MilvusClientV2Pool.getClient is null sometimes when using client pool

[dingle66]

MilvusClientV2Pool milvusClientV2Pool = new MilvusClientV2Pool(poolConfig, connectConfig); milvusClientV2Pool.getClient is null occurs sometimes!

[yhmo]

https://github.com/milvus-io/milvus-sdk-java/blob/14b9065db1ac5d0d9359a58ddc6e21565cb3a1ec/src/main/java/io/milvus/pool/ClientPool.java#L47

The ClientPool could return null for getClient() method:

    public T getClient(String key) {
        try {
            return clientPool.borrowObject(key);
        } catch (Exception e) {
            System.out.println("Failed to get client, exception: " + e.getMessage());
            return null;
        }
    }

I didn't throw an exception here, do you think it is necessary to throw the error? In my opinion, when user gets a null value, he can check the returned value and recall the getClient() again.

The client.Pool is a GenericKeyedObjectPool. The borrowObject() method internally has a timeout value to wait for a client to be created. The timeout value can be configured by PoolConfig.maxBlockWaitDuration: https://github.com/milvus-io/milvus-sdk-java/blob/14b9065db1ac5d0d9359a58ddc6e21565cb3a1ec/src/main/java/io/milvus/pool/ClientPool.java#L27

The default value of maxBlockWaitDuration is 3 seconds. Sometimes the client could not be created in 3 seconds, which might caused by network issues or milvus server being too busy to respond. You can increase this value to observe.

[xiaofan-luan]

https://github.com/milvus-io/milvus-sdk-java/blob/14b9065db1ac5d0d9359a58ddc6e21565cb3a1ec/src/main/java/io/milvus/pool/ClientPool.java#L47

The ClientPool could return null for getClient() method:

    public T getClient(String key) {
        try {
            return clientPool.borrowObject(key);
        } catch (Exception e) {
            System.out.println("Failed to get client, exception: " + e.getMessage());
            return null;
        }
    }

I didn't throw an exception here, do you think it is necessary to throw the error? In my opinion, when user gets a null value, he can check the returned value and recall the getClient() again.

The client.Pool is a GenericKeyedObjectPool. The borrowObject() method internally has a timeout value to wait for a client to be created. The timeout value can be configured by PoolConfig.maxBlockWaitDuration:

https://github.com/milvus-io/milvus-sdk-java/blob/14b9065db1ac5d0d9359a58ddc6e21565cb3a1ec/src/main/java/io/milvus/pool/ClientPool.java#L27

The default value of maxBlockWaitDuration is 3 seconds. Sometimes the client could not be created in 3 seconds, which might caused by network issues or milvus server being too busy to respond. You can increase this value to observe.

I think the right thing is to throw error. For all java users, exceptions is the only thing need to be handled and return null doesn't really make sense to me

[yhmo]

Fixed by this pr: https://github.com/milvus-io/milvus-sdk-java/pull/1170/files The exception thrown from GenericKeyedObjectPool is encapsulated by MilvusClientException and thrown out to users.

[yhmo]

The fix has been released with v2.4.9 and v2.5.0