1 files changed, 345 insertions, 0 deletions
diff --git a/src/bio.c b/src/bio.c
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+++ b/src/bio.c
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+/* Background I/O service for Redis.
+ *
+ * This file implements operations that we need to perform in the background.
+ * Currently there is only a single operation, that is a background close(2)
+ * system call. This is needed as when the process is the last owner of a
+ * reference to a file closing it means unlinking it, and the deletion of the
+ * file is slow, blocking the server.
+ *
+ * In the future we'll either continue implementing new things we need or
+ * we'll switch to libeio. However there are probably long term uses for this
+ * file as we may want to put here Redis specific background tasks (for instance
+ * it is not impossible that we'll need a non blocking FLUSHDB/FLUSHALL
+ * implementation).
+ *
+ * DESIGN
+ * ------
+ *
+ * The design is simple: We have a structure representing a job to perform,
+ * and several worker threads and job queues. Every job type is assigned to
+ * a specific worker thread, and a single worker may handle several different
+ * job types.
+ * Every thread waits for new jobs in its queue, and processes every job
+ * sequentially.
+ *
+ * Jobs handled by the same worker are guaranteed to be processed from the
+ * least-recently-inserted to the most-recently-inserted (older jobs processed
+ * first).
+ *
+ * Currently there is no way for the creator of the job to be notified about
+ * the completion of the operation, this will only be added when/if needed.
+ *
+ * ----------------------------------------------------------------------------
+ *
+ * Copyright (c) 2009-2012, Salvatore Sanfilippo <antirez at gmail dot com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   * Redistributions of source code must retain the above copyright notice,
+ *     this list of conditions and the following disclaimer.
+ *   * Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *   * Neither the name of Redis nor the names of its contributors may be used
+ *     to endorse or promote products derived from this software without
+ *     specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+
+#include "server.h"
+#include "bio.h"
+
+static char* bio_worker_title[] = {
+    "bio_close_file",
+    "bio_aof",
+    "bio_lazy_free",
+};
+
+#define BIO_WORKER_NUM (sizeof(bio_worker_title) / sizeof(*bio_worker_title))
+
+static unsigned int bio_job_to_worker[] = {
+    [BIO_CLOSE_FILE] = 0,
+    [BIO_AOF_FSYNC] = 1,
+    [BIO_CLOSE_AOF] = 1,
+    [BIO_LAZY_FREE] = 2,
+};
+
+static pthread_t bio_threads[BIO_WORKER_NUM];
+static pthread_mutex_t bio_mutex[BIO_WORKER_NUM];
+static pthread_cond_t bio_newjob_cond[BIO_WORKER_NUM];
+static list *bio_jobs[BIO_WORKER_NUM];
+static unsigned long bio_jobs_counter[BIO_NUM_OPS] = {0};
+
+/* This structure represents a background Job. It is only used locally to this
+ * file as the API does not expose the internals at all. */
+typedef union bio_job {
+    struct {
+        int type; /* Job-type tag. This needs to appear as the first element in all union members. */
+    } header;
+
+    /* Job specific arguments.*/
+    struct {
+        int type;
+        int fd; /* Fd for file based background jobs */
+        long long offset; /* A job-specific offset, if applicable */
+        unsigned need_fsync:1; /* A flag to indicate that a fsync is required before
+                                * the file is closed. */
+        unsigned need_reclaim_cache:1; /* A flag to indicate that reclaim cache is required before
+                                * the file is closed. */
+    } fd_args;
+
+    struct {
+        int type;
+        lazy_free_fn *free_fn; /* Function that will free the provided arguments */
+        void *free_args[]; /* List of arguments to be passed to the free function */
+    } free_args;
+} bio_job;
+
+void *bioProcessBackgroundJobs(void *arg);
+
+/* Make sure we have enough stack to perform all the things we do in the
+ * main thread. */
+#define REDIS_THREAD_STACK_SIZE (1024*1024*4)
+
+/* Initialize the background system, spawning the thread. */
+void bioInit(void) {
+    pthread_attr_t attr;
+    pthread_t thread;
