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| Original file line number | Diff line number | Diff line change |
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| --- | ||
| giturl: "https://github.com/blended-zio/blended-zio-jmx" | ||
| giturl: "https://github.com/blended-zio/blended-zio-jmx" | ||
| jmxsrc: "modules/blended-zio-jmx/blended-zio-jmx/jvm/src/main/scala" | ||
| jmxtest: "modules/blended-zio-jmx/blended-zio-jmx/jvm/src/test/scala" | ||
| --- | ||
| # A simple facade to the Platform MBean Server | ||
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| This service is a small wrapper around the platform MBean server within a JVM. The use case is to | ||
| have a server side component which can query for the names within the MBeanServer for a given pattern | ||
| and to retrieve the MBean Information for a given object name. All JMX specific data shall be mapped | ||
| This service is a small wrapper around the platform MBean server within a JVM. The use case is to | ||
| have a server side component which can query for the names within the MBeanServer for a given pattern | ||
| and to retrieve the MBean Information for a given object name. All JMX specific data shall be mapped | ||
| to appropriate classes, so that the data can be used later on with a simple read-only JMX REST service. | ||
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| This leads to the following, simple interface definition: | ||
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| {{< codesection file="modules/blended-zio-jmx/ziojmx/jvm/blended/zio/jmx/MBeanServerFacade.scala" section="service" >}} | ||
| {{< codesection dirref="jmxsrc" file="blended/zio/jmx/MBeanServerFacade.scala" section="service" >}} | ||
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| {{< hint info >}} | ||
| Even though the interface is defined without any environment restrictions, the actual `live` service requires that | ||
| a `Logging` service is available. We have decided to push the requirement for a `Logging` service into the instantiation | ||
| of the `live` service as we might come up with `test` instances at some point that should just mock up the interface and | ||
| does not require any logging at all. | ||
| Even though the interface is defined without any environment restrictions, the actual `live` service requires that | ||
| a `Logging` service is available. We have decided to push the requirement for a `Logging` service into the instantiation | ||
| of the `live` service as we might come up with `test` instances at some point that should just mock up the interface and | ||
| does not require any logging at all. | ||
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| We will use the [zio-logging](https://zio.github.io/zio-logging/) API to perform the actual logging. See | ||
| [this post]({{< ref "/posts/2020-09-28-ZIOLogging.md" >}}) for more details on injecting different logging backends into the | ||
| We will use the [zio-logging](https://zio.github.io/zio-logging/) API to perform the actual logging. See | ||
| [this post]({{< ref "/posts/2020-09-28-ZIOLogging.md" >}}) for more details on injecting different logging backends into the | ||
| `live` service instance. | ||
| {{< /hint >}} | ||
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| ## Querying for MBean Names | ||
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| To query for a set of MBean names with an optional is fairly straight forward wrapper around the original JMX API. | ||
| To query for a set of MBean names with an optional is fairly straight forward wrapper around the original JMX API. | ||
| We just have to translate from the case class we want to use in our API to a JMX search pattern and call the API. | ||
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| {{< codesection file="modules/blended-zio-jmx/ziojmx/jvm/blended/zio/jmx/MBeanServerFacade.scala" section="names" >}} | ||
| {{< codesection dirref="jmxsrc" file="blended/zio/jmx/MBeanServerFacade.scala" section="names" >}} | ||
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| In order to make the code a bit more readable, we encapsulate the translation within some helper methods abstracting | ||
| over the case that the pattern may be optional. It might be that a single helper method to translate the pattern | ||
| would have been sufficient, but in this case it seemed to improve the code's readability to have two helper methods. | ||
| In order to make the code a bit more readable, we encapsulate the translation within some helper methods abstracting | ||
| over the case that the pattern may be optional. It might be that a single helper method to translate the pattern | ||
| would have been sufficient, but in this case it seemed to improve the code's readability to have two helper methods. | ||
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| The `queryNames` method performs the actual JMX call and translates the resulting Java object into a `List` of | ||
