Exceptions on Reason: 'timeout' and 'null'

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Hi there,
There are some ‘timeout’ errors as follows when I run a Java Spring program with influxdb-client-java. Could someone tell me how to fix these errors? Thanks a lot.

__Steps to reproduce:__
List the minimal actions needed to reproduce the behavior.
1. setup InfluxDB version 2.7.1 on cloud VM;
2. setup a Java Spring program with Influxdb-client-java version 6.7.0;
3. setup the influx.writeTimeout = 15S;
4. write a lot of data to InfluxDB with this program;
5. run this program for at last a week, there are some 'timeout' and 'null' erros:

__Expected behavior:__
There are no 'timeout' or 'null' errors.

__Actual behavior:__
there are some 'timeout' and 'null' erros:

error logs

```
2023-06-24 17:00:15,715 WARN [RxNewThreadScheduler-1] com.influxdb.client.write.events.WriteRetriableErrorEvent: The retriable error occurred during writing of data. Reason: 'timeout'. Retry in: 18.225s.
2023-06-24 17:00:44,143 WARN [RxNewThreadScheduler-463230] com.influxdb.client.write.events.WriteRetriableErrorEvent: The retriable error occurred during writing of data. Reason: 'timeout'. Retry in: 37.234s.
2023-06-24 17:01:21,714 WARN [RxNewThreadScheduler-463231] com.influxdb.client.write.events.WriteRetriableErrorEvent: The retriable error occurred during writing of data. Reason: 'null'. Retry in: 50.281s.
2023-06-24 17:02:12,110 WARN [RxNewThreadScheduler-463232] com.influxdb.client.write.events.WriteRetriableErrorEvent: The retriable error occurred during writing of data. Reason: 'null'. Retry in: 85.256s.
2023-06-24 17:03:05,626 ERROR [RxNewThreadScheduler-463229] com.influxdb.client.write.events.WriteErrorEvent: The error occurred during writing of data
com.influxdb.exceptions.InfluxException: Max retry time exceeded.
at com.influxdb.internal.AbstractRestClient.toInfluxException(AbstractRestClient.java:102)
at com.influxdb.client.internal.AbstractWriteClient.lambda$new$8(AbstractWriteClient.java:174)
at io.reactivex.rxjava3.internal.subscribers.LambdaSubscriber.onNext(LambdaSubscriber.java:65)
at io.reactivex.rxjava3.internal.operators.flowable.FlowableDoFinally$DoFinallySubscriber.onNext(FlowableDoFinally.java:85)
at io.reactivex.rxjava3.internal.operators.mixed.FlowableConcatMapMaybe$ConcatMapMaybeSubscriber.drain(FlowableConcatMapMaybe.java:238)
at io.reactivex.rxjava3.internal.operators.mixed.FlowableConcatMapMaybe$ConcatMapMaybeSubscriber.innerSuccess(FlowableConcatMapMaybe.java:119)
at io.reactivex.rxjava3.internal.operators.mixed.FlowableConcatMapMaybe$ConcatMapMaybeSubscriber$ConcatMapMaybeObserver.onSuccess(FlowableConcatMapMaybe.java:276)
at io.reactivex.rxjava3.internal.operators.maybe.MaybeOnErrorNext$OnErrorNextMaybeObserver$NextMaybeObserver.onSuccess(MaybeOnErrorNext.java:122)
at io.reactivex.rxjava3.internal.operators.maybe.MaybeJust.subscribeActual(MaybeJust.java:36)
at io.reactivex.rxjava3.core.Maybe.subscribe(Maybe.java:5375)
at io.reactivex.rxjava3.internal.operators.maybe.MaybeOnErrorNext$OnErrorNextMaybeObserver.onError(MaybeOnErrorNext.java:97)
at io.reactivex.rxjava3.internal.operators.maybe.MaybePeek$MaybePeekObserver.onErrorInner(MaybePeek.java:147)
at io.reactivex.rxjava3.internal.operators.maybe.MaybePeek$MaybePeekObserver.onError(MaybePeek.java:134)
at io.reactivex.rxjava3.internal.operators.maybe.MaybeMap$MapMaybeObserver.onError(MaybeMap.java:95)
at io.reactivex.rxjava3.internal.operators.maybe.MaybeTimeoutMaybe$TimeoutFallbackMaybeObserver.onError(MaybeTimeoutMaybe.java:195)
at io.reactivex.rxjava3.internal.operators.maybe.MaybeError.subscribeActual(MaybeError.java:35)
at io.reactivex.rxjava3.core.Maybe.subscribe(Maybe.java:5375)