+    size_t stacksize;
+    unsigned long j;
+
+    /* Initialization of state vars and objects */
+    for (j = 0; j < BIO_WORKER_NUM; j++) {
+        pthread_mutex_init(&bio_mutex[j],NULL);
+        pthread_cond_init(&bio_newjob_cond[j],NULL);
+        bio_jobs[j] = listCreate();
+    }
+
+    /* Set the stack size as by default it may be small in some system */
+    pthread_attr_init(&attr);
+    pthread_attr_getstacksize(&attr,&stacksize);
+    if (!stacksize) stacksize = 1; /* The world is full of Solaris Fixes */
+    while (stacksize < REDIS_THREAD_STACK_SIZE) stacksize *= 2;
+    pthread_attr_setstacksize(&attr, stacksize);
+
+    /* Ready to spawn our threads. We use the single argument the thread
+     * function accepts in order to pass the job ID the thread is
+     * responsible for. */
+    for (j = 0; j < BIO_WORKER_NUM; j++) {
+        void *arg = (void*)(unsigned long) j;
+        if (pthread_create(&thread,&attr,bioProcessBackgroundJobs,arg) != 0) {
+            serverLog(LL_WARNING, "Fatal: Can't initialize Background Jobs. Error message: %s", strerror(errno));
+            exit(1);
+        }
+        bio_threads[j] = thread;
+    }
+}
+
+void bioSubmitJob(int type, bio_job *job) {
+    job->header.type = type;
+    unsigned long worker = bio_job_to_worker[type];
+    pthread_mutex_lock(&bio_mutex[worker]);
+    listAddNodeTail(bio_jobs[worker],job);
+    bio_jobs_counter[type]++;
+    pthread_cond_signal(&bio_newjob_cond[worker]);
+    pthread_mutex_unlock(&bio_mutex[worker]);
+}
+
+void bioCreateLazyFreeJob(lazy_free_fn free_fn, int arg_count, ...) {
+    va_list valist;
+    /* Allocate memory for the job structure and all required
+     * arguments */
+    bio_job *job = zmalloc(sizeof(*job) + sizeof(void *) * (arg_count));
+    job->free_args.free_fn = free_fn;
+
+    va_start(valist, arg_count);
+    for (int i = 0; i < arg_count; i++) {
+        job->free_args.free_args[i] = va_arg(valist, void *);
+    }
+    va_end(valist);
+    bioSubmitJob(BIO_LAZY_FREE, job);
+}
+
+void bioCreateCloseJob(int fd, int need_fsync, int need_reclaim_cache) {
+    bio_job *job = zmalloc(sizeof(*job));
+    job->fd_args.fd = fd;
+    job->fd_args.need_fsync = need_fsync;
+    job->fd_args.need_reclaim_cache = need_reclaim_cache;
+
+    bioSubmitJob(BIO_CLOSE_FILE, job);
+}
+
+void bioCreateCloseAofJob(int fd, long long offset, int need_reclaim_cache) {
+    bio_job *job = zmalloc(sizeof(*job));
+    job->fd_args.fd = fd;
+    job->fd_args.offset = offset;
+    job->fd_args.need_fsync = 1;
+    job->fd_args.need_reclaim_cache = need_reclaim_cache;
+
+    bioSubmitJob(BIO_CLOSE_AOF, job);
+}
+
+void bioCreateFsyncJob(int fd, long long offset, int need_reclaim_cache) {
+    bio_job *job = zmalloc(sizeof(*job));
+    job->fd_args.fd = fd;
+    job->fd_args.offset = offset;
+    job->fd_args.need_reclaim_cache = need_reclaim_cache;
+
+    bioSubmitJob(BIO_AOF_FSYNC, job);
+}
+
+void *bioProcessBackgroundJobs(void *arg) {
+    bio_job *job;
+    unsigned long worker = (unsigned long) arg;
+    sigset_t sigset;
+
+    /* Check that the worker is within the right interval. */
+    serverAssert(worker < BIO_WORKER_NUM);
+
+    redis_set_thread_title(bio_worker_title[worker]);
+
+    redisSetCpuAffinity(server.bio_cpulist);
+
+    makeThreadKillable();
+
+    pthread_mutex_lock(&bio_mutex[worker]);
+    /* Block SIGALRM so we are sure that only the main thread will
+     * receive the watchdog signal. */
+    sigemptyset(&sigset);
+    sigaddset(&sigset, SIGALRM);
+    if (pthread_sigmask(SIG_BLOCK, &sigset, NULL))
+        serverLog(LL_WARNING,
+            "Warning: can't mask SIGALRM in bio.c thread: %s", strerror(errno));
+
+    while(1) {
+        listNode *ln;
+
+        /* The loop always starts with the lock hold. */
+        if (listLength(bio_jobs[worker]) == 0) {
+            pthread_cond_wait(&bio_newjob_cond[worker], &bio_mutex[worker]);
+            continue;
+        }
+        /* Get the job from the queue. */
+        ln = listFirst(bio_jobs[worker]);
+        job = ln->value;
+        /* It is now possible to unlock the background system as we know have
+         * a stand alone job structure to process.*/
+        pthread_mutex_unlock(&bio_mutex[worker]);
+
