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Posted to user@hadoop.apache.org by Fabio <an...@gmail.com> on 2015/01/23 09:41:28 UTC
Reliability of timestamps in logs
Hi guys,
while analyzing SLS logs I noticed some unexpected behaviors, such as
resources requests sent before the AM container gets to a RUNNING state.
For this reason I started wondering how reliable is the timestamp of the
log entries.
Does log4j run on an independent thread? If yes, could it be the reason
why some log entries appear as misplaced? Or are they supposed to be in
strict execution order in any case?
I ask this because I am validating a project and I need to be pretty
sure about what happens when.
Thanks
Fabio
Re: Reliability of timestamps in logs
Posted by Fabio <an...@gmail.com>.
Thanks for the diagrams tip! I will try it.
(SLS is the Scheduler Load Simulator
http://hadoop.apache.org/docs/r2.6.0/hadoop-sls/SchedulerLoadSimulator.html
)
Regards
Fabio
On 01/27/2015 11:04 PM, Ravi Prakash wrote:
> I'm afraid I don't know what the "SLS" is. Obviously it shouldn't
> matter if it runs on the same node. I don't think hadoop code ever
> updates the system clock. In fact it shouldn't even be run with the
> perms to do so.
> It depends on log4j appenders whether they buffer and batch the
> messages before writing to disk. I would think that the timestamp
> would still be the time the messages were received (rather than the
> time they were flushed to disk)
>
> I am not sure if you know but you can get beautiful state diagrams of
> the different agents by running $mvn -Pvisualize and then using dot to
> convert the *.gv files to png . I'd found that helped me a lot
>
>
> On Monday, January 26, 2015 11:20 PM, Fabio <an...@gmail.com> wrote:
>
>
> Yes I am, does it make a difference? SLS runs on a single machine,
> wrapping the RM and simulating the nodes, thus it should use just the
> system time.
> Or do you mean there is a chance it's updating the clock while the job
> is running?
>
> Regards
>
> Fabio
>
> On 01/26/2015 08:00 PM, Ravi Prakash wrote:
>> Are you running NTP?
>>
>>
>> On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com>
>> <ma...@gmail.com> wrote:
>>
>>
>> Hi guys,
>> while analyzing SLS logs I noticed some unexpected behaviors, such as
>> resources requests sent before the AM container gets to a RUNNING state.
>> For this reason I started wondering how reliable is the timestamp of the
>> log entries.
>> Does log4j run on an independent thread? If yes, could it be the reason
>> why some log entries appear as misplaced? Or are they supposed to be in
>> strict execution order in any case?
>> I ask this because I am validating a project and I need to be pretty
>> sure about what happens when.
>>
>> Thanks
>>
>> Fabio
>>
>>
>
>
>
Re: Reliability of timestamps in logs
Posted by Fabio <an...@gmail.com>.
Thanks for the diagrams tip! I will try it.
(SLS is the Scheduler Load Simulator
http://hadoop.apache.org/docs/r2.6.0/hadoop-sls/SchedulerLoadSimulator.html
)
Regards
Fabio
On 01/27/2015 11:04 PM, Ravi Prakash wrote:
> I'm afraid I don't know what the "SLS" is. Obviously it shouldn't
> matter if it runs on the same node. I don't think hadoop code ever
> updates the system clock. In fact it shouldn't even be run with the
> perms to do so.
> It depends on log4j appenders whether they buffer and batch the
> messages before writing to disk. I would think that the timestamp
> would still be the time the messages were received (rather than the
> time they were flushed to disk)
>
> I am not sure if you know but you can get beautiful state diagrams of
> the different agents by running $mvn -Pvisualize and then using dot to
> convert the *.gv files to png . I'd found that helped me a lot
>
>
> On Monday, January 26, 2015 11:20 PM, Fabio <an...@gmail.com> wrote:
>
>
> Yes I am, does it make a difference? SLS runs on a single machine,
> wrapping the RM and simulating the nodes, thus it should use just the
> system time.
> Or do you mean there is a chance it's updating the clock while the job
> is running?
>
> Regards
>
> Fabio
>
> On 01/26/2015 08:00 PM, Ravi Prakash wrote:
>> Are you running NTP?