at io.reactivex.rxjava3.internal.operators.maybe.MaybeTimeoutMaybe$TimeoutMainMaybeObserver.otherComplete(MaybeTimeoutMaybe.java:133)
at io.reactivex.rxjava3.internal.operators.maybe.MaybeTimeoutMaybe$TimeoutOtherMaybeObserver.onSuccess(MaybeTimeoutMaybe.java:158)
at io.reactivex.rxjava3.internal.operators.maybe.MaybeTimer$TimerDisposable.run(MaybeTimer.java:58)
at io.reactivex.rxjava3.core.Scheduler$DisposeTask.run(Scheduler.java:644)
at io.reactivex.rxjava3.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:65)
at io.reactivex.rxjava3.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:56)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:750)
Caused by: java.util.concurrent.TimeoutException: Max retry time exceeded.
at com.influxdb.client.internal.AbstractWriteClient$ToWritePointsMaybe.apply(AbstractWriteClient.java:501)
at com.influxdb.client.internal.AbstractWriteClient$ToWritePointsMaybe.apply(AbstractWriteClient.java:432)
at io.reactivex.rxjava3.internal.operators.mixed.FlowableConcatMapMaybe$ConcatMapMaybeSubscriber.drain(FlowableConcatMapMaybe.java:219)
at io.reactivex.rxjava3.internal.operators.mixed.ConcatMapXMainSubscriber.onNext(ConcatMapXMainSubscriber.java:106)
at com.influxdb.client.internal.flowable.BackpressureBatchesBufferStrategy$OnBackpressureBufferStrategySubscriber.drain(BackpressureBatchesBufferStrategy.java:238)
at com.influxdb.client.internal.flowable.BackpressureBatchesBufferStrategy$OnBackpressureBufferStrategySubscriber.onNext(BackpressureBatchesBufferStrategy.java:149)
at com.influxdb.client.internal.flowable.BackpressureBatchesBufferStrategy$OnBackpressureBufferStrategySubscriber.onNext(BackpressureBatchesBufferStrategy.java:54)
at io.reactivex.rxjava3.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.tryEmitScalar(FlowableFlatMap.java:232)
at io.reactivex.rxjava3.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.onNext(FlowableFlatMap.java:150)
at io.reactivex.rxjava3.internal.operators.flowable.FlowableFilter$FilterSubscriber.tryOnNext(FlowableFilter.java:75)
at io.reactivex.rxjava3.internal.operators.flowable.FlowableFilter$FilterSubscriber.onNext(FlowableFilter.java:53)
at io.reactivex.rxjava3.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.tryEmit(FlowableFlatMap.java:270)
at io.reactivex.rxjava3.internal.operators.flowable.FlowableFlatMap$InnerSubscriber.onNext(FlowableFlatMap.java:627)
at io.reactivex.rxjava3.internal.operators.flowable.FlowableMap$MapSubscriber.onNext(FlowableMap.java:69)
at io.reactivex.rxjava3.subscribers.SerializedSubscriber.onNext(SerializedSubscriber.java:103)
at com.influxdb.client.internal.flowable.FlowableBufferTimedFlushable$BufferExactBoundedSubscriber.accept(FlowableBufferTimedFlushable.java:227)
at com.influxdb.client.internal.flowable.FlowableBufferTimedFlushable$BufferExactBoundedSubscriber.accept(FlowableBufferTimedFlushable.java:85)
at io.reactivex.rxjava3.internal.subscribers.QueueDrainSubscriber.fastPathOrderedEmitMax(QueueDrainSubscriber.java:107)
at com.influxdb.client.internal.flowable.FlowableBufferTimedFlushable$BufferExactBoundedSubscriber.run(FlowableBufferTimedFlushable.java:281)
at io.reactivex.rxjava3.core.Scheduler$Worker$PeriodicTask.run(Scheduler.java:543)
... 8 common frames omitted

```

__Specifications:__
- Client Version: Influxdb-client-java 6.7.0
- InfluxDB Version: 2.7.1
- JDK Version: JDK 8
- Platform: Linux

Start with the stack-trace entry points in AbstractRestClient.toInfluxException and AbstractWriteClient, then trace how writeTimeout and retry handling produce the logged reasons. Use the listed InfluxDB 2.7.1, client 6.7.0, JDK 8, and Linux setup to reproduce the long-running write workload. Done means the timeout and null outcomes have a confirmed cause and a validated fix or documented resolution.

Written by the indexing model from the issue text.