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Merge pull request #257 from ZhiHanZ/fail-over-test
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chore: add multi-endpoint doc and tests
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@ZhiHanZ
ZhiHanZ authored Aug 20, 2024
2 parents 62898a4 + 0bca789 commit 1fbdac7
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2 changes: 1 addition & 1 deletion databend-jdbc/src/main/java/com/databend/jdbc/DatabendConnection.java
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Expand Up @@ -644,7 +644,7 @@ DatabendClient startQueryWithFailover(String sql, StageAttachment attach) throws
sb.setStageAttachment(attach);
}
ClientSettings s = sb.build();
logger.log(Level.FINE, "retry " + times + " times to execute query: " + sql + " on " + s.getHost());
logger.log(Level.FINE, "retry " + i + " times to execute query: " + sql + " on " + s.getHost());
return new DatabendClientV1(httpClient, sql, s, this);
} catch (RuntimeException e1) {
e = e1;
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36 changes: 36 additions & 0 deletions databend-jdbc/src/test/java/com/databend/jdbc/TestMultiHost.java
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Expand Up @@ -13,6 +13,7 @@ public class TestMultiHost {
private final String DEFAULT_JDBC_URL = "jdbc:databend://localhost:8000,localhost:8002,localhost:8003/default";
private final String RANDOM_JDBC_URL = "jdbc:databend://localhost:8000,localhost:8002,localhost:8003/default?load_balancing_policy=random";
private final String ROUND_ROBIN_JDBC_URL = "jdbc:databend://localhost:8000,localhost:8002,localhost:8003/default?load_balancing_policy=round_robin";
private final String FAIL_OVER_JDBC_URL = "jdbc:databend://localhost:7222,localhost:7223,localhost:7224,localhost:8000/default?load_balancing_policy=round_robin&max_failover_retry=4";
private Connection createConnection(String url)
throws SQLException {
return DriverManager.getConnection(url, "databend", "databend");
Expand Down Expand Up @@ -115,4 +116,39 @@ public void testRoundRobinLoadBalancing()
Assert.assertEquals(unknown, 0);
Assert.assertEquals(node8000 + node8002 + node8003, 90);
}

@Test(groups = {"IT", "cluster"})
public void testFailOver()
throws SQLException {
// try connect with three nodes 1000 times and count for each node
int node8000 = 0;
int node8002 = 0;
int node8003 = 0;
int unknown = 0;
for (int i = 0; i < 30; i++) {
try (Connection connection = createConnection(FAIL_OVER_JDBC_URL)) {
DatabendStatement statement = (DatabendStatement) connection.createStatement();
// remove the effect setup commands
for (int j = 0; j < 3; j++) {
statement.execute("select value from system.configs where name = 'http_handler_port';");
ResultSet r = statement.getResultSet();
r.next();
if (r.getInt(1) == 8000) {
node8000++;
} else if (r.getInt(1) == 8002) {
node8002++;
} else if (r.getInt(1) == 8003) {
node8003++;
} else {
unknown++;
}
}
}
}
System.out.println("node8000: " + node8000 + ", node8002: " + node8002 + ", node8003: " + node8003 + ", unknown: " + unknown);

Assert.assertEquals(node8000, 90);
Assert.assertEquals(unknown, 0);
Assert.assertEquals(node8000 + node8002 + node8003, 90);
}
}
70 changes: 53 additions & 17 deletions docs/Connection.md
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Expand Up @@ -54,6 +54,40 @@ Then the above URL within warehouse DSN can be used as follows:
Connection conn=DriverManager.getConnection(url);
```

### Configure load balancing and failover

Load balancing in Databend JDBC works by routing queries to different endpoints specified in the JDBC URL based on the chosen policy. This allows for better distribution of workload across multiple Databend nodes.

#### Load Balancing Options

There are three load balancing options available:

1. **disabled**: Only routes queries to the first endpoint provided (sorted in alphabetic order).
2. **random**: Randomly distributes queries based on the query ID.
3. **round_robin**: Distributes queries evenly to each node in a circular order.

#### Configurable Parameters

| Parameter | Description | Default | Example |
|-----------|-------------|---------|---------|
| load_balancing_policy | Specifies the load balancing policy for multi-host connections. Options are "disabled", "random", and "round_robin". | disabled | jdbc:databend://localhost:8000,localhost:8002,localhost:8003/default?load_balancing_policy=random |
| max_failover_retry | Specifies the maximum number of retry attempts for failover connections. | 0 | jdbc:databend://localhost:7222,localhost:7223,localhost:7224,localhost:8000/default?max_failover_retry=4 |

#### Examples

1. Basic load balancing with round-robin policy: `jdbc:databend://localhost:8000,localhost:8002,localhost:8003/default?load_balancing_policy=round_robin`
2. Load balancing with random policy and failover configuration:: `jdbc:databend://localhost:8000,localhost:8002,localhost:8003/default?load_balancing_policy=random&max_failover_retry=3
`
3. Load balancing with SSL enabled:`jdbc:databend://localhost:8000,localhost:8002,localhost:8003/default?ssl=true&load_balancing_policy=round_robin`

**NOTICE:**

When configuring SSL, it's recommended to use the approach shown in the last example, which allows for more detailed SSL configuration including certificate verification.

Remember to replace the hostnames, ports, and file paths with your actual Databend cluster configuration and SSL certificate locations.

