feat: Migrate data from InfluxDB v1 to GreptimeDB (#18)

Signed-off-by: tison <[email protected]>

influxdb-v1-to-greptime/README.md

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+# Migrate data from InfluxDB v1 to GreptimeDB
+
+## Prerequisites
+
+You need to be able to access your InfluxDB engine path, which contains your data files. If you run a server with InfluxDB's v1.8 official Docker Image, the engine path is `/var/lib/influxdb`.
+
+## Step 1: Set up Greptime service
+
+1. Obtain a free Greptime service from [GreptimeCloud](https://console.greptime.cloud/). 
+2. Click the "Connection Information" button and find the connection string.
+3. Export the necessary environment variables:
+
+```shell
+export GREPTIME_DB="<dbname>"
+export GREPTIME_HOST="<host>"
+export GREPTIME_USERNAME="<username>"
+export GREPTIME_PASSWORD="<password>"
+```
+
+![Connection](/media/conninfo.png)
+
+## Step 2: Export data from InfluxDB v1 server
+
+You can run the following commands to export data in InfluxDB's line protocol:
+
+```shell
+export DATABASE="<dbname>"         # possible value: mydb 
+export ENGINE_PATH="<engine-path>" # possible value: /var/lib/influxdb
+
+influx_inspect export \
+    -database $DATABASE \
+    -lponly \
+    -datadir $ENGINE_PATH/data \
+    -waldir $ENGINE_PATH/wal \
+    -out /tmp/influxdb_export.lp
+```
+
+## Step 3: Import data to GreptimeDB
+
+Copy the `influxdb_export.lp` file to a working directory. Before import data to GreptimeDB, if the data file is too large, it's recommended to split the data file into multiple slices:
+
+```shell
+split -l 1000 -d -a 10 influxdb_export.lp influxdb_export_slice.
+# -l [line_count]    Create split files line_count lines in length.
+# -d                 Use a numeric suffix instead of a alphabetic suffix.
+# -a [suffix_length] Use suffix_length letters to form the suffix of the file name.
+```
+
+Now, import data to GreptimeDB via the HTTP API:
+
+```shell
+for file in influxdb_export_slice.*; do
+    curl -i -H "Authorization: token $GREPTIME_USERNAME:$GREPTIME_PASSWORD" \
+        -X POST "https://${GREPTIME_HOST}/v1/influxdb/write?db=$GREPTIME_DB" \
+        --data-binary @${file}
+    sleep 1
+done
+```
+
+You're done!