| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef APACHE_HTRACE_SAMPLER_SAMPLER_H |
| #define APACHE_HTRACE_SAMPLER_SAMPLER_H |
| |
| /** |
| * @file sampler.h |
| * |
| * Functions related to HTrace samplers. |
| * |
| * This is an internal header, not intended for external use. |
| */ |
| |
| #include <stdint.h> |
| |
| struct htrace_conf; |
| struct htrace_log; |
| struct htracer; |
| |
| /** |
| * Base class for an HTrace sampler. |
| * |
| * Implementations should begin with this class as the first member. |
| */ |
| struct htrace_sampler { |
| /** |
| * The type of the sampler. |
| */ |
| const struct htrace_sampler_ty *ty; |
| }; |
| |
| /** |
| * A table of callbacks that implements an HTrace sampler. |
| */ |
| struct htrace_sampler_ty { |
| /** |
| * The name of this probability sampler type. |
| * |
| * This is used to select the sampler via the configuration. |
| */ |
| const char *name; |
| |
| /** |
| * Create an HTrace sampler of this type. |
| * |
| * @param tracer The HTrace context to use. The sampler may |
| * hold on to this pointer. |
| * @param conf The HTrace configuration to use. The sampler |
| * must not hold on to this pointer. |
| * |
| * @return The HTrace span receciver. |
| */ |
| struct htrace_sampler *(*create)(struct htracer *tracer, |
| const struct htrace_conf *conf); |
| |
| /** |
| * Get the name of this HTrace sampler. |
| * |
| * @param smp The sampler. |
| * |
| * @return A description of this sampler object. This string |
| * must remain valid at least until the sampler |
| * is freed. |
| */ |
| const char*(*to_str)(struct htrace_sampler *smp); |
| |
| /** |
| * Sampler callback. |
| * |
| * This callback must be able to be safely called by multiple threads |
| * simultaneously. |
| * |
| * @param smp The HTrace sampler. |
| * |
| * @return 1 to begin a new span; 0 otherwise. |
| */ |
| int (*next)(struct htrace_sampler *smp); |
| |
| /** |
| * Frees this HTrace sampler. |
| * |
| * @param rcv The HTrace sampler. |
| */ |
| void (*free)(struct htrace_sampler *smp); |
| }; |
| |
| /** |
| * Get the configured fraction for the probability sampler. |
| * |
| * @param log A log to send parse error messages to. |
| * @param conf The configuration to use. |
| * |
| * @return A double between 0.0 and 1.0, inclusive. |
| */ |
| double get_prob_sampler_fraction(struct htrace_log *lg, |
| struct htrace_conf *conf); |
| |
| extern const struct htrace_sampler_ty g_never_sampler_ty; |
| extern const struct htrace_sampler_ty g_always_sampler_ty; |
| extern const struct htrace_sampler_ty g_prob_sampler_ty; |
| extern const struct always_sampler g_always_sampler; |
| |
| #endif |
| |
| // vim: ts=4:sw=4:et |