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-rw-r--r--benchmarks/http/watch.c233
1 files changed, 233 insertions, 0 deletions
diff --git a/benchmarks/http/watch.c b/benchmarks/http/watch.c
new file mode 100644
index 0000000..7367f98
--- /dev/null
+++ b/benchmarks/http/watch.c
@@ -0,0 +1,233 @@
+#define _GNU_SOURCE
+/* How fresh a view stays for many clients (docs/design/019): N clients
+ * follow a counter view while one writer moves it RATE times a second.
+ *
+ * watch PORT CLIENTS SECONDS RATE push|poll[:MS] VIEW WRITE
+ * push each client subscribes to GET VIEW (Accept: text/event-stream)
+ * poll:MS each client GETs VIEW every MS milliseconds (kept alive, its
+ * first at a random point of the first MS)
+ * The writer POSTs WRITE (a text input that adds one to the counter) on a
+ * connection of its own every 1/RATE seconds: its k-th answer means the
+ * counter is k past where it began. A client that sees the value v has
+ * every write up to v: each such write's freshness is when the client saw
+ * it less when the writer had its answer (0 when the client saw it
+ * first). Prints one JSON line: writes, clients that followed to the end,
+ * events or answers taken, the freshness percentiles (µs) and how many
+ * writes it was measured for. */
+#include <errno.h>
+#include <fcntl.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <arpa/inet.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/epoll.h>
+#include <sys/socket.h>
+#include <time.h>
+#include <unistd.h>
+
+enum { BUCKETS = 64 * 16, IN = 4096 };
+
+static uint64_t now_us(void) {
+ struct timespec t;
+ clock_gettime(CLOCK_MONOTONIC, &t);
+ return (uint64_t)t.tv_sec * 1000000u + (uint64_t)t.tv_nsec / 1000u;
+}
+
+/* Log-linear histogram: 16 buckets per power of two. */
+static uint64_t histogram[BUCKETS], samples;
+static unsigned bucket(uint64_t us) {
+ if (us < 16) return (unsigned)us;
+ unsigned power = 63u - (unsigned)__builtin_clzll(us);
+ unsigned b = (power - 3) * 16 + (unsigned)((us >> (power - 4)) & 15);
+ return b < BUCKETS ? b : BUCKETS - 1;
+}
+static uint64_t bucket_value(unsigned b) {
+ if (b < 16) return b;
+ unsigned power = b / 16 + 3;
+ return ((uint64_t)16 + b % 16) << (power - 4);
+}
+static uint64_t percentile(double p) {
+ uint64_t want = (uint64_t)(p * (double)samples), seen = 0;
+ for (unsigned b = 0; b < BUCKETS; ++b)
+ if ((seen += histogram[b]) > want) return bucket_value(b);
+ return 0;
+}
+
+typedef struct {
+ int fd;
+ bool writer, streaming;
+ char in[IN];
+ size_t used;
+ int64_t seen; /* the newest value it has seen (-1: none) */
+ uint64_t next_at; /* a poller's next request, or the writer's */
+ bool asking; /* a request is out */
+} Client;
+
+static int64_t base = -1; /* the counter when the writer began */
+static uint64_t *acked; /* by write: when its answer came (0: not yet) */
+static size_t writes, acked_count;
+static uint64_t taken;
+
+/* Connected, then non-blocking: a request goes at once. */
+static int dial(int port) {
+ int fd = socket(AF_INET, SOCK_STREAM | SOCK_CLOEXEC, 0);
+ int one = 1;
+ setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &one, sizeof(one));
+ struct sockaddr_in address = {.sin_family = AF_INET, .sin_port = htons((uint16_t)port),
+ .sin_addr.s_addr = htonl(INADDR_LOOPBACK)};
+ if (connect(fd, (struct sockaddr *)&address, sizeof(address))) { perror("connect"); exit(1); }
+ fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK);
+ return fd;
+}
+
+static void send_all(int fd, const char *text) {
+ size_t size = strlen(text), at = 0;
+ while (at < size) {
+ ssize_t n = send(fd, text + at, size - at, MSG_NOSIGNAL);
+ if (n > 0) at += (size_t)n;
+ else if (n < 0 && errno != EAGAIN && errno != EINTR) { perror("send"); exit(1); }
+ }
+}
+
+/* A client saw the counter at v: the writes it had not seen up to v are fresh as of now. */
+static void saw(Client *c, int64_t v, uint64_t now) {
+ if (base < 0 || v <= c->seen) { if (v > c->seen) c->seen = v; return; }
+ for (int64_t k = (c->seen < base ? base : c->seen) + 1; k <= v; ++k) {
+ size_t write = (size_t)(k - base - 1);
+ if (write >= writes) break;
+ uint64_t at = acked[write];
+ ++histogram[bucket(at && now > at ? now - at : 0)];
+ ++samples;
+ }
+ c->seen = v;
+}
+
+int main(int argc, char **argv) {
+ if (argc != 8) {
+ fputs("watch PORT CLIENTS SECONDS RATE push|poll[:MS] VIEW WRITE\n", stderr);
+ return 2;
+ }
+ int port = atoi(argv[1]);
+ size_t clients = (size_t)atol(argv[2]);
+ double seconds = atof(argv[3]), rate = atof(argv[4]);
+ bool push = !strcmp(argv[5], "push");
+ uint64_t every = push ? 0 : (uint64_t)atol(argv[5] + 5) * 1000;
+ const char *view = argv[6], *write_path = argv[7];
+ writes = (size_t)(seconds * rate) + 1;
+ acked = calloc(writes, sizeof(*acked));
+ Client *all = calloc(clients + 1, sizeof(*all));
+ int epoll = epoll_create1(EPOLL_CLOEXEC);
+ char request[512];
+ srand(1);
+ uint64_t start = now_us();
+ /* The followers first, opened a few hundred at a time (a subscriber asks at once); then the writer. */
+ for (size_t i = 0; i < clients; ++i) {
+ Client *c = &all[i];
+ c->fd = dial(port);
+ if (push) {
+ snprintf(request, sizeof(request), "GET %s HTTP/1.1\r\nHost: x\r\nAccept: text/event-stream\r\n\r\n", view);
+ send_all(c->fd, request);
+ }
+ c->seen = -1;
+ c->next_at = push ? 0 : start + (uint64_t)rand() % (every ? every : 1);
+ struct epoll_event event = {.events = EPOLLIN | EPOLLOUT | EPOLLET, .data.ptr = c};
+ epoll_ctl(epoll, EPOLL_CTL_ADD, c->fd, &event);
+ if (i % 200 == 199) usleep(20000);
+ }
+ Client *writer = &all[clients];
+ writer->writer = true;
+ writer->fd = dial(port);
+ struct epoll_event writer_event = {.events = EPOLLIN | EPOLLOUT | EPOLLET, .data.ptr = writer};
+ epoll_ctl(epoll, EPOLL_CTL_ADD, writer->fd, &writer_event);
+ usleep(200000); /* every follower connected */
+ /* The counter where it begins: one GET on the writer's connection. */
+ snprintf(request, sizeof(request), "GET %s HTTP/1.1\r\nHost: x\r\n\r\n", view);
+ send_all(writer->fd, request);
+ writer->asking = true;
+ struct epoll_event events[256];
+ uint64_t began = 0, end = UINT64_MAX;
+ size_t sent = 0;
+ while (now_us() < end) {
+ uint64_t now = now_us();
