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Remove bad daemon connections from the pool

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This is necessary for long-running processes like hydra-queue-runner:
if a nix-daemon worker is killed, we need to stop reusing that
connection.
This commit is contained in:
Eelco Dolstra 2016-02-24 11:39:56 +01:00
parent d5626bf4c1
commit 5f862658c3
4 changed files with 55 additions and 14 deletions
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18
src/libutil/pool.hh
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@ -33,11 +33,17 @@ class Pool
{
public:
/* A function that produces new instances of R on demand. */
typedef std::function<ref<R>()> Factory;
/* A function that checks whether an instance of R is still
usable. Unusable instances are removed from the pool. */
typedef std::function<bool(const ref<R> &)> Validator;
private:
Factory factory;
Validator validator;
struct State
{
@ -53,8 +59,10 @@ private:
public:
Pool(size_t max = std::numeric_limits<size_t>::max,
const Factory & factory = []() { return make_ref<R>(); })
const Factory & factory = []() { return make_ref<R>(); },
const Validator & validator = [](ref<R> r) { return true; })
: factory(factory)
, validator(validator)
{
auto state_(state.lock());
state_->max = max;
@ -109,11 +117,13 @@ public:
while (state_->idle.empty() && state_->inUse >= state_->max)
state_.wait(wakeup);
if (!state_->idle.empty()) {
while (!state_->idle.empty()) {
auto p = state_->idle.back();
state_->idle.pop_back();
state_->inUse++;
return Handle(*this, p);
if (validator(p)) {
state_->inUse++;
return Handle(*this, p);
}
}
state_->inUse++;