So one thing to know here is that all Java applications are going to use many threads, and just because your particular main method doesn't spawn additional threads doesn't mean library you access or use won't spawn additional threads. The other important note is that Spark doesn't actually equate "core - threads", when you request a core or something like that spark doesn't do anything special to actually make sure only a single physical core is in use.
That said, would allocating more vCpu to a driver make a difference? Probably not. This is very dependent on your own code and whether a lot of work is being done on the driver vs on the executors. For example, are you loading up and processing some data which is used to spawn remote work? If so having more cpus locally may help. So look into your app, is almost all the work inside dataframes or RDDs? Then more resources for the driver won't help. TLDR; For most use cases 1 core is sufficient regardless of client/cluster mode On Fri, Mar 6, 2020 at 11:36 AM James Yu <ja...@ispot.tv> wrote: > Pol, thanks for your reply. > > Actually I am running Spark apps in CLUSTER mode. Is what you said still > applicable in cluster mode. Thanks in advance for your further > clarification. > > ------------------------------ > *From:* Pol Santamaria <p...@qbeast.io> > *Sent:* Friday, March 6, 2020 12:59 AM > *To:* James Yu <ja...@ispot.tv> > *Cc:* user@spark.apache.org <user@spark.apache.org> > *Subject:* Re: Spark driver thread > > Hi james, > > You can configure the Spark Driver to use more than a single thread. It is > something that depends on the application, but the Spark driver can take > advantage of multiple threads in many situations. For instance, when the > driver program gathers or sends data to the workers. > > So yes, if you do computation or I/O on the driver side, you should > explore using multithreads and more than 1 vCPU. > > Bests, > Pol Santamaria > > On Fri, Mar 6, 2020 at 1:28 AM James Yu <ja...@ispot.tv> wrote: > > Hi, > > Does a Spark driver always works as single threaded? > > If yes, does it mean asking for more than one vCPU for the driver is > wasteful? > > > Thanks, > James > >