+ /* The writer's next write, and the pollers' next requests. */
+ if (base >= 0 && !writer->asking && sent < writes && now >= began + (uint64_t)((double)sent * 1e6 / rate)) {
+ snprintf(request, sizeof(request), "POST %s HTTP/1.1\r\nHost: x\r\nContent-Length: 1\r\n\r\nx", write_path);
+ send_all(writer->fd, request);
+ writer->asking = true;
+ ++sent;
+ }
+ for (size_t i = 0; !push && i < clients; ++i) {
+ Client *c = &all[i];
+ if (c->asking || now < c->next_at) continue;
+ snprintf(request, sizeof(request), "GET %s HTTP/1.1\r\nHost: x\r\n\r\n", view);
+ send_all(c->fd, request);
+ c->asking = true;
+ c->next_at += every;
+ }
+ int ready = epoll_wait(epoll, events, 256, 1);
+ now = now_us();
+ for (int e = 0; e < ready; ++e) {
+ Client *c = events[e].data.ptr;
+ for (;;) {
+ ssize_t n = recv(c->fd, c->in + c->used, IN - 1 - c->used, 0);
+ if (n == 0) { fprintf(stderr, "a connection closed\n"); exit(1); }
+ if (n < 0) break;
+ c->used += (size_t)n;
+ c->in[c->used] = 0;
+ for (;;) { /* whole answers (Content-Length) or whole events */
+ char *at = c->in;
+ if (c->writer || !push) {
+ char *head_end = strstr(at, "\r\n\r\n"), *length = strcasestr(at, "Content-Length: ");
+ if (!head_end || !length || length > head_end) break;
+ size_t body = (size_t)atol(length + 16), whole = (size_t)(head_end + 4 - at) + body;
+ if (c->used < whole) break;
+ int64_t value = body ? atoll(head_end + 4) : -1;
+ if (c->writer) {
+ if (base < 0) { base = value; began = now; end = now + (uint64_t)(seconds * 1e6) + 500000; }
+ else { acked[acked_count++] = now; }
+ } else {
+ ++taken;
+ saw(c, value, now);
+ }
+ c->asking = false;
+ memmove(c->in, c->in + whole, c->used - whole);
+ c->used -= whole;
+ c->in[c->used] = 0;
+ continue;
+ }
+ if (!c->streaming) { /* the stream's head */
+ char *head_end = strstr(at, "\r\n\r\n");
+ if (!head_end) break;
+ if (strncmp(at, "HTTP/1.1 200", 12)) { fprintf(stderr, "refused: %.40s\n", at); exit(1); }
+ c->streaming = true;
+ size_t whole = (size_t)(head_end + 4 - at);
+ memmove(c->in, c->in + whole, c->used - whole);
+ c->used -= whole;
+ c->in[c->used] = 0;
+ continue;
+ }
+ char *event_end = strstr(at, "\n\n");
+ if (!event_end) break;
+ char *data = strstr(at, "data: ");
+ if (data && data < event_end) { ++taken; saw(c, atoll(data + 6), now); }
+ size_t whole = (size_t)(event_end + 2 - at);
+ memmove(c->in, c->in + whole, c->used - whole);
+ c->used -= whole;
+ c->in[c->used] = 0;
+ }
+ }
+ }
+ }
+ size_t followed = 0;
+ for (size_t i = 0; i < clients; ++i) followed += all[i].seen >= base + (int64_t)acked_count;
+ printf("{\"clients\":%zu,\"way\":\"%s\",\"rate\":%g,\"writes\":%zu,\"followed_to_end\":%zu,\"taken\":%llu,"
+ "\"measured\":%llu,\"p50_us\":%llu,\"p90_us\":%llu,\"p99_us\":%llu,\"max_us\":%llu}\n",
+ clients, argv[5], rate, acked_count, followed, (unsigned long long)taken, (unsigned long long)samples,
+ (unsigned long long)percentile(0.5), (unsigned long long)percentile(0.9), (unsigned long long)percentile(0.99),
+ (unsigned long long)percentile(0.999999));
+ return 0;
+}
generated by cgit v1.2.3 (git 2.46.0) at 2026-10-20 13:38:34 +0000