| The `queryNames` method performs the actual JMX call and translates the resulting Java object into a `List` of | ||
| `JmxObjectName` | ||
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| {{< codesection file="modules/blended-zio-jmx/ziojmx/jvm/blended/zio/jmx/MBeanServerFacade.scala" section="helper" >}} | ||
| {{< codesection dirref="jmxsrc" file="blended/zio/jmx/MBeanServerFacade.scala" section="helper" >}} | ||
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| ## Retrieving MBean information | ||
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| The complicated part retrieving MBean information is to translate the attributes within the MBean information to an actual | ||
| case class. We assume that the MBeans do have properties which are allowed for | ||
| [OpenMBeans](https://docs.oracle.com/cd/E19206-01/816-4178/6madjde4v/index.html). | ||
| The complicated part retrieving MBean information is to translate the attributes within the MBean information to an actual | ||
| case class. We assume that the MBeans do have properties which are allowed for | ||
| [OpenMBeans](https://docs.oracle.com/cd/E19206-01/816-4178/6madjde4v/index.html). | ||
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| If we encounter an attribute that is not valid as an attribute in the sense of the Open MBean specification, we will ignore | ||
| that attribute in our mapping rather than throw an exception. As a result, some attributes _may_ be missing for certain | ||
| MBean Info objects. | ||
| If we encounter an attribute that is not valid as an attribute in the sense of the Open MBean specification, we will ignore | ||
| that attribute in our mapping rather than throw an exception. As a result, some attributes _may_ be missing for certain | ||
| MBean Info objects. | ||
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| The mapping between attributes and their case class representation happens within the `JmxAttributeCompanion` object. For the | ||
| The mapping between attributes and their case class representation happens within the `JmxAttributeCompanion` object. For the | ||
| simple types this is straight forward: | ||
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| {{< codesection file="modules/blended-zio-jmx/ziojmx/jvm/blended/zio/jmx/JmxAttributeCompanion.scala" section="simple" >}} | ||
| {{< codesection dirref="jmxsrc" file="blended/zio/jmx/JmxAttributeCompanion.scala" section="simple" >}} | ||
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| To map the complex data we will rely on ZIO's `collectPar` operator: | ||
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| {{< codesection file="modules/blended-zio-jmx/ziojmx/jvm/blended/zio/jmx/JmxAttributeCompanion.scala" section="tabdata" >}} | ||
| {{< codesection dirref="jmxsrc" file="blended/zio/jmx/JmxAttributeCompanion.scala" section="tabdata" >}} | ||
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| Note, that whithin `JmxAttributeCompanion` the overall signature is | ||
| Note, that whithin `JmxAttributeCompanion` the overall signature is | ||
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| ```scala | ||
| def make(v: Any): ZIO[Any, IllegalArgumentException, AttributeValue[_]] | ||
| ``` | ||
| This means that the error handling is in the responsibility of the user of the `make` effect. | ||
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| {{< codesection file="modules/blended-zio-jmx/ziojmx/jvm/blended/zio/jmx/MBeanServerFacade.scala" section="attribute" >}} | ||
| {{< codesection dirref="jmxsrc" file="blended/zio/jmx/MBeanServerFacade.scala" section="attribute" >}} | ||
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| Here, the `orElse` operator will handle the error by just ignoring the attribute that was faulty. | ||
| Here, the `orElse` operator will handle the error by just ignoring the attribute that was faulty. | ||
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| ### Representation of an entire MBean Info | ||
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| The entire MBean Info object contains the `JmxObjectName` it belongs to and a Map of attribute names to their corresponding values. | ||
| In other words, the attributes of a MBean Info can be represented by an instance of `CompositeAttributeValue`. | ||
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| {{< codesection file="modules/blended-zio-jmx/ziojmx/jvm/blended/zio/jmx/JmxAttribute.scala" section="beaninfo" >}} | ||
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| In other words, the attributes of a MBean Info can be represented by an instance of `CompositeAttributeValue`. | ||
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| {{< codesection dirref="jmxsrc" file="blended/zio/jmx/JmxAttribute.scala" section="beaninfo" >}} |
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