Dear Jeremy and Stephen,
Thank you for answers. I this issues I face is not bound exclusively to
assigned memory but behavior of eviction policies. After all, without
proper eviction or expiry policy, each amount of memory will eventually
be exceeded. Small size of memory makes it simply easier to test. To be
honest I do not see a point in testing eviction with 50GB of memory, if
it cant be configured for 512MB. Expiry policy proved to work, but it
will not preventing node from crash, as there always might be high write
ratio causing memory to fill.
Both LRU and FIFO eviction policies in default configuration do not take
into account overall memory allocation, they work only with on heap
caches. Unless memory size is explicitly specified they will rely on
over-provisioned memory, or assume that memory assignment is right. This
is possible only if cache entry have a predictable.
Another point is that above eviction policies are dedicated to on-heap
caches and are told to have no affect to off-heap region, why is so? By
looking at sources I see CacheOffheapEvictionManager and
GridCacheEvictionManager, but I can't grasp what enables eviction of
entries from off heap memory managed by Ignite.
Given that my use case is continuous operation with variety of entries
having various sizes I can't assume on-heap cache with LRU nor FIFO,
especially that they do not impact off heap memory. I also can't risk
filling in memory managed by Ignite due to lack of clear eviction policy
during peak load.
As far I can understand from DataRegionConfiguration, its eviction
mechanism works for whole pages, but I haven't seen this happening.
Could it be due to fact that single cache entry in my test exceeds
maximum page size (16MB)?
Best regards,
Łukasz
On 30.01.2023 10:32, Stephen Darlington wrote:
Ignite is designed to work as a cluster with a lot of memory. A single node
with 512Mb of memory just isn’t what most people are testing with. I’ve seen
similar issues when people use tiny nodes. I don’t see anything immediately
wrong with your configuration, but if it works with more memory, that’s your
problem.
On 28 Jan 2023, at 00:35, Łukasz Dywicki <[email protected]> wrote:
Hello again,
I've spent another day on this issue looking at configuration and with cluster
larger than configured backup count ignite did the work.
After that I reverted to testing of single node with minimal configuration and
come to the point that the only way to keep Ignite survive load was setting
ExpiryPolicy to very low value (10s).
To me it seems that Ignite behavior is to preserve all entries in memory at any
cost, even if there is a risk of running into OOM. Is that true?
I would like to change this behavior and make sure that entries do not expire
because of time as long as there is memory available to store them. They should
be evicted by appropriate EvictionPolicy only if memory fills up.
To me it looks like DataStoreSettings do not make any impact in this regard. At
least setting page eviction to LRU do not change it.
Please let me know if I am doing something wrong as I can not prove Ignite to
be working stable. Even with such basic objectives I outlined in earlier mail.
Kind regards,
Łukasz
On 27.01.2023 00:58, Łukasz Dywicki wrote:
Dear all,
I come across use of Apache Ignite to cache results of expensive computation
operation.
Objectives are basic:
- Keep most of "hot" data in memory
- Offload cold part to cache store
- Keep memory utilization under control (evict entries as needed)
While it sounds basic, it doesn't seem to fit Ignite defaults.
What I am testing now is behavior with large objects which can grow up to 10 mb
(serialized) or 25 mb (json representation). Usually objects will stay far
below that threshold, but we can't make assumption on that.
I began testing various configurations of Ignite in order to facilitate
offloading of memory contents to database. So far I am stuck for two days at
Ignite/application itself running out of memory after processing several of
such large objects. While I know that storing 10 mb blob in database is not the
best idea, I have to test that behavior too.
By observing database contents I see that number of entries there grows, but
cache do not seem to be evicted. When I try to switch eviction, it does require
onheap to be switched on, and it still fails with LRU eviction policy.
So far I ended up with a named cache and default region configured as below:
```
IgniteConfiguration igniteConfiguration = new IgniteConfiguration();
igniteConfiguration.setDataStorageConfiguration(new DataStorageConfiguration()
.setDefaultDataRegionConfiguration(new DataRegionConfiguration()
.setPersistenceEnabled(false)
.setInitialSize(256L * 1024 * 1024)
.setMaxSize(512L * 1024 * 1024)
.setPageEvictionMode(DataPageEvictionMode.RANDOM_LRU)
.setSwapPath(null)
.setEvictionThreshold(0.75)
)
.setPageSize(DataStorageConfiguration.MAX_PAGE_SIZE)
);
CacheConfiguration<SessionKey, ExpensiveObject> expensiveCache = new
CacheConfiguration<>()
.setName(CACHE_NAME)
.setBackups(2)
.setAtomicityMode(CacheAtomicityMode.ATOMIC)
.setCacheStoreFactory(cacheJdbcBlobStoreFactory)
.setWriteThrough(true)
.setOnheapCacheEnabled(true)
.setEvictionPolicyFactory(new LruEvictionPolicyFactory<>(1024))
.setReadThrough(true);
igniteConfiguration.setCacheConfiguration(
expensiveCache
);
```
What I observe is following - the cache keeps writing data into database, but
it does not remove old entries fast enough to prevent crash.
JVM parameters I use are fairly basic:
-Xms1g -Xmx1g -XX:+AlwaysPreTouch -XX:+UseG1GC -XX:+ScavengeBeforeFullGC
-XX:+DisableExplicitGC
The store mechanism is jdbc blob store. Exceptions I get happen to occur in
Ignite itself, processing (application code writing cache) or communication
thread used to feed cache. I collected one case here:
https://gist.github.com/splatch/b5ec9134cd9df19bc62f007dd17a19a1
The error message in linked gist advice to enable persistence (which I did via
cache store!), increase memory limit (which I don't want to do), or enable
eviction/expiry policy (which somehow miss behave).
To me it looks like self defense mechanisms Ignite has are being tricked
leading whole application to crash.
Can you please advise me which settings to tune and how in order to get Ignite
more stable under such load?
Kind regards,
Łukasz