>>
>>
>> On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com>
>> <ma...@gmail.com> wrote:
>>
>>
>> Hi guys,
>> while analyzing SLS logs I noticed some unexpected behaviors, such as
>> resources requests sent before the AM container gets to a RUNNING state.
>> For this reason I started wondering how reliable is the timestamp of the
>> log entries.
>> Does log4j run on an independent thread? If yes, could it be the reason
>> why some log entries appear as misplaced? Or are they supposed to be in
>> strict execution order in any case?
>> I ask this because I am validating a project and I need to be pretty
>> sure about what happens when.
>>
>> Thanks
>>
>> Fabio
>>
>>
>
>
>
Re: Reliability of timestamps in logs
Posted by Fabio <an...@gmail.com>.
Thanks for the diagrams tip! I will try it.
(SLS is the Scheduler Load Simulator
http://hadoop.apache.org/docs/r2.6.0/hadoop-sls/SchedulerLoadSimulator.html
)
Regards
Fabio
On 01/27/2015 11:04 PM, Ravi Prakash wrote:
> I'm afraid I don't know what the "SLS" is. Obviously it shouldn't
> matter if it runs on the same node. I don't think hadoop code ever
> updates the system clock. In fact it shouldn't even be run with the
> perms to do so.
> It depends on log4j appenders whether they buffer and batch the
> messages before writing to disk. I would think that the timestamp
> would still be the time the messages were received (rather than the
> time they were flushed to disk)
>
> I am not sure if you know but you can get beautiful state diagrams of
> the different agents by running $mvn -Pvisualize and then using dot to
> convert the *.gv files to png . I'd found that helped me a lot
>
>
> On Monday, January 26, 2015 11:20 PM, Fabio <an...@gmail.com> wrote:
>
>
> Yes I am, does it make a difference? SLS runs on a single machine,
> wrapping the RM and simulating the nodes, thus it should use just the
> system time.
> Or do you mean there is a chance it's updating the clock while the job
> is running?
>
> Regards
>
> Fabio
>
> On 01/26/2015 08:00 PM, Ravi Prakash wrote:
>> Are you running NTP?
>>
>>
>> On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com>
>> <ma...@gmail.com> wrote:
>>
>>
>> Hi guys,
>> while analyzing SLS logs I noticed some unexpected behaviors, such as
>> resources requests sent before the AM container gets to a RUNNING state.
>> For this reason I started wondering how reliable is the timestamp of the
>> log entries.
>> Does log4j run on an independent thread? If yes, could it be the reason
>> why some log entries appear as misplaced? Or are they supposed to be in
>> strict execution order in any case?
>> I ask this because I am validating a project and I need to be pretty
>> sure about what happens when.
>>
>> Thanks
>>
>> Fabio
>>
>>
>
>
>
Re: Reliability of timestamps in logs
Posted by Fabio <an...@gmail.com>.
Thanks for the diagrams tip! I will try it.
(SLS is the Scheduler Load Simulator
http://hadoop.apache.org/docs/r2.6.0/hadoop-sls/SchedulerLoadSimulator.html
)
Regards
Fabio
On 01/27/2015 11:04 PM, Ravi Prakash wrote:
> I'm afraid I don't know what the "SLS" is. Obviously it shouldn't
> matter if it runs on the same node. I don't think hadoop code ever
> updates the system clock. In fact it shouldn't even be run with the
> perms to do so.
> It depends on log4j appenders whether they buffer and batch the
> messages before writing to disk. I would think that the timestamp
> would still be the time the messages were received (rather than the
> time they were flushed to disk)
>
> I am not sure if you know but you can get beautiful state diagrams of
> the different agents by running $mvn -Pvisualize and then using dot to
> convert the *.gv files to png . I'd found that helped me a lot
>
>
> On Monday, January 26, 2015 11:20 PM, Fabio <an...@gmail.com> wrote:
>
>
> Yes I am, does it make a difference? SLS runs on a single machine,
> wrapping the RM and simulating the nodes, thus it should use just the
> system time.
> Or do you mean there is a chance it's updating the clock while the job
> is running?
>
> Regards
>
> Fabio
>
> On 01/26/2015 08:00 PM, Ravi Prakash wrote:
>> Are you running NTP?
>>
>>
>> On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com>
>> <ma...@gmail.com> wrote:
>>
>>
>> Hi guys,
>> while analyzing SLS logs I noticed some unexpected behaviors, such as
>> resources requests sent before the AM container gets to a RUNNING state.
