zeek/src/Trigger.cc

#include "zeek/Trigger.h"

#include <algorithm>
#include <cassert>

#include "zeek/DebugLogger.h"
#include "zeek/Desc.h"
#include "zeek/Expr.h"
#include "zeek/Frame.h"
#include "zeek/ID.h"
#include "zeek/Reporter.h"
#include "zeek/Stmt.h"
#include "zeek/Traverse.h"
#include "zeek/Val.h"
#include "zeek/iosource/Manager.h"
#include "zeek/telemetry/Manager.h"

using namespace zeek::detail;
using namespace zeek::detail::trigger;

// Callback class to traverse an expression, registering all relevant IDs and
// Vals for change notifications.

namespace zeek::detail::trigger {

// Used to extract the globals and locals seen in a trigger expression.
class TriggerTraversalCallback : public TraversalCallback {
public:
    TriggerTraversalCallback(IDSet& _globals, IDSet& _locals) : globals(_globals), locals(_locals) {}

    TraversalCode PreExpr(const Expr*) override;

private:
    IDSet& globals;
    IDSet& locals;
};

TraversalCode trigger::TriggerTraversalCallback::PreExpr(const Expr* expr) {
    // We catch all expressions here which in some way reference global
    // state.

    switch ( expr->Tag() ) {
        case EXPR_NAME: {
            const auto* e = static_cast<const NameExpr*>(expr);
            auto id = e->Id();

            if ( id->IsGlobal() )
                globals.insert(id);
            else
                locals.insert(id);
        };

        default:
            // All others are uninteresting.
            break;
    }

    return TC_CONTINUE;
}

class TriggerTimer final : public Timer {
public:
    TriggerTimer(double arg_timeout, Trigger* arg_trigger)
        : Timer(run_state::network_time + arg_timeout, TIMER_TRIGGER) {
        Ref(arg_trigger);
        trigger = arg_trigger;
        timeout = arg_timeout;
        time = run_state::network_time;
    }

    ~TriggerTimer() override { Unref(trigger); }

    void Dispatch(double t, bool is_expire) override {
        // The network_time may still have been zero when the
        // timer was instantiated.  In this case, it fires
        // immediately and we simply restart it.
        if ( time )
            trigger->Timeout();
        else {
            TriggerTimer* timer = new TriggerTimer(timeout, trigger);
            timer_mgr->Add(timer);
            trigger->timer = timer;
        }
    }

protected:
    Trigger* trigger;
    double timeout;
    double time;
};

Trigger::Trigger(std::shared_ptr<WhenInfo> wi, const IDSet& _globals, std::vector<ValPtr> _local_aggrs, double timeout,
                 Frame* f, const Location* loc) {
    timeout_value = timeout;
    globals = _globals;
    local_aggrs = std::move(_local_aggrs);
    have_trigger_elems = true;

    cond = wi->Cond();
    body = wi->WhenBody();
    timeout_stmts = wi->TimeoutStmt();
    is_return = wi->IsReturn();

    timer = nullptr;
    delayed = false;
    disabled = false;
    attached = nullptr;

    if ( loc )
        name = util::fmt("%s:%d-%d", loc->filename, loc->first_line, loc->last_line);
    else
        name = "<no-trigger-location>";

    if ( f )
        frame = f->CloneForTrigger();
    else
        frame = nullptr;

    DBG_LOG(DBG_NOTIFIERS, "%s: instantiating", Name());

    if ( is_return && frame ) {
        Trigger* parent = frame->GetTrigger();
        if ( ! parent ) {
            reporter->Error("return trigger in context which does not allow delaying result");
            return;
        }

        parent->Attach(this);
        f->SetDelayed();
    }

    // Make sure we don't get deleted if somebody calls a method like
    // Timeout() while evaluating the trigger.
    Ref(this);

    if ( ! Eval() && timeout_value >= 0 ) {
        timer = new TriggerTimer(timeout_value, this);
        timer_mgr->Add(timer);
    }
}

void Trigger::Terminate() {
    if ( is_return ) {
        auto parent = frame->GetTrigger();

        if ( ! parent->Disabled() ) {
            // If the trigger was already disabled due to interpreter
            // exception, an Unref already happened at that point.
            parent->Disable();
            Unref(parent);
        }

        frame->ClearTrigger();
    }

    Disable();
    Unref(this);
}

Trigger::~Trigger() {
    DBG_LOG(DBG_NOTIFIERS, "%s: deleting", Name());

    for ( ValCache::iterator i = cache.begin(); i != cache.end(); ++i )
        Unref(i->second);

