avalanche mitigation

first, Cache avalanche Cache Avalanche We can simply understand that due to the original cache failure, the new cache is not in the period (for example: we set the cache with the same expiration time, at the same time a large area of cache expiration), all should have access to the cache of the request to query the database, and the database CPU and memory caused great pressure, Serious results in database

the natural cache. The request is sent directly to the database. If the concurrent access to this key is too large, the database will be overwhelmed. Solution: 1. Use a filter to hash all data that cannot exist in the database to a large bitmap. If the key does not exist in the database, it will be intercepted by bitmap. 2. Check the key that is null and the resume key value pair in the cache, which is a little shorter than the expiration time, such as 5 minetes.Cache

One: Memcached cache avalanche Phenomenon(1) Cause: Usually by a node failure, resulting in other nodes cache hit rate drop, the missing data in the cache query, a short period of time caused by the database server crashes. Restart the DB, the short-term is also crushed, but the cached data increased some, DB repeated multiple start, multiple caches can be established, the DB can be stable operation.Or because the cache is periodically invalidated, su

Cache avalancheThe cache avalanche may be because the data is not loaded into the cache, or the cache is invalidated by a large area at the same time, causing all requests to go to the database, causing the database CPU and memory load to be too high, or even downtime.Solution Ideas:1, using the lock count, or use a reasonable number of queues to avoid cache failure when the database caused too much pressure. This approach can alleviate the pressure o

Cache penetration ConceptAccess to a nonexistent key, the cache does not work, the request will penetrate into the DB, when the traffic is large, the db will be hung off.Solution SolutionsUsing the bitmap filter, a large enough to store the key that may be accessed, the nonexistent key is filtered directly;Access key does not query the value in db, also writes null values to the cache, but can set a shorter expiration time.Cache Avalanche ConceptA lar

Cache avalancheThe cache avalanche may be because the data is not loaded into the cache, or the cache is invalidated by a large area at the same time, causing all requests to go to the database, causing the database CPU and memory load to be too high, or even downtime.Solution Ideas:1, using the lock count, or use a reasonable number of queues to avoid cache failure when the database caused too much pressure. This approach can alleviate the pressure o

Cache avalancheThe cache avalanche may be because the data is not loaded into the cache, or the cache is invalidated by a large area at the same time, causing all requests to go to the database, causing the database CPU and memory load to be too high, or even downtime.Solution Ideas:1, using the lock count, or use a reasonable number of queues to avoid cache failure when the database caused too much pressure. This approach can alleviate the pressure o

The cache Avalanche Cache Avalanche is due to the original cache invalidation (expired) and the new cache is not in the period. All requests to query the database, and the database CPU and memory caused great pressure, serious will cause database downtime. Thus forming a series of chain reaction, causing the whole system collapse. (1) In this case, the general concurrency is not particularly high time, the

cache penetration : Usually the cache is based on key to find value, if the cache does not exist, then go to the db to find, if found, the Key->value write to the cache. However, for some of the data that does not exist in the cache each time to find, so every time to find in DB, DB can not find so can't write cache, so reciprocating, then lost the meaning of the cache. WORKAROUND: The query is empty to db, but the cache expiration time of this data need to be set to a little bit; all possible

Since distributed systems make different types of services, in one system 1, different services may be called, such as services A, B, C, and the service and service will also call each other, such as service D, E will invoke service A; When service a fails to be invoked, System 1, Service D, and service e fail, resulting in a service avalanche due to a service problem that causes multiple systems or services to be unavailable. Therefore, a fuse is p

I. Delegation The delegate is actually the function pointer in C ++. You can point this pointer to the type of function that is known when the delegate is defined. For example: Public delegate void to connect to the database delegate ();Indicates a

There's a strange phenomenon under Android's WebView and its own browser.Phenomenon :1, if the input box inputs or textarea (z direction, that is, the upper layer) has a div, when the div is clicked to make the div hidden, input will get focus,

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1.Cache penetration:Query a data that does not exist. For example, to query an article table with a nonexistent ID, the database is accessed every time. If someone maliciously destroys the ID, it is likely to directly affect the database. Solution:

We used to have deep reverence for the words printed on paper. We once looked at experts and believed in authoritative institutions. The day before yesterday, I was playing a healthy TV program on the TV, saying that if there is a cross on the palm

request, the host list of available services is obtained from the Service Registration Discovery Center Eureka, the host of the service instance is computed after the load balancing algorithm is calculated, and the request is forwarded, so that internally serves the external caller, or the dependency coupling between internal services turns into a dependency on Eureka.#3 gets the service from the client load Balancer Ribbon to a specific instance of the backend service after obtaining services

optimization of e-commerce website can not be separated from the stress test of simulating real environment. And think Bollen communication is the expert in this field. In recent years, Si Bollen based on Avalanche e-commerce website testing solution has been for many customers to complete this aspect of testing, such as: A telecommunications operator Hospital line system, a well-known large-scale video portal product booking/snapping system, an auth

risk is to determine the criteria for the definition, evaluation, and sequencing of the risk. An important part of this is determining the thresholds for each type of risk. The risk threshold is the monitoring and control point for the risk, and the risk mitigation plan must be considered when the risk is ultimately assessed to have an impact over the threshold. The implementation of a risk mitigation plan

attract the attention of managers. On the one hand, different risk types and sources may have different risk probabilities, influences, stakeholders, risk thresholds, and other basic parameters. Defining risk parameters mainly involves determining the risk definition, evaluation and sorting criteria. It is important to determine the threshold of various risks. A risk threshold is a risk monitoring and control point. When the impact of a risk assessment exceeds the threshold, you must consider i

From:https://support.oracle.comWhat is "Oracle javavm Component Database PSU"?Oracle JAVAVM Component Database PSU is released as part of the Critical Patch Update program from October onwards.IT consists of separate patches: One for JDBC clients-applicable to client, Instant client, Database and Grid oracle_homes.This is a referred to as "JDBC Patch" in the rest of this document. One for the Oracle JAVAVM component within, the Oracle database-applicable to Database oracle_homes onl