81 lines
3.1 KiB
C++
81 lines
3.1 KiB
C++
// Example 05 — Error Handling & Diagnostics
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//
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// Demonstrates observable failure modes and the diagnostics system:
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//
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// 1. ChannelOverflowError — a fast producer saturates a slow consumer.
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// When the channel is full, push() throws ChannelOverflowError.
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// The node's run_loop catches it and prints to stderr.
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// Channel statistics (overflows, peak fill) accumulate for the report.
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//
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// 2. Custom diagnostics handler — instead of the default periodic table,
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// install a handler that surfaces only the metrics you care about.
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//
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// 3. net.print_diagnostics() — print a full report at any time.
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//
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// Pipeline: [producer] --int--> [slow_consumer]
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#include <kpn/kpn.hpp>
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#include <chrono>
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#include <iostream>
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#include <thread>
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// ── Node functions ────────────────────────────────────────────────────────────
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// Produces at ~100/s — faster than the consumer can keep up (50 ms each)
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static int producer() {
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std::this_thread::sleep_for(std::chrono::milliseconds(10));
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static int n = 0;
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return ++n;
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}
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// Slow consumer: 50 ms per item — will cause channel to fill and overflow
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static void slow_consumer(int x) {
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std::this_thread::sleep_for(std::chrono::milliseconds(50));
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std::cout << "[consumed] " << x << '\n';
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}
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// ── main ──────────────────────────────────────────────────────────────────────
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int main() {
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using namespace kpn;
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// Capacity=4: fills up quickly when producer outpaces consumer 5:1
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auto prod = make_node<producer> (out<"v">{}, /*capacity=*/4);
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auto cons = make_node<slow_consumer> (in<"v">{}, /*capacity=*/4);
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Network net;
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// --8<-- [start:diagnostics_handler]
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// Custom diagnostics handler — fires on the watchdog interval.
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// Print a concise one-liner rather than the full table.
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net.set_diagnostics_handler([](const std::vector<NodeSnapshot>& nodes,
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const std::vector<ChannelSnapshot>& channels) {
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std::cout << "[diag] ";
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for (auto& n : nodes)
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std::cout << n.name << "=" << n.throughput_fps << "fps ";
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for (auto& c : channels)
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std::cout << "channel fill=" << static_cast<int>(c.fill_pct()) << "% "
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<< "overflows=" << c.overflows;
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std::cout << '\n';
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});
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// --8<-- [end:diagnostics_handler]
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net.set_watchdog_interval(std::chrono::milliseconds(200));
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net.add("prod", prod)
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.add("cons", cons)
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.connect("prod", prod.template output<"v">(), "cons", cons.template input<"v">())
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.build();
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std::cout << "producer: 10ms/item, consumer: 50ms/item, capacity=4\n"
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<< "Overflow messages appear on stderr; diagnostics on stdout.\n\n";
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net.start();
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std::this_thread::sleep_for(std::chrono::milliseconds(800));
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net.stop();
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// Full report after shutdown — overflow and drop counts are preserved
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std::cout << '\n';
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net.print_diagnostics();
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}
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