Retry and backoff working properly.

clients/c/test.c

@@ -1,8 +1,11 @@
 #include <assert.h>
+#include <errno.h>
+#include <math.h>
 #include <pthread.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <string.h>
+#include <strings.h>
 #include <time.h>
 #include <unistd.h>
 
@@ -14,6 +17,12 @@
 #define COSMO_CHECK_SECONDS 10
 
 #define min(a, b) ((a) < (b) ? (a) : (b))
+#define max(a, b) ((a) > (b) ? (a) : (b))
+
+#define DELAY_MIN_MS 250
+#define DELAY_MAX_MS 32000
+#define DELAY_EXPONENT 1.1
+#define DELAY_STAGGER_FACTOR 10
 
 typedef struct {
   char client_id[COSMO_UUID_SIZE];
@@ -23,6 +32,7 @@ typedef struct {
   pthread_cond_t cond;
   bool shutdown;
   json_t *command_queue;
+  uint64_t next_delay_ms;
 
   pthread_t thread;
 } cosmo;
@@ -33,6 +43,8 @@ typedef struct {
 
   char *recv_buf;
   size_t recv_buf_len;
+
+  int64_t retry_after;
 } cosmo_transfer;
 
 static size_t cosmo_read_callback(void *ptr, size_t size, size_t nmemb, void *userp) {
@@ -55,6 +67,18 @@ static size_t cosmo_write_callback(void *ptr, size_t size, size_t nmemb, void *u
   return to_read;
 }
 
+static size_t cosmo_header_callback(char *ptr, size_t size, size_t nmemb, void *userp) {
+  cosmo_transfer *transfer = userp;
+  size_t length = size * nmemb;
+#define RETRY_AFTER_HEADER "Retry-After: 0\r\n"
+#define RETRY_AFTER_HEADER_SIZE (sizeof(RETRY_AFTER_HEADER) - 1)
+  if (length == RETRY_AFTER_HEADER_SIZE &&
+      strncasecmp(ptr, RETRY_AFTER_HEADER, RETRY_AFTER_HEADER_SIZE) == 0) {
+    transfer->retry_after = 0;
+  }
+  return length;
+}
+
 static char *cosmo_build_rpc(cosmo *instance, json_t *commands) {
   json_t *to_send = json_pack("{sssssO}", "client_id", instance->client_id, "instance_id", instance->instance_id, "commands", commands);
   assert(to_send);
@@ -77,6 +101,8 @@ static bool cosmo_send_http_int(cosmo *instance, cosmo_transfer *transfer, CURL
   curl_easy_setopt(curl, CURLOPT_READDATA, transfer);
   curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, cosmo_write_callback);
   curl_easy_setopt(curl, CURLOPT_WRITEDATA, transfer);
+  curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, cosmo_header_callback);
+  curl_easy_setopt(curl, CURLOPT_HEADERDATA, transfer);
   curl_easy_setopt(curl, CURLOPT_TIMEOUT, COSMO_CHECK_SECONDS);
   res = curl_easy_perform(curl);
 
@@ -103,11 +129,16 @@ static char *cosmo_send_http(cosmo *instance, char *request) {
     .send_buf = request,
     .send_buf_len = strlen(request),
     .recv_buf = NULL,
-    .recv_buf_len = 0
+    .recv_buf_len = 0,
+    .retry_after = -1
   };
 
   int ret = cosmo_send_http_int(instance, &transfer, curl);
 
+  if (transfer.retry_after >= 0) {
+    instance->next_delay_ms = transfer.retry_after * 1000;
+  }
+
   curl_easy_cleanup(curl);
   free(request);
 
@@ -168,9 +199,12 @@ static void *cosmo_thread_main(void *arg) {
 
   assert(!pthread_mutex_lock(&instance->lock));
   while (!instance->shutdown) {
-    while (json_array_size(instance->command_queue)) {
+    if (json_array_size(instance->command_queue)) {
       json_t *commands = instance->command_queue;
       instance->command_queue = json_array();
+      instance->next_delay_ms = pow(instance->next_delay_ms, DELAY_EXPONENT);
+      instance->next_delay_ms = min(DELAY_MAX_MS, max(DELAY_MIN_MS, instance->next_delay_ms));
+      instance->next_delay_ms += random() % (instance->next_delay_ms / DELAY_STAGGER_FACTOR);
 
       assert(!pthread_mutex_unlock(&instance->lock));
       json_t *to_retry = cosmo_send_rpc(instance, commands);
@@ -179,8 +213,26 @@ static void *cosmo_thread_main(void *arg) {
       json_array_extend(instance->command_queue, to_retry);
       json_decref(to_retry);
     }
+
+    if (json_array_size(instance->command_queue)) {
+      struct timeval tv;
+      assert(!gettimeofday(&tv, NULL));
+
+      struct timespec ts;
+      if (tv.tv_usec + ((instance->next_delay_ms % 1000) * 1000) > 1000000) {
+        // Carry
+        ts.tv_sec = tv.tv_sec + (instance->next_delay_ms / 1000) + 1;
+        ts.tv_nsec = (tv.tv_usec * 1000) + ((instance->next_delay_ms % 1000) * 1000000) - 1000000000;
+      } else {
+        ts.tv_sec = tv.tv_sec + (instance->next_delay_ms / 1000);
+      }
+
+      int wait = pthread_cond_timedwait(&instance->cond, &instance->lock, &ts);
+      assert(wait == 0 || wait == ETIMEDOUT);
+    } else {
       assert(!pthread_cond_wait(&instance->cond, &instance->lock));
     }
+  }
   assert(!pthread_mutex_unlock(&instance->lock));
   return NULL;
 }
@@ -190,6 +242,7 @@ static void cosmo_send_command(cosmo *instance, json_t *command) {
   assert(command);
   assert(!pthread_mutex_lock(&instance->lock));
   json_array_append_new(instance->command_queue, command);
+  instance->next_delay_ms = 0;
   assert(!pthread_cond_signal(&instance->cond));
   assert(!pthread_mutex_unlock(&instance->lock));
 }
@@ -232,6 +285,7 @@ void cosmo_subscribe(cosmo *instance, json_t *subject, json_int_t messages, json
 
 cosmo *cosmo_create(char *client_id) {
   curl_global_init(CURL_GLOBAL_DEFAULT);
+  srandomdev();
 
   cosmo *instance = malloc(sizeof(cosmo));
   assert(instance);
@@ -249,6 +303,7 @@ cosmo *cosmo_create(char *client_id) {
 void cosmo_destroy(cosmo *instance) {
   pthread_mutex_lock(&instance->lock);
   instance->shutdown = 1;
+  instance->next_delay_ms = 0;
   pthread_cond_signal(&instance->cond);
   pthread_mutex_unlock(&instance->lock);
   assert(!pthread_join(instance->thread, NULL));
@@ -268,7 +323,7 @@ int main(int argc, char *argv[]) {
   json_t *subject = cosmo_subject("foobar", NULL, NULL);
   cosmo_subscribe(instance, subject, -1, 0);
   json_decref(subject);
-  sleep(5);
+  sleep(120);
   cosmo_destroy(instance);
 
   return 0;