Jaeger is composed of different components, each potentially running in its own host. It might be the case that one of these moving parts isn’t working properly, causing spans to not be processed and stored. When something goes wrong, make sure to check the items listed here.
Before everything else, make sure to confirm what is the sampling strategy. By default, Jaeger uses a probabilistic sampling strategy, with a 1/1000th chance that the span will be reported. Typically, the sampling strategy can be set via the environment variables JAEGER_SAMPLER_TYPEand JAEGER_SAMPLER_PARAM, but refer to the Jaeger Client’s documentation for the language you are using for more details about which sampling strategies are available.
When using the Jaeger Java Client, the strategy is usually printed out via the logging facility provided by the instrumented application when creating the tracer: Some Jaeger clients are able to log the spans that are being reported to the logging facility provided by the instrumented application. Typically, this can be done by setting the environment variable JAEGER_REPORTER_LOG_SPANSto true, but refer to the Jaeger Client’s documentation for the language you are using. When using the Jaeger Java Client, spans are reported like the following: