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diff --git a/VES5.0/evel/evel-library/code/evel_library/readme.md b/VES5.0/evel/evel-library/code/evel_library/readme.md new file mode 100644 index 00000000..3cf57083 --- /dev/null +++ b/VES5.0/evel/evel-library/code/evel_library/readme.md @@ -0,0 +1,236 @@ +# EVEL Library Overview {#mainpage} + +# Introduction + +The ECOMP Vendor Event Listener ("EVEL") library encapsulates the use of +AT&T's JSON API to the collector function within the ECOMP infrastructure. + +As such, it provides a reference implementation of the EVEL JSON API which +can either be directly as part of a project or can be used to inform the +independent implementation of an equivalent binding to the API in another +development environment. + +This section provides an overview of the library and how it is integrated +into the target application. If all you want is a set of instructions to +get you started, the @ref quickstart "Quick Start" section is for you. If +you want a more in-depth understanding of the _EVEL Library_ then this section +provides an overview and then you can read the detailed API documentation for +each function. The documentation for evel.h is a good starting point, since +that defines the public API of the _EVEL Library_. + +# Library Structure + +The API is designed to be used on multi-process platforms where each process +may be multi-threaded. Each process using this library will create an +independent HTTP client (using libcURL). Each process will have a single +thread running the HTTP client but that thread receives work on a +ring-buffer from however may threads are required to implement the function. + +**Note**: libcurl imposes a constraint that it is initialized before +the process starts multi-threaded operation. + +# Typical Usage + +The library is designed to be very straightforward to use and lightweight to +integrate into projects. The only serious external dependency is on libcURL. + +The supplied Makefile produces a single library **libevel.so** or +**libevel.a** which your application needs to be linked against. + +Each process within the application which wants to generate events needs to +call ::evel_initialize at the start of day (observing the above warning +about not being MT safe at this stage.) The initialization specifies the +details of where the API is located. Management of configuration is the +responsibility of the client. + +Once initialized, and now MT-safe, there are factory functions to produce +new events: +- Faults - ::evel_new_fault +- Measurements - ::evel_new_measurement +- Report - ::evel_new_report +- State Change - ::evel_new_state_change +- Syslog - ::evel_new_syslog +- Other - ::evel_new_other +- Mobile Flow - ::evel_new_mobile_flow + +There is also a factory function ::evel_new_mobile_gtp_flow_metrics to create +the parameter gtp_per_flow_metrics, which is then configured and passed to the +::evel_new_mobile_flow factory function. + +The event structures are initialized with mandatory fields at the point of +creation and optional fields may be added thereafter. Once set, values in +the structures are immutable. + +Once the event is prepared, it may be posted, using ::evel_post_event, at +which point the calling thread relinquishes all responsibility for the +event. It will be freed once successfully or unsuccessfully posted to the +API. If, for any reason, you change your mind and don't want to post a +created event, it must be destroyed with ::evel_free_event. + +Finally, at the end of day, the library can be terminated cleanly by calling +::evel_terminate. + +## Example Code + +The following fragment illustrates the above usage: + +```C + + if (evel_initialize(api_fqdn, + api_port, + api_path, + api_topic, + api_secure, + "Alice", + "This isn't very secure!", + EVEL_SOURCE_VIRTUAL_MACHINE, + "EVEL demo client", + verbose_mode)) + { + fprintf(stderr, "Failed to initialize the EVEL library!!!"); + exit(-1); + } + + ... + + fault = evel_new_fault("My alarm condition", + "It broke very badly", + EVEL_PRIORITY_NORMAL, + EVEL_SEVERITY_MAJOR); + if (fault != NULL) + { + evel_fault_type_set(fault, "Bad things happen..."); + evel_fault_interface_set(fault, "My Interface Card"); + evel_fault_addl_info_add(fault, "name1", "value1"); + evel_fault_addl_info_add(fault, "name2", "value2"); + evel_rc = evel_post_event((EVENT_HEADER *)fault); + if (evel_rc != EVEL_SUCCESS) + { + EVEL_ERROR("Post failed %d (%s)", evel_rc, evel_error_string()); + } + } + +``` + +The public API to the library is defined in evel.h. The internal APIs +within library are defined in separate headers (<em>e.g.</em> +evel_internal.h), but these should not need to be included by the code +using the library. + +# Example Application + +A simple command-line application to generate events is provided as part of +the source package (the above code fragment is taken from that application). + +The following illustrates its operation to a co-located "test-collector": +``` +$ ./evel_demo --fqdn 127.0.0.1 --port 30000 --path vendor_event_listener --topic example_vnf --verbose +./evel_demo built Feb 26 2016 18:14:48 +* About to connect() to 169.254.169.254 port 80 (#0) +* Trying 169.254.169.254... * Timeout +* connect() timed out! +* Closing connection #0 +* About to connect() to 127.0.0.1 port 30000 (#0) +* Trying 127.0.0.1... * connected +* Connected to 127.0.0.1 (127.0.0.1) port 30000 (#0) +* Server auth using Basic with user 'Alice' +> POST /vendor_event_listener/eventListener/v1/example_vnf HTTP/1.1 +Authorization: Basic QWxpY2U6VGhpcyBpc24ndCB2ZXJ5IHNlY3VyZSE= +User-Agent: libcurl-agent/1.0 +Host: 127.0.0.1:30000 +Accept: */* +Content-type: application/json +Content-Length: 510 + +* HTTP 1.0, assume close after body +< HTTP/1.0 204 No Content +< Date: Fri, 04 Mar 2016 15:37:22 GMT +< Server: WSGIServer/0.1 Python/2.6.6 +< +* Closing connection #0 +* About to connect() to 127.0.0.1 port 30000 (#0) +* Trying 127.0.0.1... * connected +* Connected to 127.0.0.1 (127.0.0.1) port 30000 (#0) +* Server auth using Basic with user 'Alice' +> POST /vendor_event_listener/eventListener/v1/example_vnf HTTP/1.1 +Authorization: Basic QWxpY2U6VGhpcyBpc24ndCB2ZXJ5IHNlY3VyZSE= +User-Agent: libcurl-agent/1.0 +Host: 127.0.0.1:30000 +Accept: */* +Content-type: application/json +Content-Length: 865 + +* HTTP 1.0, assume close after body +< HTTP/1.0 204 No Content +< Date: Fri, 04 Mar 2016 15:37:22 GMT +< Server: WSGIServer/0.1 Python/2.6.6 +< +* Closing connection #0 +* About to connect() to 127.0.0.1 port 30000 (#0) +* Trying 127.0.0.1... * connected +* Connected to 127.0.0.1 (127.0.0.1) port 30000 (#0) +* Server auth using Basic with user 'Alice' +> POST /vendor_event_listener/eventListener/v1/example_vnf HTTP/1.1 +Authorization: Basic QWxpY2U6VGhpcyBpc24ndCB2ZXJ5IHNlY3VyZSE= +User-Agent: libcurl-agent/1.0 +Host: 127.0.0.1:30000 +Accept: */* +Content-type: application/json +Content-Length: 2325 + +* HTTP 1.0, assume close after body +< HTTP/1.0 204 No Content +< Date: Fri, 04 Mar 2016 15:37:22 GMT +< Server: WSGIServer/0.1 Python/2.6.6 +< +* Closing connection #0 +^C + +Interrupted - quitting! +$ +``` + +# Restrictions and Limitations + +## Constraint Validation + +The _EVEL Library_ has been designed to be production-safe code with the +emphasis at this stage being in correctness of operation rather than +raw performance. + +The API tries to check as much information as possible to avoid misuse and +will **assert()** if constraints are not satisfied. This is likely to lead +to the rapid discovery of coding errors by programmers, but does mean that +the application can fail abruptly if the library is misused in any way. + +## Performance + +The default Makefile avoids aggressive optimizations so that any core-files +are easy to interpret. Production code should use greater optimization +levels. + +As described above, the HTTP client is single threaded and will run all +transactions synchronously. As transactions are serialized, a client that +generates a lot of events will be paced by the round-trip time. + +It would be a straightforward enhancement to use the multi-thread API into +libcurl and use a pool of client threads to run transactions in parallel if +this ever became a bottleneck. + +## Logging + +The initialization of the library includes the log verbosity. The verbose +operation makes the library very chatty so syslog may get rather clogged +with detailed diagnostics. It is possible to configure syslog to put these +events into a separate file. A trivial syslog.conf file would be: + +``` + +# Log all user messages so debug information is captured. + +user.* /var/log/debug +``` + +If verbose logging is enabled, the cURL library will generate information +about the HTTP operations on **stdout**. + |