStore);
for (Strings::iterator i = storeNames.begin(); i != storeNames.end(); ++i) {
Path p = canonPath(nixStore + "/" + *i);
if (live.find(p) == live.end()) {
debug(format("dead path `%1%'") % p);
dead.insert(p);
} else
debug(format("live path `%1%'") % p);
}
return dead;
}

24
src/libstore/gc.hh Normal file
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@ -0,0 +1,24 @@
#ifndef __GC_H
#define __GC_H
#include "storeexpr.hh"
/* Determine the set of "live" store paths, given a set of root store
expressions. The live store paths are those that are reachable
from the roots. The roots are reachable by definition. Any path
mentioned in a reachable store expression is also reachable. If a
derivation store expression is reachable, then its successor (if it
exists) if also reachable. It is not an error for store
expressions not to exist (since this can happen on derivation store
expressions, for instance, due to the substitute mechanism), but
successor links are followed even for non-existant derivations. */
PathSet findLivePaths(const Paths & roots);
/* Given a set of "live" store paths, determine the set of "dead"
store paths (which are simply all store paths that are not in the
live set). */
PathSet findDeadPaths(const PathSet & live);
#endif /* !__GC_H */

View file

@ -40,9 +40,5 @@ PathSet storeExprRoots(const Path & nePath);
PathSet storeExprRequisites(const Path & nePath,
bool includeExprs, bool includeSuccessors);
/* Return the list of the paths of all known store expressions whose
output paths are completely contained in the set `outputs'. */
PathSet findGenerators(const PathSet & outputs);
#endif /* !__NORMALISE_H */

View file

@ -388,7 +388,7 @@ static void invalidatePath(const Path & path, Transaction & txn)
subs2.push_back(*j);
else
found = true;
if (!found) throw Error("integrity error in substitutes mapping");
// !!! if (!found) throw Error("integrity error in substitutes mapping");
writeSubstitutes(txn, *i, subs);
/* If path *i now has no substitutes left, and is not valid,

View file

@ -3,6 +3,7 @@
#include "globals.hh"
#include "normalise.hh"
#include "gc.hh"
#include "archive.hh"
#include "shared.hh"
#include "dotgraph.hh"
@ -32,17 +33,6 @@ static void opRealise(Strings opFlags, Strings opArgs)
}
/* Delete a path in the Nix store directory. */
static void opDelete(Strings opFlags, Strings opArgs)
{
if (!opFlags.empty()) throw UsageError("unknown flag");
for (Strings::iterator it = opArgs.begin();
it != opArgs.end(); it++)
deleteFromStore(*it);
}
/* Add paths to the Nix values directory and print the hashes of those
paths. */
static void opAdd(Strings opFlags, Strings opArgs)
@ -220,6 +210,60 @@ static void opIsValid(Strings opFlags, Strings opArgs)
}
static void opGC(Strings opFlags, Strings opArgs)
{
if (opFlags.size() != 1) throw UsageError("missing flag");
if (!opArgs.empty())
throw UsageError("no arguments expected");
/* Do what? */
string flag = opFlags.front();
enum { soPrintLive, soPrintDead, soDelete } subOp;
if (flag == "--print-live") subOp = soPrintLive;
else if (flag == "--print-dead") subOp = soPrintDead;
else if (flag == "--delete") subOp = soDelete;
else throw UsageError(format("bad sub-operation `%1% in GC") % flag);
Paths roots;
while (1) {
Path root;
getline(cin, root);
if (cin.eof()) break;
roots.push_back(root);
}
PathSet live = findLivePaths(roots);
if (subOp == soPrintLive) {
for (PathSet::iterator i = live.begin(); i != live.end(); ++i)
cout << *i << endl;
return;
}
PathSet dead = findDeadPaths(live);
if (subOp == soPrintDead) {
for (PathSet::iterator i = dead.begin(); i != dead.end(); ++i)
cout << *i << endl;
return;
}
if (subOp == soDelete) {
/* !!! What happens if the garbage collector run is aborted
halfway through? In particular, dead paths can always
become live again (through re-instantiation), and might
then refer to deleted paths. => check instantiation
invariants */
for (PathSet::iterator i = dead.begin(); i != dead.end(); ++i) {
printMsg(lvlInfo, format("deleting `%1%'") % *i);
deleteFromStore(*i);
}
}
}
/* A sink that writes dump output to stdout. */
struct StdoutSink : DumpSink
{
@ -298,8 +342,6 @@ void run(Strings args)
if (arg == "--realise" || arg == "-r")
op = opRealise;
else if (arg == "--delete" || arg == "-d")
op = opDelete;
else if (arg == "--add" || arg == "-A")
op = opAdd;
else if (arg == "--query" || arg == "-q")
@ -312,6 +354,8 @@ void run(Strings args)
op = opValidPath;
else if (arg == "--isvalid")
op = opIsValid;
else if (arg == "--gc")
op = opGC;
else if (arg == "--dump")
op = opDump;
else if (arg == "--restore")