>> For this reason I started wondering how reliable is the timestamp of the
>> log entries.
>> Does log4j run on an independent thread? If yes, could it be the reason
>> why some log entries appear as misplaced? Or are they supposed to be in
>> strict execution order in any case?
>> I ask this because I am validating a project and I need to be pretty
>> sure about what happens when.
>>
>> Thanks
>>
>> Fabio
>>
>>
>
>
>
Re: Reliability of timestamps in logs
Posted by Ravi Prakash <ra...@ymail.com>.
I'm afraid I don't know what the "SLS" is. Obviously it shouldn't matter if it runs on the same node. I don't think hadoop code ever updates the system clock. In fact it shouldn't even be run with the perms to do so.It depends on log4j appenders whether they buffer and batch the messages before writing to disk. I would think that the timestamp would still be the time the messages were received (rather than the time they were flushed to disk)
I am not sure if you know but you can get beautiful state diagrams of the different agents by running $mvn -Pvisualize and then using dot to convert the *.gv files to png . I'd found that helped me a lot
On Monday, January 26, 2015 11:20 PM, Fabio <an...@gmail.com> wrote:
Yes I am, does it make a difference? SLS runs on a single machine, wrapping the RM and simulating the nodes, thus it should use just the system time.
Or do you mean there is a chance it's updating the clock while the job is running?
Regards
Fabio
On 01/26/2015 08:00 PM, Ravi Prakash wrote:
Are you running NTP?
On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com> wrote:
Hi guys,
while analyzing SLS logs I noticed some unexpected behaviors, such as
resources requests sent before the AM container gets to a RUNNING state.
For this reason I started wondering how reliable is the timestamp of the
log entries.
Does log4j run on an independent thread? If yes, could it be the reason
why some log entries appear as misplaced? Or are they supposed to be in
strict execution order in any case?
I ask this because I am validating a project and I need to be pretty
sure about what happens when.
Thanks
Fabio
Re: Reliability of timestamps in logs
Posted by Ravi Prakash <ra...@ymail.com>.
I'm afraid I don't know what the "SLS" is. Obviously it shouldn't matter if it runs on the same node. I don't think hadoop code ever updates the system clock. In fact it shouldn't even be run with the perms to do so.It depends on log4j appenders whether they buffer and batch the messages before writing to disk. I would think that the timestamp would still be the time the messages were received (rather than the time they were flushed to disk)
I am not sure if you know but you can get beautiful state diagrams of the different agents by running $mvn -Pvisualize and then using dot to convert the *.gv files to png . I'd found that helped me a lot
On Monday, January 26, 2015 11:20 PM, Fabio <an...@gmail.com> wrote:
Yes I am, does it make a difference? SLS runs on a single machine, wrapping the RM and simulating the nodes, thus it should use just the system time.
Or do you mean there is a chance it's updating the clock while the job is running?
Regards
Fabio
On 01/26/2015 08:00 PM, Ravi Prakash wrote:
Are you running NTP?
On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com> wrote:
Hi guys,
while analyzing SLS logs I noticed some unexpected behaviors, such as
resources requests sent before the AM container gets to a RUNNING state.
For this reason I started wondering how reliable is the timestamp of the
log entries.
Does log4j run on an independent thread? If yes, could it be the reason
why some log entries appear as misplaced? Or are they supposed to be in
strict execution order in any case?
I ask this because I am validating a project and I need to be pretty
sure about what happens when.
Thanks
Fabio
Re: Reliability of timestamps in logs
Posted by Ravi Prakash <ra...@ymail.com>.
I'm afraid I don't know what the "SLS" is. Obviously it shouldn't matter if it runs on the same node. I don't think hadoop code ever updates the system clock. In fact it shouldn't even be run with the perms to do so.It depends on log4j appenders whether they buffer and batch the messages before writing to disk. I would think that the timestamp would still be the time the messages were received (rather than the time they were flushed to disk)
I am not sure if you know but you can get beautiful state diagrams of the different agents by running $mvn -Pvisualize and then using dot to convert the *.gv files to png . I'd found that helped me a lot
On Monday, January 26, 2015 11:20 PM, Fabio <an...@gmail.com> wrote:
Yes I am, does it make a difference? SLS runs on a single machine, wrapping the RM and simulating the nodes, thus it should use just the system time.
