devenv: better loki environment (#49383)

* devenv: rename loki to loki-promtail

* devenv: new loki devenv entry with fake data generation

devenv/docker/blocks/loki-promtail/docker-compose.yaml

@@ -0,0 +1,14 @@
+  # datasource URL: http://localhost:3100/
+  loki:
+    image: grafana/loki:latest
+    ports:
+      - "3100:3100"
+    command: -config.file=/etc/loki/local-config.yaml
+  promtail:
+    image: grafana/promtail:latest
+    volumes:
+      - ./docker/blocks/loki-promtail/promtail-config.yaml:/etc/promtail/docker-config.yaml
+      - /var/log:/var/log
+      - ../data/log:/var/log/grafana
+    command:
+      -config.file=/etc/promtail/docker-config.yaml

devenv/docker/blocks/loki/data/Dockerfile

@@ -0,0 +1,3 @@
+FROM node:16-alpine
+
+COPY data.js /home/node/data.js

devenv/docker/blocks/loki/data/data.js

@@ -0,0 +1,107 @@
+const http = require('http');
+
+if (process.argv.length !== 3) {
+  throw new Error('invalid command line: use node sendLogs.js LOKIC_BASE_URL');
+}
+
+const LOKI_BASE_URL = process.argv[2];
+
+// helper function, do a http request
+async function jsonRequest(data, method, url, expectedStatusCode) {
+  return new Promise((resolve, reject) => {
+    const req = http.request(
+      {
+        protocol: url.protocol,
+        host: url.hostname,
+        port: url.port,
+        path: `${url.pathname}${url.search}`,
+        method,
+        headers: { 'content-type': 'application/json' },
+      },
+      (res) => {
+        if (res.statusCode !== expectedStatusCode) {
+          reject(new Error(`Invalid response: ${res.statusCode}`));
+        } else {
+          resolve();
+        }
+      }
+    );
+
+    req.on('error', (err) => reject(err));
+
+    req.write(JSON.stringify(data));
+    req.end();
+  });
+}
+
+// helper function, choose a random element from an array
+function chooseRandomElement(items) {
+  const index = Math.trunc(Math.random() * items.length);
+  return items[index];
+}
+
+// helper function, sleep for a duration
+async function sleep(duration) {
+  return new Promise((resolve) => {
+    setTimeout(resolve, duration);
+  });
+}
+
+async function lokiSendLogLine(timestampMs, line, tags) {
+  // we keep nanosecond-timestamp in a string because
+  // as a number it would be too large
+  const timestampNs = `${timestampMs}000000`;
+  const data = {
+    streams: [
+      {
+        stream: tags,
+        values: [[timestampNs, line]],
+      },
+    ],
+  };
+
+  const url = new URL(LOKI_BASE_URL);
+  url.pathname = '/loki/api/v1/push';
+
+  await jsonRequest(data, 'POST', url, 204);
+}
+
+function getRandomLogLine(counter) {
+  const randomText = `${Math.trunc(Math.random() * 1000 * 1000 * 1000)}`;
+  const maybeAnsiText = Math.random() < 0.5 ? 'with ANSI \u001b[31mpart of the text\u001b[0m' : '';
+  return JSON.stringify({
+    _entry: `log text ${maybeAnsiText} [${randomText}]`,
+    counter: counter.toString(),
+    float: Math.random() > 0.2 ? (100 * Math.random()).toString() : 'NaN',
+    label: chooseRandomElement(['val1', 'val2', 'val3']),
+    level: chooseRandomElement(['info', 'info', 'error']),
+  });
+}
+
+const SLEEP_ANGLE_STEP = Math.PI / 200;
+let sleepAngle = 0;
+function getNextSineWaveSleepDuration() {
+  sleepAngle += SLEEP_ANGLE_STEP;
+  return Math.trunc(1000 * Math.abs(Math.sin(sleepAngle)));
+}
+
+async function main() {
+  const tags = {
+    place: 'moon',
+  };
+
+  for (let step = 0; step < 300; step++) {
+    await sleep(getNextSineWaveSleepDuration());
+    const timestampMs = new Date().getTime();
+    const line = getRandomLogLine(step + 1);
+    lokiSendLogLine(timestampMs, line, tags);
+  }
+}
+
+// when running in docker, we catch the needed stop-signal, to shutdown fast
+process.on('SIGTERM', () => {
+  console.log('shutdown requested');
+  process.exit(0);
+});
+
+main();

devenv/docker/blocks/loki/docker-compose.yaml

@@ -1,14 +1,13 @@
-  # datasource URL: http://localhost:3100/
   loki:
     image: grafana/loki:latest
     ports:
       - "3100:3100"
-    command: -config.file=/etc/loki/local-config.yaml
-  promtail:
-    image: grafana/promtail:latest
-    volumes:
-      - ./docker/blocks/loki/promtail-config.yaml:/etc/promtail/docker-config.yaml
-      - /var/log:/var/log
-      - ../data/log:/var/log/grafana
-    command:
-      -config.file=/etc/promtail/docker-config.yaml
+
+  data:
+    build: docker/blocks/loki/data
+    command: node /home/node/data.js http://loki:3100
+    depends_on:
+      - loki
+    # when loki starts, there might be some time while it is not
+    # accepting requests, so we allow data.js to restart on failure.
+    restart: "on-failure"