    Unref(frame);
    UnregisterAll();

    Unref(attached);
    // Due to ref'counting, "this" cannot be part of pending at this
    // point.
}

void Trigger::ReInit(std::vector<ValPtr> index_expr_results) {
    assert(! disabled);
    UnregisterAll();

    if ( ! have_trigger_elems ) {
        TriggerTraversalCallback cb(globals, locals);
        cond->Traverse(&cb);
        have_trigger_elems = true;
    }

    for ( auto g : globals ) {
        Register(g);

        auto& v = g->GetVal();
        if ( v && v->Modifiable() )
            Register(v.get());
    }

    for ( auto l : locals ) {
        ASSERT(! l->GetVal());
    }

    for ( auto& av : local_aggrs )
        Register(av.get());

    for ( const auto& v : index_expr_results )
        Register(v.get());
}

bool Trigger::Eval() {
    if ( disabled )
        return true;

    DBG_LOG(DBG_NOTIFIERS, "%s: evaluating", Name());

    if ( delayed ) {
        DBG_LOG(DBG_NOTIFIERS, "%s: skipping eval due to delayed call", Name());
        return false;
    }

    // It's unfortunate that we have to copy the frame again here but
    // otherwise changes to any of the locals would propagate to later
    // evaluations.
    //
    // An alternative approach to copying the frame would be to deep-copy
    // the expression itself, replacing all references to locals with
    // constants.

    Frame* f = nullptr;

    try {
        f = frame->CloneForTrigger();
    } catch ( InterpreterException& ) {
        // Frame contains values that couldn't be cloned. It's
        // already been reported, disable trigger.
        Disable();
        Unref(this);
        return false;
    }

    f->SetTrigger({NewRef{}, this});

    ValPtr v;
    IndexExprWhen::StartEval();

    try {
        v = cond->Eval(f);
    } catch ( InterpreterException& ) { /* Already reported */
    }

    IndexExprWhen::EndEval();
    auto index_expr_results = IndexExprWhen::TakeAllResults();

    f->ClearTrigger();

    if ( f->HasDelayed() ) {
        DBG_LOG(DBG_NOTIFIERS, "%s: eval has delayed", Name());
        assert(! v);
        Unref(f);
        return false;
    }

    if ( ! v || v->IsZero() ) {
        // Not true. Perhaps next time...
        DBG_LOG(DBG_NOTIFIERS, "%s: trigger condition is false", Name());
        Unref(f);
        ReInit(std::move(index_expr_results));
        return false;
    }

    DBG_LOG(DBG_NOTIFIERS, "%s: trigger condition is true, executing", Name());

    v = nullptr;
    StmtFlowType flow;

    try {
        v = body->Exec(f, flow);
    } catch ( InterpreterException& e ) { /* Already reported. */
    }

    if ( is_return ) {
        Trigger* trigger = frame->GetTrigger();
        assert(trigger);
        assert(frame->GetTriggerAssoc());
        assert(trigger->attached == this);

#ifdef DEBUG
        const char* pname = util::copy_string(trigger->Name());
        DBG_LOG(DBG_NOTIFIERS, "%s: trigger has parent %s, caching result", Name(), pname);
        delete[] pname;
#endif

        auto queued = trigger->Cache(frame->GetTriggerAssoc(), v.get());
        trigger->Release();
        frame->ClearTrigger();

        if ( ! queued && trigger->TimeoutValue() < 0 )
            // Usually the parent-trigger would get unref'd either by
            // its Eval() or its eventual Timeout(), but has neither
            Unref(trigger);
    }

    Unref(f);

    if ( timer )
        timer_mgr->Cancel(timer);

    Disable();
    Unref(this);

    return true;
}

void Trigger::Timeout() {
    if ( disabled )
        return;

    DBG_LOG(DBG_NOTIFIERS, "%s: timeout", Name());
    if ( timeout_stmts ) {
        StmtFlowType flow;
        FramePtr f{AdoptRef{}, frame->CloneForTrigger()};
        ValPtr v;

        try {
            v = timeout_stmts->Exec(f.get(), flow);
        } catch ( InterpreterException& e ) { /* Already reported. */
        }

        if ( is_return ) {
            Trigger* trigger = frame->GetTrigger();
            assert(trigger);
            assert(frame->GetTriggerAssoc());
            assert(trigger->attached == this);

#ifdef DEBUG
            const char* pname = util::copy_string(trigger->Name());
            DBG_LOG(DBG_NOTIFIERS, "%s: trigger has parent %s, caching timeout result", Name(), pname);
            delete[] pname;
#endif
            auto queued = trigger->Cache(frame->GetTriggerAssoc(), v.get());
            trigger->Release();
            frame->ClearTrigger();

            if ( ! queued && trigger->TimeoutValue() < 0 )
                // Usually the parent-trigger would get unref'd either by
                // its Eval() or its eventual Timeout(), but has neither
                Unref(trigger);
        }
    }

    Disable();
    Unref(this);
}

void Trigger::Register(const ID* const_id) {
    assert(! disabled);
    ID* id = const_cast<ID*>(const_id);
    notifier::detail::registry.Register(id, this);

    Ref(id);
    objs.emplace_back(id, id);
}

void Trigger::Register(Val* val) {
    if ( ! val->Modifiable() )
        return;

    assert(! disabled);
    notifier::detail::registry.Register(val->Modifiable(), this);

    Ref(val);
    objs.emplace_back(val, val->Modifiable());
}

void Trigger::UnregisterAll() {
    DBG_LOG(DBG_NOTIFIERS, "%s: unregistering all", Name());

    for ( const auto& o : objs ) {
        notifier::detail::registry.Unregister(o.second, this);
        Unref(o.first);
    }

    objs.clear();
}

void Trigger::Attach(Trigger* trigger) {
    assert(! disabled);
    assert(! trigger->disabled);
    assert(! trigger->delayed);

#ifdef DEBUG
    const char* pname = util::copy_string(trigger->Name());
    DBG_LOG(DBG_NOTIFIERS, "%s: attaching to %s", Name(), pname);
    delete[] pname;
#endif

    Ref(trigger);
    attached = trigger;
    Hold();
}

bool Trigger::Cache(const void* obj, Val* v) {
    if ( disabled || ! v )
        return false;

    ValCache::iterator i = cache.find(obj);

    if ( i != cache.end() ) {
        Unref(i->second);
        i->second = v;
    }

    else
        cache.insert(ValCache::value_type(obj, v));

    Ref(v);

    trigger_mgr->Queue(this);
    return true;
}

Val* Trigger::Lookup(const void* obj) {
    assert(! disabled);

    ValCache::iterator i = cache.find(obj);
    return (i != cache.end()) ? i->second : 0;
}

void Trigger::Disable() {
    UnregisterAll();
    disabled = true;
}

void Trigger::Describe(ODesc* d) const { d->Add("<trigger>"); }

void Trigger::Modified(notifier::detail::Modifiable* m) { trigger_mgr->Queue(this); }

Manager::Manager() : iosource::IOSource() { pending = new TriggerList(); }

Manager::~Manager() { delete pending; }

void Manager::InitPostScript() {
    trigger_count = telemetry_mgr->CounterInstance("zeek", "triggers", {}, "Total number of triggers scheduled");
    trigger_pending =
        telemetry_mgr->GaugeInstance("zeek", "pending_triggers", {}, "Pending number of triggers", "", []() {
            return trigger_mgr ? static_cast<double>(trigger_mgr->pending->size()) : 0.0;
        });

    iosource_mgr->Register(this, true);
}

double Manager::GetNextTimeout() { return pending->empty() ? -1 : run_state::network_time + 0.100; }

void Manager::Process() {
    DBG_LOG(DBG_NOTIFIERS, "evaluating all pending triggers");

    // While we iterate over the list, executing statements, we may
    // in fact trigger new triggers and thereby modify the list.
    // Therefore, we create a new temporary list which will receive
    // triggers triggered during this time.
    TriggerList* orig = pending;
    TriggerList tmp;
    pending = &tmp;

    for ( TriggerList::iterator i = orig->begin(); i != orig->end(); ++i ) {
        Trigger* t = *i;
        (*i)->Eval();
        Unref(t);
    }

    pending = orig;
    orig->clear();

    std::swap(tmp, *pending);
}

void Manager::Queue(Trigger* trigger) {
    if ( std::find(pending->begin(), pending->end(), trigger) == pending->end() ) {
        Ref(trigger);
        pending->push_back(trigger);
        trigger_count->Inc();
        iosource_mgr->Wakeup(Tag());
    }
}

void Manager::GetStats(Stats* stats) {
    stats->total = static_cast<unsigned long>(trigger_count->Value());
    stats->pending = pending->size();
}

} // namespace zeek::detail::trigger