Or do you mean there is a chance it's updating the clock while the job is running?
Regards
Fabio
On 01/26/2015 08:00 PM, Ravi Prakash wrote:
Are you running NTP?
On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com> wrote:
Hi guys,
while analyzing SLS logs I noticed some unexpected behaviors, such as
resources requests sent before the AM container gets to a RUNNING state.
For this reason I started wondering how reliable is the timestamp of the
log entries.
Does log4j run on an independent thread? If yes, could it be the reason
why some log entries appear as misplaced? Or are they supposed to be in
strict execution order in any case?
I ask this because I am validating a project and I need to be pretty
sure about what happens when.
Thanks
Fabio
Re: Reliability of timestamps in logs
Posted by Ravi Prakash <ra...@ymail.com>.
I'm afraid I don't know what the "SLS" is. Obviously it shouldn't matter if it runs on the same node. I don't think hadoop code ever updates the system clock. In fact it shouldn't even be run with the perms to do so.It depends on log4j appenders whether they buffer and batch the messages before writing to disk. I would think that the timestamp would still be the time the messages were received (rather than the time they were flushed to disk)
I am not sure if you know but you can get beautiful state diagrams of the different agents by running $mvn -Pvisualize and then using dot to convert the *.gv files to png . I'd found that helped me a lot
On Monday, January 26, 2015 11:20 PM, Fabio <an...@gmail.com> wrote:
Yes I am, does it make a difference? SLS runs on a single machine, wrapping the RM and simulating the nodes, thus it should use just the system time.
Or do you mean there is a chance it's updating the clock while the job is running?
Regards
Fabio
On 01/26/2015 08:00 PM, Ravi Prakash wrote:
Are you running NTP?
On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com> wrote:
Hi guys,
while analyzing SLS logs I noticed some unexpected behaviors, such as
resources requests sent before the AM container gets to a RUNNING state.
For this reason I started wondering how reliable is the timestamp of the
log entries.
Does log4j run on an independent thread? If yes, could it be the reason
why some log entries appear as misplaced? Or are they supposed to be in
strict execution order in any case?
I ask this because I am validating a project and I need to be pretty
sure about what happens when.
Thanks
Fabio
Re: Reliability of timestamps in logs
Posted by Fabio <an...@gmail.com>.
Yes I am, does it make a difference? SLS runs on a single machine,
wrapping the RM and simulating the nodes, thus it should use just the
system time.
Or do you mean there is a chance it's updating the clock while the job
is running?
Regards
Fabio
On 01/26/2015 08:00 PM, Ravi Prakash wrote:
> Are you running NTP?
>
>
> On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com> wrote:
>
>
> Hi guys,
> while analyzing SLS logs I noticed some unexpected behaviors, such as
> resources requests sent before the AM container gets to a RUNNING state.
> For this reason I started wondering how reliable is the timestamp of the
> log entries.
> Does log4j run on an independent thread? If yes, could it be the reason
> why some log entries appear as misplaced? Or are they supposed to be in
> strict execution order in any case?
> I ask this because I am validating a project and I need to be pretty
> sure about what happens when.
>
> Thanks
>
> Fabio
>
>
Re: Reliability of timestamps in logs
Posted by Fabio <an...@gmail.com>.
Yes I am, does it make a difference? SLS runs on a single machine,
wrapping the RM and simulating the nodes, thus it should use just the
system time.
Or do you mean there is a chance it's updating the clock while the job
is running?
Regards
Fabio
On 01/26/2015 08:00 PM, Ravi Prakash wrote:
> Are you running NTP?
>
>
> On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com> wrote:
>
>
> Hi guys,
> while analyzing SLS logs I noticed some unexpected behaviors, such as
> resources requests sent before the AM container gets to a RUNNING state.
> For this reason I started wondering how reliable is the timestamp of the
> log entries.
> Does log4j run on an independent thread? If yes, could it be the reason
> why some log entries appear as misplaced? Or are they supposed to be in
> strict execution order in any case?
> I ask this because I am validating a project and I need to be pretty
> sure about what happens when.
>
> Thanks
>
> Fabio
>
>
Re: Reliability of timestamps in logs
Posted by Fabio <an...@gmail.com>.