+        /* Process the job accordingly to its type. */
+        int job_type = job->header.type;
+
+        if (job_type == BIO_CLOSE_FILE) {
+            if (job->fd_args.need_fsync &&
+                redis_fsync(job->fd_args.fd) == -1 &&
+                errno != EBADF && errno != EINVAL)
+            {
+                serverLog(LL_WARNING, "Fail to fsync the AOF file: %s",strerror(errno));
+            }
+            if (job->fd_args.need_reclaim_cache) {
+                if (reclaimFilePageCache(job->fd_args.fd, 0, 0) == -1) {
+                    serverLog(LL_NOTICE,"Unable to reclaim page cache: %s", strerror(errno));
+                }
+            }
+            close(job->fd_args.fd);
+        } else if (job_type == BIO_AOF_FSYNC || job_type == BIO_CLOSE_AOF) {
+            /* The fd may be closed by main thread and reused for another
+             * socket, pipe, or file. We just ignore these errno because
+             * aof fsync did not really fail. */
+            if (redis_fsync(job->fd_args.fd) == -1 &&
+                errno != EBADF && errno != EINVAL)
+            {
+                int last_status;
+                atomicGet(server.aof_bio_fsync_status,last_status);
+                atomicSet(server.aof_bio_fsync_status,C_ERR);
+                atomicSet(server.aof_bio_fsync_errno,errno);
+                if (last_status == C_OK) {
+                    serverLog(LL_WARNING,
+                        "Fail to fsync the AOF file: %s",strerror(errno));
+                }
+            } else {
+                atomicSet(server.aof_bio_fsync_status,C_OK);
+                atomicSet(server.fsynced_reploff_pending, job->fd_args.offset);
+            }
+
+            if (job->fd_args.need_reclaim_cache) {
+                if (reclaimFilePageCache(job->fd_args.fd, 0, 0) == -1) {
+                    serverLog(LL_NOTICE,"Unable to reclaim page cache: %s", strerror(errno));
+                }
+            }
+            if (job_type == BIO_CLOSE_AOF)
+                close(job->fd_args.fd);
+        } else if (job_type == BIO_LAZY_FREE) {
+            job->free_args.free_fn(job->free_args.free_args);
+        } else {
+            serverPanic("Wrong job type in bioProcessBackgroundJobs().");
+        }
+        zfree(job);
+
+        /* Lock again before reiterating the loop, if there are no longer
+         * jobs to process we'll block again in pthread_cond_wait(). */
+        pthread_mutex_lock(&bio_mutex[worker]);
+        listDelNode(bio_jobs[worker], ln);
+        bio_jobs_counter[job_type]--;
+        pthread_cond_signal(&bio_newjob_cond[worker]);
+    }
+}
+
+/* Return the number of pending jobs of the specified type. */
+unsigned long bioPendingJobsOfType(int type) {
+    unsigned int worker = bio_job_to_worker[type];
+
+    pthread_mutex_lock(&bio_mutex[worker]);
+    unsigned long val = bio_jobs_counter[type];
+    pthread_mutex_unlock(&bio_mutex[worker]);
+
+    return val;
+}
+
+/* Wait for the job queue of the worker for jobs of specified type to become empty. */
+void bioDrainWorker(int job_type) {
+    unsigned long worker = bio_job_to_worker[job_type];
+
+    pthread_mutex_lock(&bio_mutex[worker]);
+    while (listLength(bio_jobs[worker]) > 0) {
+        pthread_cond_wait(&bio_newjob_cond[worker], &bio_mutex[worker]);
+    }
+    pthread_mutex_unlock(&bio_mutex[worker]);
+}
+
+/* Kill the running bio threads in an unclean way. This function should be
+ * used only when it's critical to stop the threads for some reason.
+ * Currently Redis does this only on crash (for instance on SIGSEGV) in order
+ * to perform a fast memory check without other threads messing with memory. */
+void bioKillThreads(void) {
+    int err;
+    unsigned long j;
+
+    for (j = 0; j < BIO_WORKER_NUM; j++) {
+        if (bio_threads[j] == pthread_self()) continue;
+        if (bio_threads[j] && pthread_cancel(bio_threads[j]) == 0) {
+            if ((err = pthread_join(bio_threads[j],NULL)) != 0) {
+                serverLog(LL_WARNING,
+                    "Bio worker thread #%lu can not be joined: %s",
+                        j, strerror(err));
+            } else {
+                serverLog(LL_WARNING,
+                    "Bio worker thread #%lu terminated",j);
+            }
+        }
+    }
+}