Failover retry occur only for connection issues (java.net.ConnectException), other exception will NOT trigger retry

## Connection parameters

The driver supports various parameters that may be set as URL parameters or as properties passed to DriverManager. Both
Expand All @@ -75,20 +109,22 @@ String url="jdbc:databend://databend:secret@0.0.0.0:8000/hello_databend";

### Parameter References

| Parameter | Description | Default | example |
|------------------------|---------------------------------------------------------------------------------------------------------------------------|---------|-------------------------------------------------------------------------|
| user | Databend user name | none | jdbc:databend://0.0.0.0:8000/hello_databend?user=test |
| password | Databend user password | none | jdbc:databend://0.0.0.0:8000/hello_databend?password=secret |
| SSL | Enable SSL | false | jdbc:databend://0.0.0.0:8000/hello_databend?SSL=true |
| sslmode | SSL mode | disable | jdbc:databend://0.0.0.0:8000/hello_databend?sslmode=enable |
| copy_purge | If True, the command will purge the files in the stage after they are loaded successfully into the table | false | jdbc:databend://0.0.0.0:8000/hello_databend?copy_purge=true |
| presigned_url_disabled | whether use presigned url to upload data, generally if you use local disk as your storage layer, it should be set as true | false | jdbc:databend://0.0.0.0:8000/hello_databend?presigned_url_disabled=true |
| wait_time_secs | Restful query api blocking time, if the query is not finished, the api will block for wait_time_secs seconds | 10 | jdbc:databend://0.0.0.0:8000/hello_databend?wait_time_secs=10 |
| max_rows_in_buffer | the maximum rows in server session buffer | 5000000 | jdbc:databend://0.0.0.0:8000/hello_databend?max_rows_in_buffer=5000000 |
| max_rows_per_page | the maximum rows per page in response data body | 100000 | jdbc:databend://0.0.0.0:8000/default?max_rows_per_page=100000 |
| connection_timeout | okhttp connection_timeout param | 0 | jdbc:databend://0.0.0.0:8000/default?connection_timeout=100000 |
| query_timeout | time that you wait a SQL execution | 90 | jdbc:databend://0.0.0.0:8000/default?query_timeout=120 |
| null_display | null value display | \N | jdbc:databend://0.0.0.0:8000/hello_databend?null_display=null |
| binary_format | binary format, support hex and base64 | hex | jdbc:databend://0.0.0.0:8000/default?binary_format=hex |
| use_verify | whether verify the server before establishing the connection | true | jdbc:databend://0.0.0.0:8000/default?use_verify=true |
| debug | whether enable debug mode | false | jdbc:databend://0.0.0.0:8000/default?debug=true |
| Parameter | Description | Default | example |
|------------------------|---------------------------------------------------------------------------------------------------------------------------|----------|-------------------------------------------------------------------------|
| user | Databend user name | none | jdbc:databend://0.0.0.0:8000/hello_databend?user=test |
| password | Databend user password | none | jdbc:databend://0.0.0.0:8000/hello_databend?password=secret |
| SSL | Enable SSL | false | jdbc:databend://0.0.0.0:8000/hello_databend?SSL=true |
| sslmode | SSL mode | disable | jdbc:databend://0.0.0.0:8000/hello_databend?sslmode=enable |
| copy_purge | If True, the command will purge the files in the stage after they are loaded successfully into the table | false | jdbc:databend://0.0.0.0:8000/hello_databend?copy_purge=true |
| presigned_url_disabled | whether use presigned url to upload data, generally if you use local disk as your storage layer, it should be set as true | false | jdbc:databend://0.0.0.0:8000/hello_databend?presigned_url_disabled=true |
| wait_time_secs | Restful query api blocking time, if the query is not finished, the api will block for wait_time_secs seconds | 10 | jdbc:databend://0.0.0.0:8000/hello_databend?wait_time_secs=10 |
| max_rows_in_buffer | the maximum rows in server session buffer | 5000000 | jdbc:databend://0.0.0.0:8000/hello_databend?max_rows_in_buffer=5000000 |
| max_rows_per_page | the maximum rows per page in response data body | 100000 | jdbc:databend://0.0.0.0:8000/default?max_rows_per_page=100000 |
| connection_timeout | okhttp connection_timeout param | 0 | jdbc:databend://0.0.0.0:8000/default?connection_timeout=100000 |
| query_timeout | time that you wait a SQL execution | 90 | jdbc:databend://0.0.0.0:8000/default?query_timeout=120 |
| null_display | null value display | \N | jdbc:databend://0.0.0.0:8000/hello_databend?null_display=null |
| binary_format | binary format, support hex and base64 | hex | jdbc:databend://0.0.0.0:8000/default?binary_format=hex |
| use_verify | whether verify the server before establishing the connection | true | jdbc:databend://0.0.0.0:8000/default?use_verify=true |
| debug | whether enable debug mode | false | jdbc:databend://0.0.0.0:8000/default?debug=true |
| load_balancing_policy | Specifies the load balancing policy for multi-host connections. Options are "disabled", "random", and "round_robin". | disabled | jdbc:databend://localhost:8000,localhost:8002,localhost:8003/default?load_balancing_policy=random |
| max_failover_retry | Specifies the maximum number of retry attempts for failover connections. | 0 | jdbc:databend://localhost:7222,localhost:7223,localhost:7224,localhost:8000/default?max_failover_retry=4 |

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