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fix: stream large API responses to stop heap-exhaustion truncation

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Serving /api/history (and /api/forecasts) built a ~12 KB String +
JsonDocument every 15 s; over days this fragmented the ESP8266 heap until
the TCP stack could no longer send a full response, causing the web page
to fail with ERR_CONTENT_LENGTH_MISMATCH. Stream both array endpoints via
chunked transfer (small stack buffer, no big allocations). Add free-heap
to /api/current and Serial, plus a low-memory safety restart (history is
persisted first).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
oskarvitalii
2026-07-21 06:57:09 +07:00
co-authored by Claude Opus 4.8
parent 1e923249f6
commit 4b59b8936b
2 changed files with 31 additions and 19 deletions
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WeatherPredictor/WeatherPredictor.ino
+9
View File
@@ -88,6 +88,15 @@ void loop() {
tSample = now;
sampleNow();
displayRender(g_state);
Serial.printf("heap=%u maxblock=%u\n", ESP.getFreeHeap(), ESP.getMaxFreeBlockSize());
// Safety net: if the largest contiguous block gets too small, the TCP stack
// can no longer send responses. Persist and reboot to defragment.
if (ESP.getMaxFreeBlockSize() < 6000) {
Serial.println(F("Low memory -> saving history and restarting"));
historySave();
delay(50);
ESP.restart();
}
}
if (now - tHistory >= HISTORY_INTERVAL_MS) {
WeatherPredictor/web_server.cpp
+22 -19
View File
@@ -27,41 +27,44 @@ static void handleCurrent() {
doc["haveTrend"] = g_state.haveTrend;
doc["forecast"] = g_state.haveTrend ? g_state.forecast.text : "Collecting data...";
doc["category"] = g_state.haveTrend ? categoryShort(g_state.forecast.category) : "...";
doc["heap"] = ESP.getFreeHeap(); // for monitoring memory health
String out;
serializeJson(doc, out);
server.send(200, "application/json", out);
}
// Streamed (chunked) so we never build a large String/JsonDocument on the heap.
static void handleHistory() {
JsonDocument doc;
JsonArray arr = doc.to<JsonArray>();
server.setContentLength(CONTENT_LENGTH_UNKNOWN);
server.send(200, "application/json", "");
server.sendContent("[");
char buf[80];
int n = historyCount();
for (int i = 0; i < n; i++) {
Sample s = historyGet(i);
JsonObject o = arr.add<JsonObject>();
o["t"] = s.epoch;
o["msl"] = s.mslHpa;
o["temp"] = s.tempC;
snprintf(buf, sizeof(buf), "%s{\"t\":%lu,\"msl\":%.1f,\"temp\":%.1f}",
i ? "," : "", (unsigned long)s.epoch, s.mslHpa, s.tempC);
server.sendContent(buf);
}
String out;
serializeJson(doc, out);
server.send(200, "application/json", out);
server.sendContent("]");
}
// Streamed (chunked). Forecast phrases contain no quotes/backslashes, so they
// are safe to embed directly in JSON.
static void handleForecasts() {
JsonDocument doc;
JsonArray arr = doc.to<JsonArray>();
server.setContentLength(CONTENT_LENGTH_UNKNOWN);
server.send(200, "application/json", "");
server.sendContent("[");
char buf[128];
int n = flogCount();
for (int i = n - 1; i >= 0; i--) { // newest first
for (int i = n - 1, first = 1; i >= 0; i--, first = 0) { // newest first
FcastEntry e = flogGet(i);
JsonObject o = arr.add<JsonObject>();
o["t"] = e.epoch;
o["cat"] = categoryShort((WxCategory)e.cat);
o["text"] = forecastTextForLetter(e.letter);
snprintf(buf, sizeof(buf), "%s{\"t\":%lu,\"cat\":\"%s\",\"text\":\"%s\"}",
first ? "" : ",", (unsigned long)e.epoch,
categoryShort((WxCategory)e.cat), forecastTextForLetter(e.letter));
server.sendContent(buf);
}
String out;
serializeJson(doc, out);
server.send(200, "application/json", out);
server.sendContent("]");
}
static void handleGetSettings() {