Yes I am, does it make a difference? SLS runs on a single machine,
wrapping the RM and simulating the nodes, thus it should use just the
system time.
Or do you mean there is a chance it's updating the clock while the job
is running?
Regards
Fabio
On 01/26/2015 08:00 PM, Ravi Prakash wrote:
> Are you running NTP?
>
>
> On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com> wrote:
>
>
> Hi guys,
> while analyzing SLS logs I noticed some unexpected behaviors, such as
> resources requests sent before the AM container gets to a RUNNING state.
> For this reason I started wondering how reliable is the timestamp of the
> log entries.
> Does log4j run on an independent thread? If yes, could it be the reason
> why some log entries appear as misplaced? Or are they supposed to be in
> strict execution order in any case?
> I ask this because I am validating a project and I need to be pretty
> sure about what happens when.
>
> Thanks
>
> Fabio
>
>
Re: Reliability of timestamps in logs
Posted by Fabio <an...@gmail.com>.
Yes I am, does it make a difference? SLS runs on a single machine,
wrapping the RM and simulating the nodes, thus it should use just the
system time.
Or do you mean there is a chance it's updating the clock while the job
is running?
Regards
Fabio
On 01/26/2015 08:00 PM, Ravi Prakash wrote:
> Are you running NTP?
>
>
> On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com> wrote:
>
>
> Hi guys,
> while analyzing SLS logs I noticed some unexpected behaviors, such as
> resources requests sent before the AM container gets to a RUNNING state.
> For this reason I started wondering how reliable is the timestamp of the
> log entries.
> Does log4j run on an independent thread? If yes, could it be the reason
> why some log entries appear as misplaced? Or are they supposed to be in
> strict execution order in any case?
> I ask this because I am validating a project and I need to be pretty
> sure about what happens when.
>
> Thanks
>
> Fabio
>
>
Re: Reliability of timestamps in logs
Posted by Ravi Prakash <ra...@ymail.com>.
Are you running NTP?
On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com> wrote:
Hi guys,
while analyzing SLS logs I noticed some unexpected behaviors, such as
resources requests sent before the AM container gets to a RUNNING state.
For this reason I started wondering how reliable is the timestamp of the
log entries.
Does log4j run on an independent thread? If yes, could it be the reason
why some log entries appear as misplaced? Or are they supposed to be in
strict execution order in any case?
I ask this because I am validating a project and I need to be pretty
sure about what happens when.
Thanks
Fabio
Re: Reliability of timestamps in logs
Posted by Ravi Prakash <ra...@ymail.com>.
Are you running NTP?
On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com> wrote:
Hi guys,
while analyzing SLS logs I noticed some unexpected behaviors, such as
resources requests sent before the AM container gets to a RUNNING state.
For this reason I started wondering how reliable is the timestamp of the
log entries.
Does log4j run on an independent thread? If yes, could it be the reason
why some log entries appear as misplaced? Or are they supposed to be in
strict execution order in any case?
I ask this because I am validating a project and I need to be pretty
sure about what happens when.
Thanks
Fabio
Re: Reliability of timestamps in logs
Posted by Ravi Prakash <ra...@ymail.com>.
Are you running NTP?
On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com> wrote:
Hi guys,
while analyzing SLS logs I noticed some unexpected behaviors, such as
resources requests sent before the AM container gets to a RUNNING state.
For this reason I started wondering how reliable is the timestamp of the
log entries.
Does log4j run on an independent thread? If yes, could it be the reason
why some log entries appear as misplaced? Or are they supposed to be in
strict execution order in any case?
I ask this because I am validating a project and I need to be pretty
sure about what happens when.
Thanks
Fabio
Re: Reliability of timestamps in logs
Posted by Ravi Prakash <ra...@ymail.com>.
Are you running NTP?
On Friday, January 23, 2015 12:42 AM, Fabio <an...@gmail.com> wrote:
Hi guys,
while analyzing SLS logs I noticed some unexpected behaviors, such as
resources requests sent before the AM container gets to a RUNNING state.
For this reason I started wondering how reliable is the timestamp of the
log entries.
Does log4j run on an independent thread? If yes, could it be the reason
why some log entries appear as misplaced? Or are they supposed to be in
strict execution order in any case?
I ask this because I am validating a project and I need to be pretty
sure about what happens when.
Thanks
Fabio